The First Professional Scientist: Robert Hooke and the Royal Society of London (Science Networks. Historical Studies)

Science Networks . Historical Studies Founded by Erwin Hiebert and Hans Wußing Volume 39 Edited by Eberhard Knobloch, Helge Kragh and Erhard Scholz

Editorial Board: K. Andersen, Aarhus D. Buchwald, Pasadena H.J.M. Bos, Utrecht U. Bottazzini, Roma J.Z. Buchwald, Cambridge, Mass. K. Chemla, Paris S.S. Demidov, Moskva E.A. Fellmann, Basel M. Folkerts, München P. Galison, Cambridge, Mass. I. Grattan-Guinness, London J. Gray, Milton Keynes

R. Halleux, Liège S. Hildebrandt, Bonn Ch. Meinel, Regensburg J. Peiffer, Paris W. Purkert, Bonn D. Rowe, Mainz A.I. Sabra, Cambridge, Mass. Ch. Sasaki, Tokyo R.H. Stuewer, Minneapolis H. Wußing, Leipzig V.P. Vizgin, Moskva

Robert D. Purrington

The First Professional Scientist Robert Hooke and the Royal Society of London

Birkhäuser Basel · Boston · Berlin

Author: Robert D. Purrington Tulane University Dept. Physics New Orleans, LA 70118 USA e-mail: [email protected]

Library of Congress Control Number: 2009920472 Bibliographic information published by Die Deutsche Bibliothek Die Deutsche Bibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data is available in the Internet at http://dnb.ddb.de

ISBN 978-3-0346-0036-1 Birkhäuser Verlag AG, Basel - Boston - Berlin This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. For any kind of use permission of the copyright owner must be obtained. © 2009 Birkhäuser Verlag AG Basel · Boston · Berlin P.O. Box 133, CH-4010 Basel, Switzerland Part of Springer Science+Business Media Printed on acid-free paper produced from chlorine-free pulp. TCF ∞ Cover illustration: Plate from Hooke’s published Cutler Lecture “Animadversions on the First Part of the Machina Coelestis ...” showing an equatorial quadrant driven by a conical or circular pendulum. See also p. 210. Printed in Germany ISBN 978-3-0346-0036-1

e-ISBN 978-3-0346-0037-8

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To Loraine

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Contents Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xi

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii 1

Restoring Robert Hooke . . . . . . . . . . . . . . . . . . . . . . . . . Hooke and London . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2

Robert Hooke, Indefaticable Genius: Hooke and London The Diary . . . . . . . . . . . . . . . . . . . . . . . . . . . Hooke and Wren . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . .

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13 18 22 24 25

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Promoting Physico-Mathematical-Experimental Learning: Founding the Royal Society of London . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Society of the Muses: The First Decade . . Focused Energies: The Laws of Motion . . . Concluding the First Decade . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . .

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45 53 56 58

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Crisis and Consolidation: 1672–1687 . . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

65 69

6

The Society After the Principia: 1688–1703 . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Scientific Virtuoso: Hooke 1655–1687 . . . . . . . . . . . . . . . . . . First Discoveries . . . . . . . . . . . . . . . . . . Hooke and the Royal Society, 1662–1677 . . . . . Hooke and Oldenburg, 1675–1677 . . . . . . . . . Hooke and the Society after Oldenburg; 1677–1687 “Restless Genius: ” Hooke as Scientist . . . . . . . The Hooke Folio, 2006 . . . . . . . . . . . . . . . Conclusion: Micrographia . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . .

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81 84 91 98 101 114 115 118

And All Was Light: Hooke and Newton on Light and Color . . . . . .

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Hooke’s Theory of Light Newton’s Theory . . . . Debate after 1672 . . . . Annotations . . . . . . .

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137 139 140 144

The Nature of Things Themselves: Robert Hooke, Natural Philosopher . . . . . . . . . . . . . . . . . . .

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Introduction . . . . . . . . . . . Hooke’s Natural Philosophy . . Light; Matter, and Motion . . . . Natural Philosophy and Newton Conclusion . . . . . . . . . . . Annotations . . . . . . . . . . .

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149 150 153 157 159 160

10 The System of the World: Hooke and Universal Gravitation, the Inverse-square Law, and Planetary Orbits . . . . . . . . . . . . .

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Introduction: Hooke and Planetary Dynamics . . . . . . . Halley and Newton . . . . . . . . . . . . . . . . . . . . . Huygens . . . . . . . . . . . . . . . . . . . . . . . . . . . Hooke and Universal Gravitation . . . . . . . . . . . . . . Hooke and Newton, 1679 . . . . . . . . . . . . . . . . . . Hooke’s “Laws of Circular Motion” . . . . . . . . . . . . Newton, Gravitation, and the Kepler Problem, 1665–1987 . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . .

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165 171 173 174 177 182 187 189 190

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11 The Omnipotence of the Creator: Robert Hooke, Astronomer Telescopes and Optics . Hooke As An Observer Comets . . . . . . . . Stellar Parallax . . . . Conclusion . . . . . . Annotations . . . . . .

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205 207 214 216 220 220

12 The Last Remain: Hooke After the Principia, 1687–1703 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . Hooke and Newton . . . . . . . . . . . . . . . . . . . . . . 1687–1703 . . . . . . . . . . . . . . . . . . . . . . . . . . Annotations . . . . . . . . . . . . . . . . . . . . . . . . . .

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227 227 229 231 237

Epilogue . . . Introduction Legacy . . . Conclusion Annotations

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241 241 243 247 248

Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Acknowledgments This book had its genesis in a Newton symposium which I hosted with the late Frank Eddington Durham at the tercentenary of the Principia in 1987 as well as in a quartercentury of discussions with Professor Durham on the history of physics in general and the seventeenth century in particular. His insights have been invaluable and it is to him that I owe my greatest debt. I would especially like to thank the very able and helpful staff of the library of the Royal Society, and in particular the librarians, Karen Peters and Keith Moore. Ms. Peters was librarian when I began this project and Mr. Moore helped me finish it. I particularly thank him for providing me with a digital copy of the 2006 Hooke folio before it was made generally available. I also thank the Guildhall Library of the City of London, the British Museum Library, the Science Library, and the Imperial College library, for their expert assistance and cooperation. I would further like to thank Tulane University for a sabbatical leave in the spring of 1999 which allowed me to search the archives of the Royal Society and the Guildhall Library, thus to encounter some of the primary sources for this work for the first time. Other visits to resources in the UK over the last decade and a half – most particularly the entire 1992–3 academic year – were also supported in whole or in part by the university. In addition, thanks are due the staff of the Howard-Tilton Library at Tulane for their patience, professionalism, and dedication in building a valuable collection of secondary works on seventeenth century science. I owe a special debt to Eleanor Elder. I would also like to thank my editor at Birkh¨auser, Karin Neidhart, for her help in bringing this project to completion. A further debt is owed to several historians and scientists with whom I have had fruitful conversations, some brief, some lengthy. In particular, I acknowledge discussions with Michael Nauenberg, Lisa Jardine, Michael Cooper, Mordechai Feingold, Ellen Tan Drake, and Hentie Louw which have provided important insights.

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Preface Notwithstanding some skepticism on the subject, few would disagree with the assertion that if there was ever a transformation in science which deserved the name revolution, that which occurred in seventeenth-century science was it. More so even than the one that took place in the first three decades of the twentieth century, or that wrought by Darwin. It may not have looked like a revolution to those participating in it, but that kind of perspective requires historical distance. In any event, the last two decades have seen Robert Hooke rise from almost total obscurity to the point that he is nearly fashionable, something that would have been unimaginable not so very long ago. Much of this has resulted from tercentenary enthusiasm attending the anniversary of his death, which was celebrated in 2003,1) though it had its beginnings early in the last century, notably at the 300th anniversary of his birth in 1635, an example of how the ebb and flow of reputations has too often turned on such insubstantial accidents of chronology. On the other hand, and a bit ironically, some of this new appreciation of Hooke’s place in seventeenth-century science came out of a recognition that the hero-worship with which Newton was treated during much of the twentieth century was distinctly uncritical. The best example, perhaps, is a conference held at the Royal Society in the summer of 1988, only a year after the monumental celebration of the 300th anniversary of the Principia.2) Hooke’s first biographer, Margaret ‘Espinasse, published her account of his life and work in 1956, more than three centuries after his birth. This remained the only life of Hooke for over 40 years, but two ambitious and detailed biographies, by Stephen Inwood and Lisa Jardine, appeared in 2003–4,3) and several other studies were published in the same period, including an excellent scientific biography by Alan Chapman and a detailed study of Hooke’s role in the rebuilding of London after the fire by Michael Cooper.4) The result is that the public is slowly learning something about the man, and even something of his science. The evidence of Hooke’s role in the Royal Society has always been present in its archives, but these were available only to scholars and little use was made of them. Hooke’s importance was made abundantly clear in Thomas Birch’s distillation of the journals of the Society for 1660–1687, published as the History of the Royal Society of London in 1756,5) but by the late nineteenth and early twentieth century Birch was also hard to find. Birch’s work, which was a transcription of the first quarter-century or so of the journals of the Society, and which therefore displays Hooke’s contri-

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butions on virtually every page, was published only 28 years after Newton’s death, but Hooke had been dead over a half-century and had already been largely forgotten. Forgotten or not, Birch revealed Hooke’s central role in those formative years of what was for all practical purposes the world’s first scientific society. By the twentieth century, with Birch residing in rare book rooms, the process of reviving Hooke’s reputation was a painfully slow one, stimulated by the recovery of his fascinating Diary and its publication in 1935, the advocacy of a few Hooke partisans, and, after the war, the ‘Espinasse biography and the reprinting of Birch in 1968. Its wider availability has made Hooke’s critical role in the Society much more accessible and evident, even though the work summarizes Society meetings only through 1687, more than fifteen years before his death. As we proceed, we will generally assume that when Birch quotes from the Journal Book of the Society, he does so accurately. While this is not absolutely true, it is very nearly so; omissions and errors are infrequent and not generally significant. In many or most cases I have checked Birch against the original. Of course the Secretary may not have accurately represented all discussions which took place, but we have no way of knowing.6) The impending tercentenary of Hooke’s birth (1935) not only saw publication of the best known part of his Diary, but his championing by Robert Gunther, who devoted four volumes of his Early Science in Oxford to “that Oxonian, Robert Hooke”. By the time Gunther published his Volume X, which contained Hooke’s less famous later Diary, describing his activities between 1688 and 1693, Europe was on the verge of war. Gunther also reprinted all of Hooke’s published Cutler Lectures in facsimile, again making them generally available for the first time. As England recovered after the war, interest in Hooke was revived by E.N. Da C. Andrade’s Wilkins Lecture to the Royal Society in 1948 (see Chapter 1) which revealed to a wider scientific audience Hooke’s role in the founding of early modern science. ‘Espinasse’s account of his life and work was published in the next decade, and when Birch’s History was reprinted, finally making it widely available, it exhibited once and for all Hooke’s essential role in the early history of the Society and his important place in the early scientific revolution. Yet little was written about him in the following three decades until Ellen Tan Drake wrote extensively of his role in founding the science of geology, in 1996. The last 30 years have largely been devoted to the absorption of this material. This has gradually led to a new understanding of Hooke’s role in the formative first four decades of the Royal Society, and of Hooke the human being. As other resources have become available, including Turnbull’s Newton correspondence (1959) and the discovery of some of Hooke’s dynamical manuscripts and their decipherment, his importance as a dynamicist and the influence he had on Newton and the Principia have had to be reevaluated. Finally, work by architectural historians and students of the rebuilding of the City of London after the fire, especially by Michael Cooper, and fleshed out by innumerable Diary entries, have made clear Hooke’s place as one of Restoration London’s most important architects, and a major force in rebuilding the City.

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But for most of the twentieth century Hooke has been ignored – indeed, it could be said that Hooke’s eclipse has been his identity (to paraphrase Adam Gopnik). At best he has been represented only by a cartoon image which emphasized his supposed quarrelsome nature and outsized claims. The same might be said of the two centuries that followed 1703, as his death, the passing of his friends and colleagues, especially Boyle (1691) and Wren (1723), Newton’s ascendency in the Royal Society (he was its president from Hooke’s death until 1727), and most importantly, the triumph of Newton’s method, led to a swift decline in Hooke’s reputation, and eventually to his being forgotten altogether. Little remained other than his masterpiece, Micrographia, and the law of elasticity, “Hooke’s Law,” which is all that most physicists, who should know him best, know of him.7) Two major forces shaped Hooke’s professional life. One, the Great Fire of London, in 1666, pushed him into a career of surveying, construction, and architecture that spanned a quarter-century, gained him prestige, partnership with Wren, and as it turned out, wealth. The other, the founding of the Royal Society in 1660, his employment as its Curator three years later, and the 40 years of service he gave to what was the central commitment of his life, is the principal focus of this book. For Hooke’s early role in the Society, there was no model, no precedent. He was, effectively, the first of a breed, the professional scientist,8) paid for his services as an experimental scientist or philosopher. As will become evident, the Royal Society of London, perhaps still the world’s most prestigious scientific institution, would very likely have foundered without Hooke’s contributions to it over four decades. Initially it would be the experiments he was charged to bring in at every weekly meeting that provided the Society’s raison d’etre, and later, his lectures on pneumatics, microscopy, gravitation, comets, and, more broadly, natural philosophy, which gave the Society some intellectual coherence, especially as Boyle’s health declined and Wren’s attention was diverted elsewhere. The story of the Society’s founding and its early struggles to survive as essentially the world’s first scientific institution is told in many places, but what has not been described in detail, at least until very recently, is Hooke’s critical role in the Society’s formative early years and, in turn, its role in his rich and complex life. Hooke, almost by default, became one of the most important figures in the process of institutionalization of science, which began with the founding of the Society in 1660. The same can be said of Henry Oldenburg, the Society’s long-time secretary, who while not personally involved in the discoveries of Society members and the discourses which characterized its meetings, patiently tended to the Society’s correspondence, and almost personally made it an international society, with foreign members and correspondents who included Huygens, Leibniz, Spinoza, Hevelius, Cassini, and others. This work for the Society is enshrined in the thirteen volumes of Oldenburg’s correspondence, almost all on scientific matters, compiled by Rupert and Marie Boas Hall. As the Halls put it, «To foreigners it was Henry Oldenburg who represented the Royal Society . . . »9) There is a certain irony in the fact that the two men who more than anyone else kept the Royal Society alive in its first two decades, Hooke and Oldenburg, ended up as bitter enemies.10)

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Hooke had a dual role in the early years of the Society, initially as a young employee with great promise but no status, and soon in a role which gradually grew so that by his early 30s he had become the most important source of insights into the many problems in natural philosophy which came before the Society. Much of what we know of Hooke comes from his rich and fascinating Diary which he kept, off and on, from his 30s into his mid-50s. The first and most important part of the Diary was lost for two centuries, which means that our understanding of who Hooke was is relatively recent, helping to explain why he faded so completely from view during the eighteenth and nineteenth centuries, when essentially nothing was written about him. The diaries are among the most valuable resources available to scholars trying to understand Restoration natural philosophy and the role of the Royal Society in English science, and as we try to flesh out a picture of Hooke from his own words, these sketchy and telegraphic memoranda – fascinating, provocative, maddingly incomplete – are our raw material. They make it possible for us to trace his daily activities and give us some insight into his inner life. They also tell us much about his relationship to the Royal Society, supplementing what we learn from its journals, but these brief and hasty jottings raise as many questions as they answer. Yet in their daily entries and private purpose, the diaries reveal Hooke the human being in his most unguarded moments.11) To supplement the Diary and to provide much-needed context, it is especially crucial in Hooke’s case, with his complex and rich human interactions and his dealings with people of all stations, to consult the lives of his colleagues and contemporaries Wren, Boyle, Halley, Wilkins, Oldenburg, and others, in England and on the continent, and to read their correspondence, where available.12) And to get a feel for the period and the London in which Hooke lived, a city in which the plague still raged, and which burned in the Great Fire of 1666, one can do no better than the admittedly Proustian task of reading through the diary of his friend Samuel Pepys.13) The quintet of contemporaries, Boyle, Wren, Newton, Halley, and Hooke, epitomize much of Restoration science. Hooke was important in the lives of each of the others, and a close friend of all but Newton. Unlike Newton, whose massive correspondence has been edited by Turnbull and others14) (and which includes important exchanges with Hooke), Hooke, as a creature of London, had little need for epistolary relationships, with the result that his correspondence is meager and uncollected. But because he attended virtually every Royal Society meeting for nearly 40 years, the archives of the Society tell us an enormous amount about his scientific career. Nonetheless, and despite recent interest in Hooke, very little has been added to the record of his life and work since shortly after his death, the main exceptions being the recovery of the early Diary in 1891, the patient combing of the archives of the City of London by Michael Cooper, the recent realization of the importance of some of Hooke’s dynamical manuscripts, and an unexpected discovery in 2006 of a cache of his notes and letters which created a firestorm of publicity and the sale of the documents for close to $1M.15) This major and thoroughly unexpected discovery keeps alive the hope that unknown papers may yet be found. In what follows, we will

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make use of the so-called “Hooke Folio” to shed light on some lacunae in the Society archives and the resultant controversies which have lain unresolved for 300 years. An unexpected consequence of this interest in Hooke’s science is that his important contribution to the architecture of the City of London is finally and belatedly being recognized as well. These two sides of Hooke’s creativity, his natural philosophy and his architecture, are, of course, of a piece, and yet we can never know precisely how he saw his own career and how these activities, those of scientist and Curator of the Royal Society, and those of the surveyor, architect, creator of codes and practices, etc., contributed to his personal identity. Finally, a note on calendrical matters. The Gregorian Reform took place in England only in 1752, so that all dates will be given in the Julian or Old Style. However, the reader will not have to be reminded that the Catholic countries, France, Italy, and Spain, had been using the Gregorian calendar since 1582. In the seventeenth century, the difference between the two calendars was 10 days, so that 8 August 1671 O.S. would be 18 August 1671 N.S. As another example, Hooke noted in his Diary for 10 December 1688, «Shortest Day.», whereas in France the winter solstice was celebrated on 20 December. With the turn of the century, the difference grew to 11 days (after 29 February 1699/1700 O.S.). Where confusion might result, we will offer the reader some guidance. With apology, we will use the somewhat cumbersome 1672/3 for dates in 1673 between January 1 and March 25, since one will encounter that usage almost everywhere in documents from the time, e.g., Hooke’s Diaries, Birch’s History of the Royal Society of London, etc. The new year began on 25 March, essentially the vernal equinox. Occasionally we will be unable to resist the modest anachronism of speaking of, say, Christmas 1687, as being at «the end of 1687,» and for that inconsistency, we offer in advance an apology. We note that Hooke died on 3 March 1702/3, so that it would not be incorrect to say either that he died in 1702 or 1703. Nonetheless, 3 March 2003 was the 300th anniversary of Hooke’s death. When all is said and done, it is not the job of the historian to take sides, but rather to describe and interpret what transpired, to the best of one’s ability. In Hooke’s case it is sometimes difficult to maintain this level of objectivity, for reasons alluded to above and which will become obvious. But in the end, the reader will have to come to his own opinion about the very complex character and life of Robert Hooke.

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Annotations 1) Conferences were held at the Royal Society and in Oxford in the tercentennial year of 2003. The volumes which emerged from those gatherings, Cooper and Hunter (2005) and Kent and Chapman (2005), contain many interesting and detailed papers on aspects of Hooke’s life and his science. Some of these will be referenced in the text. 2) The 1987 celebrations also provided the genesis of the author’s interest in Hooke. See Durham and Purrington, 1989. 3) Inwood (2003), Jardine (2004). There is much interesting detail in these studies which is outside the scope of the present work. 4) Cooper, 2003. 5) Birch painstakingly recounts the activities at every meeting of the Society and of its Council, often giving the full text of a paper delivered by a member. 6) The draft minutes from Oldenburg’s tenure do exist and now (2006) we have Hooke’s raw minutes which have been recovered after over 300 years. 7) To the question of why Hooke descended into obscurity in the century after his death, various answers have been given, and we address some of these below. One, clearly, is the triumph of Newton’s method, as Hooke’s Baconian principles were passing out of favor. The eighteenth century saw the widespread application of Newton’s techniques, manifested most clearly in the mathematical physics of Euler, Laplace, Lagrange, and others. Newton’s ire may or may not have been another factor. The nineteenth century saw the formulation of thermodynamics and electromagnetism, fields of which the seventeenth century was only dimly aware, and in which Hooke could play only the smallest role. One could say that Hooke’s influence was felt primarily on Newton, and in what we might think of as peripheral scientific fields, geology and biology. 8) Hooke was, indeed, in a very real sense the first professional scientist. In assenting to this title, however, Michael Cooper has predicted some will object to “professional,” some to “scientist,” some to “first,” and perhaps even to “the.” 9) CHO, Volume X, p. xxvii. 10) There is an important new biography of Oldenburg by Marie Boas Hall: M.B. Hall (2002). 11) Here we refer to the first of Hooke’s diaries, or at least the earliest extant part. We examine the diaries in Chapter 2, but suffice it to say at this point that the first Diary begins on March 10, 1672, with no fanfare at all – mainly recounting meteorological observations for the first 10 months – and comes to an inauspicious ending, largely through neglect, in May 1683, being continuous only up to about the end of 1680 – which is what Adams and Robinson published. Whether the diaries are parts of a more or less continuous whole, or whether we have all of what Hooke wrote, we will likely never know.

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12) The Boyle correspondence has been recently published by Michael Hunter, et al. (Hunter, Clericuzio and Principe, 2001). Previously one had to resort to Birch’s collection in The Life and Works of the Honorable Robert Boyle, 6 vols., London, 1772. Even more relevant to this narrative is the massive correspondence of the Society’s long-time secretary, Henry Oldenburg, The Correspondence of Henry Oldenburg, in 13 volumes, edited by Rupert and Marie Boas Hall (1965–86). There are new biographies of Wren (Lisa Jardine) and Halley (Allan Cook); see the bibliography. 13) Though the literature on Restoration and Augustan England is vast. 14) Turnbull, et al. (1959) 15) Michael Cooper’s patient scouring of the records of the City of London and its many parishes, showing precisely Hooke’s role in rebuilding the City after the fire, is especially notable. Some of the work will be cited below, but see Cooper on Hooke’s surveying work for the City of London (Cooper, 1997, 1998a, 1998b, 2000, 2003). Hooke’s crucial dynamical paper is discussed in Chapter 10. The recently discovered Hooke manuscripts were obtained for the Royal Society at a cost of $940,000, about half of which was provided by the Wellcome Trust. The implications of this collection for our understanding of Hooke and his work will be discussed in due course.

Chapter 1

Restoring Robert Hooke In 1947, in the wake of World War II, the Royal Society of London established the Wilkins Lectures in the history of science in honor of John Wilkins, one of its founding members and its first secretary. Wilkins himself was the subject of the first lecture, in 1948, but when Edward Neville da Costa Andrade delivered the second Wilkins Lecture the next year (on 15 December), his subject was Robert Hooke. At this point few knew anything of Hooke, except for his Micrographia, published at the start of his career and of his service to the Society. Thus it might be said that it was Andrade’s lecture which caused Hooke to be taken seriously again after nearly three centuries. Hooke’s Diary had been published a little over a decade earlier, creating some curiosity about him which went largely dormant during the war. This nascent resurgence of interest in Hooke, after two hundred years in which virtually nothing was written about him, had begun as the 300th anniversary of his birth approached, and was highlighted by publication of the Diary in the tercentenary year, 1935. The reprinting of much of Hooke’s work by Gunther in his Early Science in Oxford between 1930 and 1938,1) including the later Diary and the Cutler Lectures, did much to stimulate interest in Hooke, and in the same period the ascerbic Andrade was already drawing attention to Hooke. Interestingly, the two of them, Andrade and Gunther, while alike in advocating Hooke, were personal antagonists. Margaret ‘Espinasse’s post-war biography (1956), suggested to her by Jacob Bronowski, and the first real life of Hooke, also helped turn the tide.2) Although there was not another biography until almost the turn of the century, Marjorie Hope Nicholson’s 1965 study of Pepys’ role in the early Royal Society, which highlighted Hooke’s crucial role, was also influential. Robert Hooke was born at Freshwater on the Isle of Wight, where his father was curate of All Saints Church, on July 18, 1635.3) A sickly child who survived childhood illnesses and whose health would never be entirely robust as an adult,4) Hooke was apparently schooled at home for a time, probably destined for the ministry, but his poor health and probably his physical limitations seem to have caused his father to abandon his schooling and to leave him to his own devices. According to Hooke himself, he was intrigued by things mechanical – as was the young Newton,

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of course – busying himself with models, dismantling clocks, and so on. He also explored the cliffs and bays around Freshwater, collecting marine fossils and noting their presence in rocks well above the sea. His father’s subsequent plan to apprentice him to some trade, perhaps watch-making, was foreclosed by his death when Hooke was 13, leaving the young Robert, again like Newton, fatherless5) . Having shown promise in illustration, Hooke was soon sent to London to apprentice to the noted portrait painter Sir Peter Lely.6) In this respect, he was no different from a great many aspiring young men from rural and provincial England who flocked to London in the sixteenth and seventeenth centuries to apprentice to a trade.7) An aversion to oil paints8) supposedly forced Hooke to abandon his putative career as a painter, with the happy result that he was sent to Westminster School, probably at about age 15, where he caught the attention of the Headmaster, Dr. Richard Busby, who took him under his wing.9) Hooke would maintain a life-long friendship with this famous educator, with whom he lodged, eventually designing a church for him nearly 30 years later. Hooke had two or three great mentors in his life: Busby, who kindled, or at least sustained, the intellectual fires that drove his genius, John Wilkins, who did the same at Oxford, and Robert Boyle, who served as his first model of a natural philosopher and provided the 20 year old Hooke a laboratory in Oxford in which to work. All became lifelong friends. At Westminster Hooke received the usual classical education (which is evident throughout his mature writing), learned Euclid, and indulged his interests in things mechanical.10) He also discovered, or at least developed, his musical interests there, learning to play the organ. These talents served him well, for at age 18 (1653) he was sent up to Oxford’s Christ Church College as a chorister and servitor.11) His friend Richard Waller saw it this way, «as ’tis often the Fate of Persons great in Learning to be small in other Circumstances, his were but mean.» Oxford was in Puritan hands in 1653 when Hooke would have arrived there. But with the moderate John Wilkins as Master of Wadham College (a post he had held since 1648), a number of the members of the London “1645 group” (see Chapter 4), many of whom had royalist leanings, had migrated (or fled) to Oxford and Wadham to be near him. Wilkins’ galaxy included such important figures as John Wallis, Seth Ward, Laurence Rooke, Thomas Willis, William Petty, and even the young prodigy Christopher Wren, only three years Hooke’s senior, who had come to Oxford in 1649 and received his M.A. in the year Hooke arrived. All of these men would become important figures in Restoration science and in the Royal Society, and most would play an important role in Hooke’s life. If Hooke went up to Oxford in about 1653, he would have ordinarily taken his B.A. in about 1656–7, though there is no evidence that he did, or even that he matriculated. We do know that he had the M.A. degree conferred on him in 1662– 1663,12) his first full year of employment by the Royal Society.13) At what point he came to the notice of Wilkins is not entirely clear, though according to Hooke, he was first «brought into the acquaintance of these great Men» (referring to members of the Oxford club; see Chapter 4) in «about the year 1655,» that is, at age 20.14) The precocious Hooke, who shared Wilkins’ interest in the possibility of human flight,15) probably met him through the vehicle of the Oxford club, and through him came

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3

into contact with other members of the group. Wilkins apparently commended him to Willis, a noted anatomist, through whom he probably met Seth Ward, and in 1654 or 1655 he became Willis’ chemical assistant. According to Hooke himself, Ward, Savilian Professor of Astronomy, friend of Wren’s, and eventually Bishop of Salisbury, introduced him to the pleasures of astronomy in 1655. Astronomy was from that point on an interest that Hooke never lost, one which would often provide motivation and opportunity for application of his mechanical ingenuity and would keep his mind on the problem of planetary motion.16) Indeed, after Horrocks and before Flamsteed and Halley, and despite the fitful character of his studies, Hooke was probably England’s most important astronomer. With neither money nor position, Hooke might well have foundered but for the exposure the Oxford group afforded him. At best he would have ended up as a country parson like his father and brothers. But in Oxford, and in particular through the Oxford society, the bright undergraduate could display his ingenuity and inventiveness and meet scholars and other virtuosi who would soon form the nucleus of the Royal Society. Wilkins, Willis, and Ward, and in the end, especially Boyle, provided models for the budding natural philosopher. The dazzling Wren was another, but he would become far more than that as the two struck up a friendship which eventually blossomed into an architectural partnership. They were friends and colleagues for nearly a half-century, working virtually side-by-side in the process of rebuilding London after the fire, and constantly arguing scientific issues over coffee or in Wren’s home. It was Wilkins who invited Boyle, the 28 year old aristocrat17) , to join him in Oxford, and who likely introduced Hooke to him. Not long after Boyle arrived in Oxford, say by 1658, he took Hooke as his assistant, an apprenticeship which led to his employment as Curator of Experiments for the recently formed Royal Society. Both Wilkins and Boyle would remain Hooke’s faithful friends until their deaths, which for Wilkins was in 1672, at age 58, but for Boyle would be two decades later. The internship with Boyle, which lasted until Hooke went to work for the Royal Society in late 1662, was the crucial event in shaping Hooke the natural philosopher. When Hooke left Boyle and Oxford for London, he was an experienced 27 year old who had already met a number of England’s scientific luminaries, including Wren, who was building a reputation for brilliance. The young Hooke stood on the threshold of a long and productive scientific career. So it was that he became a professional scientist, arguably the very first of a new breed, occupying a position which would provide him with the opportunity, and, alas, the obligation, to carry out hundreds of experiments over a period of more than 30 years.18) The position also provided him a forum for discussion of his many ideas, while he quickly matured into an independent natural philosopher. His importance to the Society slowly grew as his weekly experiments came to provide it with much of its raison d’etre. During at least the Society’s first two decades (and especially throughout the 1660s and in the years following Henry Oldenburg’s death in 1677), there would almost literally have been no Royal Society without Hooke. In his apprenticeship with Boyle, Hooke not only was schooled in the practice of experimental natural philosophy, but he also absorbed his mentor’s ideas on the

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nature of mechanical and corpuscular philosophy, of which Boyle was to become one of the most ardent exponents. And by about 1658 Hooke had, in his words, «contriv’d and perfected the Air-pump for Mr. Boyle . . . ,»19) something Boyle confirms.20) The experiments which elucidated “Boyle’s Law” most likely were carried out largely by Hooke, but he in turn acknowledged the earlier work of Richard Townely, who with Henry Power deserves much of the credit for discovery of this relationship between volume and pressure.21) That the mechanically inclined Hooke grew into a natural and experimental philosopher while under the tutelage of Boyle is evident, but Boyle was as much a polemicist for experimental philosophy as an experimental scientist, per se, so that we can assume that Hooke’s role in these pneumatic experiments was crucial. That said, the impact of Boyle’s New Experiments Physico-Mechanical Touching the Springiness of the Air of 1660 can hardly be exaggerated. The details of Hooke’s relationship with the “gentleman scientist” Boyle, the discoveries which resulted, and Boyle’s sponsorship of Hooke to the Royal Society, will be left to other chroniclers,22) but as it happened, Hooke was named to the post of Curator of experiments for the Royal Society on November 12, 1662, 23) with the «thanks of the society [to Boyle] for dispensing with him for their use», and he provided the first experiments one week later. Hooke’s style, while very much his own, owed a lot to Boyle, a heritage which would cut both ways, providing both a model and, one might say, a straight-jacket. Thus began Robert Hooke’s long association with the Royal Society, with which we will deal at length. For the moment, however, and in the next chapter as well, we will flesh out the picture of Hooke as a human being, and in particular, as a Londoner whose life and work was entirely shaped by that city, with its opportunity and optimism, its intellectual and social ferment, yet at the same time, its poverty, pollution, and disease.

Hooke and London No portrait is known to exist of Hooke,24) so that we have to rely on written accounts of his appearance. By all testimony he was stooped, perhaps a victim of scoliosis, had piercing eyes, thin, unruly brown hair (but sometimes wore a periwig), and rushed about with enormous energy. The churches he worked on with Wren, the buildings he built, the surveying he did after the fire, the coffee-houses and taverns he frequented – all these rarely took him more than 15 blocks or so from his lodgings in Gresham College, in the northeast corner of the City, where Society meetings were held for long periods of time as well.25) Sometimes his duties or his friendship with Dr. Richard Busby sent him to Westminster and frequently he walked in St. James’s Park (a mile and a half from St. Paul’s) with Wren, who had his office nearby, or others, occasionally encountering the King (Charles II), who knew him well. We can imagine that for his time, at least, Hooke was fairly fit, despite the continual health problems enumerated in his Diary. Never owning a carriage, he walked several miles every day in carrying out his many duties. On occasion he recorded walking to Islington, just outside London Wall, or to Highgate. On rare occasions he went somewhere on the

Hooke and London

Fig. 1

5

Gresham College in Bishopsgate. By permission of the Guildhall Library, Corporation of the City of London.

Thames by boat, Greenwich, for example, where he helped design and build the observatory. Even less frequently he would venture into the country, as he did during the height of the plague in 1665, and when he visited Oxford in June 1680. Like Newton, he never traveled abroad. Hooke’s business transactions as commissioner, surveyor, and architect took place almost entirely within greater London, and usually within the City itself. Indeed, virtually his entire adult life was led in that area of a few square miles that he walked daily, regularly calling at Wren’s or at Boyle’s sister’s, or stopping at a coffeehouse or a work site. His milieu was London, where he spent the last forty years of his life and from whose environs he rarely strayed. During much of that long period in London he not only was a versatile and inventive scientist and a pivotal figure in the Royal Society, but was also a city planner, architect, engineer, surveyor for the City following the fire of 1666, assistant, colleague, and partner to Wren in rebuilding the churches of London, and, on his own, or with Wren, architect of many of them. For those 40 years he lived within walking distance of the Guildhall in the City, residing for most of that time in rooms in Gresham College (Fig. 1) in Bishopsgate, where he was Professor of Geometry, frequenting the coffee-houses around Cornhill and

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Fig. 2: Bedlam or Bethlem Hospital, designed by Hooke, 1674–6.

the Royal Exchange (Fig. 3) visiting tradesmen, instrument makers, and booksellers, throwing himself into the life of the City with boundless energy. It is impossible to imagine Hooke in any other setting than London, the largest city in the world when he lived there, its skies often dark with smoke, its streets reeking of both poverty and wealth, a product of the huge gap between the privileged and those at the bottom of the social and economic ladder. Yet as the 300th anniversary of his death in 1703 approached, there existed not a single tribute to that “restless genius” anywhere in London.26) Even “The Monument”, which he, with Wren’s help, erected on Fish Street Hill to mark the start of the Great Fire, bears no trace of his name. Although Hooke was an extraordinarily inventive scientist and a standard-bearer in the scientific revolution, his second career, which began with the Great Fire of London in 1666, was hardly less important to him. Initially he was a Royal Surveyor, charged with the problems of demolition and rebuilding of the residential and commercial structures of the City of London after the fire. He soon became responsible for overseeing compliance with codes and practices, began working with Wren on the parish churches of the City, and eventually became, for all practical purposes, his architectural partner. Furthermore, he undertook his own major architectural projects, including the massive College of Physicians and Bedlam (or Bethlem) Hospital.27) (Fig. 2) These projects, now, of course, long gone, were his largest. He built the

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Royal College of Physicians between 1672 and 1678, and Bedlam in 1674–76.28) With Wren (presumably) he designed and built the Monument during 1672–77, and his work on the churches of the northeast part of the City took place mostly between 1670 and 1685.29) The partnership with Wren in building Greenwich Observatory also dates from the late 1670s. Walking around London today one would find no obvious evidence that Hooke had ever lived. The secular buildings which have always been known to have been his are long gone, and Gresham College in the City, where Hooke had his rooms, was pulled down in 1767.30) Yet there is indeed much that remains in the City of London that shows the touch of his hand, though it remains mostly unacknowledged. Architectural scholarship has shown that Hooke played a role that was barely second to Wren’s in rebuilding the 51 parish churches of the City after the fire, and that about half of them can be considered largely Hooke’s – primarily those in the northeast corner of the City near where he lived.31) Only about a dozen of these “Hooke” churches remain and all have been modified over time to a greater or lesser degree, four having been again rebuilt after being gutted during the Blitz of World War II. But they all serve as a testament to Hooke’s energy, versatility, and talent as an architect. And if one visits these churches, for example, St. Peter Cornhill, St. Edmund the King, and St. Mary Abchuch, it is not hard to see the Hooke style in them. On the whole the architecture is derivative, but then the same can be said of Wren, though he possessed an architectural genius that Hooke did not. But Hooke was well-schooled in the classic works of architecture, from Vitrivius to Palladio, and one sees evidence of that in his architecture. Of course some of the attributions to Hooke are still in dispute and it is hard to know how much of a role Wren may have played in any one of these churches. It is not unlikely that he ultimately had to “sign off” on many or most of them, but his role may have been pro forma. One of Hooke’s strengths was that he was better equipped than most of his contemporaries to solve the practical problems of design and construction. In the case of the Monument (Fig. 3), it is, as we said, difficult to assess with certainty the relative roles of Hooke and Wren, but Hooke was on site almost daily at the peak of construction, and only rarely is there evidence that Wren also there. It would not be unreasonable to consider it largely a Hooke structure. The recent revelation that the Monument was designed so that it could be used as a zenith telescope adds fascinating detail to its design and construction,32) though it has long been known that Hooke used what he called the “piller” to carry out experiments on the variation of barometric pressure and gravity with height. Unlike some of his contemporaries, Newton in particular, Hooke was a thoroughly social and gregarious being, with friends from the lowest to the highest station. He mixed equally well with men of the trades, whose work he supervised, instrument makers and craftsmen, professionals such as physicians and clerics, natural philosophers including Boyle, Wren, and Halley, and even men of the world like Samuel Pepys. In the next chapter we will try to develop an image of who Hooke was as a human being, before turning our attention to his science and his role in the Royal Society.

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Fig. 3: Hooke’s haunts in the Cornhill area, with Jonathan’s and Garraways noted.

Annotations 1) Robinson and Adams (1935); R.T. Gunther (1930), Vols. VI, VII, VIII, X, and XIII, 1930–38. 2) Andrade (1950), ‘Espinasse, 1956. The latter work clearly fails to reflect modern studies and to some extent modern historiography. But by the same token, it is fresh and original, influenced not at all by current fashions. 3) For details of Robert Hooke’s early life, we are mostly dependent upon the Life offered by Richard Waller in 1705 in his collection of Hooke’s unpublished works, The Posthumous Works of Dr. Robert Hooke. This was in turn based on a “History of my own life” which Hooke began in 1697 but never completed. While only a brief summary of his early years will be given here, the reader can consult Waller’s Life, appended to The Diary of Robert Hooke (Robinson and Adams, 1935). Gunther’s The Life and Works of Robert Hooke, published in two parts (Part I in Vol. VI and Part II in Vol. VII of Gunther (1930–38) in 1930 is actually the most detailed recounting of Hooke’s life, concentrating, of course, mostly on his science, quoting extensively from Waller and Hooke himself. John Ward’s Lives of the Gresham Professors (1740) also contains a short biography of Hooke, as does John Aubrey’s Brief Lives (Dick, 1949), pp. 165– 6. Other sources include the final chapter of ‘Espinasse’ biography, (‘Espinasse 1956), Andrade’s 1949 Wilkins Lecture (Andrade, 1950), and the introduction to Drake’s Restless Genius (Drake, 1996). Now we have biographies by Inwood (2003) and Jardine (2004).

Annotations

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Hooke had an older sister Katherine and an older brother John, who eventually hanged himself. 4) «. . . very imfirm and weakly . . . » is how Richard Waller described him. (Gunther, 1930, Vol VI). 5) Hooke’s father died in October 1648, leaving him a legacy of $40. 6) Ironically, his portrait of Charles II now graces the walls of the Royal Society, but there is none of Hooke. 7) Beier and Finlay (1986), pp. 10, 15 (and references therein). 8) Or so the story goes. 9) Busby was renowned for his flogging, but had a strong influence on, among others, John Locke, three years older than Hooke, who also went up to Christ Church College, Oxford from Westminster, and John Dryden, who came to Westminster in 1644; Wren was also there. Busby, who was headmaster for 55 years, died in 1695 at age 89. He was a royalist who nonetheless thrived when the school was dominated by parliamentarians. He boarded a number of students at a time, deriving some income from each. 10) Aubrey said that «at school he was very mechanicall, and (amongst other things) he invented thirty severall wayes of Flying.» He went on to say that «He was never a King’s Scholar, and I have heard Sir Richard Knight (who was his school-fellow) say that he seldome saw him in the schoole.» Brief Lives, O.L. Dick, ed., 1949, p. 165. “In schoole” did not refer to the premises of Westminster, but only to the large common room known by that name. 11) Aubrey says 1658, but is evidently in error, though this is when Hooke first appears in Oxford records. As we noted earlier, when Hooke went up to Oxford it was in Puritan hands, and there would not have been church or chapel music. 12) See Gunther, VI, p. 12, n. 1. Hooke overlapped with John Locke at Westminster School and went up to Christ Church, Oxford a year or so after Locke, three years Hooke’s senior, who matriculated at Oxford in 1652. 13) Though in May 1663, a list of the registered fellows of the Society included “Thomas Sprat, M.A.,” but only “Mr. Robert Hooke.” Only Hooke had no title of any kind (Esq., D.D., M.D., LL.D., knight, bart., lord). 14) As Waller put it, Hooke «began to shew himself to the World» in 1655 (PW, p. iii). 15) Wilkins gave Hooke a copy of his Mathematical Magick, a popular work which he published in 1648. The strong friendship which grew up between them was only terminated by Wilkins’ death in 1672. 16) Ward had signed the Puritan Covenant in 1649, allowing him to return to the Oxford he had fled earlier, and he became Savilian Professor of Astronomy. He abandoned academic life in favor of a religious career in 1660, eventually becoming Bishop of Salisbury, but was an original member of the Royal Society.

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Hooke’s construction of refracting, and later, reflecting telescopes was an integral part of his interest in optics. His Diary recounts many observations, frequently with Halley and especially of comets and eclipses, but of Jupiter and Saturn as well. Most were made from his lodgings at Gresham College in London. On the whole, however, his observing was fairly casual and unsystematic, and with the exception of comets, he contributed little to astronomical science, despite a few “firsts.” He was more interested in timing, telescope driving mechanisms and sights, and, of course, lens and mirror grinding. See Chapter 9. 17) Boyle, the 7th Earl of Cork (Ireland), had been experimenting on his estate in Dorset when Wilkins persuaded him to come to Oxford in 1655–6. Christopher Wren received his M.A. from Wadham in 1657, having himself been influenced by Wilkins, Rooke, Ward, and Wallis. 18) As the reader will discover, Hooke’s dedication to his duties as Curator waned as he took on more and more responsibilities as surveyor and architect, but also when he became, briefly, Secretary of the Society, and finally, as his powers began to decline in the 1690s. For a while Hooke commuted between Oxford and London, and often stayed with Lady Ranelagh, Boyle’s sister. 19) Waller’s Life in Gunther (1930), vol. VI, p. 8; PW, p. iii. 20) Boyle, New Experiments. 21) What we know as pV = constant, a special case of the ideal gas law, pV = n RT , when T , the absolute temperature, is constant. 22) In particular Michael Hunter, whose forthcoming biography will be the definitive one of Boyle. 23) The previous week, on 5 November, his appointment was first mentioned. 24) It has been suggested that in view of his unprepossessing appearance, Hooke may have been reluctant to sit for a portrait. He does not seem, however, to have had much vanity, and there is little doubt that the Society did have a portrait. When Zacharias von Uffenbach visited the Society in 1710, he reported seeing portraits of “Boyle and Hoock.” (‘Espinasse, 1956, p. 13; Chapman, 1996). Although Jardine (2004) has claimed the discovery of a portrait of Hooke in London’s Natural History Museum, previously thought to be of John Ray, it now seems that the portrait is of Jan Baptist van Helmont. 25) The City, with an area of one square mile, is the “historic core” of Greater London, dating from medieval times. It was originally defined by the defensive “London Wall,” with its various “bars” and gates, or openings, including Bishopsgate, near which Gresham was located. 26) A situation which finally changed on 3 March 2005, with the installation of a memorial to Hooke in Westminster Abbey. Hooke went to Westminster School and worked on repairs at the Abbey at various times in his 50s. See the epilogue. 27) Bedlam, or Bethlem, or Bethlahem.

Annotations

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28) See “Hooke and Bedlam,” (Heyman, 2006) in Cooper and Hunter (2006). Another Hooke structure was the Montague House, which burned in 1686, but whose facade survived and which was later the first home of the British Museum. 29) On the Hooke churches, see Jeffery, 1996. 30) Apparently only one of the public houses frequented by Hooke survives, the George and Vulture. See the information on taverns and coffee-houses mentioned in Hooke’s Diary, in Robertson and Adams (1935). 31) See Jeffrey (1996), who wrote (p. 176) that «without Hooke, or someone of his calibre, Wren could not have entertained the task of rebuilding the churches.» As many as 23–24 churches have been attributed in whole or in part to Hooke, some in partnership with Sir Christopher, but others mostly alone, so that while almost all other evidence of Hooke’s time on this Earth has vanished, hundreds of tourists every day look upon his works with awe, never knowing who the architect really was. 32) Nichols (1999), Jardine (2002). Hooke evidently had this possibility in mind, though one should not think of the Monument as essentially a laboratory. There is today a wooden cover in the entrance level of the Monument that, lifted, allows one to see into the lower area from which zenith observations would have been made.

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Chapter 2

Robert Hooke, Indefaticable Genius1): Hooke and London The enigma (or enigmas) of Hooke, perhaps more than any other figure of the Scientific Revolution, raises the question “Who was Robert Hooke?”2) For if there is still much to learn about Hooke, we do know that he was not a person who aroused feelings of indifference. He was lionized by many as ingenious, honest, and generous, while others dismissed him with contempt or hatred as mean, irascible, and, worse, one who claimed the discoveries of others. Even today, despite an explosion of writing on Hooke, no clear view of him emerges, and the situation is not so different from three centuries ago, with partisans showing near reverence for him and detractors finding unworthy motives in almost everything he did. If he was held in high regard by important scientific figures like Christopher Wren, Robert Boyle, and Edmond Halley, revered by such men of the world as Samuel Pepys, major church figures like Seth Ward and John Tillotson, and by his chroniclers John Aubrey and Richard Waller, he also made important enemies. Among these, eventually, were Henry Oldenburg, long-time Secretary of the Society, and Viscount Lord Brouncker, its president for a decade and a half, as well as major continental scientific figures like Huygens and Leibniz. And, of course, Newton. In part, simple rivalry or jealousy was involved, but Hooke was at the very least “touchy” as Andrade, a Hooke admirer, called him, and there is no doubt that he was vigorously protective of his discoveries and reputation. Hooke was not always easy to get along with, and to some extent the same is true today. Among modern commentators, Bryan Little, one of the many Wren biographers, who leaned heavily on Hooke’s Diary, calls him a «warped and over sensitive man,» and the Boyle biographer R.E.W. Maddison noted that Hooke «had the reputation of being difficult and crabbed.»3) Lisa Jardine has pronounced him «notoriously difficult to please.»4) Hooke’s evident animus for Oldenburg is one of the reasons that many have dismissed him as a malcontent, but there is very much to be said on Hooke’s side in this matter, and as it turns out he had good reasons for his suspicions.5) Nor was he alone in his sentiments: Wren, for example, had no more

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Chapter 2. Robert Hooke, Indefaticable Genius

use for Oldenburg than Hooke. Hooke’s regard for Lord Brouncker, the Society’s long-time president, was also very low, an estimate Pepys seconded when he called Brouncker a «rotten hearted, false man, as any else I know . . . »6) To the sharp-eyed and meticulous Pepys, Hooke at age 30 was «the most and promises the least, of any man in the world that I ever saw.»7) Not long after Hooke’s death in 1703, the same year Pepys died, Waller, secretary of the Royal Society and publisher of Hooke’s Posthumous Works, saw him as one of the «Ornaments of the last Century». Even Newton’s famous «If I have seen further it is by standing on the shoulders of Giants,» was an observation prompted by Hooke’s earlier work in optics, and made in a letter to him.8) Leona Rostenberg, one of those who has studied Hooke’s library, saw him as a «most erudite, gregarious, occasionally cantankerous scientist . . . ,» and ‘Espinasse pictured him as a man of «warm and tender heart, too generous and too busy with ideas to go on bearing rancour . . . »9) Michael Cooper, In his groundbreaking studies of Hooke’s work as City Surveyor, has pronounced him «extraordinarily well organised, fair-minded, efficient and astonishingly energetic.»10) In the public sphere, surveying, arbitrating disputes over boundaries or codes, and in designing private residences, mansions, for Royalty or the City, his competence was apparently exceptional. No doubt Hooke could be difficult, but he led a rich, complex, and, one suspects, satisfying life, in spite of rather precarious health, frequent grumbling about slights, and the bad luck he had to toil in Newton’s shadow in his later years, convinced that Newton had stolen the secret of planetary motion from him. But the picture that emerges is of an energetic, warm and gregarious person, friend to the great and small, somewhat acerbic, perhaps cantankerous, and certainly jealous of his reputation. As an indication of how Hooke’s reputation has grown in the last half-century, we note that Mordechai Feingold entitled his contribution to the Hooke 2003 symposium at the Royal Society “Robert Hooke: Gentleman of Science.”11) So if there is nothing to indicate other than that Hooke was a person of the highest personal rectitude, and that his most evident characteristics, after his boundless energy and «indefatigable genius,» seem to have been straightforwardness, honesty, and generosity, he could bridle quickly when slighted by someone who seemed to think himself his superior, and he seems to have a well-justified expectation that his accomplishments and his service to the Royal Society would bring him respect. His tolerance of the scoundrel or poseur, whether Lord or laborer, was very slight; as Waller said of him, «He had a piercing Judgment into the Dispositions of others . . . » The Diary constantly reflects disappointment with the integrity, fairness, or competence of the people with whom he dealt on a daily basis, including not a few in the Society itself. In short, much of his reputation for being difficult comes from disappointment in his expectations of others. At the same time, he was very human, and hero worship is no more justified in Hooke’s case than it is in Newton’s. Hooke’s generous personality also comes through in his relationships with those dependent upon him. He helped the impecunious John Aubrey through bad times by lending him money, buying books from him to stave off bankruptcy, letting him use

Chapter 2. Robert Hooke, Indefaticable Genius

15

his rooms as a place to receive mail when he was without a permanent residence, and often putting him up.12) Although he seems to have been fair to his domestic help, the sexual exploitation of his housekeepers, candidly recounted in his Diary, if of the time (note Pepys’ liberties with his own staff and Brouncker’s reputation, for example), will give the modern reader pause, and indeed may have offended some of Hooke’s more fastidious companions.13) Aside from this disappointing, and even appalling weakness, it may be that his worst personal failing (though given the challenges he faced, it is not clear that he could have done much better) was his inability to bring many of his ideas to completion or even to publish them, by virtue of which he was himself responsible for squandering the fruits of his creative intellect.14) As already noted, no portrait of Hooke is known to exist (despite some wishful thinking) and contemporary accounts, primarily those by Waller and Aubrey, are models of brevity. For the most part, our only recourse is to his now famous Diary (or diaries), one written in his late 30s into his 40s, the other in his 50s. They are intimate and in many ways revealing, but at the same time maddeningly terse and telegraphic. They describe details of his daily existence, and often those of his contemporaries, but give us precious few details of his scientific life. In particular, we learn almost nothing of his scientific work habits, what his laboratory or experimental space at Gresham might have been like, and so on. We find passages such as «Set up the new magneticall experiiment about 4 p.m. . . . ,»15) but anything more specific is quite rare. What we do learn is that Hooke was in constant motion, observing, juggling diverse experiments, meeting members of the Royal Society, seeing Wren almost daily on architectural projects, conferring with tradesmen and builders, making the rounds of his favorite coffee-houses and, though less frequently, taverns. His was a restless, rich life, full of social interactions, and yet, while he had many friends, often of high station, few of his acquaintances left substantial accounts of him. His lifelong friend Christopher Wren left almost nothing in the form of reminiscence and his extant correspondence is, like Hooke’s, quite small. Both, it might be said, were too busy for introspection and retrospection. Few letters passed between them because they saw each other almost daily; they were creatures of London who had little need for the post. Hooke and his mentor Boyle often communicated by mail, but Hooke had no regular correspondence with any scientist elsewhere in the country, or abroad, with the exception of Halley, with whom he kept in touch when the latter was traveling. Unlike a Newton or a Wallis, sequestered in provincial Cambridge or Oxford, and whose only means of communication was the letter, Hooke wrote few. Most of his surviving correspondence is to be found in the collections of more famous figures like Newton, Boyle, Flamsteed, and Halley. Even as Secretary of the Society from 1677 to 1682 his correspondence was relatively meager. But while he was not a prolific correspondent, the letters we have are sensitive, articulate, and interesting. He wrote little about himself, apart from a an aborted biographical sketch, but such testimony is often untrustworthy anyway – in Newton’s case, the much later recollections of his early years are notoriously self-serving. Although Hooke was anything but a dandy, his Diary reveals a definite interest in the state of his wardrobe and regularly records the purchase of quality material for

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Chapter 2. Robert Hooke, Indefaticable Genius

his clothing. By all accounts he was quite presentable and certainly not embarrassed to be in the company of the King, despite a pronounced stoop, as we hear from Waller in this famous description: «As to his person he was but despicable, being very crooked, tho’ I have heard from himself, and others, that he was strait till about 16 Years of Age when he first grew awry, by frequent practicing, turning with a Turn-lath, and the like incurvating Excercises, being but of a thin weak habit of body, which increas’d as he grew older, so as to be very remarkable at last: This made him but of low Stature, tho’ by his Limbs he shou’d have been moderately tall. he was always very pale and lean, and laterly nothing but Skin and bone, with a meagre Aspect, his Eyes grey and full, with a sharp ingenious Look whilst younger; his Nose but thin, of a moderate height and length; his Mouth meanly wide, and upper Lip thin; his Chin sharp, and Forehead large; his Head of a middle size. He wore his own Hair of a dark Brown colour, very long and hanging neglected over his Face uncut and lank, which about three Year before his death he cut off, and wore a Periwig. He went stooping and very fast . . . having but a light Body to carry, and a great deal of Spirits and Activity, especially in his Youth.»16) John Aubrey’s recollection was similar to Waller’s, but emphasized his inventiveness and virtue: «He is but of midling stature, something crooked, pale faced, and his face but little below, but his head is lardge; his eie full and popping, and not quick; a grey eie. He has a delicate head of haire, browne, and of an excellent moist curle. He is and ever was very temperate, and moderate in dyet &c. As he is of prodigious inventive head; so he is a person of great vertue an goodness . . . He is certainly the greatest mechanick this day in the world . . . In fine (which crowns all) he is a person of great suavity and goddnesse.»17) Hooke never married, indeed, could not have done so and retained the Gresham professorship which he held for the last 40 years of his life. Many other important figures of early modern science never married, for example, Newton, Huygens, Leibniz, Locke, Hume, Hobbes and Kant. Boyle was ardently celibate.18) In this regard, Wren and Halley, notable family men, are important exceptions. Unlike Newton, Hooke had a fondness for the opposite sex, and that he took advantage of the vulnerable girls who lived with him as housekeepers, and presumptively coerced them into sexual relationships, is revealed in his own hand. Given his normal sex drive, as evidenced by numerous other Diary entries, the presence of young ladies in his house and his position of power over them, and perhaps his inability to form sensual bonds with women based on equality, it was almost inevitable that Hooke should take advantage. In Hooke’s defense, we note that he never lost interest in his former housekeeper Nell Young’s welfare after she left his service and married. She often visited him on a Sunday morning, and Hooke was ready to offer assistance. His relationship with his niece Grace is more surprising, but in the absence of any real knowledge of the

Chapter 2. Robert Hooke, Indefaticable Genius

17

affair, it is a dead end. His evident concern for her health, his apprehension when she was out, his devastation when she died in 1687, have prompted some to call her his “mistress” or even “common-law wife.”19) Waller wrote that «In the beginning of the Year 1687 his Brother’s Daughter, Mrs. Grace Hooke dy’d, who had liv’d with him several Years, the concern for whose Death he hardly ever wore off, being observed from that time to grow less active, more Melancholy and Cynical.»20) Granting this failing on Hooke’s part, however, and offering no defense of it, one can see it as part and parcel of a rich and vigorous social and sensual life, reflecting enormous physical and intellectual energy. Coupled with the garrulous and gregarious nature we see evidenced in his habitual visits to coffee-houses and taverns and his full social life, we are furnished the image of a vigorous and vital young man in his late thirties, taking life at the full. They surely form a contrast with the repressed and reclusive Newton, sequestered in Cambridge, seeing almost no one. As we shall see, Hooke’s health was precarious, or at any rate, a constant preoccupation. Indeed, he has been called a hypochondriac. He was in constant search for nostrums and experimental cures for his many real (and imagined?) ailments, and records at length his various means of purging himself, or of trying to get a good night’s sleep. In spite of this somewhat frail health and a whole host of physical problems which often dominated his daily life, Hooke was full of energy, covering much of the City daily, almost always on foot, and there is little evidence that these nagging maladies had any considerable effect on his activity or his concentration, at least until his declining years. We find him hurrying all over the City and beyond, visiting Wren or Boyle, stopping at this coffee house or that tavern, taking care of the business of the Society, assisting Wren with his numerous rebuilding projects, tending to his own architectural jobs and his obligations as Surveyor for the City of London, meeting with various committees and contractors, dealing with tradesmen, visiting instrument makers, lecturing once a week as Gresham Professor of Geometry, carrying out his own experiments, making astronomical observations, and so on. Few have had as full a life as Robert Hooke and only in his sixties did he slow down. Further light is shed on Hooke’s personality by his great and enduring friendship with three of the most important and revered figures of English science in the seventeenth century, Wren, Boyle, and Halley. These relationships lasted some 25– 30 years, terminating only with Boyle’s death in 1691 and Hooke’s own in 1703. In Boyle’s bequest, he willed to Hooke «my best microscope and my best Loadstone which I shall have att the time of my death.» His close friendship with Westminster School’s Dr. Richard Busby (1606–95), begun in his student days, also lasted a lifetime. John Wilkins, responsible for the resurgence of science in Oxford and the main force in the foundation of the Society, was a mentor and friend, and Hooke devotedly visited him on his deathbed. Hooke and Halley became acquainted when Halley was in his late teens, socialized some in the late 70s, and finally met regularly over coffee in the period of the later Diary. Frequently they made astronomical observations together. The generous and diplomatic Halley managed to maintain warm relations with Hooke even as he was bringing the great work of Hooke’s nemesis Newton, into print. In this he had to balance his considerable regard for Hooke and his admira-

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Chapter 2. Robert Hooke, Indefaticable Genius

tion of Newton, trying to assuage the latter’s feelings about Hooke and at the same time delicately preserving his friendship with the prickly Gresham Professor, who felt so deeply wronged. Hooke was witness to Halley’s will in 1693, and Halley in turn helped ease Hooke’s final infirm years. Other close friends in the Society included John Aubrey, John Hoskins,21) and William Holder. Beyond that, Hooke had a large group of companions, some in the Society, most not, with whom he regularly drank coffee and “discoursed” at dozens of coffee-houses and taverns.22) Hooke frequently dined at Boyle’s or Wren’s23) and was welcome in the homes of other highly ranked members of the Society such as Lord Brounker. He was a friend of Seth Ward, who later would be Bishop of Exeter and then of Salisbury (Sarum), and he was often in the company of John Tillotson who would become Archbishop of Canterbury. He and Samuel Pepys saw each other frequently, often in each other’s lodgings. Hooke’s counsel was clearly sought out, he was obviously someone to be listened to, and all the evidence is that he was an interesting companion, with whom it was profitable to while away some time over coffee or a pint. He was also acquainted with Charles II and was employed as an architect by several important private clients, in addition to the official work he did for the City of London as surveyor and architect. The Royal Society met virtually in his rooms at Gresham College until his death and members were often there to help with experiments on days other than meeting days.

The Diary While we would wish that the Diary shed much more light on Hooke’s laboratory at Gresham College and the measurements he made there, or his thoughts as he prepared a discourse for the Society, or on the details of meetings, rather than the brief hints we actually get, it is invaluable nonetheless, especially when read along with the Journal Book or Birch. It is for that reason, and not so much because of what it tells us about Hooke as a person, that we examine here the two extant parts of the Diary. It is almost miraculous that the first and most famous part of Hooke’s Diary survived to find a home in the Guildhall Library of the Corporation of the City of London at the end of the nineteenth century. It was not sold with Hooke’s other effects after his death in 1703, and never came into the possession of the Royal Society. It disappeared completely for nearly two centuries, between 1714, when Richard Waller died, and 1891.24) Eventually the difficult task of transcribing it from Hooke’s scribble was carried out and it was brought into print in 1935 by Henry Robinson and Walter Adams, who were given permission by the Corporation to publish it.25) The original, still in the Guildhall Library, begins in March 1672 and continues until May 1683. This first part of the Diary was begun when Hooke was nearly 37, finishing his first decade as Curator, and well into his career as surveyor and supervisor of construction. The second part, which picks up in 1688 after a more than five year hiatus, was published at almost the same time (1935) by Oxford’s Robert Gunther,26) who had unsuccessfully sought permission to bring the earlier part into print as well. It may be idle to ask why Hooke kept a Diary, but it is clear that he was not writing for posterity. It is very unlikely that he imagined that other eyes would one

The Diary

19

day scrutinize these quick, candid, and personal jottings, but he probably found it irresistible to keep some sort of log, given the importance he attached to “registering” experimental trials and observations. He does recount experiments and occasional astronomical observations, but unfortunately, given our interest in his science, and after a brief and promising start, he gives almost no data. He kept the Diary solely for his own purposes, in many ways a kind of memo book,27) noting transactions, recording new cures for sleeplessness or a sour stomach, and so on, but it also allowed him to privately vent his spleen over slights and insults he received and the stupidity and recalcitrance of workmen with whom he had to deal. The Diary commences, unceremoniously, with «Memoranda begun: March 10, 1671/2,» and for several weeks it consists mostly of meteorological records. It may be, as Michael Cooper has speculated, that Hooke used his survey books to keep personal notes prior to starting the Diary.28) But by July or August of 1672 the Diary as we know it is beginning to take shape, and continues in that vein for eight full years. For reasons at which one can only guess, perhaps because he was so busy, Hooke’s interest in or time to devote to the Diary began to wane in late 1680 and by the time it ends three years later the entries have gotten very sketchy. In transcribing the Diary for publication, Robinson and Adams chose to skip the first five months of mainly meteorological data and the last 2 12 years of half-hearted jottings.29) Its beginning, as we now have it, coincides with Newton’s first communication to the Society on light, but that may be entirely coincidental. The manner in which it begins, with meteorological data, suggests that Hooke had not been writing a diary before that point. The second or later Diary (British Library MS. Sloane 4024), commenced in November of 1688 and ended abruptly in 1693, but as passed down to us has a gap of about 2 12 years, from March 1690 to December 1692. Additional fragments were published by Gunther in his Early Science in Oxford,30) initially in Vol. VII, consisting of scattered entries from 1681 to 168331) plus one from 1695 (MS. Sloane 1039 in the British Museum).32) . Thus the two parts of the Diary span, interruptedly, more than two decades, 1672–93, with nearly eight years missing. These lacunae are crucial years in Hooke’s life, especially the period 1680 to 1688, when his influence was at its zenith and Newton was moving toward the Principia.33) And, of course the year 1687, when the Principia was published and Grace died. To fill in the gaps we mostly have the archives of the Society itself34) , a modest amount of correspondence, and a few comments by friends and colleagues. Wren, who could have given a rich account of Hooke and of their relationship, personal and professional, was too busy to leave much to posterity other than his buildings. None of the sections of the Diary ends in a way signaling an impending or intentional interruption, nor do later parts take note of any resumption,35) suggesting, or at least raising the possibility, that Hooke may have kept a diary throughout this entire period (1672–93), or even beyond it.36) Unlike the earlier diary, which is on large pages, the later one was a pocket diary, measuring about 6 × 10 cm, and in its present form contains about 40 pages. Its last entry, on Tuesday August 8, 1693 is

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Chapter 2. Robert Hooke, Indefaticable Genius

perfunctory and unrevealing: «At Jon. [athan’s] Pag, Gof, Lod, Spen o.»37) Hooke was then less than a month past his 58th birthday, with slightly less than ten years to live. An examination of the Diary as it now exists in the British Library makes it clear that fragments, or at least large sections, were bound together at some later time into one volume, again suggesting a more nearly continuous document may have once existed. This later Diary concerns itself far more with politics and affairs of state than the earlier one, something which is especially true in 1688–9, but those were heady times, as William prepared to land in England and wrest the throne from James II. Like Pepys’ diary, Hooke’s gives us a window into his life and also some insight into life in seventeenth-century London, but his mostly telegraphic style, nearly devoid of verbs, is much more laconic: «At Mr. Haaks. Mr. Hoskins here. Tryd reflex microscope &c . . . ».38) But it also provides us with a slightly different perspective on Society meetings from Birch or the Journal Book, as Hooke comments on what transpired, who attended, and sometimes tells us at least a bit about experiments he was working on. These comments are sometimes helpful, but are never very expansive. If we had to construct his career as an experimental natural philosopher from the Diary we would be mostly in the dark. As lagniappe, the diaries also make it possible to trace the movements of important figures like Wren and Halley, and many others, who left no such memoranda. For example, the reason we know Secretary Oldenburg died in London is that Hooke records the event. It is not that Hooke’s life as a scientist is absent from the Diary, but one has to work rather hard to extract it from the often routine details of everyday obligations and transactions. Usually there is a comment, on a Wednesday or Thursday, about the weekly meeting of the Royal Society, but it is typically very brief, e.g., «to Arundel House. Shewd Experiment of microscope and presented Hevelius his book.»39) Sometimes there are only vague allusions to a paper which may turn out to be important later in this narrative, sometimes we find references to an observation of Saturn, or an eclipse, perhaps with Halley, or others. Very occasionally there is a reference to an encounter with Huygens or Newton. Infrequently there is more meat, and rarely there is some real scientific detail, as we shall see below. Controversies of a technical nature which found their way into the pages of the Diary include that with Hevelius on the issue of telescope sights, and with Huygens over the spring-regulated watch.40) The Diary often recounts conversations with Wren on purely scientific matters, usually at a coffee house, and the same is true of his discussions with Halley. A notable example is planetary motion.41) Frequently the often cryptic references can be fleshed out by examining Birch or the minutes or journals of the Society.42) Other than Hooke’s own published work, and perhaps a hint or two from the Diary, these documents of the Society, or Birch’s summaries, are the raw material out of which we must construct his scientific life, especially for the years for which there is no diary. The state of Hooke’s health is a major preoccupation, as indicated by hundreds of entries, and yet for a person who almost always «slept not well» he seems to have been remarkably vigorous. His social life, which not only involved habitual visits to Garaways or Jonathan’s43) in the Cornhill area (Fig. 3), and a host of other coffeehouses and taverns, often several times in a day and often with Society members,

The Diary

21

bespeaks an enormous amount of energy. We also learn of frequent dining at Wren’s, Boyle’s44) (Lady Ranelagh’s, Boyle’s sister), Lord Brounker’s, innumerable transactions with tradesmen, shopkeepers, and so on,. Despite this, his health was never robust and seems to have been declining as early as the 1670s when he was not yet 40. Indeed John Collins wrote James Gregory just after Christmas 1672 that «Mr Hooke is in a consumption and unlikely to recover.»45) Taken as a whole the diaries show a straightforward and pragmatic personality little concerned with fashion or fad, with not much expressed envy of those in higher stations – and he worked or socialized with such persons every day. Energy and equanimity in the face of a frenetic pace are what come to mind when one immerses himself in these writings. Nonetheless, much of Hooke’s reputation for being irascible and jealous comes from the Diary, although contemporaries were not silent on the matter. There are not infrequent passages in which he grumbles about the outcome of some transaction with a tradesman or with someone who owes him money or to whom he owes it,46) or, perhaps, a slight by someone in or near the Royal Society, or another of high station. These comments are often very sharp, and jump out at the reader who has been lulled to sleep by «at Garways . . . went out not all day . . . Home . . . DH [Dined Home] . . . Mr. Boyles . . . » Thus we read “Fitch a knave”, “Player a fox”, “Oliver a villain”, “Tompion a slug”, and so on, often without context or explanation. Many of these epithets are directed at workmen or shopkeepers and hence are of mild interest at best. Some of these passages refer to Sir J. Cutler, in honor of whom Hooke’s Cutler Lectures were named, and who while ostensibly Hooke’s patron, rarely met any obligation to him.47) One can hardly blame Hooke for his exasperation with and dislike of Cutler. Other comments, involving major figures in the Society, such as its long-time secretary Henry Oldenburg, are of much greater interest to the historian of science. For example, Hooke talks about Oldenburg’s «treachery,» his «fals suggestions,» calls him a «lying Dog,» and says at one point that Oldenburg «fled at my sight.»48) And there are others.49) As we have said, Lord Brouncker, first president of the Society, was sometimes the subject of Hooke’s ire, as was the long-time treasurer, Abraham Hill, another for whom Hooke’s admiration was very low.50) After Oldenburg died in 1677 and Hooke and Nehemiah Grew were appointed to jointly share the secretary’s duties, there are frequent angry references to Grew, Hill, and various others, especially Daniel Colwall, who was treasurer until 1679, and who is the target of Hooke’s feelings on several occasions (e.g., «Colwall a dog»). There are even occasional outbursts directed against his fast friends Wren, Boyle, and Halley51) although calm seems to have returned very quickly. Hooke lived his entire adult life in London, where his favored form of communication was the meeting at a coffee-house, at which he would regularly (often several times a day) meet friends, colleagues like Wren, Halley, and Hoskins, and tradesmen and others with whom he had to transact business. For over a quarter-century, up to the 1690s, he saw Wren almost daily, and in the 80s almost as frequently saw Halley. He often met Wren at a church or other building site, but frequently at a convenient coffee-house, and most of his many meetings with Halley took place at Jonathan’s in Exchange Alley. He saw Boyle mostly at his lodgings, but also frequently wrote

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Chapter 2. Robert Hooke, Indefaticable Genius

to him, as something of a shut-in who was not often at Royal Society meetings and certainly not a habitu´e of the coffee-house or tavern.52) The visits to Wren’s home or meetings with him on architectural matters usually take place a couple of times a week,53) and meetings with Boyle are almost as frequent, though he was often not in town. These daily rounds, calling on friends, visiting job sites, stopping at his several favorite coffee-houses, were, as we have said, almost always made on foot.

Hooke and Wren Hooke’s relationship with Wren (Fig. 4) deserves special comment. The two of them had a common mentor and patron in John Wilkins at Oxford,54) where they apparently became acquainted, and began a lifelong friendship. That friendship blossomed when they both assumed major civic duties after the fire, but they were also colleagues and partners, and it might not be too much to say that family aside, each was the most important person in the other’s life.55) Wren evidently introduced Hooke to microscopy and was materially involved in his becoming Surveyor for the City and eventually a builder and architect. For over two decades, Hooke was Wren’s close associate in rebuilding the northeast portion of the City of London.56) Before the Restoration, their prospects were not terribly different, with Wren’s royalist family reduced to near poverty. But their stations changed markedly after the monarchy was restored, as Wren rapidly rose in influence and favor and Hooke was left to find his way to a career through the good offices of others, eventually a paid position at the Royal Society. Both of them scientific virtuosi, with sharp minds and diverse interests which overlapped significantly, for nearly forty years they argued natural philosophy in their favorite coffee-houses or at Wren’s home or office. Wren might well have been London’s outstanding scientist had he not turned so completely toward architecture. Or, on the other hand, he might have spent his entire career in Oxford, and perhaps even been a challenge to Newton. His early options would have been to go into the church, following his father, into medicine, which he seriously considered, or to take a professorship, as he did for a while at Oxford. The fateful decision to assume the posts of Surveyor- General and Surveyor of the Kings Works, responsibility for rebuilding the churches of the City, and ultimately, that of designing and supervising construction of the new St. Paul’s Cathedral, determined the course of his career and indeed his life. By the 1670s, natural philosophy had for him been almost relegated to a hobby, to be discussed and debated with Hooke on nearly a daily basis, amidst their meetings on architectural matters. Yet philosophy was undoubtedly his first love and he never quite put it behind him (in part because his architecture continually put demands on his knowledge of mechanics). So frequently did the two of them discuss scientific issues, as we learn from Hooke’s Diary, that it is hard to tell who is responsible for any insight which they seem to have had at about the same time. An example is the inverse-square law of gravity, at which they apparently both arrived around 1677, and almost certainly before Newton.57) Similarly, the extent to which they shared responsibility for their architectural projects remains elusive. In the rebuilding of the parish churches of the

Hooke and Wren

Fig. 4

Christopher Wren (1627–1723). Geoffrey Kneller portrait. c National Portrait Gallery, London.) (

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Chapter 2. Robert Hooke, Indefaticable Genius

City, Wren clearly had the senior role, but many of those churches were designed largely or entirely by Hooke. Since, as we have said, neither man was much of a letter-writer, and since they spent most of their lives within a 20 minute walk of each other, there are very few letters between them. As a result, what evidence we have of how they shared responsibility comes from Hooke’s Diary and from parish records, the latter usually only compounding the mystery, since often payments are made to both men. We learn from the second Diary that in later years the two met less frequently, as Hooke’s responsibilities as surveyor and commissioner waned along with his architectural practice and Wren continued to be consumed with St. Paul’s. Still they managed to see each other regularly in the 1680s and early 90s, often at Mans coffee house, once or twice at Wren’s or his daughter’s, despite the early stages of Hooke’s deteriorating health, and the fact that Wren rarely had time for Society meetings. Hooke was Wren’s valued colleague and friend, but in a way Wren was Hooke’s lifeline. From this association he got status, intellectual stimulation and ideas, architectural work, and friendship.

Conclusion Hooke’s broad range of interests was undoubtedly widened by his job as Curator of experiments to the Royal Society, but equally it reflects his own character and personality. The term “polymath” seems almost to have been coined for Hooke. Intellectually, as we shall see, he was omnivorous, interested in everything from pneumatics, microscopy, magnetism, gravitation, capillarity, and planetary motion, to the circulation of the blood, the structure of trees and plants, and metallurgy. He was one of the major figures in the history of horology, was one of the first geologists, and for a time was one of England’s most important astronomers. And he was in constant contact with instrument makers, opticians, and other craftsmen, with whom he exchanged ideas about design and construction of instruments, fabrication of optics, and so on. After the fire, as Hooke became heavily involved in his second career as surveyor, inspector, architect, composer and enforcer of construction codes and practices, constantly negotiating with carpenters, stone masons, and so on, he had less time for his responsibilities as Curator. His architectural work, which peaked in the late 1670s but continued into the 1690s, involved royal, ecclesiastical, and private design and construction, gave him added prestige and income. But this work interfered dramatically with his obligations to the Society, and more importantly, took time that he might have had to think about philosophy. That Hooke was distracted from Society business in this intensely busy period is not hard to understand. Hooke’s final years were increasingly melancholy, as his health declined, Grace died, and many of his friends, notably Boyle and Busby, passed away. By 1691 – the year in which Boyle died – Hooke was nearly blind in one eye, and on several occasions between 1689 and 1693 he speaks in his Diary of his «melancholy,» of being «weary», and «sad.»58) It is apparent that he became something of a recluse in his last years as he grew ever weaker, but as late as August 1693 he was still keeping

Annotations

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to a relatively vigorous schedule. He may indeed have become embittered in the last decade or so of his life as some accounts say, in the face of failing health, the death of Grace, and perhaps because of Newton’s triumph over him. But this is not the Robert Hooke of the previous four decades. When he died, Hooke left an estate of more than $9000, a quite considerable fortune which he had mostly saved from his surveying and architectural duties. A frugal man, except when it came to book purchases, he rarely entertained, got around on foot, and never traveled abroad. His total income from 40 years of scientific employment was well under $4000, but that allowed him to lay aside something like $300–400 per annum from his other duties. It was regretted by all that in the misery of his last days, he failed to leave his estate to the Royal Society. In some sense, however, his legacy was the Society itself.59)

Annotations 1) The title of this chapter is taken from Waller’s life of Hooke in The Posthumous Works of Dr. Robert Hooke, p. xxvii. 2) As also did Steven Shapin in Hunter and Schaffer (1989). 3) Little (1975), p. 91; Maddison (1969), p. 135. 4) Jardine (2004), p. 151. 5) Notwithstanding Hall’s “Why Blame Oldenburg,” (Hall and Hall, 1962a), as we shall see. 6) Brounker was, however, an important mathematician. See, e.g., Stedall (2000). 7) Samuel Pepys, Diary. It is unfortunate that Pepys’ failing eyesight forced him to terminate his diary at the end of May 1669, long before his deep involvement with the Society. His final entry contained these words: «And thus ends all that I doubt I shall ever be able to do with my own eyes in the keeping of my journall . . . And so I betake myself to that course, which [is] almost as much as to see myself go into the grave – for which, and all the discomforts that will accompany my being blind, the good God prepare me.» (The Diary of Samuel Pepys, 1976, Vol. 9, 564–5.) Pepys would die 34 years later, in the same year as Hooke, having put his name on the frontispiece of the Principia, as President of the Royal Society. John Evelyn, in his own diary, recounted on 4 August 1665 (in the midst of the plague) that he «called at Durdans, where I found Dr. Wilkins, Sir William Petty, and Mr. Hooke . . . perhaps three such persons together were not to be found elsewhere in Europe, for parts and ingenuity.» (The Diary of John Evelyn, 1901, Vol. II, p. 8.) Evelyn, an original fellow of the Society, and Pepys, eventually became presidents. Both, however, were largely bystanders to the scientific revolution. 8) Newton to Hooke, 5 Feb. 1676, Corresp., 1, 416. 9) ‘Espinasse (1956), p. 140.

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10) Cooper (2000, 2003). 11) Feingold (2006). 12) Lord Thanet wrote him that «Your lodging [being] like an enchanted castle, being never to be found out, I shall in the future direct my Letters to Mr Hooke’s chamber in Gresham Colledge, as you desire . . . » Thanet to Aubrey, 19 April 1675, in Anthony Powell, John Aubrey and his Friends, London, 1988. 13) Lord Brouncker was a noted womanizer. See Cook (1998), p. 45. Among other things, Hooke provided for the education of his boy, the orphan Tom Gyles. 14) In most cases, Hooke could later point to the Journal or Register Books of the Society as proof of what he had said or shown before the Society, although he had a long battle with Oldenburg over what he saw was the latter’s deliberate failure to record some of his discoveries or inventions. Nonetheless, by frequently failing to publish the many ideas that he scattered to the winds, he allowed others to come along later (and independently) claim the discoveries for themselves. 15) Diary I, p. 300 (8 July 1677). Often we can cross-check the Diary with the Journal Books or Birch to see what experiment was referred to. 16) In Waller’s introduction to his compilation titled Posthumous Works of Dr. Robert Hooke (1705). The Posthumous Works was dedicated to Newton (as well as to the Council and fellows), who was in his second year as president of the Royal Society. Manuel (1968) sees this as adding a «posthumous insult to the injuries Hooke had endured during his lifetime . . . » Hooke no doubt would have seen it that way, but the dedication would have been entirely proper. 17) John Aubrey, Brief Lives. O.L. Dick, ed., pp. 165–6. On Aubrey himself, the introduction to the latter work is especially useful, and for a fuller study, Hunter (1975). Aubrey was an extraordinary character of the widest possible interests, above all an antiquarian. Among other things he called attention to Avebury and what are now called the “Aubrey stones” and made a detailed survey of Stonehenge, resulting in a ring of filled holes known as the “Aubrey holes.” He describes climbing Silbury Hill in Wiltshire with Charles II. Once landed gentry, he was reduced to borrowing small sums from Hooke, and in 1686 left his papers on Wiltshire to Hooke in case he died before returning to London. 18) To many, science was inherently masculine, and others have written, in this context, of “homosociability.” See, for example, Schiebinger (2003). Perhaps things are not so different today. 19) On more than 20 occasions in the period (1672–80) covered by the first Diary. It is interesting, perhaps, that Hooke’s most ardent defenders have, nonetheless, been women: Louise Patterson, Margaret ‘Espinasse, and Ellen Tan Drake. Even Marjorie Hope Nicholson. I make this point not in justification of Hooke’s transgressions, but because it suggests that those most sensitive to the issue are able to look beyond it.

Annotations

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20) Waller (1705). The Life of Dr. Robert Hooke. 21) According to Halley, Hooke broke with Hoskins over an incident following the presentation on 28 April 1686 by Dr. Vincent of a copy of the first part of the Principia to the Society. Halley’s account appears in his letter to Newton on 29 June, where he says that Hoskins, who as vice-president was in the chair, said of the Principia that it was «so much the more to be prized, for that it was both Invented and perfected at the same time.» According to Halley, «this gave Mr Hook offense that Sr John did not at that time, make mention of what he had, as he sd, discovered to him [Newton]. Upon which they two, who till then were the most inseparable cronies, have since scarce seen one another, and are utterly fallen out.» Halley to Newton, 29 June 1686; Corresp. II, 442–3. The evidence from Hooke’s later Diary is equivocal. Before March 1689, Hooke and Hoskins meet several times at Jonathan’s, but on 6 March (meeting) Hooke writes that «Hoskins belged me, as he does every time.» Again, in March 1692/3, after a long period of neutral entries recounting coffee at Jonathan’s with Hoskins among others, Hooke writes «HM. and Aubery, Hoskins tools.» 22) See, for example, the list of over 100 coffee-houses and taverns cited by Hooke in his earlier Diary, given by Robinson and Adams (1935). 23) During some periods, this was an almost weekly occurrence, especially at Wren’s. In the case of Boyle, it was at the home of his sister, Katherine Jones, Lady Ranelagh. 24) According to Keynes, the Diary was in the possession of Hooke’s heir Elizabeth Stephens until 1708, when it passed to Waller. Upon his death it went to William Derham, who died in 1735. In 1891 it was purchased with other books from Moor Hall, Harlow, Essex, by the Corporation of the City of London. Moor Hall was owned by the Henshaw family at the time of the death of Derham, and Thomas Henshaw was a major figure in the Royal Society in the 1670s and 80s. Perhaps as miraculous was the recent discovery of the “Hooke Folio” after three full centuries. See Chapter 7. 25) Robinson and Adams (1935). The preface to this work describes in greater detail the disposition of the Diary during those two centuries (pp. v–viii). Written in Hooke’s crabbed hand, the Diary is sometimes nearly, or indeed actually, illegible. But a remarkable document nonetheless. 26) It forms the bulk of Volume X of Gunther’s Early Science in Oxford (Gunther, 1930–38). 27) For Saturday, 19 December 1674, Hooke inserted the following order from the “controuler:” Sir You are forthwith to pay to Mr. R. Hooke Surveyor of New building out of the moneys arising up by the Impositions layd upon Coles the sum of one hundred pounds in full satisfaction for his frequent Directions and attendances at and in Relation to Fleet Channell and the publique works of this City for the space of three years and upwards . . . ” 28) Cooper (1998a) p. 30, and Cooper (2003).

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29) Though, as noted, Robinson and Adams did not reprint the five months of mainly meteorological observations beginning in March 1672, or the sketchy entries from the end of 1680 until May 1683. In fact, the choice of 1 August 1672 by Robinson and Adams was largely arbitrary, there being considerable narrative prior to that date. See the original in the Guildhall Library. Hooke recorded barometric pressure and temperature daily until the end of April 1673. While he measured temperature relative to the freezing point of water, and was the first to do so, the other fixed point necessary to standardize the temperature scale was arbitrary. A “lovely summers day” was recorded as “Th. 8.”, so that the scale was not very different from the later one of Celcius, based on the boiling point of water as well. His mercury barometer readings increased as the barometer dropped, ranging from a “high” of about 0 to a “low” of about 200. On one occasion, his readings changed from 0 to 195 in a single day, etc., meaning that one unit was probably less than 1/100 inch. 30) Five volumes of this work (Gunther, 1930–38), VI, VII, VIII, X, and XIII, are devoted to that Oxford man, Robert Hooke; they were published between 1930 and 1938, bracketing the tercentenary year of Hooke’s birth, 1935. Volume VI contains Waller’s Life of Hooke which he appended to the edition of Hooke’s Posthumous Works he published, as secretary of the Royal Society, in 1705. Extracts from John Ward’s Lives of the Gresham Professors (Ward, 1740) and Aubrey’s Brief Lives have been interleaved. The rest of Vol. VI is a summary of Hooke’s scientific work up to 1672 drawn from Birch and from Derham (1726). Gunther’s Vol. VII continues this chronology to Hooke’s death in 1703. The Cutlerian Lectures are reprinted in Volume VIII, while Volume X is devoted mainly to the second Diary (Diary II) 1688–93, but also contains Hooke’s early work An Attempt for the Explication of the Phaenomena, in facsimile. Finally, Volume XIII contains a reprinting of the Micrographia, in facsimile. 31) Which overlap the latter stages of the first Diary. 32) In addition to the published diaries, there are several small fragments, October 1681 to September 1683, and 1 June 1695, in MS. Sloane 1039, covering about three months of 1695. These are found in Gunther, Vol. VII, pp. 577, 591–2, 600–602, 605?, 622, and 759 (Sloane MS 1039). The Diary entries from 1681– 83 (all except the last one) were found on narrow slips of paper. They resemble the earlier Diary in their laconic character, as do those in MS. Sloane 4024, from 1688–93. The individual dates are 25 Oct. 1681, March 1682, 18 July (bday)-1 November 1682 (13 entries), 27 December 1682, 22 September 1683. The final fragment (VII, 759) for June 1, 1695, just before Hooke’s 60th birthday, is in a much more fleshed-out narrative style, e.g., «I stayd with Mr. Blount and Mr. Hally from 8 to neer 12 a’clock, then went and dined at the Roman in Queen Street, with Sir Christopher Wren, Mr. Blount, and his cozen Mr. Aldersey . . . » 33) Full title, Philosophiae Naturalis Principia Mathematica, or Mathematical Principles of Natural Philosophy.

Annotations

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34) Including, of course, Birch’s summary in his volume IV. We now, as of 2006, have Hooke’s rough minutes from 1677–82 (see Chapter 4) but there isn’t very much new there. 35) Whether there was, or indeed is, more to the Diary, is beyond our ken. Though the second Diary, as it exists in the Sloane collection, begins on 1 November 1688, suggesting either the initiation of a new book or, alternatively, a new resolution, that portion concludes on 9 March 1690, not quite a year and a half later. It resumes, as always without comment, on 5 December 1692 and a review of what we know of Hooke’s life from the Society’s archives shows nothing that might offer an explanation. Similarly, the final entry on 8 August 1693 gives no clue that writing will not resume the next day. Altogether an enigma, though it may mean nothing more than that material was scattered after Hooke’s death. 36) In his life of Hooke, appended to the Posthumous Works, Waller refers to Hooke’s Diary entry following his legal victory over Cutler on 18 July 1696. This entry is not now known to exist. 37) Referring to friends Alexander Pitfield, Richard Waller, Godfrey Copley, and Francis Lodwick, all F.R.S. On Lodwick, see Salmon (1972). The “o” implies nothing of interest happened at Jonathan’s Coffee-House. 38) Pepys’ diary spans a decade in 11 volumes, while Hooke’s gives us a similar span of daily entries in just over 450 pages, as published. 39) Thursday, November 20, 1763. Which we are to read, in modern terms, as “Hevelius’ book,” or “Helvelius’s book.” The meetings were then being held in Arundel House. 40) 7 June 1674: «Wrote against Hevelius.» 21 June: «Prosecuted Hevelius.» 41) This was just before Hooke wrote his fateful letter to Newton, on 24 November 1679, (Corresp., pp. 297–8.) asking for Newton’s opinion on his idea that planetary motions consist of a motion by the tangent and a central attraction. This problem was much on the minds of Hooke, Wren, and Halley, and eventually the latter went to Cambridge early in 1684 and posed the problem to Newton. See Chapter 10. 42) These are principally the Council Minutes and the Journal Books. 43) Garaways Coffee-House was in Exchange Alley, Cornhill. Exchange or “Change” Alley is still there in the Cornhill area, between Cornhill and Lombard Streets, close by the Royal Exchange. Jonathan’s, also in Exchange Alley was also visited almost daily, and in the second Diary, covering 1688–93, it was the favored venue. See below. See also the section on taverns and coffee-houses in Robinson and Adams (1935) and Gunther’s comments in the preface to vol X (Gunther, Op. Cit.). 44) Boyle lived with his sister (Katherine, Lady Ranelagh) in fashionable Pall Mall. Maddison lists some of Boyle’s neighbors, including Nell Gwyn (p. 133). In the Diary, Boyle is always “Mr. Boyle,” and Wren is “Dr. Wren” or “Sir Ch.

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Chapter 2. Robert Hooke, Indefaticable Genius Wren,” showing – even in his private diary – a respect for the stations of his friends Wren and Boyle, in stark contrast to some of the wilder claims made about Hooke, namely that he violated the gentleman’s code when he used terms like “knave” or “cur[r]” to describe people like Oldenburg or Cutler, who he felt had treated him falsely. He seemed to respect social niceties without resentment or any puffery.

45) Collins to Gregory, 26 December 1672, Corresp. I, 255 n. 17. Westfall also says that Hooke was suffering from consumption and was not expected to survive, but this is based on the letter from Collins to Gregory. The Diary begins in August 1672, and Hooke is indeed unwell, as he often was, but he was vigorously active and it seems that Collins was mistaken as to the seriousness of Hooke’s latest malady, although they had seen each other in October. 46) Indeed a high proportion of these angry remarks refer to masons, bricklayers (Samuell), surveyors, and others with which he worked. 47) «Demanded of Sir J. Cutler my money. He fooled.» 13 August 1674. Cutler had met his obligation to Hooke in the 1660s, but became disenchanted when the Society and Hooke changed the focus of the lectures, which he had intended to be on the history of trades. 48) Respectively, these entries occur on 6 March 1674/5, 20 January 1675/6, 8 November 1675, and 26 May 1677. 49) For example, on Oldenburg: 5 March, 25 March, 8 April, 10 June, 8 November, all in 1675, when their relationship had hit bottom, as well as 20 January 1675/6 and 26 May 1677. 50) On Brouncker, 8 April, 29 April, and 10 June, also 1675. Also many complaints about Hill (treasurer) and Grew. Hill was born the same year as Hooke, but outlived him by 18 years. See also fn. 63. 51) On Wren, see 25 May 1675, 1 June 1675, 10 December 1675; Boyle, 3 November 1675, and 5 February 1678. On 5 October 1680 he writes «Aubrey impudent.» Some have expressed shock over the occasional grumbling about Wren or Boyle, but these were clearly momentary annoyances. 52) Though that did happen occasionally, as Hooke records. Fellows of the Society often met at the Crowne Taverne in Threadneedle Street after meetings at nearby Gresham College. Evidently it was a reputable house. Boyle was a fixture at Society meetings in the early years of the Society. 53) Examples: «At the Colledge . . . At St. Stephens, Walbrook. Bow, Paules.» Referring to the College of Physicians, which Hooke designed, St. Stevens, Walbrook, Mary Le Bow, St. Paul’s, being constructed by Wren, but with some assistance from Hooke. Occasionally he met with Wren three times in a single day.

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54) Lisa Jardine’s 2003 Wilkins Lecture, entitled “Dr. Wilkins’s Boy Wonders,” addressed Wren and Hooke, among others. 55) Lisa Jardine has suggested that neither «formed a lasting relationship with any other person,» a statement which one might want to modify somewhat in Hooke’s case, but is nevertheless substantially true. Much has been written on Wren’s architecture, of course, but a compact source of information about him and his works is Wren by Margaret Whinney (1971). 56) As one of the City Surveyors, as Wren’s partner, and in his own architectural projects. He was Wren’s colleague on the Commission which oversaw the rebuilding of the City. The Court picked Wren, Pratt, and May as members of the Crown Commission and the Corporation of the City of London chose Hooke, Mills, and Jarman. The commissioners appointed by the Rebuilding Act of 1670 were Wren, Hooke, and Edward Woodroffe. Woodroffe died in 1675. Evidently Wren and Hooke were the most active and effective members of the Commission and Wren would soon become Surveyor General. Wren and Hooke both offered radical plans for a new London, and Evelyn offered his own. None of these plans was adopted, tradition and commercial and political considerations holding sway; most of the chaotic plan of the old City was retained. On Hooke’s role in designing and building these churches, see Paul Jeffrey (1996). Between 1671 and 1684, Hooke was apparently working on an average of 8 churches at any given time. 57) See Chapter 10. Hooke, as we shall see, had believed in universal gravitation since 1665. 58) For example, 4 January 1689; 21 January, 28 February, and 1 March 1690 (those cold damp winters!). On 17 June 1693 he was «weary,» and a month later (14 July) he was «sad.» Again, on 7 August he was «weary.» 59) Some accounts describe him as a “miser” in his last days, irrationally afraid of being penniless while hoarding a fortune.

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Chapter 3

Promoting Physico-MathematicalExperimental Learning: Founding the Royal Society of London Except for the early formative years in Oxford, Hooke’s entire scientific life was devoted to the Royal Society of London. It defined him, and to a considerable extent, he defined it. Initially only the Society’s first Curator of experiments – a position he held for nearly four decades – Hooke soon became the lifeblood of the Society in the critical early years when it was struggling to establish itself as, essentially, the world’s first professional scientific society.1) And while natural philosophers and mathematicians had gained positions at court in various ways, many had patrons, and some held university positions, Hooke, as the first scientific “employee” of the world’s first scientific institution, deserves to be considered the first professional scientist. With this in mind, it would make little sense to think of understanding Hooke’s career as a natural philosopher without first studying the Society itself, its origins, who its members were and therefore who were his colleagues, how meetings were conducted, Hooke’s own role in those meetings, and the difficulties encountered by the Society as it struggled through its first three decades. In doing so, we will not give any special attention to Hooke’s science per se, which will be the focus of Chapter 7. The group that would be chartered as the “Royal Society” on 15 July 1662 had actually been formally meeting for nearly two years, having been founded after a Wren lecture in late November of 1660 as civil unrest began to ebb following the Restoration.2) But very much the same group had been gathering informally in Gresham College for a year or so before that, until, as the Protectorate breathed its last breath, meetings were suspended in 1659. And it had earlier predecessors going back more than a decade, as we shall see. But according to John Aubrey, referring to the last year or so of the decade, the group first «mett at the Bull-head Taverne in Cheapside, till it grew to big for a Clubb.» Following which, «The first beginning of the Royal Society (where they putt discourse in paper and brought it to use) was in the Chamber of William Ball, Esqr . . . They had meetings at Taverns before, but

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’twas here where it formally and in good earnest settup: and so they came to Gresham College parlour.»3) These modest beginnings were further foreshadowed by groups that met in London as early as the 1640s and then in Oxford in the following decade, so it is hard to draw the line and say «here the Society originated.» These earlier groups, who helped create the climate leading to the formation of the Society, included the Royal College of Physicians, which was a kind of model for the Royal Society, John Amos Comenius’ “Invisible College,” which involved men like Boyle and Wilkins who would found the Royal Society, but also important figures like Samuel Hartlib, the “great intelligencer of Europe” and mathematician John Pell. The Baconian Comenians shared members with the most important of the organized groups, the so-called “1645 group,” which met in London in the Civil War years.4) Important members included the mathematician John Wallis, Wilkins, Dr. Jonathan Goddard, Dr. George Ent, and Theodore Haak. According to Wallis, by 1648 the group had begun to break up, as several members, including Wallis, migrated to Oxford under the religious pressures of the period5) . John Wilkins had gone to Oxford as Warden of Wadham College in 1648 and immediately began attracting scientific scholars around him, Seth Ward being among the first. Soon Laurence Rooke, William Neile, the young Christopher Wren, and others joined him. This scientific circle which formed around Wilkins and the others was augmented by William Petty, Thomas Willis, Dr. Jonathan Goddard, Matthew Wren, and Ralph Bathurst, all later important members of the Royal Society. Barbara Shapiro has observed of Wilkins that «wherever he was . . . it was there that the nation’s most creative and active scientific circle came into being.»6) Two of the most important figures he attracted were Wallis and the young but already illustrious Etonian Robert Boyle (Fig. 5) who Wilkins induced to move to Oxford in 1655–6, when he was still short of thirty; Boyle would stay in Oxford for more than a decade. This group, which met at the lodgings of Petty, then Wilkins, and finally Boyle, known to us as the “Oxford Society”, “Oxford club,” or “Oxford Philosophical Society,”7) actually met for four decades, despite the fact that important members had long since moved back to London, on the eve of the Restoration. Many of its members came from the earlier group who had accompanied Wilkins to the relative security of Oxford in 1648–9, following the execution of Charles I.8) Like the earlier Invisible College and the 1645 Group, the Oxford club was a largely informal one, lacking officers, written minutes, or a journal.9) According to Thomas Sprat in his History of the Royal Society, speaking of the Oxford society, «their meetings were as frequent, as their affairs permitted: their proceedings rather by action, [than] discourse; cheifly [sic] attending some particular Trials, in Chymistry, or Mechanicks: they had no Rules nor Method fix’d: their intention was more. . . to communicate to each other. . . their discoveries, which they could make in so narrow a compass, [rather] than an united, constant, or regular inquisition . . . Their manner likewise, is to assemble in a private house, to reason freely upon the works of Nature . . . »10) And «they continued [meeting] without any great Intermissions, till about the year 1658. But then being call’d away to several parts of the Nation, and

Chapter 3. Founding the Royal Society of London

c National Portrait Gallery, London.) Fig. 5: Robert Boyle, after Kerseboom. (

35

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Chapter 3. Founding the Royal Society of London

the greater part of them coming to London, they usually met at Gresham College, at the Wednesdays, and Thursdays Lectures of Dr. Wren, and Mr. Rooke . . . »11) Thus, as the Protectorate crumbled and the monarchy was on the verge of being reestablished, many of the Oxford group had returned to London, including Wren and Wilkins, some, like Wren and Rooke, to become Gresham Professors, a migration that led to the founding of the new society only months after the Restoration. This did not happen immediately as, according to Sprat «. . . they were scattered by the miserable distractions of that Fatal year[1659] . . . till the continuance of their meetings there might have made them run the hazard of the fate of Archimedes: For then the place of their meeting was made a quarter for Soldiers.»12) Notwithstanding Wallis, who claimed a direct and continuous evolution from the informal “1645 group”13) to the Royal Society, thus placing its origin in London, we can reasonably think of the Royal Society as emerging from a reuniting of the two parts of the 1645 group, those who moved to Oxford, many of them Royalists, and those who stayed behind in London.14) If Sprat’s History, published in 1667 while the Society was still very much in its infancy, is the most direct source of information on its founding, one has to keep in mind that Sprat was a prot´eg´e of Wilkins, the figure around whom the Oxford circle formed and chair at the first meeting of the new Society, and thus was something of an apologist for the Society.15) The informal meetings at Gresham apparently went on, during term, for more than a year – despite the disruptions of the final days of the Protectorate – and it was following a Wren lecture at Gresham on 28 November 166016) that twelve of the group retired to the rooms of Laurence Rooke, Gresham Professor of Geometry and Wren’s predecessor as Professor of Astronomy, where «something was offered about a design of founding a college for the promoting of physico-mathematical experimental learning.»17) They agreed to meet weekly, initially on Wednesdays at 3 in the afternoon18). Wilkins was appointed to the Chair at this first meeting, and William Croune, register, or secretary. A list of 37 additional persons who «if they desire it, might be admitted before any others» was drawn up, and at the second meeting a week later, Sir Robert Moray noted that the King (Charles II), had been informed of their action and had offered encouragement.19) At the meeting following, Moray again reported the King’s approval, and Wren was asked to prepare an experiment for the next weekly meeting. Moray was chosen the Society’s first president on 6 March. Such were the modest and hopeful beginnings of the Royal Society, which would have to wait for a year and a half for its Royal charter. From the beginning, fellows of the Society were to be admitted only by election, and it was declared that «no person should be admitted into the society, without scrutiny, except such as were of, or above, the degree of baron,» something that was reaffirmed in October 1662. The 49 persons either present at the first meeting or offered immediate admission included many, if not most, of the figures who would dominate the Royal Society for the next two decades.20) Membership would be limited to 55, but again «. . . any person of, or above, the degree of baron might be admitted as supernumeraries . . . »21) Sprat explained that men of all religions and professions were admissible, but that «the farr

Chapter 3. Founding the Royal Society of London

37

greater Number are Gentlemen, free, and unconfin’d,» by which he meant the freedom from having to earn a living. He continued that «If any caution will serve, it must be this; to commit the Work to the care of such men, who, by the freedom of their education, the plenty of their estates, and the usual generosity of their Noble Bloud, may be well suppos’d to be most averse from such sordid distractions.»22) Hooke, of course, was not one of those «gentlemen, free and unconfin’d,» but rather at the time an apprentice to Boyle and soon to be making his living entirely as an employee of the Society.23) Not surprisingly, the class-consciousness expressed in Sprat’s words had a downside, for it meant that at any time a significant fraction of members were essentially gentlemen dilettantes, indulging themselves in a fashionable diversion. It also caused discomfiture for Hooke, who had no clear social position. Moray, with his ties to the crown, had been principally responsible for the royal charter, and had also presided at early meetings, but Viscount Brouncker was chosen to be the first president when the Society was officially Chartered as the “Royal Society” in July 1662. Brouncker would hold the office for 15 years. Wilkins and Henry Oldenburg became the first secretaries, a position the latter would hold until his death in 1677.24) Although Wilkins had been at the center of the Oxford group and had presided over the first meeting of the new society, with his former connections to Cromwell, he would have been too controversial to be a choice for president shortly after the Restoration. The twenty members of the Council were a sort of “who’s who” of the early Society, including Moray, Boyle, Wallis, Wren, Wilkins, Oldenburg, Kenelme Digby, Paul Neile, William Petty, Jonathan Goddard, John Evelyn, and Thomas Henshaw. There was one Lord (Brouncker) and four Knights of the Realm (Moray, Digby, Niele, and Petty), two doctors of divinity (Wilkins and Ward), three M.D.s, and one L.L.D. (Wren). All men of privilege. The first charter served less than a year, a second one being passed on 22 April 1663. The Society had its critics from the very beginning, including some from the College of Physicians whose members resented the Society’s forays into medicine. Others opposed or ridiculed the Society because natural philosophy was thought not to be a suitable preoccupation for a gentleman, or because it was imagined that it would lead to free thought and atheism. Still others thought that puttering with strange pieces of apparatus or debating arcane theories, such as the weight of the air, simply silly.25) Hobbes’ bitter dismissal is well known: «Those Fellows of Gresham who are most believed, and are as masters of the rest, dispute with me about their physics. They display new machines, to show their vacuum and trifling wonders, in the way that they behave who deal in exotic animals, which are not to be seen without payment. All of them are my enemies.»26) Critics like Henry Stubbe («a Man of as much Acrimony as Wit») urged Boyle to abandon the Society with the advice that «the only reparation you can make for that fatal error, is to desert it . . . »27) Stubbe was a vigorous opponent of the entire

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program of the Society’s alliance with Latitudinarian clerics, reflecting his distaste for a clerically dominated society and his advocacy of a return to a purer form of Christianity. 28) Another conservative Anglican, Robert South, was also a detractor, and when Wren’s Sheldonian Theater was dedicated in Oxford on 9 July 1669, South, as University Orator, took the opportunity to denounce the Society and the New Philosophy.29) But the support of the King30) and his chartering of the Society, along with the participation of important figures from the gentry, aristocracy, clergy, wealthy physicians, and other men of means and position, led to its gradually assuming an important role in the life of Restoration England. As we have seen, the young Society saw itself as thoroughly Baconian, and if Bacon’s philosophy was rather liberally interpreted by the founders, they certainly believed that what they were doing in forming a society for the promotion and establishment of a new philosophy of nature31) was an implementation of Bacon’s ideas. Indeed, Joseph Glanvill thought that «Salomon’s House in [Bacon’s] NEW ATLANTIS» was a «Prophetick Scheam of the ROYAL SOCIETY.»32) And in his History, Sprat wrote of «one great Man, who had the true Imagination of the whole extent of this Enterprise, as it is now set on foot; and that is, the Lord Bacon.» He continued that if his [Sprat’s] desires had prevailed «with some excellent Friends of mine, who engaged me to this Work: there should have been no other Preface to the History of the Royal Society, but some of his Writings.»33) Although Sprat seems to have fully equated the “experimental philosophy” with Bacon, he did offer some caveats.34) This Baconian antidote to the substantially a priori science of the Cartesians and the relics of Peripatetic or Aristotelian natural philosophy was doubtless needed, though rival views about what the mechanical philosophy actually was coexisted within the Society. It is an interesting and crucial fact that while the movement to found a new philosophy involved mainly university men at the outset, e.g., Wilkins, Ward, Wallis, Wren, and a number of others, that rather than being of the universities, it was in many respects an opposition to an antiquated curriculum, especially in science, that still clung to its Aristotelean roots. That the Society, as the vehicle for carrying out this replacement of the old by the new, came to be dominated, in membership and influence, at least, by gentlemen of means and status, including the clergy, reflects the way in which the movement comported with other tendencies in church and society after the Restoration. The new (mechanical) philosophy was seen as providing an explanation of the natural order of things, which would be an important tool in advancing moderate Protestantism and in combating atheism through what might be called natural theology. Some of its advocates, like Wilkins, Ward, and Barrow, prominent figures in the Society, were also influential Latitudinarian clerics who helped cement this bond between the mechanical philosophy and capitalist Christianity.35) At one and the same time, it supported a particular social ideology and fostered order in the political realm. Thus came into being effectively the world’s first scientific institution, the Royal Society of London, now nearly 350 years old. It had many trials and reverses ahead, but in just over a quarter-century it would be responsible for bringing into print New-

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ton’s Principia, whose only peers, perhaps, are Copernicus’ De Revolutionibus and Darwin’s Origin. The Society’s motto was, and is, “Nullius in verba,” “bound to no man’s word,” or “take no man’s word (for it).”

Annotations 1) Despite Italian antecedents which were not exclusively scientific in nature. The Accademia dei Lincei (Academy of the Lynx) was founded before 1603, but disbanded after Galileo’s difficulty with the church. It had a journal of sorts as early as 1609. The later Accademie del Cimento (Academy of Experiment) was founded in 1657 by students of Galileo, but it lasted only a decade and its briefly published journal was founded after the Transactions. 2) The story of the founding of the Royal Society of London «for the promoting of Physico-Mathematicall-Experimental Learning» has been told in detail elsewhere, making it unnecessary to give more than the bare outlines here. Indeed, Michael Hunter has asked whether there is anything new to be said about the Society (M. Hunter and P. Wood (1966). The authoritative contemporary account is that of Sprat, in his History of the Royal Society, written just six years after the Society’s founding (published in 1667), and under the direction of some of its founding members. For this last reason, however, its objectivity can be questioned. Recent works include: Purver (1967); Hunter (1989), Marie Boas Hall(1991), Stewart (1992), etc. The literature is vast. A. Rupert Hall’s introduction to Birch is also important. For background, the monumental work of Charles Webster, The Great Instauration (Webster, 1976) is indispensable, but for criticism of Webster’s thesis of an alliance between Puritanism and science, see Henry (1992). Hunter’s The Royal Society and its Fellows 1660–1700 (Hunter 1994a) is invaluable. 3) Quoted in O.L. Dick’s introduction to Aubrey’s Brief Lives, p. liii. One can, if he wishes, extend the line of descent further into the 1640s, e.g., the trio Thomas Harriot, Walter Warner, and Robert Hues, «the Earl of Northumberland’s three Magi,» or the Welbeck circle, which included Thomas Hobbes. See John Henry, «The Scientific Revolution in England,» in Porter and Teich, The Scientific Revolution in National Context, and references therein. 4) Some sources include Shapiro (1989) and references therein (e.g., p. 260), Purver (1967), Chapter 4. See also Webster (1976), Chapter II, “The Spiritual Brotherhood.” The idea of a “universal college,” or loose network of philosophers was widespread in the seventeenth century. But Comenius’ visit to London in 1641–2 under the sponsorship of William Hartlib provided the initial impetus that led to the Invisible College, the 1645 group, and eventually, the Royal Society. Apparently members of the Invisible College included Wilkins, Wallis, Boyle, Theodore Haak, and at least six others, all of whom were founders or early members of the Society. See also Stimson (1935) or Greengrass, et al.

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(1995). Boyle’s sister, Lady Ranelagh, was very much involved with the circle around Hartlib. See Jardine (2002), p. 88. 5) Wallis’ accounts appear in his “A Defence of the Royal Society,” and in “Account of Some Passages of His Own Life,” which appeared in Thomas Hearne’s edition of Peter Langtoft’s Chronical in 1725. Charles I was executed in 1649, leading to the Republic and in four years Cromwell and the Protectorate, and Puritan ascendancy. This lasted less than a decade. Oxford was in Puritan hands when the moderate Wilkins went there as Warden of Wadham College, but he attracted both Puritan and Anglican (royalist) scholars. 6) Shapiro (1969), p. 125. 7) The “Oxford club” seems not to have had a formal name, but is often referred to in contemporary documents as “the clubb.” 8) Sprat lists Ward, Boyle, Wilkins, Petty, Matthew Wren, Wallis, Goddard, Willis, Bathurst, Christopher Wren, and Rooke as «the principal, most constant of them.» 9) It did have a set of rules governing its activities, however. See Purver (1967), p. 111. It evidently thrived, however, having, according to Seth Ward, about 30 members in 1652. See Robinson (1949). 10) Sprat, p. 56. 11) Wren and Rooke were joined by Brouncker, Brereton, Neil, Evelyn, Henshaw, Slingsby, Clark, Ent, Ball, Hill, Crone, and others. Sprat, p. 57. Wren became professor of astronomy in 1657, when Rooke switched from that post, which he had held for five years, to Professor of Geometry. Wren left Gresham to become Savilian Professor of Astronomy at Oxford in 1661, and Rooke died in 1662. 12) Sprat, pp. 56–8. Sprat wrote to Wren that «This Day I went to visit Greshamcollege, but found the Place in such a nasty condition, so defiled and the smells so infernal that, if you should now come to make use of your tube, it would be like Dives looking out of Hell into heaven.» Sprat described the building’s “noisesome condition”, and wrote of “infernal smells” and other indignities . . . Sprat to Wren, Parentalia, p. 254. Archimedes, it is traditionally said, was slain by a Roman soldier in Syracuse as he worked on a problem in geometry. 13) Wallis made this claim in 1678, some thirty years after the fact. The 1645 group was Boyle’s “Invisible College”. See Birch, I, 2. 14) Barbara Shapiro’s John Wilkins (Shapiro, 1969) contains a good summary pp. 25–28. 15) In his introduction to Birch, Rupert Hall compared Sprat and Thomas Birch’s History by saying that «while Thomas Sprat had taken for himself the role of the Royal Society’s apologist, Birch assumes that of its chronicler.» 16) Wren had been named Gresham Professor of Astronomy in 1657.

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17) Whence the title of this chapter. Birch, I, p. 3; Record of the Royal Society, p. 7. Rooke’s contributions as a natural philosopher were primarily in astronomy, and especially astronomical methods for determining longitude. See Ronan, 1960. 18) The Society met at Gresham College until 9 January 1666/7, when, following the Great Fire, it moved to Arundel House. The Society met there for over six years, but at a meeting of the Council on 9 Oct 73 was invited back «by a committee of the professors of Gresham College and another of the Mercers company.» At the time, the Earl of Norwich «could not but take it very unkindly» if they should move from Arundel. He later relented, and on 6 November, the Council decided to move, largely to be near Hooke’s rooms, where he could more easily offer experiments. The Society’s space at Gresham College is described in Johnson (1940). Typically meetings commenced at 3 in the afternoon. 19) Moray (or Murray), a Royalist who went into exile with Charles I in 1646, was instrumental in obtaining a royal charter for the society. Moray’s connections were undoubtedly the reason why he became the Society’s first president, rather than, say, Wilkins, with his relation by marriage to Cromwell. Boyle also had ties to the monarchy; his sister-in-law, Elizabeth Killigrew had a child by Charles II in 1648, when Boyle was 21 (Jardine, 2002). 20) Present at the first meeting, according to the Journal Book, and as reported by Birch, were Viscount Brouncker, Robert Boyle, David Bruce, Paul Neile, John Wilkins, Jonathan Goddard, William Petty, William Balle, Laurence Rooke, Christopher Wren, and Abraham Hill. The list of forty included Digby, Evelyn, Henshaw, Ward, Wallis, and Oldenburg, along with, for some reason, Boyle and Wren who were already present. Croune was picked as “register,” though absent (a not uncommon occurrence even then?). Boyle was proposed on 26 December, along with Oldenburg. Was it his well-known reluctance to sign an oath that had delayed things? 21) It was also proposed that members of the College of Physicians and of the science faculties of the two universities be admitted as supernumeraries. Birch, I, pp. 5–6. In editing Birch, Rupert Hall lists the fellows in the 1663–87 period, that is, after the second charter of 1663 (22 April). He also gives the members before the second charter who were not reelected. One of the original members, Lawrence Rooke, died in 1662, as did John Gauden. Hunter (1994). 22) Sprat, p. 68. 23) At least until 1666 or 1667, when his duties as surveyor began to provide as much income, or more. Hooke accumulated over $8000 in about 35 years, an average of over $200 per year, far more than the $30–50 provided by the Society or the $80 he had been promised. 24) The name, Royal Society, was suggested by John Evelyn. Between its founding and the Royal charter, Moray usually presided over Society meetings, but sometimes Wilkins, and even Boyle were in the chair. Brouncker was an important mathematician who played a significant role in mathematical developments

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involving the quadrature of curves, infinite series, continued fractions, and so on. He was also Chancellor to Charles II’s queen, Catherine. 25) Thomas Shadwell’s The Virtuoso of 1676 parodied the experimental philosophers of the Royal Society. Hooke’s Diary for 2 June describes his attendance at the play: «With Godfrey and Tompion at Play. Met Oliver there. Damned Dogs. Vindica me Deus. People almost pointed.» He comments again the next day. See Chapman (1996). 26) Hobbes, Dialogus Physicus, 1661, 1668, p. 236–7. See Shapin and Schaffer (1985), Chapter IV. Boyle, in turn, attacked Hobbes in his “Animadversions on Mr. Hobbes Problemata de Vacuo” of 1674. 27) R. Palmer, quoted in Maddison (1969), p. 137. Stubbe to Boyle, 4 June 1670. Maddison, p. 138; See also Appendix B in Sprat, on Stubbe’s attacks. 28) Stubbe’s strongest attack on the Society and Sprat’s history of it came in A Censure upon Certain Passages contained in the History of the Royal Society. The definitive work on Stubbe is Jacob (1983). In particular, his Chapter 5 focuses on the Royal Society. Conflicting views on some of the issues raised there have been given by Hunter among others: Hunter (1994), p. 16, n. 3 and Hunter (1990). In this work we can only hint at the complexities which are revealed in studies such as these. The bibliography and references offer some guide to the literature. 29) Wallis to Oldenburg, 16 July 1669. Glanvill to Oldenburg, 19 July. CHO, VI, 129–30 (letter #1246), pp. 137–8 (#1248). Glanvill’s letter also addresses Stubbe’s attacks. The Hall’s notes to these letters are, as usual, full of information. 30) The King himself was known to ridicule the Society. Pepys’ records that he «mightily laughed at Gresham College, for spending time weighing of ayre, and doing nothing else since they sat.» Pepys’ diary, 1 February 1663/4. For other critics, see Record of the Royal Society (1940), pp. 40–44. 31) «For improving of natural knowledge,» in its own formulation. 32) Glanvill, Scepsis Scientifica, 1665, John Owen, ed., London, 1885, p. lav. Quoted in Sprat, p. xii. Bacon’s New Atlantis was published three years after his death, in 1627. 33) Sprat, p. 35–6. 34) Sprat cautioned that «whoever has fix’d on his Cause, before he has experimented; can hardly avoid fitting his Experiment, and his Observations, to his own Cause, which he had before imagined, rather than the Cause to the truth of the Experiment in it self,» p. 108. Furthermore, referring to the founders of the Society, «as their purpose was, to heap up a mixt Mass of Experiments, without digesting them into any perfect model . . . and whatever they have recorded, they have done it, not as compleat Scheames of opinions, but as bar, unfurnis’d Histories.» Sprat, p. 115. Nonetheless, Sprat did acknowledge that after a «severe

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examination of the particulars,» the new method must not rest there; rather «It must advance those Principles, to the finding out of new effects, . . . from experimenting to Demonstrating and from demonstrating to Experimenting again.» Sprat, p. 31. Others in the Society were more concerned about unguided experimentation including the mathematician William Niele. See Hunter and Wood (1966), p. 52–3. 35) This passage reflects Margaret Jacobs’ reading of the evidence from the period of the Restoration (Jacob, 1976). For a different skeptical view, see Henry (1992), pp. 190–202. Ward became Bishop of Sarum (Salisbury), and Wilkins Bishop of Chester. Isaac Barrow, Newton’s sponsor, was a noted sermonizer.

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Chapter 4

Society of the Muses: The First Decade1) The importance of the Royal Society in the early scientific revolution is reflected in the detailed studies of its activities during the first several years of its existence which have been written, centering on the kinds of investigations that were carried out, how they were witnessed and registered, and how they supported, or were interpreted in terms of the mechanical philosophy. In this chapter we summarize the activities and challenges of the new Society during these early years, always keeping in mind the fact that our particular interest is in Hooke and his role in it, even though we will devote our attention to the Society itself, rather than Hooke per se. The central issue of Hooke’s science and how it was facilitated, or sometimes hindered, by his position as Curator, will be the subject of a subsequent chapter. In this chapter we will concentrate on the period 1660–1672 because these were the formative years of the Society, when it was defining what it was, when it had to establish a sustaining membership, and was attempting to devise a continuing experimental program and cultivate an extensive foreign correspondence. It also had to overcome in this “decade” the almost simultaneous blows of the last gasp of the plague in 1665–6 and the Great Fire of London in September of the latter year. As regards Hooke, this period coincides almost exactly with his first ten years with the Society, 1662–72. It also concludes just as Newton appeared on the scene for the first time, which provides a kind of natural break, and it is also in 1672 that Hooke began to write his Diary, which sheds light on Society affairs in the following decade. In its first years, the Society addressed all manner of inquiry into nature, according to the interests of members, with little regard to any program or plan of investigation. Some issues were pursued more systematically than others, an important example being pneumatics, which reappeared at frequent intervals, many of the experiments being initially provided by Boyle, but Hooke was involved in these and other experimental work almost from the outset. Among other early issues addressed at meetings was Brouncker’s interest in the recoil of guns, a practical topic which came up frequently for a while, and a whole

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host of technical issues including siphoning, primitive chemistry, and early magnetic experiments with lodestones, but also speculation about insects, poisons, vipers, including their supposed generation from a powder made from their livers and lungs, and so on. There was strong and continuing interest in the natural history of foreign lands, clearly reflecting the burgeoning trade and exploration with far corners of the Earth. The wonders that Hooke revealed in his exquisite drawings of objects viewed with his microscope caused a sensation when the drawings (Fig. 6) and the work of natural philosophy he built around them, the Micrographia, were published. Hooke’s honored place in the history of microscopy comes less from his contributions to the design of the microscope, which were modest, than from his discoveries with it – including his discovery of the plant cell – which were the stimulus for a long correspondence between the Society and the Dutch microscopist Leeuwenhoek, starting in the 1670s. Studies with the simple pendulum, which would be an ongoing interest of Society members, appear almost at the very beginning, in late 1661. The pendulum was intrinsically interesting in the way that what would later be thought of as living and dead force (our kinetic and potential energies) would be interchanged, but for the most part these explorations were motivated more by the need for accurate timing, particularly at sea, where the issue was navigation and the precise determination of longitude. This was an interest of the King, who consequently encouraged Hooke’s work on time pieces.2) It was also an enthusiasm Hooke shared with his great contemporary, and in many ways, competitor, Christian Huygens, whose career paralleled his in major respects. Huygens’ interest in the pendulum went far beyond its use in time-keeping, important as that may have been, but then so did Hooke’s. Hooke’s theory of the «rising of water in slender glass-pipes» (capillarity), which led to his first scientific paper, was debated by the Society in mid-1661 and Sir William Persall «entertained the society with some magnetical experiments» in early 1662. Magnetism would be a persistent interest throughout the decade and indeed much later, though little progress would result. It would not emerge from this descriptive stage for a century and a half, when the relationship between currents and magnetism was discovered. There was much interest in practical knowledge, including the character of varnishes, the making of cloth from sheep’s wool, the production of marbled paper, making tar and pitch, the sounding of depths in the sea, wine production, minerals, coal mines and wind-mills, etc. Indeed much of the business of the early Society had a very practical or utilitarian character to it. Although an inventory of the issues in which the Society was interested shows remarkable diversity, one must admit that most questions were not pursued very far. Only in a few cases can these inquiries be said to have led to a real understanding of a specific phenomenon. Not untypical of some of the chimera pursued by the Society was a story recounted by Wilkins of «a maid in Holland, who voided seed by urine, which being sown grew,»3) and Robert Southwell provided the Society with «a great horn, said to be an unicorn’s» the next year. One cannot emphasize too often, however, that natural philosophy in this early period was very much in an immature cataloging

Chapter 4. Society of the Muses: The First Decade

Fig. 6: Hooke’s drawing of a female gnat from Micrographia of 1665.

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or “taxonomic” stage, in which standards of proof were still being worked out and it was not clear which phenomena were real or important, and which were not. Not infrequently some astronomy crept in, particularly regarding Saturn and its rings, which was very much a topic of interest in this period; Jupiter, especially phenomena of its Galilean satellites; occasionally a comet; and there were regular accounts of eclipses. Although very much a descriptive science at this stage, astronomy was of interest for its own sake, and had been since the early work of Harriot and Horrocks, but the issue of determining longitude arose in this context as well. In an attempt to develop an experimental program, fellows were initially urged to bring in experiments themselves, and in April 1662 we find that «It was resolved, that every member of the society shall consider against the next meeting of some experiment, which he will undertake himself.» But seven months later (5 November) with only a modest response, Robert Moray was proposing the employment of a curator to provide some direction and to prepare experiments. Hooke, already known to many of the Fellows as Boyle’s assistant, was picked (though it was some time before his position was made official) and in only two weeks provided his first experiments. From the beginning he was charged with preparing «three or four» experiments for each meeting. This allowed him some latitude to pursue his own interests, though frequently there was clear direction from fellows, resulting, once again, in a somewhat haphazard and undirected collection of experiments. But until Hooke’s attentions began to be diverted elsewhere by his work as surveyor and architect, Society meetings became more focused, often centering on one of his experiments or an explication of one. He would provide these demonstrations, off and on, for the better part of 40 years, but frequently there was tension between these duties and other obligations he assumed over time. Before long the Society felt the need to again examine the experimental program to see how it might best be carried out, and in 1664 it decided to organize itself around eight committees, including one for collecting and registering observations and experiments. In late April 1663 the Society received its second charter from Charles II,4) marking a new beginning for the Society, which had the document read before them on 13 May, after which a Council was chosen. A week later, on 20 May, 114 individuals were registered as fellows of the Society. It was in that same spring that Wren presented the Society with a model of what would become the Sheldonian Theatre in Oxford, marking the start of his turn away from natural philosophy and the beginning of a long and distinguished architectural career, a career which would heavily involve his friend Hooke. A nascent interest in the natural history of the earth on the part of the Society was exhibited in discussions of petrified wood, involving especially Hooke and William Brereton. Hooke would return to these issues again and again, treating changes in the earth as dynamical processes to be understood, and rescuing them from the realm of pure speculation. Considerable attention was also given to the ability of fish to survive out of water, and in the problems of sounding the depth of the sea and in bringing up water from the depths, to which purpose Hooke proposed some contrivances in September 1663. Such issues were a part of a wider interest in the properties of the air, how it enabled

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respiration, and how it supported fire. In November 1663 Moray suggested using a thermometer to determine «the degrees of heat in a man’s body in fevers . . . ,» but «the physicians present conceived, that there would be little certainty in it.» There was continued interest in pneumatic experiments, including the troublesome problem of the “anomalous suspension” of water,5) first noted by Huygens in 1661 and revealed by him in a letter to Moray in January 1662. This episode is an important one for several reasons. In principle it called into question the accepted theory of the way in which a mercury or water column was supported by the weight of the air,6) but because the experiments were being carried out in London and on the continent, often with differing results, it raised thorny issues of reproducibility or replication and therefore witnessing. Huygens had found that if water that had been purged of air was used in a water barometer, and the device was placed in a receiver from which a substantial portion of the air was removed by pumping, the water would tend to remain suspended rather than descending with the lowered pressure as expected. The same thing was sometimes observed with a mercury barometer as well. This phenomenon, which was at first found difficult to reproduce in England, was used by one side (Huygens’) as an indication of a good vacuum, and on the other (Hooke, Boyle) as a sign of an inadequate or poor one. Air-pumps of disparate designs yielded different results, and there was no adequate theory to explain either the presence of the phenomenon, or its absence. It was in the midst of this dispute that Hooke became Curator, in November 1662. Continued failure to reproduce the suspension in London either with water or mercury led Huygens to come to London the following May, and he and Hooke worked, perhaps side by side, into August.7) On only this single occasion would these two founders of modern science interact productively. Anomalous suspension of water was finally successfully accomplished at Gresham College, with Boyle later showing that the effect could be obtained even without using an air pump. The suspicion arose that the diameter of the tubes (“canes”) employed in the experiments might be crucial. In early 1663/4 it was ordered that any experiment ought to be repeated, «for the sake of more accuracy and certainty,» reflecting a growing understanding of the importance of multiple trials in any experimental investigation. The Society took its role of “publicly” witnessing experiments very seriously, and occasionally it was called upon to provide novel experiments for some special event, or to divert the King. At about the same time, the Society became interested in having cadavers to dissect (by Drs. Goddard, Charleton, and Clarke), marking the start of a series of physiological experiments involving living animals, cadavers, and in a case or two, living humans. And for the first time the Society gave thought to publishing books written by its fellows. One of the first beneficiaries would be Hooke himself. It also took interest in Chelsea College for the first time, eventually leading to its acquisition and in due course, lengthy efforts to make use of it, and eventually to dispose of it.8) Although it was granted to the Society in the third Royal Charter of April 1669, hopes that it would provide a permanent home for the Society never materialized. At the end of 1664, the Society was exploring Huygens’ idea of a universal measure, a standard of length which would be defined by a simple pendulum of spec-

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ified properties, though the idea goes back to Mersenne in 1644.9) Of special interest was the “seconds pendulum,” which Hooke and Brouncker found had a length of 3 feet 1 23 inch, and later almost exactly 39 inches.10) The second could not be given a precise empirical definition until the pendulum clock of Huygens was invented and calibrated against astronomical sources. Experiments in generating “air” by applying aquafortis to oyster-shells11) caught the Society’s attention in the first few months of 1664/5, representative of an early interest in what we know as chemistry. Boyle and others devoted much of their time in the laboratory to such studies at a time when the distinction between chemistry and alchemy had little meaning. On the astronomical side there was considerable interest in comets, the stimulus in this case being the comet of 1664, which had been observed by Hooke, Huygens, the Danish astronomer Hevelius, and others. A common theory was that comets traveled in straight lines, a view held by Huygens, Hevelius, Wallis, and for a while, Wren, though never, apparently, by Hooke. Hooke would speak and write extensively about comets, notably in his “Cometa”, published in 1678, based on the comets of 1664 and 1677, and his “Discourse of Comets” of 1682, which only reached print over two decades later in his Posthumous Works. We will have more to say about Hooke’s astronomy in due course, but it is interesting to note here that while he did make some observations of comets, most of his extensive writing is devoted to their nature and structure and the implications for natural philosophy. On 1 March 1664/5, the Council declared that the Philosophical Transactions, to be edited by its secretary Henry Oldenburg, should be printed on the first Monday of every month, starting a run that, except for a hiatus in 1677–82 due to Oldenburg’s death and Hooke’s taking over as Secretary, continues to this day. Number 1 is dated 6 March 1664/5, and contains a reference to Hooke’s observations of Jupiter.12) For well over a decade, while handling the difficult job of managing the Society’s correspondence, Oldenburg dutifully published the Transactions, from which he derived much of his income.13) For all practical purposes the first true scientific journal, the Philosophical Transactions did not actually become an official publication of the Royal Society for over a century (1776), when it took on the name Philosophical Transactions of the Royal Society.14) The journal would overcome repeated obstacles during its first forty years of publication, but survives today as the oldest (almost) continuously published scientific periodical. In the midst of a discussion of cold, stimulated by Boyle’s Experimental History of Cold,15) which came out in April 1665, perhaps elaborating on Moray, Hooke proposed a standard for heat and cold, which is generally considered to represent the first calibration of a thermometer, though with only one fixed point (the freezing point of water) it was a modest advance. Boyle was still coming to London for most meetings, though he was no longer on the Council. He would move from Oxford back to London to reside with his sister in Pall Mall in 1668, and would live there, where he had his laboratory, for the final 23 years of his life. By late June 1665 the rampage of the plague had forced the Society to adjourn its meetings indefinitely and none were held during the next eight months, finally

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resuming on 14 March 1665/6; Philosophical Transactions Nos. 6–8 were published in Oxford during this recess. Many members left town, including Hooke, who joined Petty and Wilkins in retreating to Durdens near Epsom in Surrey, where they engaged in experimentation.16) Others, like Wallis and Boyle, experimented in Oxford, or wherever they resided,17) and some members met informally in Oxford during the fall of 1665. Wren took the opportunity to travel abroad, especially in and near Paris, mostly studying architecture, but Oldenburg remained in his house in Pall Mall near Boyle’s sister’s (Lady Ranelagh), and noted that the pestilence had affected the neighborhood, which also included Brouncker’s residence.18) By the end of November deaths had declined by 90% and in January many were beginning to return to London. The Council resumed meeting on 21 February and the Society itself met three weeks later. We might recall that Newton was gone from Cambridge for almost precisely the same period, from sometime in the summer of 1665 until March 1666. The plague not having fully run its course, he soon left again, returning almost a year later.19) What happened in Wolsthorpe during that period is the stuff of legend. But the Society boldly met through the summer of 1666, only to be greeted by a new disaster, when on Sunday, 2 September, the Great Fire started in Pudding Lane.20) Unlike the pestilence, the fire was no respecter of status, devastating many of the wealthier parts of the city, including the highly commercial Cornhill area. (Fig. 7). But also unlike

Fig. 7

Map showing the area devastated by the Great Fire of 1666. Gresham College is denoted by T, and the Cornhill area is at the left center. By permission of the Guildhall Library, Corporation of the City of London.

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the plague, the loss of life was very low, perhaps under 20 individuals, despite enormous property damage. Under the heading 5 September 1666 (the day the fire was quenched), when the Society would have met, we read that «the Society could not meet by reason of the dreadful fire in London.» Gresham College was spared, being on the northeastern edge of the devastated area,21) but use of the undamaged College by City officials prompted an invitation from Charles Howard for the Society to move its meetings to Arundel House, in the Strand, west of the burned area. Hooke, with no other option, managed to retain his rooms in Gresham, but the Society had to look elsewhere and in November the Society was still having problems with a meeting-place, and after giving some consideration to other alternatives, including York House and the possibility of moving to Westminster, it accepted Howard’s offer and began meeting at Arundel House in January.22) A consideration was that Gresham College was thought by some to be of too great a distance from «the habitations of the greatest number of the society» and «very inconvenient to meet in, especially in the winter season.»23) On the other hand, a move would make it difficult for Hooke to transport delicate equipment for experiments at meetings,24) and the Society would return to Gresham within the decade. At the meeting of 19 September 1666 Hooke offered a plan for rebuilding the City, on the heels of proposals already submitted by Wren and Evelyn. Hooke’s differed from theirs in that it was first presented to the Society rather than to City Officials or to the King,25) but eventually all the plans, each of which involved major realignment of the winding streets of the old City, were rejected, with the result that the layout of present-day London – the City, that is – largely mirrors the plan of midseventeenth-century London. Many have deplored the lost opportunity, but at least as many have breathed a sigh of relief that the historic layout of the City survives to this day. The fire disrupted publication of the Transactions for a time and destroyed unsold copies which had been stored at St. Paul’s, and it also dealt the final blow to the old medieval cathedral,26) which was soon razed, in large measure at Wren’s advice. The printer Martin (Martyn) resumed the role of the Society’s publisher with Transaction No. 21 in January 1666/7.27) In the same month, in making its move to Arundel House, the Council decided to move its meetings to Thursday, from 3 to 6 in the afternoon.28) In the spring of 1667 there were discussions of Sprat’s History, which would be published later in the year, and on 23 May it was reported that Margaret, Duchess of Newcastle, desired to attend a meeting of the Society, and she was duly entertained by a series of experiments performed for her at the next meeting. This auspicious occasion must have represented the first attendance of a woman at a meeting of the Royal Society. On 4 December 1666, Moray, recognizing the rather incoherent program of experiments and demonstrations at meetings, proposed that the Council address the question of whether they ought to consist of, «a continued series of experiments, taking in collateral ones, as they were offered, or by going on in that promiscuous way, which had hitherto obtained.»29) Perusal of the minutes or Birch’s History makes evident the somewhat haphazard approach to experimentation, due largely to the lack

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of any program other than the fancy of the members and, perhaps, that of Hooke, the Curator. At one point, «considering the want of experiments at their public meetings,» the Council thought to present a medal to fellows for each experiment they produced.30) If the Society had some difficulty establishing a coherent program of experiments at meetings, certain issues continued to be pursued with some consistency, perhaps even doggedly, including the phenomena of the tides, especially by Wallis, various applications of pendula, mostly by Hooke, the nature of magnetism, and so on. Much of the Society’s preoccupation from the latter half of 1666 into the spring and summer of the next year was with issues of anatomy and various kinds of transfusion of blood from one animal to another.31) There was continued interest in astronomical questions, but not much of a coherent program. On 19 December 1667, Oldenburg reported on some observations of «spots lately discovered in Mars» by Cassini and the inference that the planet rotated on its axis. Hooke had reported the same phenomena 21 months earlier, deriving a period of rotation of about 24 hours, but neither he nor Oldenburg are recorded as noting that fact.32) In early 1666/7 the issue of Cutler’s promise to pay Hooke $50 per annum was addressed seriously for the first time, and on 27 September, the Society took possession of Chelsea College, hoping that it might become the site for a «college for their meetings,» but in fact would be little more than an albatross.33) An attempt to solicit funds from wealthy members for a building, possibly near Arundel House, was begun the following January and by May $1000 had been subscribed. On 22 June Hooke produced a draft of the building and was ordered to look into the buying of the materials and of contracting with workmen. Henry Howard, the Society’s host at Arundel House, also provided a drawing. Construction was deferred to the spring of 1668/9, and, as with the Chelsea College episode, in the end came to nothing. On 10 October Sprat’s History was presented to the Society by John Wilkins. There was some feeling that Sprat was long on generalities and short on detail, a view Oldenburg expressed to Boyle, and Joseph Glanvill’s Plus Ultra of the following year was intended to meet this objection.34) The Society first gave thought to transfusing blood into a man in the same month, imagining that it might be «most advisable to try it upon some mad person in the hospital of Bedlam.»35) Soon the Society had a volunteer who, for a guinea, would allow sheep’s blood to be transfused into him, and the experiment was quickly tried. The minutes note that the experiment was «made in a great crowd of spectators, which would not admit of that exactness, which was designed . . . » Somewhat surprisingly, the man is noted as having survived, though for how long is not recorded. Although it seems not to have been a major interest of his, and indeed he seems to have found it somewhat distasteful, Hooke was frequently called upon to carry out animal experiments, on his own or with Dr. Richard Lower.

Focused Energies: The Laws of Motion At the first meeting after the summer recess, on 22 October 1668, Hooke proposed « that . . . experiments of motion might be prosecuted, thereby to state at last the nature

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and laws of motion . . . » This suggestion was immediately taken up by the Society, and was the beginning of a concerted attack on the problem of collisions, heretofore dominated by Descartes’ clearly inadequate theory,36) that went on into the spring of 1669. In many respects it was a unique event in the Society’s early history, which more typically saw a somewhat haphazard program of experiments and demonstrations. At the next meeting, Hooke followed up with a that «experiments be made to see, whether all hard bodies, that rebound, do not so upon the account of having springy particles in them . . . »37) And on 5 November, after an experiment allowing a feather to fall in an evacuated vessel, he suggested experiments «to determine the question concerning the communication of motion.» Interestingly for an organization which held its Baconian heritage in such high regard, the Society responded to Hooke’s suggestions by inviting Wallis, Wren, and Huygens to offer their theories of collisions, thus overlooking the young Hooke, who was evidently not seen as a likely source of theoretical insight into the dynamics of collisions. Further, President Brouncker, ever the good mathematician, even suggested that the experiments Hooke proposed might be unnecessary, since both Huygens and Wren «had already taken great pains to examine that subject, and were thought to have found a theory to explicate all the phaenomena of motion.» Perhaps not the best example of the Society sticking to its Baconian principles. So it was decided that Oldenburg should write to Huygens and Wren to see if they would communicate their «speculations and trials of motion» to the Society. Undeterred, Hooke proposed to resurrect experiments which had originally been carried out two years earlier, involving the collision of balls suspended by fibers, and he again speculated that the rebound of hard bodies might be due to their having “springy particles” in them.38) The experiments were soon performed, and Hooke was ordered «to think upon other experiments for the making out of this hypothesis about motion, which is that no motion dies, nor is any motion produced anew.»39) It was also moved «that since the society was upon the disquisition of the nature, principles, and laws of motion, all authors, who had written on that subject, and delivered their hypotheses concerning it, might be consulted and examined, and an account of their opinions brought in, to see, what had already been done in this matter.» By 12 November Wren and Huygens had responded,40) John Collins was asked to study what Descartes and others had written on the subject, and Oldenburg was to solicit a discourse from Wallis. Hooke continued his experiments on the springiness of bodies, but the experimental investigation which he had originally proposed continued to be pushed in a strongly theoretical direction. But if he was relegated to the role of testing the theories of Wren, Wallis, and Huygens, Hooke was, in fact, interested in the deeper questions of dynamics, including the cause of rebound, as opposed to a merely kinematic description. At the meeting of 26 November Oldenburg announced the receipt of Wallis’ paper on the general laws of motion, and a fortnight later another letter from him was read. Hooke was still experimenting on rebound at that meeting, but he was ordered to provide experiments specifically to test the theories of Wallis and Huygens. Wren’s theory was presented on 17 December, and Hooke was again urged to perform

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experiments to verify the theories, but, perhaps belatedly, was also asked to share his own ideas «on the cause of springiness.»41) According to Birch, others, including Brouncker, Ward, and Hooke himself, also had “considered” the subject. Hooke was being listened to, but was not in the favored galaxy of Huygens, Wren, and Wallis. Huygens’ contribution was read on 7 January and he soon provided additional papers on the subject which were distributed to Brouncker, Ward, Wallis, Pell, Wren, Neile, Croune, and Hooke for comment, and Wren’s own “hypothesis of motion” was ordered to be printed in the Transactions.42) Apparatus failure cut short attempts to test Huygens’ and Wren’s theories in late January, but on 4 February trials were successfully carried out on Wren’s theory. A letter from Huygens acknowledged that his and Wren’s theories were “conformable,”43) and his interest in how Wren had proved his theorems prompted an exchange of ciphered forms of their discoveries, which were duly recorded in the Society’s Register Book. On 18 February experiments were carried out with “springy” bodies, again to test Wren’s theory of motion, and interest continued into April, with Croune also being asked to test Huygens’ four rules of motion.44) A year later the relationship between Huygens and the Society was so close that Huygens made provisions for some of his papers to be delivered to it in the event of his death, which at one point he thought might be imminent.45) This study of collisions, or more generally, of “the laws of motion,” which we have followed in some detail, is a rare example of a topic pursued by the Society in a coherent, sustained way, in this case for the better part of a year, effectively ending when the Society adjourned in July for the summer.46) It was further unusual in the extent to which the theories of Wren, Wallis, Huygens, and Brouncker dominated over experiment. Hooke’s proposal to carry out experiments to determine “the nature and laws of motion” had stimulated an enormously fruitful dialogue which had shown the inadequacy of Descartes’ rules for elastic collisions, and had led to the correct ones for perfectly elastic or perfectly inelastic collisions (Wallis’ “soft impact”), based essentially on Descartes’ conservation of “quantity of motion.”47) There was even some consideration of the quantity mv2 , Leibniz’ vis viva, in which Huygens had long been interested, and in this connection Hooke attempted an experiment to show that «the strength of a body moved is in a duplicate proportion to its velocity.»48) These experiments, one employing a pendulum with variable weight and length of fiber,49) and the other, measuring the velocity of falling water as a function of distance fallen, were first attempted on 7 January, apparently failing because of frost «disordering the instrument»50) , but were conducted successfully at subsequent meetings. Hooke carried out another experiment two weeks later (28 January), designed to establish «that a body, once put in motion, would move perpetually, if it met not with resistance,» not a novel idea to be sure, but one that could bear careful testing by an original and talented experimentalist. In experiments carried out in February it was noted that the effect of the resistance of the air on the motion of a pendulous body depended on the “arch” through which the body moved, that is, the displacement and hence the speed. It was also found that «the impediment to motion decreased in a greater proportion than the decrease of the velocity.»51) Further experiments were tried in the late winter of the

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following year, which proposed to compare the behavior of a pendulum in a vacuum with one oscillating in compressed air.52) At the time, Hooke was working on a “magnetical watch,” which employed a magnetic balance which evidently consisted of a magnetic needle oscillating in a magnetic field, and was driven or restored by a spring. He was also interested in the way the «magnetical power decreases at several distances.»53)

Concluding the First Decade Despite these fruitful studies of 1668–9, and indeed in the midst of them, the Council and the Society as a whole decided in February to establish two committees involving 16 active members «to advise and agree together about the best ways of carrying on this work to the satisfaction of the society.» Hooke was offered the services of an assistant, who would receive $5 per quarter, reflecting the fact that by this time he was well into his complementary career as commissioner, surveyor, and eventually, builder and architect, and that it was affecting his performance as Curator.54) The Journal Book reveals that on five occasions between June 1669 and November 1670 he was absent or unprepared to offer experiments.55) In April 1669 William Croune (or Croone) was asked to continue experiments testing the laws of motion, in preference over Hooke, it would seem, although he requested Hooke’s assistance. In May the dangers or benefits of ingesting mercury were debated, prompted by a query from the physician of the Prince of Tuscany. Boyle, among others, saw little harm, but the outcome of the disquisitions seemed equivocal. Many of the founders of modern science undoubtedly suffered mercury poisoning, including perhaps Boyle, Hooke, Newton, and even Faraday. At the same time both Wren and Hooke proposed grinding machines which would generate hyperboloidal and ellipsoidal surfaces, as a means of improving various optical devices. Discussions, sometimes involving foreign correspondents, continued through the winter, and attempts to get either Hooke or Wren to provide practical grinding machines continued into the next decade. Hooke dropped a real bombshell at the meeting of 15 July 1669 when he «intimated, that he was observing in Gresham-college the parallax of the earth’s orb,»56) a discovery which would have finally established the earth’s annual motion.57) We discuss this important question later, but suffice it to say at this point that during the previous spring he had found the time, despite all his other duties, to design and construct a zenith telescope at Gresham College for the purpose of making these delicate measurements. A year later, on 28 July 1670, he reported that, in the secretary’s words «he had already found so much, as to suspect some parallax of the earth’s orb, and conceived, that it would be more sensible a half a year later.» Further observations were not forthcoming (See Chapter 11). In the fall of 1669, a request from the King stimulated an interest in measuring a degree of arc on the earth’s surface. Hooke was a member of a committee of eight chosen to consider how to do this.58) The following June he was “ordered” to carry out the necessary measurements “in the next vacation.” Repeated promises and further

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urging never bore fruit.59) One senses that it was not something that Hooke cared much about. There continued to be interest in the tides, especially Wallis’s theory, as well as in the variation of the compass needle from true north. Along with the problem of longitude, these issues were of special importance to an island and seafaring nation. On 24 November 1670 there was discussion, stimulated by a letter from Wallis, of the question of whether an object dropped vertically and one projected horizontally from the same height, would strike the ground at the same time. That this issue was still considered debatable shows that the implications of the Fourth Day of Galileo’s Two New Sciences had not been fully absorbed.60) Experiments performed in January and February were inconclusive. Perhaps the most interesting pneumatic experiments of late winter 1670/71 were the attempts to build a receiver large enough to hold a man, so that the effects of breathing lowered atmospheric pressure could be examined.61) Ever curious, Hooke chose himself as the first subject, finding «not any inconvenience upon the exhaustion of the little air drawn out of it.» In a further test, he reported that he had reduced the air pressure by 10% and «had felt no other inconvenience but that of some pain in his ears at the breaking out of the air included in them, and the like pain upon the readmission of the air pressing the ear inwards.»62) On 23 March he mentioned that he had stayed in the receiver for over 15 minutes with the pressure reduced by one quarter, with similar results, noting that a candle he had with him went out long before he felt any of «that inconvenience in his ears.»63) Word of Newton’s remarkable reflecting telescope had been circulating since 1669 and the Society’s interest in it prompted Isaac Barrow to provide it to the Society in December 1671. Immediately thereafter (at the final December meeting), in the secretary’s words, «Mr. Isaac Newton, professor of mathematics in the university of Cambridge, was proposed candidate by the lord bishop of Salisbury,»64) and he was elected at the next meeting, in early January. The telescope, which magnified 38 times, was quickly examined by several members, probably including Hooke, and it was demonstrated at the 18 January meeting, where it caused a sensation.65) But this was not to be the end of the matter. On the same day in a letter to Oldenburg, Newton widened his contacts with the Society by alluding to «a philosophical discovery,» being, in his judgement «the oddest, if not the most considerable detection, which hath hitherto been made in the operations of nature.»66) This was a reference to his experiments with light and color, which he began to reveal in a letter to Oldenburg on 6 February, read to the Society two days later.67) Newton had come out. Westfall writes that «Swept along by the success of his telescope, Newton stepped publicly into the community of natural philosophers to which he had hitherto belonged in secret.»68) For the next 15 years the relationship between Newton and the Society would be complicated, and with Hooke, full of tension. It would be 31 years before Newton would become its president, just a few months after Hooke’s death. After Newton’s letter was read by Oldenburg69) , Hooke, Boyle, and Ward were asked «to peruse and consider it, and bring in a report of it to the Society.»70) Hooke, who saw himself as, and indeed was, the Society’s expert on light, color, and optics, was quick to offer comments in a letter to Oldenburg the next week, though he «had

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not above three or 4 hours»71) for its perusal. Newton would not have to wait long to hear about them. Hooke at once disputed Newton’s interpretation of the experiments, and, somewhat inconsistently, argued that the latter had gotten his ideas on color from Hooke’s own Micrographia. As for Newton, this belated entry into public discourse had quickly proved contentious, and nothing was more distasteful to him than contention and controversy. Thus began a heated dialogue, mostly through Oldenburg as intermediary, which poisoned the relationship between the two of them – Newton and Hooke – even before it began. Newton’s theory stimulated a series of experiments throughout the spring, mostly by Hooke, largely confirming Newton’s results, and yet Hooke remained steadfastly unconvinced of the correctness of Newton’s interpretation of them, and said so. Newton’s initial reply by way of Oldenburg was guarded, but his full response, when it finally came in June, was vitriolic. Giving as good as he got, he would claim that Hooke’s theory of light was, to use Westfall’s words, «only an embroidery on Descartes’.» We devote a separate chapter to this interesting and important issue. The resumption of meetings in the fall of 1672 following the summer recess, saw a return to the old problem of anomalous suspension, which still had not been settled when Huygens’ paper on the subject was published in the Transactions in August, venturing the cause as aether pressure.72) As we have seen, the phenomenon had caused much consternation a decade earlier, centering around whose air pump was better, Huygens’ or Boyle’s. Because Shapin and Schaffer’s Leviathan and the Air-Pump73) is an extended examination of this and related questions, we will not consider it in detail. What followed was more correspondence, notably from Wallis, who was able to show that the pressure of the aether was not likely to be the cause.74) Hooke, with his experience with capillarity, as we now call it, might have been expected to offer this as an explanation. Thus concluded (whether in December or March) the year 1672,75) the tenth year of Hooke’s service as Curator, the year of the commencement of his Diary, of the death of Wilkins, of the admission of Newton to membership, and of the start of the lengthy quarrel between these two Restoration philosophers. The Society would have many hard years ahead, some of which are recounted below and in succeeding chapters as we proceed to describe Hooke’s career.

Annotations 1) Oldenburg to Hevelius, 18 Feb. 1662/3; CHO, Vol. I, letter no. 262. 2) Charles II also sponsored the career of the first Astronomer Royal, John Flamsteed, and the establishment of the Royal Observatory at Greenwich, designed by Wren and Hooke with Hooke playing a role in supervising construction. 3) Birch, 1, 53. 4) In which the name “Royal Society of London” is perhaps used for the first time, i.e., Sodales Regalis Societatis Londini. The 20 members, including the

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president Lord Brouncker, the members of the Council, and secretary Henry Oldenburg are alluded to in the charter. 5) The important issue of replication, which is the subject of Shapin and Schaffer’s Chapter VI (1985)), had never previously drawn so much attention. Since the air-pumps used in London and in Paris were not identical, there was a real question whether the same phenomena were being studied. 6) Going back to Torricelli (who invented the mercury barometer in about 1643), or earlier. 7) It was in the late spring of 1663 that Huygens visited the Society for the second time, Wren showed his plans for the Sheldonian Theatre, the Society’s second charter was issued, and the Council met for the first time. In June Hooke was elected a Fellow. 8) Beginning as early as 9 March 1673/4. See the footnote in Birch, 1, 391. 9) The Society’s first expression of interest was in 1660. 10) When the meter was defined in France in 1791 as the ten-millionth part of the distance from the equator to the pole, the result was very close to the length of the “seconds pendulum” (sensu Hooke), and in fact the meter was first defined in 1790 as the length of a pendulum with a period of 2 seconds. This arises 2 from the fact in the modern √ that g/π (MKS) is very nearly unity. The period sense is 2π l/g, so that T = 1 sec implies l = (1/4)(g/π 2), or about 1/4 m (9.8 inches). But the “period” of the “seconds pendulum” was being measured by Hooke (and most others) from one extreme to the other, that is, one half the period in the modern sense, hence l = T 2(g/π 2 ) ≈ 1 m, since T = 2 s and l = 39.15 in. Hooke obtained the value 39.05 inches (.99 m)in December 1664 (Birch, I, 511) in an experiment performed at Lord Brouncker’s residence. In 1660 Huygens settled on the value of 9 12 inches (translating to 38.0 sensu Hooke) for the length of the seconds pendulum; he was thinking of the full period. In a letter to Boyle in 1664, Hooke described a 180-ft pendulum erected in St. Paul’s cathedral as performing “each single vibration” in 6 seconds, which, again, is one-half the period; the latter he described as a “turn and return.” (Hooke to Boyle, 25 August 1664; see Hunter, et al. (2001). The calculated value is 7.4 seconds. Although the second was 1/86,400th of a mean solar day, the mean solar day is not an empirical quantity. Before Huygens’ pendulum clock there could be no standard for the second, and even with the pendulum clock, the definition is thoroughly circular. That is, the second is one-half the period of the seconds pendulum, whose length is a meter, which was defined in terms of the seconds pendulum. The situation was resolved when the French defined the meter in geographical terms. 11) The “air” or gas produced was carbon dioxide, resulting from the reaction of aquafortis (nitric acid) with what was essentially calcium carbonate.

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12) The title page has “Philosophical Transactions: giving some Accompt of the present Undertakings, Studies, and Labours of the Ingenious in many considerable parts of the World.” The first number consisted of summaries, or abstracts, in Oldenburg’s words, of a number of philosophical events and discoveries, including Hooke’s noting of a spot on Jupiter, comments on Boyle’s Experimental History of Cold, observations of a comet by a corresponding member Azout, and a list of the publications of the late Pierre de Fermat. The early Transactions are available in facsimile reprint form by Neiuwkoop, Amsterdam (1963–4), and now on the internet via JSTOR. 13) For details one should consult M. B. Hall (2002). Oldenburg’s job was especially difficult in the dangerous years of the mid 1660s, when correspondence with Europe might be suspected of containing political intelligence, and indeed such a suspicion did fall on Oldenburg at one time or another. 14) See the discussion in the previous chapter. There were ephemeral publications before the Philosophical Transactions, and for a century, the PT were not officially a publication of the Society. 15) Presented to the Society as New Experiments and Observations touching Cold, on 12 April 1665. 16) On 7 August 1665 Pepys passed through Durdens on the way to London. He reported that «I found Dr. Wilkins, Sir William Pettit, & Mr. Hooke contriving Chariots, new rigges for ships, a Wheele for one to run races in, & other mechanical inventions, & perhaps three such persons together were not to be found elsewhere in Europ, for parts & ingenuity.» Boyle also spent about a month there with Hooke. See Jardine (2004), pp. 113–117. On 21 March 1665/6 Hooke lectured on gravity experiments he had done in a deep well “near Banstead Downs” in Surrey. Hooke found his attempts to detect any variation in the weight of an object were defeated by the smallness of the effect, but discussed using a pendulum instead, and the analogies between gravity and magnetism. Birch, 2, pp. 69–72. 17) At the meeting of 14 March, Wallis was asked to tell the Society about the experiments that had been performed by members in Oxford the previous summer. Wallis, not being much of an experimental philosopher, deferred to Boyle, who was not present. 18) Indeed, Oldenburg wrote to Boyle on 10 August that he was putting his affairs in order. Hunter, et al. (2001), v, 330. Brouncker apparently also had a residence in Covent Garden (Pepys’ diary for 5 January 1665/6). 19) Westfall (1980), Chapter 5. 20) It has been been claimed that the fire was largely responsible for the end of regular plague irruptions in London. There were other factors, of course. The City was rebuilt in less than a decade. One accessible account is Milne (1986). 21) The fire came within not much more than 100 yards of Gresham. See Fig. 7.

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22) There had been meetings in the rooms of Walter Pope, Gresham Professor of Astronomy. 23) Charles was the younger brother of Henry Howard, who became Duke of Norfolk in 1677. He made the offer on 19 September (Birch 2, 114). The Society began courting Henry Howard at least by late November and elected him a Fellow on 28 November and to the Council two days later. In turn, he offered the Society his library on 2 January, «to be disposed thereof by them as their property,» and on 4 January, the Council accepted Howard’s offer to meet at Arundel House. Howard offered the Society land adjacent to Arundel House (near the Strand, where Arundel St. now is) upon which it intended to built its “College.” 24) Such a worry was expressed on 25 July 1667, for example. 25) Oldenburg told Wren that if his proposal had been submitted to the Society for its ratification, it would have given the Society «a name, and made it popular, and availed not a little to silence those, who ask continually, What have they done?» Oldenburg to Boyle, 18 September 1666. Quoted in Birch 2, 115. 26) Which, however, was graced with a somewhat incongruous colonnaded portico due to Inigo Jones. 27) No. 17, dated 9 September was printed by John Martin and James Alestry. When publication resumed in London, it was by “John Martyn.” Number 18, dated 22 October, was printed by John Crook in Duck Lane, Little-Britain; No. 19, dated 19 November, by «John Crook neer the Blew Anchor in Duck Lane; and Mose Pits [sic] at the White-Hart in Little-Britain;» No. 20, 17 December, by Moses Pitts alone. 28) Thursday meetings began on Feb. 14, 1667. By order of the Council on 10 April 1672, they were switched back to Wednesday, and the Wednesday meetings resumed on 24 April. On October 30, 1673, they again reverted to Thursday, where they remained until the beginning of 1681 (January 1680/81), the decision having been made on 2 December 1680 to return them to Wednesday. They remained there throughout Hooke’s life. 29) Birch, 2, pp. 131–2. To repeat, passages like this one are extracts from Birch, which are more or less verbatim transcriptions from the Journal Book of the Society. Hence, it is the secretary, in this case Oldenburg, who is paraphrasing Moray’s remarks. 30) Birch 2, 265. 31) Experiments which had begun in Oxford in the 1650s. 32) Hooke had discovered Jupiter’s “Great Red Spot” in 1666 as well. See Birch, 2, p. 98. 33) Negotiations, principally over legal issues, dragged on into December, but once the Society had the property, nothing was done to improve it, despite much hand-wringing. The Society only received the Royal patent in April 1669 (Birch 2, p. 363–71: «The new patent from his Majesty, dated April 8, 1669, granting

62

34)

35) 36) 37) 38)

39) 40)

41)

42)

43) 44) 45) 46)

Chapter 4. Society of the Muses: The First Decade Chelsea College to the society, together with some additional privileges and powers was read.» (13 May 1669) Charles II eventually changed his mind and decided to put it to a different use. In 1672 it was proposed to use Chelsea College as a prison. (Birch 3, 42). Birch indulged himself in a long footnote (600 words, more or less) on the matter (2, p. 297). Glanvill was rector of Bath Abbey (St. Peter and St. Paul). Plus Ultra was presented to the Society on 18 June 1668. Birch, 2, 202, 204. Lower’s experiments on dogs continued unabated. For example, his fourth rule of impact, which says that a smaller body impacting a larger one at rest cannot set it in motion. Ibid, pp. 315–16. This important insight was ventured at the meeting of 29 October 1668. Birch (2, 316) says that «Mr Hooke moved, that experiments might be made to see, whether all hard bodies, that rebound, do not so upon account of having springy particles in them . . . » Furthermore, «He conceiving, that if there were to be had a body absolutely hard, dots it would not rebound at all.» Birch 2, 315, 316, 318, 320. Three years earlier, a skeptical Spinoza had written to Oldenburg about his countryman Huygens as follows: «As for his treatise on motion, about which you also enquire, I think it is vain to expect it. It is so long since he began to boast that he had discovered by calculation laws of motion and laws of nature quite different from those of Descartes . . . yet so far he has given no example of this.» Spinoza to Oldenburg, fall 1665 (CHO, II, p. 541). Volume V of Oldenburg’s correspondence (CHO) contains a series of letters, mostly between Wallis and Oldenburg and between the latter and Huygens on the similarities among the theories of Wren, Wallis, and Huygens. An indirect exchange, via Oldenburg, between William Niele and Wallis on the laws of motion, is represented by several letters in the same volume. These continue into Volume VI. While some of Neile’s notions were clearly wrong, and noted as such by Wallis, others, especially those involving the motion of systems of particles, are quite interesting. For example, the letter to Oldenburg 1 June 1669 (Letter No. 1197, Vol. VI, CHO). Wallis’ contribution was published in the Philosophical Transactions, vol. iii, no. 43, p. 864, 11 January 1668/9; Wren’s paper immediately succeeded it, on p. 867, while Huygens’ was in vol. iv, no. 46, p. 925. Descartes’ ideas on elastic impact were presented in Part II of his Principles of Philosophy, in the form of seven rules. Huygens letter, in Latin, was published in PT, No. 46, 12 April 1669. Birch 2, 424. This episode was not, however entirely unique. One thinks of the long series of experiments in pneumatics, or the studies of blood transfusion, for example. The

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Society would adjourn in the heat of the summer, when, as Oldenburg wrote, «the greater part of polite society goes to the country for the long vacation.» Oldenburg to Huygens, 6 September 1669 (CHO, VI, 223). 47) Wren’s theory was based on a related postulate of his own. 48) Or «that the force in moving bodies is in a duplicate proportion to their celerities, so that there is required a quadruple weight to double to velocity.» This idea he presumably got from Huygens. It was William Willughby who introduced «ye summe of ye Q. of ye Velocities» into the discussion. Willughby to Oldenburg, 21 June 1669 (CHO, Vol. VI, pp. 63–4.). 49) Three trials were made with weights of 2, 8, and 32 oz. The lengths of the fiber supporting the masses were, apparently, in the same ratio, 1:4:16. This resulted in frequencies in the ratio 1:2:4 (12, 24, and 48 vibrations in a fixed time). Hence the velocities were in the ratio 1:2:4, showing that «there is required a quadruple weight to double the velocity.» A very nice experiment. In the other experiment, it was found that «the falling water was to be raised four times the height to run out with double the celerity.» Birch, 2, 339. 50) We note that this period was during what is sometimes called the “Little Ice Age,” a five century long period of unusually cold winters associated with a prolonged minimum in solar activity. See Fagan (2000). The Thames froze over several times in Hooke’s lifetime, including 1663, 1666, 1677, 1684, and 1695. There was an especially notable “frost fest” on the frozen Thames in the winter of 1683/4. See Evelyn’s diary. 51) An early recognition of the fact that air resistance depended more strongly on the velocity than linearly. 52) Birch, 2, 427, 429, 431–2. 53) Birch, 2, 350, 354–6, 359–360, 372, 374. 54) For example, the College of Physicians, which was begun at this time c. 1671). 55) «Mr. Hooke being absent, the experiments of motion were not prosecuted» (11 Feb. 1668/9); «Excused himself for having prepared no experiments . . . » (17 June 1669; «excused himself for not bringing them in, he having had some avocations of a public nature . . . ;» «Mr. Hooke being absent, the society, instead of experiments . . . » (10 Feb. 1669/70); «Mr. Hooke being absent from this meeting, no experiments were provided.» (24 Nov. 1670). For 2 December Birch records that «Mr. Hooke being called upon for the experiments appointed for this meeting, he excused himself for not bringing them in, he having had some avocations of a public nature, which had hindered him . . . » 56) Birch, 2, 394. He had two data points at this stage. See Chapters 7 and 11. 57) It is not out of the question that he might have detected what we call “stellar aberration,” the change in direction of a light ray from a star due to the earth’s

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motion through space, though his data hardly support this interpretation. See the discussion in the chapter on Hooke’s astronomy. 58) Birch, 2, 398. 59) In April 1671 he was promising «to do it within a month.» 60) Something Galileo claimed in his Dialogue in 1632. Though the contrary opinion, due to Fabri, was correct if one takes into account air resistance. 61) Described in a Journal Book entry for 9 February 1670/71. 62) Birch, 2, 469, 470. 63) This would correspond to an altitude of about 2500m, which certainly would not be sufficient to extinguish a candle . . . One wonders how accurately the pressure drop was measured. 64) That is, Seth Ward. Birch, 2, 501. 65) It was apparently the first to be constructed, but barely, and far from the first proposed. Newton got his idea from James Gregory’s Optica promota of 1663 but the concept of a reflecting (“catadiotrical”) telescope was considerably older, perhaps going back to Leonard Digges in the sixteenth century. On the other hand, the particular design, which we call “Newtonian,” was original. Newton’s may have been the first functioning instrument, but Hooke may have been the first to build a Gregorian telescope. See Corresp. I, 151–2. 66) 18 January 1671/2; Corresp. I, 82; Birch, 3, 5. 67) Corresp., I, 92–102 68) Westfall (1980), p. 237. 69) For which the author was «solemnly thanked . . . for this ingenious discourse . . . » Birch, 3, p. 9. 70) Hooke to Oldenburg, 15 February 1671/2, Corresp. I, 110–114. 71) Hooke to Brouncker, June 1672, Corresp., I, 198. 72) Huygens, PT, no. 86 (19 August 1672), 5027–30. 73) Shapin and Schaffer (1985). Readers of Leviathan and the Air-Pump will strive in vain to find any hint of the actual (which I do not put in quotes) explanation of this phenomenon, thereby being left to choose between the theories of Huygens, Wallis, Brouncker, and others. It cannot be irrelevant how closely, or distantly, seventeenth-century observers approached the explanation we now know to be correct. 74) Wallis to Oldenburg, 2 and 5 October 1672, CHO, Vol. IX, pp. 275–80. 75) That is, whether on 31 December or 24 March, the end of the year in the Julian Calendar.

Chapter 5

Crisis and Consolidation: 1672–1687 As the Royal Society embarked on its second decade, it went through a deep existential crisis as initial enthusiasms began to fade and two of its original and most influential members, Robert Moray and John Wilkins, died.1) More than half the members were in arrears and meetings had become lifeless, often because Hooke was occupied with his outside duties as surveyor and architect.2) Two other influential members, William Petty and Seth Ward, returning after having been out of town for long periods, were shocked by the state of the Society. Specifically the issue was «. . . the want of good experimental entertainment at their meetings, and from the neglect of the members in paying their weekly contribution . . . ». Vice-President Petty hoped «to put new vigour into the meetings of the Society,»3) proposing that fellows should be charged with bringing in experiments every week and that legal proceedings might be initiated against fellows in arrears. Soon the active members embarked on a plan of rejuvenation, centered around getting more members involved and in making subscriptions legally binding.4) The crisis came to a head in 1674, beginning with the wholesale ejection of members who were inactive or in arrears, and the discontent would eventually culminate in the removal of the Society’s long-time president, Lord Brouncker, in the elections of November 1677. Brouncker’s ouster came in the wake of Oldenburg’s death in September of the same year, an event which seemed to generate a much wider desire for change. Hooke evidently played a significant role in this “coup”, and we find in his Diary discussions in October, the intent of which was «to spread the Designe of choosing new president . . . »; he noted that «All things seem to goe on well for new president.»5) According to Hooke, those pushing for change included Wren, Hoskins, Grew, and Aubrey.6) Eventually Sir Joseph Williamson was chosen president, after both Wren and Boyle had been approached by Hooke, and presumably others, to see if they would serve.7) Hooke’s involvement in discussions over the direction the Society should take show that at this stage he represented a strong and independent voice, though there was still tension with other members, especially the treasurer Abraham Hill,8) but on occasion with the influential John Hoskins and Thomas Henshaw as well.9) In the election in which Brounker was replaced, Hooke

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was voted onto the Council for the first time and chosen co-secretary. Some reversals notwithstanding, he would be on and off the Council for the rest of his life. But despite these changes in direction, the Society would continue to struggle, prompting another round of reforms twenty years later, by which time Hooke was in failing health and not much of a factor. For reasons discussed in detail in Chapter 7, Hooke had become notably disaffected with the Society in the mid 1670s, but Oldenburg’s death and other changes in the Society had rekindled his enthusiasm, and he threw himself back into its discussions and provided regular experiments for several years (he had prepared hardly a dozen experiments in the three years previous to the secretary’s death). Publication of the Philosophical Transactions had been suspended shortly after Oldenburg’s death,10) and on 8 December 1679 the Council declared «that the secretaryies take care to have a small account of philosophical matters, such as were the Transactions by Mr. Oldenburg, and under the same title, published once a quarter at least . . . » Hooke, as Secretary, is quoted as saying that «he would see what he could do in it, but could not as yet undertake it absolutely.»11) He had, in fact, already begun to produce such a journal, for in October he had sent to the printer the first number of the Philosophical Collections, his answer to Oldenburg’s Transactions. Hooke’s decision not to simply continue the Transactions was undoubtedly motivated partly by a desire to distance himself from the journal published by his nemesis (see below), and with the benefit of hindsight this may seem ill-conceived, knowing as we do that except for this brief hiatus, the Transactions have been published continuously for over 300 years. Hooke, of course did not have that luxury, since when the last of Oldenburg’s Transactions were published two years after his death, they were only 14 years old. They were the creature of Oldenburg rather than an official journal of the Society, and Hooke was seeking a new medium for publishing «such Physical, Anatomical, Chymical, Mechanical, Astronomical, Optical, or other Mathematical and Philosophical Experiments and Observations;» that is, there was for him a real philosophical difference at issue. In 1681 he advertised that the Collections would come out at least once a month, and indeed the last five or six eventually did, with the final number coming out in April 1682,12) but the seven issues printed in nearly four years stood in stark contrast to Oldenburg’s average of over 11 Transactions per year. 13) It is not unlikely that had Hooke published the Philosophical Collections as faithfully as Oldenburg had done with his Transactions, he might have succeeded in replacing it. As it happened he did not. As co-secretary he initially was to handle the minutes and Nehemiah Grew the correspondence, although that was never entirely the case and on 26 December 1678 he was «desired for the future to keep the correspondence of the Society.» Thus, for a while, Hooke simultaneously held the two most important positions in the Society, other than the leadership posts, which at times were merely ceremonial. But Hooke’s diligence in maintaining the Society’s correspondence with continental scientists never equaled Oldenburg’s. He continued to be heavily involved in an array of architectural and construction projects, on his own and with Wren,14) and in addition to his work as Secretary, still functioned as Curator of experiments, indeed with a

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renewed enthusiasm. All this left him with less time for correspondence than Oldenburg, who had little else to distract him.15) The Letter Book (Early Letters) of the Society records only 15 letters written by Hooke during the five years he was Secretary (1677–82), though he certainly wrote more. Moreover, unlike Hooke, Oldenburg had not been a participant in the scientific investigations which were the subject of his correspondence, making him in a sense (at least superficially) more of an “honest broker,” a disinterested chronicler and communicator. On the whole, this was Oldenburg’s critical role almost from the founding of the Society until his death. By contrast, Hooke as Secretary not only was over-committed, but had already developed testy relationships with some of the Society’s continental correspondents, most especially Huygens, but Hevelius and Leibniz as well.16) His suspicion, justified or not, that his ideas were being stolen by others, must have further inhibited the free flow of information about Society affairs through the vehicle of his correspondence. By the time Hooke was given responsibility for managing the correspondence of the Society,17) exchanges with foreign members and other virtuosi had already declined substantially, and it would decline still further under him. And, as a measure of how thinly he was spreading himself, in July 1679 he was told to hire Denys Papin18) to assist him with experimental demonstrations. Finally, and reflecting dissatisfaction with his performance, but deeper divisions in the Society as well, Hooke was voted off the Council and replaced as secretary in the elections of November 1682, clearing the way for the resurrection of the Transactions. When publication was resumed in January 1682/3, the preface of No. 143, the first number of the new series, noted that «Although the writing of these Transactions, is not to be looked upon as the Business of the Royal Society: yet in regard they are a Specimen of many things which lie before them . . . And because, moreover the want of them for these four last years, wherein they have discontinued, is much complained of . . . » The 1680s saw a growing gap between the more traditional Baconians in the Society, including naturalists Martin Lister and Tancred Robinson, and those who advocated a mathematical description of nature, led by Oxford’s Wallis and eventually other Newtonians, as the implications of Newton’s Principia came to be appreciated, from the late ‘80s on. Dublin’s William Molyneux was especially dismissive of those who were «for rejecting all kinds of useful knowledge except ranking and filing of shells, insects, fishes, birds, etc. under their several species and classes.»19) The influence of Newton (as well as Huygens and other mathematicians) was already being felt. Reflecting this division, Robinson complained that the Society «may have great men in their numbers, but alas very little souls, and narrow minds . . . »20) The rapidly evolving science of medicine, increasingly yielding to a more experimental, analytical and quantitative approach, but still a prisoner of its history, was a notable battleground. On a more mundane level, Molyneux also noted that many of the Society’s problems were due to the fact that its secretary was elected annually, was often unpaid, and not infrequently was a casualty of Society politics, as happened to Hooke in 1682, his friend Richard Waller in 1709, and Hans Sloan in 1713.

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Chelsea College, acquired with great hope and anticipation, but now only a liability, was disposed of early in 1682 (1681/2), putting an end to the dream of a “philosophical college.” The Society had returned to Gresham College in 1674 after nearly a decade at Arundel House, and it continued to meet there until 1710, when it purchased the house of Dr. Brown in Crane Court, Fleet Street. It was in November of 1684 that the Society received a copy of Newton’s De Motu, sometimes considered a “first-draft” of the Principia, which resulted from Halley’s earlier trip to Cambridge. All of this is elaborated upon in Chapter 10. Shortly thereafter, at the annual election held on 1 December 1684, Samuel Pepys was chosen president, a position he would occupy for two years, just long enough to have the honor of granting the Imprimatur of the Society for the publication of Newton’s Principia, on 5 July 1686.21) In 1685–6 a constant concern was the drain on the Society’s resources caused by its decision to publish Willoughby’s History of Fishes, a situation that would cause some discomfiture to Halley, who would soon have to personally bear the cost of bringing the Principia into print.22) Clerk of the Society from the beginning of 1686, Halley was largely neglecting his own duties as he attempted to keep the Principia project – which he understood to be of monumental importance – on track. The contrast between these two projects, The History of Fishes and the Principia, highlights the schism in the Society which was coming to a head at the end of 1685, flaring up after the St. Andrew’s Day elections23) , when the newly elected secretaries, Tancred Robinson and Francis Aston, abruptly resigned.24) They, along with zoologist Lister, had been heavily involved in the printing of Willoughby’s work. Acrimony continued throughout 1686, with Halley under constant attack as he oversaw the printing of the Principia, which despite much controversy at the time, would ultimately decide the direction the Society would take,25) and in November an attempt was made to remove him from his post.26) As we saw earlier, Hooke’s first Diary effectively ends in 1680, picking up again only eight years later, so we have none of his views on this philosophical revolution in the Society, but he seems not to have been much involved in the dispute. Very much a Baconian, Hooke nonetheless had philosophical affinities with both sides and if there was no love lost between himself and Newton, Halley was a close friend. In June of 1686 the Council had ordered «that Mr. Newton’s book be printed, and that Mr. Halley undertake the business of looking after it, and printing it at his own charge . . . »! Poor Halley, whose financial situation was sufficiently precarious that he had accepted the job of Clerk for the Society, not only had to extract the Principia from a somewhat reluctant Newton – who had threatened to withhold Book Three – and personally edit it and prepare the woodcuts, but bear the costs of its publication as well.27) But without his position as Clerk, Halley might very well not have made the fateful trip to Cambridge in 1684 which led directly to the Principia (see Chapter 10). After that work appeared in April 1687, Halley suffered the further disappointment of having his salary paid in copies of the History of Fishes, in lieu of the $50 due him.28) Hooke, who was one of the five Council members present on the occasion of that decision, was offered a similar arrangement for payment of the

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arrears due him. Not surprisingly, he asked for six months to consider the offer, and since he was ordered paid $60 in currency in November and December, it seems that his decision was in the negative. John Vaughan, Earl of Carbery, succeeded Pepys as president in 1686, very nearly having his name on the title page of the Principia instead of Pepys. When Thomas Birch concluded his monumental History of the Royal Society nearly threequarters of a century later with the year 1687, he was implicitly recognizing the publication of the Principia as a watershed for the Society, at least from the perspective of his time.

Annotations 1) Moray died in 1673, the year after Wilkins. 2) Hooke’s responsibilities for the City churches began with the Churches Rebuilding Act of 1670, a responsibility he shared with Wren and Edward Woodroffe. 3) Petty, 29 September 1674, in Birch, III, 136. Petty made important contributions to the mathematics of taxation and to the nature of population growth, the latter in his “Essay Concerning Multiplications of Mankind” of 1682. 4) Hooke was interested in making criteria for membership in the Society more rigorous, though it is doubtful that such a reform would have been practicable in the late seventeenth century. See Royal Society Classified Papers, xx. 50, Folios 92–94, Document C in Hunter and Wood (1986), p. 87–92. 5) Hooke’s Diary records discussions about the presidency on more than a halfdozen occasions in October, and they continued into November. We also see Hooke beginning to campaign for the post of Secretary. 6) Diary I, 8, 9, and 11 October 1677. Grew is credited with isolating MgSO4 . 7) Diary I, 10 and 11 October 1677. 8) Hooke’s laconic Diary sometimes creates problems for the sleuth, as when, on 29 November 1677, he notes «At Crown taverne, Henshaw, Hill, Grew, Colwall, Hoskins, Hill, . . . » referring to Oliver Hill and Abraham Hill. The next day he notes that “Mr. Hill” was elected treasurer, and on 19 December he grumbles, «Hill a dog for Grew.» 9) One of the casualties of the commotion in the Society in the fall of 1677 may have been the relationship between Hooke and Sir John Hoskins. They were clearly good friends up until December of that year, when Hooke began observing that «Sir J. Hoskins not really my friend . . . », and “with Hoskins, noe true freind.» (26 and 28 Dec.). Things had improved by the following April, but there would be another crisis following the publication of the Principia. Yet Hooke joined Hoskins for coffee at Jonathan’s, usually as part of a larger group, in the period covered by both diaries, and Jonathan’s was often where Hooke and Henshaw met in the 1680s. Hoskins was president in 1682–3, and would

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preside over a large percentage of meetings, as vice-president, in the 1690s, when absentee aristocrats led the Society. 10) Six Transactions (Nos. 137–142) appeared in the year and a half after Oldenburg’s death, the last being dated Jan-Feb 1678/9. 11) Birch, 3, 514. 12) ‘Espinasse (1956) listed the contents of all seven Collections, published between 1679 and 1682. Only two were Hooke’s own contributions. 13) On March 1, 1665 Oldenburg was ordered to publish the Philosophical Transactions the first Monday of each month «if he have sufficient matter for it.» The first number was dated March 6, 1665. He published 136 numbers in the following 12 years, and six were published after his death before the Transactions were suspended in February 1678/9. That Hooke was still interested in resurrecting his Collections is indicated by three Diary entries in 1689. Following a discussion at Jonathan’s coffeehouse on January 9, Hooke wrote that he had mentioned «continuing Lectures & Collect, if Royal Society would pay for 60. Agreed by all.» Nothing ever came of this idea. See Johns (2000) for further information on Hooke’s Collections and his difficulties in having it printed. 14) Most of the secular rebuilding was done between 1668 and 1676, while the churches were mostly rebuilt after 1674. Construction was largely finished by 1690, except for steeples. Most of Hooke’s own architecture and supervision of his own buildings, took place in the 1670s: the College of Physicians, c1671– 79; Bedlam Hospital, 1674–76; the Monument, 1673–76. He spent considerable time on other projects, such as Bridewell Hospital(1671–74), Montague House, Ragley Hall, Willen church, and Aske’s Almhouses, Hoxton (1689–93]. See, for example, ‘Espinasse (1956), Chap. 5, Louw (2006), and Batten (1936–7). Greenwich Observatory is another important building project in which Hooke was involved, and though the extent of his role in the design and construction of the latter is not entirely clear, we do know that he was deeply involved in it. For example, on 28 July 1675 he wrote in his Diary: «To Greenwich. Set out Observatory.» In addition to references to laying out Greenwich which can be found in the Diary, see F. Willmoth (1991). 15) Though see Marie Boas Hall, Henry Oldenburg (M.B. Hall, 2002), for the latter’s various schemes for making a living. 16) In the case of Leibniz, the issue was his calculating machine, which Hooke chose to improve without, perhaps, giving due attention to his continental contemporary’s priority. Huygens, of course, had done the very same thing with Hooke’s balance-spring watch. And one could stretch the analogy to say that because Hooke gave Newton the key to the Principia that that prize was his. 17) «That Mr. Hooke be desired for the future to keep the correspondence of the Society; and that the same shall be continued by the help of a small Journal of some particulars read in the Society . . . And Mr. Hooke was desired to draw up

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a specimen of the said Journal propounded by him against the next meeting of the Council.»Birch, 3, pp. 450–1. 18) Papin, 12 years Hooke’s junior, had earlier been an assistant to Huygens, and worked with Boyle from 1675 until 1679, when he became Hooke’s assistant. He left London in 1687 for Germany. There he made important contributions to the nascent science of steam technology, including a high-pressure boiler and a proposal in 1707 for a ship to be powered by a “fire engine.” This issue, and the possibility that the source of Papin’s ideas may ultimately have been Thomas Savery, is discussed in Stewart (1992), p. 24, and references therein. Savery and Newcomen worked on the atmospheric engine simultaneously, with Newcomen consulting Hooke on pneumatic questions. So Hooke played some small role in the invention of the steam engine. Eventually, Newcomen developed the first practical steam engine, in about 1711. Papin died in poverty in London around 1712. 19) Molyneux to Halley, 8 April 1686. The letter was read to the Society at the 21 April meeting. Birch, 3, 479–9. 20) Feingold (2001), p. 89. 21) Though Halley, quite appropriately, had the honor of presenting it to the king. 22) The History of Fishes was completed by John Ray. 23) St. Andrew’s Day was (and is) 30 November. 24) «Without any apparent cause,» according to Halley. Halley to Molyneux (suppl. to letter-book, iv, p. 329). 25) For elaboration, see Feingold (2001). 26) Birch, 3, 505. 27) It is thought that approximately 500 copies of the first edition were printed (Cohen and Whitman, 1999). Halley was elected clerk on 27 January 1685/6. Although the clerk was supposed to be unmarried and childless, Halley was given a special dispensation since he had married in 1682. But his assumption of this paid position after his father’s death in 1683/4 required him to resign his fellowship in the Society for a time, since the clerk, who replaced the position of paid secretary, could not be a Fellow. It ought to be noted that, In contrast to what others have argued, Cook (1998) thinks that Halley had quite ample income in this period (at least $60 per year from his father, to begin with). 28) He received 50 copies, plus another 20 to cover another $20 owed him.

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Chapter 6

The Society After the Principia: 1688–1703 The Society continued to experience a malaise into the 1690s, with, as we have seen, a growing divide between the Newtonians and natural historians. At the anniversary meeting in November 1688 when elections ought to have taken place, there was no quorum; rescheduled in April, there were again too few votes.1) For a decade in the 1660s, Hooke’s experiments had formed the centerpiece of Society meetings, and then for nearly a score of years thereafter there often would have been little substance at meetings without the discussions he provided. But as the new decade opened, with his physical and intellectual vigor beginning to decline, Hooke was no longer able to carry the Society on his own. His experimental contributions had been waning for some time, even though his architecture and building activities were also winding down, and increasingly his comments at meetings were retrospective. By 1690 or 1691 his torch as the intellectual leader of the Society had begun to pass to Halley, even though there was hardly a meeting at which he did not speak, and even though Halley was often gone. 2) But as Halley slowly began to assume the role that Hooke had played for nearly three decades, he did so in a characteristic Halley manner. He was much more a mathematician than Hooke, and frequently his comments were on mathematical questions.3) But Hooke would continue to be an important presence for another decade, and he attended nearly every meeting even into 1701.4) In addition to Halley and Hooke, the names of Sloane, Hoskins, Southwell (president 1690–95) as well as Evelyn, Henshaw, and Hunt, are prominent in the minutes for the early 90s. Boyle, as was his wont, and in declining health, was rarely if ever present, but on 19 December 1688 «Mr Boyle sent his man» to perform an experiment, and he did the same three weeks later.5) The choice of Lord Montague (1695–98) and the Lord Chancellor, Lord Sommers (1698–1703) as presidents continued the recent practice of having an eminent figurehead leading the Society, leaving it without any real leadership at a crucial time when its membership was dwindling, and as Hooke faded and Halley spent much time abroad, it was drifting intellectually. Sir John Hoskins, as Vice-president, had

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to preside over virtually every meeting for the better part of a decade, and he along with Sir Hans Sloane, who shared secretarial duties with Waller, provided what little direction there was. Newton’s eventual election as President in November 1703 restored scientific leadership to the Society; he would miss only three Council meetings during his first 20 years in office.6) Echoing the larger problems of the Society, the resurrected Transactions went through hard times in the late 1680s and early 90s, with only five numbers being published between December 1687 and October 1692, an average of one per year. And almost as though the Principia left everyone speechless, none at all were published in the years 1688–90.7) According to the Council minutes for 27 November 1689 Hooke offered «to print Treatises in the Nature of Philosophical Transactions» and it was agreed that the Society would purchase 60 copies if he did.8) Nearly a year later little progress had been made when the Council ordered that «. . . Mr. Hook have the postage of all Letters of Philosophical Correspondence allowed him on condition that he publish Transactions or Collections as formerly, and that in Consideration thereof, the Society will take off Sixty Books according to the Order of Council November 27th 1689.»9) As late as the following January Hooke reported of a meeting that there was «much talk of transactions to little purpose.»10) Despite what we can assume were good intentions, little happened, and the situation only changed in February 1692/93, when Waller announced he would be handling the Society’s correspondence and the Transactions as well; publication resumed, again at the rate of about one per month. Correspondence with the continent and other parts of the British Isles had also flagged, and in April 1691 it was ordered that «Dr Gale, Dr Aglionby, Mr Waller & Mr Halley be a Committee to Consider of the means of reestablishing the Societys Correspondence.»11) In this period the secretaries were Thomas Gale, who served between 1685 and 1693 (also 1679–81), and would become Dean of York,12) Richard Waller in 1687–1709, and Hans Sloane, who succeeded Gale and was sharing the office with Waller when Hooke died. But it was Halley, as Clerk, who had principal responsibility for the Transactions in those lean years between 1686 and 1692. Throughout the 1690s, the Society, guided by Hooke and Halley, pursued its interests in problems associated with negotiating the seas, including, as before, depth sounding, diving bells, determining the speed and direction of a ship through the water, weighing a ship, magnetic variation, and as always, determining longitude. We address Hooke’s role in these investigations in Chapter 12. Halley continued as Clerk into 1696, followed Flamsteed as Astronomer Royal in 1720, and later would be on the Board of Longitude, responsible for awarding the prize that John Harrison (1693–76) finally won (more or less) in 1773. But he continued to travel widely, not satiated by his voyage at age 20 to St. Helena in 1676–8, and was especially interested in the problems of magnetic variation, determination of longitude, and the tides. The culmination of this interest in science at sea was his command of the vessel Paramour, which was to study magnetic variation by circumnavigating the globe.13) Although he set sail in 1698, preparations had been underway for several years, and this occupied much of the time he might have devoted to the Society and the Transactions.14)

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In the last decade of the century Halley discoursed on light and optics, refraction by diamonds, on measuring the speed of a bullet and the flow of water from a vessel, the force of flowing water on a body, the earth’s magnetic field, the resistance of the aether to the earth’s motion through it, on various mathematical questions involving infinities,15) the so-called “Florentine problem,”16) extracting the roots of equations, etc. In this remarkable diversity of interests, we might be excused for seeing the influence of Hooke’s omnivorous intellect on Halley. Both Hooke and Halley contributed to the unrelenting interest in the problem of determining longitude at sea, and the related navigational problem of the compass variation was one in which Hooke had been interested long before Halley studied it extensively on his voyages. The complex problem of the moon’s motion was at the center of Halley’s attempts to find a reliable way to solve the problem of finding longitude at sea or in distant places. In the absence of accurate timing,17) and with the realization that the use of eclipses of Jupiter’s moons for the purpose, as Galileo had proposed, was unfeasible at sea, the best hope was the moon.18) Others, such as Flamsteed, were also interested in this challenging problem, though this common interest led mostly to acrimony. On his Atlantic voyage Halley used both astronomical techniques, but the lunar method, based on stellar appulses or eclipses of the moon, required an adequate lunar theory, which, even after the Principia, did not exist.19) Newton’s lunar theory, “perfected” by 1702, while undoubtedly a great theoretical triumph, was not equal to the practical task of generating precise lunar positions over long periods of time, and Halley’s great contribution was to recognize that eclipse cycles, especially the period of 19 eclipse years which he misnamed the “Saros,” was the key to accurate prediction. This discovery resulted from his efforts to reconcile ancient Babylonian astronomical observations (especially of eclipses) with predictions, and he ultimately invoked a retarding effect on the Earth’s rotation due to the aether. His provocative conclusion was that if the earth’s rotation was slowing, then the «Eternity of the World was hence to be Demonstrated impossible.»20) We find Halley speaking of lunar theory and the Saros cycle of 223 months at meetings in November and December 1692, 21) but his involvement with the problem had actually begun a decade earlier, though his father’s death had induced him, as we have noted, to take a position as the Society’s Clerk, interrupting his lunar observations. However, this interest never waned, and he pursued it vigorously as Astronomer Royal. This preoccupation with lunar theory represented an intersection of his friendship with Newton and his role in the birth of the Principia, with his interest in accurate determination of longitude, though some of Halley’s earliest observations of eclipses were made with Hooke. In March 1692/3 an experiment «on the strength of Mr Waller’s loadstone» involved taking actual data – a much-neglected practice at meetings in this period. In November of 1693, a Mr. Roberts of Dublin argued that it was futile to attempt to observe the annual parallax of the Earth, because the fixed stars are «. . . so far remote that the motion of Light rapid as it is, is longer a coming from the fixt stars, than an East India voyage may be performed.» An interesting and surprisingly accurate observation, though one whose implications were clearly misunderstood.

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On 19 April 1699, by which time he had been living in London for three years, Newton made one of his rare appearances at a meeting when he commented on Omerique’s Analysis Geometrica. He was again present on 16 August, displaying an improvement of the sighting device that Halley had used to determine longitude, presumably a sextant. The Society then adjourned until October, whence, on the 25th we find that «Dr Hook said that the Instrument mentioned last meeting was of his own Invention before ye year 1665 . . . ,» a modest “dig” at Newton. Previously, in July and August, Hooke had revived his earlier ideas about parallax and further discoursed «in Vindication of his Astronomical works.»22) Thirty years had passed since his attempts to measure parallax without, it appears, much evolution of his understanding of it. Little of the Society’s business in this post-Principia period reflects the upheaval which the Principia would eventually cause, the only exception being some of Halley’s discourses on the moon, which ranged from his attempts to date events in the history of classical Rome and Greece from lunar phenomena, to calculations of contemporary phenomena. If there was a shift away from natural history before Newton came to preside over the Society (and we have alluded to some in the previous chapter), it was indeed small, but there was certainly growing tension. Although the Society’s correspondence had declined greatly since Oldenburg’s days, there was still a good deal of foreign intelligence, and the twenty-year correspondence with the microscopist Leeuwenhoek continued. In the fall of 1700 letters were read from Leibniz, Cassini, and de Moivre, while Halley, and sometimes Hooke, would report what had appeared in the French Journal des Sc¸avans. Hooke continued to remind those assembled of his earlier discoveries, especially when some new claim of priority was made, and occasionally Halley would attack his nemesis Flamsteed, as on 1 June 1992 when he read a paper «being a vindication» of his observations at St. Helena «from some groundless Exceptions of Mr. Flamsteed.»23) There was almost no hint of the nascent controversy over the priority over invention (should one say discovery?) of the calculus, which began when Leibniz published his own version in 1684. The appearance of the third volume of Wallis’ Opera in 1699, in which Newton’s priority was made clear, caused nary a ripple, and the controversy simmered for over a decade before exploding in fireworks in 1711.24) One notes, however, that on 19 May 1700 «Dr Hook read Dr Wallis’s letter to Mr Leibnitz concerning measuring curv’d lin’d figures . . . » Halley again edited the Transactions between 1714 and 1719, when he was Secretary. He would die in 1742 at the age of 85, still Astronomer Royal, far outliving all the others who appear in this narrative except Hans Sloane, even including Wren who lived to the age of 90, dying in 1723, and Newton, who at his death in 1727 was 84. Boyle, Huygens, and Hooke, along with Pepys and Locke, had all died within a 12 year period at the end of the century. Hooke’s death came on 3 March 1702/3 and Newton quickly assumed the presidency at the November elections later that year. Just three weeks after Hooke’s death, the Society was informed by the City of London that it must now move its possessions from Gresham College where Hooke had been the last professor in residence, and though it was given a respite, in 1710 it made its move to Crane Court.

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The Society had survived its first four decades as the world’s preeminent scientific society, though not without recurring crisis. At the very center of the scientific revolution, it was the stage upon which the experimental philosophy was visibly put into practice and given some formal structure in terms of witnessing and replication. It brought into being the first real scientific journal, created and nurtured a wideranging correspondence among the leading mathematicians and natural philosophers of Europe and, if somewhat reluctantly, brought Newton’s great work into print. Well over a century later, in some respects still a prisoner of its aristocratic origins, the state of the Society prompted Charles Babbage to deplore the decline of English science, stimulating the establishment of the British Association for the Advancement of Science by David Brewster and others as an alternative.25) But today, nearly three and one half centuries after its founding, the Royal Society of London thrives, and is still perhaps the most prestigious scientific society in the world.

Annotations 1) According to Hooke, «about 23» members were present. The election was postponed to St. George’s Day. In his Diary for 23 April Hooke writes «Royal Society met, but not enough to make an election.» (Gunther, 1935, Vol. X, p. 115). 2) It needs to be emphasized that the reason we know Hooke was present, or Halley, is because something was contributed that found its way into the minutes. So as Hooke’s health declined, it is possible that he had nothing to say at one meeting or another, though there is not much evidence of that. As an example, however, he was apparently present on 14 and 21 November 1688, based on his Diary, but does not appear in the minutes (Journal Book). 3) On Halley, see Cook’s recent biography Edmond Halley: Charting the Heavens and the Seas (Cook, 1998), as well as the somewhat dated Edmond Halley by Angus Armitage (Armitage, 1966). 4) That Hooke may not have been entirely happy with Halley’s new role is suggested by passages such as these: «Hallys way to lash guns absurd», Diary II, 14 December 1692, Gunther X, p. 197; «Halley read a paper of taking Right Ascension and Declination of Stars: the same with what I have printed.» Ibid, p. 199, 21 December 1692. 5) Although Boyle regularly attended meetings in the early years of the Society, his participation declined substantially in later years. Actually his pattern of attendance is quite interesting, and somewhat perplexing, with Boyle frequently passing on Council meetings but attending general Society meetings the same day, a pattern which deserves some attention. 6) Westfall (1980), pp. 627–630. Conduitt said that Newton was Sloane’s second choice, after Christopher Wren, who had been president once before.

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7) With apologies to Mordechai Feingold. No transactions at all were published in the years 1688–90. But between 1692 and 1705, the average was nearly 9 per year. In fact, the problems with the Transactions were inseparable from that of finding a stationer or printer who would take on the job of publishing them, especially after their interruption during Hooke’s tenure as secretary. See, above all, Adrian Johns’ Miscellaneous Methods (Johns, 2000). But the suspension of publications in 1688–90 was not unrelated to the worsening political situation. In 1691 the editor noted that the suspension was due to «the unsettled posture of Publick Affairs.» In 1698 the Society began the practice of dating the Transactions from January 1 rather than March 25. 8) Almost a year earlier, on 9 January 1688/9, a meeting day, Hooke had raised the issue with those present at Jonathan’s after the meeting; he records «Agreed by all.» Gunther, X, p. 89. In his Diary entry for 27 November 1689 Hooke wrote that «I propounded Collections. Hill found tricks: voted against me.» (Ibid, p. 167). 9) Council Minutes, 27 November 1689 and 22 October 1690. 10) Journal Book, 25 January 1692/3. 11) Less than a month earlier, Hooke wrote in his Diary for 7 December 1692 «A councell of Royal Society Hosk[ins] and Hill; shuffled of Plot and Mr Waller, and made Hally to be Secretary. None els sayd anything, soe councell brake up, nothing done: noe Transactions, noe correspondence.» 12) Gale was born in the same year as Hooke (1635/6 anyway), was also a product of Westminster School, and died less than a year before him. 13) In the end Halley sailed below 52◦ South latitude where he had a close call sailing among icebergs in a heavy fog, in February 1698 (Armitage, 1966, p. 143). The Paramour was 64 ft long. 14) When he returned in 1699, he, who had always been addressed in the minutes simply as “Hally”, became “Captain Hally.” 15) One of his lectures on infinities came on Ash Wednesday, 13 February 1688/9. It was on this day that William and Mary were offered and accepted the English throne. 16) Which involved the curve described by the intersection of a cylinder and a sphere. Wallis’s and David Gregory’s solutions were published in the Transactions for January 1692/3 (17, pp. 584–6) and 1693/4 (18, pp. 25–29). 17) One notes that despite the efforts of both Hooke and Huygens and the controversy between them, the invention of the balance-spring time-piece had little direct impact on the problem of determining longitude for the better part of a century.

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18) This involved the timing of lunar appulses or eclipses, which would occur at essentially the same instant wherever they were visible, though the former is affected by parallax. See fn. 21. 19) See, for example, Kollerstrom (2000). As is usual with Newton’s mathematical works, the ultimate source is Whiteside (1967, Vol. VI). He speaks of Newton’s «relentless, courageous efforts,» and his «fudging it in a sophisticated but logically unfounded manner.» He also quotes Machin describing the lunar theory as «all sagacity,» and Newton himself as saying that “his head never ached but with his studies on the moon.» 20) Journal Book, 19 October 1692. Halley’s interests were as wide as Hooke’s, and his experience of the world much greater. His studies of the chronology of the classical world included applications of his astronomical knowledge and calculational ability to date events in the Greco-Roman world. For example, he argued in the Philosophical Transactions for March 1691 (v. 17, No. 192, p. 495) that Julius Caesar had landed in Britain on 26 Aug, 55 B.C. (Gunther’s A.D. is a typo). Hooke commented in his Diary only «Hally of Caesar’s landing.» (Gunther, 1935, vol. X, p. 181. Halley’s comments on eclipses and the “Saros cycle” of 223 months on 2 November 1692 were related to this work on chronology. It is difficult to know whether Halley was consciously trying to shed his reputation as a skeptic or unbeliever, with future positions in mind, or whether he was undergoing a conversion. Or for that matter, whether Whiston and others were right in their judgment on him. It is said, however, that he failed in his attempt to obtain the Savilian professorship in astronomy at Oxford in 1691 because of his questionable beliefs. 21) Journal Book, 2 and 23 November, and 7 and 21 December, 1692. See, for example, Armitage (1966), pp. 46–48. An entertaining account of Halley’s interest in the problem of the moon is in Steel (2001), pp. 89–93. Hooke’s Diary entry for 7 December noted that «Hally spake of a way of his to solve the Moons motions, being an improvement of Horrocks.» Halley was interested in eclipses, especially lunar eclipses, for two reasons. First as a test of Newton’s lunar theory, and second, as a way of determining the longitude. He also tried to use the Moon’s position for the same purpose (see above). Lunar eclipses have several advantages over their solar counterparts, especially the fact that the timing of the several “contacts” is the same for all observers viewing the eclipse. Comparing the calculated time at Greenwich, say, with the local time yields the longitude. Halley had first discussed eclipse prediction using the Saros cycle when on 16 October 1689 he showed that, starting from the total lunar eclipse of 8 September 1671 (Old Style), he was able to predict the eclipse of 19 September 1689, 223 lunations later. In his Diary for that date, Hooke writes: «at 12.39 12 mane [a.m.] began Eclypse of the Moon. Immersion at 1.36. Emersion at 3.18; the end at 4.19. Sat up to 5 mane.»

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Chapter 6. The Society After the Principia (Gunther, 1935, Vol. X, 149). Evidently he did not view it with Halley, although he was in town since Hooke had coffee with him at Jonathan’s the previous day. Nineteen eclipse years of 346.6 days span a duration of 18.03 years. The consequence is that nearly identical eclipses repeat every 18 years and 10–11 days, though displaced slightly in latitude and by about 115◦ in longitude. The history of lunar theory is a fascinating one that would take us far beyond the purpose of this chapter on the Royal Society. Briefly, however, Newton’s attempts to derive an accurate representation of the moon’s motion from gravitational theory was a failure. The result was that he adopted the sixty year old “theory” – or rather, kinematic model – of Jeremy Horrocks. This description of the moon’s motion was the basis for Newton’s “Theory of the Moon,” published in 1702 in David Gregory’s Astronomiae elementa. Halley’s insight was that he could improve Newton’s parameterization by using the Saros cycle whose length of 18+ years allowed accurate calibration. Good sources on the lunar theory are Cohen (1975) and Kollerstrom (2000).

22) Journal Book, meetings of 19 July and 2 August 1699. 23) Journal Book. If Halley was something of a Hooke prot´eg´e, he was also Flamsteed’s, until he assumed the task of bringing the Principia into print and they fell out. 24) Westfall (1980), chapter 14, but especially p. 712ff. 25) And indeed, the BAAS was at the forefront of British Science in the nineteenth century.

Chapter 7

Scientific Virtuoso: Hooke 1655–1687 First Discoveries Robert Hooke’s four decade-long scientific career is inseparable from the Royal Society of London, to which he devoted his entire scientific life.1) The Society was the vehicle through which he became a natural philosopher, and in many respects it made possible his other important career, as surveyor, builder, and architect, however much those two careers conflicted with each other. Although Hooke’s scientific life began in Oxford when he was not yet 20, little is known of his activities until 1658, when he first appears on the books of Christ Church College, despite the fact that he spent as much as nine years there, between about 1653 and 1662. 2) This was a crucial formative period for the young Hooke, who arrived at Oxford straight from Westminster School and the tutelage of Dr. Busby, but left nearly a decade later as a maturing young scientist3) to become the Royal Society’s Curator of experiments. Thus began Hooke’s career as effectively the first professional scientist. It seems to have been in 1655–56 that Hooke made his first original contribution to science. In fragments of an autobiography written in 1697 he recounted his early attempts to improve the pendulum clock for timing astronomical observations, and reported that «in the Year 1656 or 57, I contriv’d a way to continue the motion of the Pendulum, so much commended by Ricciolus in his Almagestum, which Dr. Ward had recommended to me to peruse.» This is assumed to describe Hooke’s invention of the recoil anchor escapement, which would eventually replace the verge and crown wheel escapement that Huygens had invented in 1658. This discovery is not without some controversy, since the earliest extant clock with an anchor escapement is one made by William Clement, dated 1671, and Joseph Knibb has also been given credit. But the evidence favors Hooke, including references in the minutes of the Society from 1669, describing what was probably the anchor escapement.4) It was, in any case, effectively the first of a very long string of inventions. But Hooke had already become interested in the important and nagging problem of determining longitude at sea, which required a clock that could maintain long-term accuracy under the harsh conditions of a rolling ship in hostile weather. With that in

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mind, he discarded the pendulum and constructed model clocks, and eventually a pocket-watch, which were spring-regulated, possibly as early as 1658, when he was 23. Although he was advised by Lord Brouncker and Sir Robert Moray to seek a patent for the discovery, for a variety of reasons he chose not to do.5) As it turned out, that was a bad decision, so that when Huygens introduced his own spring-regulated watch over 15 years later (1675), Hooke was reduced to a somewhat belated claim of priority, in an entirely disagreeable episode that pitted him against not only Huygens, but Brouncker, Oldenburg, and other Society members as well. That Hooke invented a spring-controlled escapement is beyond dispute; whether it was a spiral spring, as was Huygens’, is another matter.6) Hooke worked in Boyle’s laboratory in Oxford for at least four years, beginning in 1659 and eventually leaving in late 1662 to assume the position of Curator of experiments for the young Society.7) During the time he was in Boyle’s employ, he assisted him with experiments and constructed the air pump which he and Boyle used in a series of successful pneumatic experiments (Fig. 8). The pump was described in Boyle’s New Experiments, Physico-Mechanicall, Touching The Spring of the Air, and its Effects of 1660, his first published scientific writing and the first notable work of Restoration Science. Hooke wrote of «the Honorable Mr. Boyle’s pneumatic engine» that in 1658–9 he, Hooke, «contriv’d and perfected . . . for Mr. Boyle, having first seen a Contrivance for that purpose made for the same honorable Person by Mr. Greatorex, which was too gross to perform any great matter.» Boyle’s description of the design of the air-pump was similar: «. . . I put both Mr. G. and R. Hook . . . to contrive some Air Pump, that might not like the other, need to be kept under water and might be more easily maintained. And after an unsuccessful tryal or two of ways propos’d by others, the last named Person fitted me with a Pump, anon to be described.»8) Within a few months the relation between volume and pressure, popularly known as “Boyle’s Law,” was established. Laying aside the question whether this law should properly be associated with the names of Henry Power and Richard Towneley rather than Boyle, it is clear that major credit for Boyle’s contribution is due Hooke.9) In some respects, these pneumatic experiments represented Boyle’s most successful experimental effort, and the rest of his career consisted of experiments in chemistry and/or alchemy, writings about experiments and experimentation, and above all, his extensive and influential writings on natural philosophy.10) Judging from the rest of his experimental career and weighing the preface to New Experiments in which he recounts the health problems 11) that plagued him in the period during which the pneumatic experiments were performed, it is clear that he relied heavily on Hooke, not only to construct the pump, but to carry out the experiments (though he also employed a “pumper.”) Nevertheless, Hooke was Boyle’s assistant and apprentice, and it is certain that Boyle, who was 8 years Hooke’s senior, who had been involved in

Chapter 7. Scientific Virtuoso: Hooke 1655–1687

Fig. 8

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Boyle’s air-pump, designed by Hooke. From Boyle’s New Experiments, Physico-Mechanicall. By permission of the Royal Society of London.

scientific activity, mostly chemical, since his early twenties,12) and had been a member of the “Invisible College,” did propose and guide these experiments carried out by the young Hooke. In the years that he apprenticed to Boyle, Hooke not only worked with the air pump and on the related phenomena of the rise and fall of the barometer, but on

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the thorny problem of capillarity as well. His first published work was a treatise on the subject, “An Attempt for the Explication of the Phenomena Observable in an Experiment Published by the Honorable Robert Boyle”,13) published in 1661. In the dedicatory preface to this work, Hooke paid homage to his mentor and patron in language so elaborate and florid that it probably will astonish the peruser of his curt and laconic Diary: «I must therefore with the Persian offer to you, as he to the Sun, what he believes himself to have received from it. And therefore I trust my endeavouring to soar aloft with the Eagle, to enjoy the Influence of the most Glorious Light of the world, will find a Pardon, and be judged much better, than a hovering and Fluttering with the silly Fly about the dim and fading Flame of a candle . . . » He also hoped that he might be successful in offering «this Oblation, which is but a few drops taken out of the River (as I may so speak) of the Phaenomena of Nature (which passes by, and is scarce regarded by any, though free for all) that is, some few observations, which though but mean and obvious, yet I think scarce deligently taken notice of by any; and though jumbled together in a careless, if any Method, yet the best I had leisure to throw it into.» Soon Hooke would leave Boyle’s employ and assume the duties of Curator of experiments for the Royal Society.

Hooke and the Royal Society, 1662–1677 Almost everything that we know of Hooke’s role in the Royal Society, which is where his scientific virtuosity was displayed, comes from its archives,14) especially the Journal Books or Birch’s abridgement of those journals (up to 1687) in his History of the Royal Society of 1756. The Diary, which as we have it, begins in 1672, tells us more of Hooke the man than of Hooke the scientist. Early on he had very little independence, and frequently – perhaps as often as not – his experimental investigations were determined by the interests of members, thus diverting him from other more fruitful or more fundamental studies, or at the very least, from his own interests. He almost always had a clearer idea than his contemporaries of which problems were important and which were not, even in these early years, but his ability to pursue his own ideas was compromised by his obligations as Curator. One can only speculate how coherent a scientist he might have become had he enjoyed, say, Boyle’s independence, or, for that matter, Newton’s. Thus he would pursue a problem for a while, and when the interests of the Society turned elsewhere, so, it seems, did his. Some problems come up time and again over a long period of time, such as that of “elliptic motion”, but few are pursued systematically or continuously.

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Too often the result was that others eventually took a problem out of Hooke’s hands, as Newton did in the case of planetary motion. But whatever his shortcomings, his failure to bring projects to completion, his inability to systematize his knowledge, sometimes even to translate an idea into an experiment, Hooke had a remarkable ability to think a problem through and to formulate an explanation which was rational and sound. His superb physical intuition shines through in all his work. As one turns the pages of Birch’s History, or the original Journal Book, he is constantly struck by the fact that Hooke’s explanation of a phenomenon is almost always the clearest and most plausible, contrasting starkly with the sometimes romantic speculations of other members. Only rarely do we see someone else, a Wren, or Wallis, or Petty, speak with the same clarity and sound physical reasoning that is typical of Hooke. Not infrequently his explanations foreshadow those given decades or more later, which is not to say that he was anything but a product of his time, because he manifestly was. One of the consequences of the omnivorous character of Hooke’s interests and the direction he got from members is that summarizing his scientific career is difficult. With one or two exceptions, it has no “arc” to it, no progression toward a climax or great achievement. The main exceptions were his sometimes fitful focus on the problem of planetary motion for two decades, beginning in 1665, and his life-long interest in changes in the earth, vulcanism, and earthquakes. Apart from these important questions, we see him returning time and again to many of the same topics, without substantial progress.15) As we learned in the previous chapter, Hooke became the Society’s Curator of experiments in late 1662. For better or worse, he would hold this position for over two decades, and for all practical purposes, twice that, offering experiments, discoursing on a wide range of topics, gradually becoming the central scientific figure in the Society. Those four decades would also see his evolution into a major figure in Restoration natural philosophy, but there would be many rocky times ahead, both for Hooke and the society he served. Much has been made of the effect of Hooke’s status as a mere employee of the Society, whose membership consisted mostly of men of means: aristocrats and other gentry, clergy, physicians, and academics. While he was without wealth or a clearly defined social status, he was the son of the curate of a small parish and had an Oxford degree. The Church was an option, but otherwise he was without prospects. The decision to take a paid position with the Society, carrying with it at best modest status, combined with his lack of independent means, meant that he would never be the social equal of his Society colleagues. His position was far above that of the tradesmen which whom he dealt on a daily basis, or the instrument makers with whom he exchanged design ideas and fabrication techniques. And yet even his appointment as Professor of Geometry at Gresham College in 1665, obtained with Wilkins’ help, and his election as a Fellow of the Society (FRS) in 1663, effected only a modest change in his status in the Society. Brilliance and inventiveness would carry him only so far, and he was at members’ beck and call for nearly two decades. Before he became Curator at the end of 1662,16) he was often “desired” to bring in an experiment for the edification of the membership. When he became an employee, however, the

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form of request changed to “ordered,”17) and remained that way until the early 1670s, when his growing prestige and international reputation demanded somewhat greater respect.18) Even then it was only with great difficulty that he escaped the fact that he was an employee, a position which provided some members with the excuse to treat him as a subordinate. The innate schizophrenia of his status as an employee on the one hand, and, increasingly, the central scientific figure in the Society, was a source of tension that is evident on virtually every page of his Diary and is a major source of his reputation as a malcontent. Throughout his service for the Society there was grumbling about the way he was acquitting himself as Curator,19) especially in the aftermath of the Fire, when his other duties, as surveyor, engineer, and architect, came to occupy much of his time. This criticism was often deserved, because he was seriously over-committed, but he was often unhappy with what he perceived as dismissive treatment by some Fellows, more on the grounds of status than performance. Hooke would be in his fifties before it could be said that he gained a kind of universal respect. We can divide Hooke’s long association with the Society more or less naturally into several distinct episodes, as his attention was diverted to one task or another or as his personal star rose or fell. We might think of these as consisting of the first decade or a bit less, when his experiments were the life-blood of the Society, his reputation was on the rise, and he had only just begun to be heavily involved in surveying and architectural duties; the next six years which preceded the death of Oldenburg in 1677, characterized by intense work with Wren and for the City, but as well by the controversies with Newton, Leibniz, Hevelius, Huygens, and Oldenburg in the mid-70s; the succeeding decade in which a rewarding period of influence in the Society ended unhappily with the publication of the Principia and the death of his niece and ward Grace; and the final fifteen years of consolidation and decline, which nonetheless were ones in which he seems to have achieved a kind of honored peace.20) On 10 April 1661, only four months after the Society’s founding, Robert Hooke’s name first appears in the Journal Book, when it is proposed that the subject of the next meeting’s “debate” be Hooke’s tract “An Attempt for the Explication of the Phenomena,” on capillarity. Richard Waller later wrote that «This, together with his former Performances, made him much respected by the R. Society . . . »21) A year and a half later, in November 1662, Moray made the proposal to employ a curator, who would furnish three or four «considerable experiments» for each meeting, «and expecting no recompence till the society should get a stock enabling them to give it.»22) Probably upon Wilkins’ recommendation, Hooke was proposed and formally approved at the next meeting, and in recognition of his lack of means, was provided a salary. The 27 year-old’s first experiments as Curator were performed on 19 November. Thus began the long and mutually beneficial association which would last until Hooke’s death forty years later. It would nonetheless have fateful consequences for him, since he would be charged with offering several experiments for every meeting, something he did, week in and week out, with greater or lesser diligence, for a quarter-century. This played into one of his strengths, his remarkable range and ver-

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satility, but it also contributed to, or perhaps was the cause of, his greatest weakness: an inability, a reluctance, or a lack of opportunity, to pursue a line of inquiry to a conclusion. Many of these experiments were proposed by members, so that Hooke’s investigations were divided between his own proposals and ideas put forth by members. As an example, on 7 January 1662/3 he carried out two of his own fundamental experiments, to investigate differences in weight in warm and cold bodies (!) and the effect of temperature on the refraction of light, that he had proposed the previous week. But then he was directed to show how to make colored glass from white. Being Curator was a mixed blessing, to be sure, but the forum it gave him was one he could not have achieved in any other way. Hooke was elected a Fellow in June 1663 «and exempted from all charges,» reflecting his penurious state, but also his evident usefulness to the Society even at this early stage in his career. This change in his affairs, when he was not quite 28 years old, marked a significant promotion from mere employee to member. The following six or eight years were extremely active for him, as he satisfied his obligations as Curator by providing weekly experiments, and it was also a period of rapid maturation for him, in which he gradually became an essential figure in the Society, without whom it would have had little reason to exist. By early September 1664 Hooke had taken up residence at Gresham College, in anticipation that he would be made «professor of the histories of trades,» under the patronage of Sir John Cutler. Cutler soon founded a series of lectures, with Hooke as “professor,” for which he was supposed to be paid $50 yearly. In fact there was rarely any money forthcoming, a situation that was an irritation for Hooke for most of his professional life. In return for this anticipated beneficence, Cutler was made an honorary member of the Society.23) On 23 November 1664, it was proposed to license what would be Hooke’s magnum opus, Micrographia; the book, which established him as one of the founders of the science of microscopy24) (Figs. 6 and 9) was published the next year. He was not yet 30. These studies of Hooke’s with the microscope represented an intersection of his wide interests in natural philosophy and practical optics, dramatically supplemented by his talent as an illustrator. His drawings of small creatures seen under the microscope, some of the greatest masterpieces of early scientific illustration, created a sensation. Although he would never again manage an intellectual project of this scale, it established his reputation in England and on the continent, and influenced two of the greatest figures of seventeeth-century science, Huygens and Newton. We discuss Micrographia, which is far more than a book on microscopy, below. At the same meeting which authorized publication of Micrographia, the Council of the Society decided to have «a curator by office, and to allow him pro tempore 30 l. per annum . . . », and Wilkins nominated Hooke for the post, whose duties he had been faithfully performing for two years anyway. The Council took until 28 December to give Hooke final approval, recommending him to the entire Society, which elected him Curator “for perpetuity” on 11 January. The whole process had taken seven weeks, or, less generously, two years. It was assumed that Hooke’s salary would be supplemented by Cutler in return for «reading lectures of experimental phi-

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Fig. 9: Frontispiece from Micrographia.

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losophy», although as we have seen, this rarely materialized. Three weeks later the nature and conditions of Hooke’s proposed lectures, on “the History of Nature and Art”, were still being debated in the Council. Finally, on 20 March 1664/5, he was elected Gresham Professor of Geometry, a position he would hold until his death, and one which provided him with rooms, including a laboratory and a place where the Society would eventually meet, off and on, for much of the next 45 years.25) But the plague had already broken out in that bitter winter of 1664–5 and soon many of those who could, fled to the country. The Society continued meeting through the end of June, when meetings were suspended indefinitely,26) and Hooke, as we learned earlier, retreated to Durdens with Petty and Wilkins. As many as 6000 people were dying weekly at the height of the pestilence in the late summer of 1665, but by early December it was beginning to abate. The Society finally resumed meeting after nearly a year’s hiatus in April of 1666, and, uncharacteristically, continued to gather through the summer. The brief period of optimism that followed the waning of the plague in the winter and early spring of 1665–6 was thoroughly dashed by the fire which broke out in Pudding Lane on 2 September 1666, destroying 80% of the City of London in the four days it raged. Gresham was spared, being just beyond the northeast edge of the blackened area (Fig. 7), and the Society decided not to suspend its meetings, missing only the one scheduled for 5 September – clearly hoping to play a role in the recovery of the City. Hooke’s plan for rebuilding the City was presented less than two weeks after the flames were extinguished, and Wren and Evelyn, Peter Mills, and others also offered proposals. Although Hooke’s hastily submitted plans were rejected by the King, he could not have imagined at the time how much his life would change in the aftermath of the conflagration. For soon he was heavily involved in surveying the ruins and overseeing demolition. With no discernible background in codes and practices, construction, or architecture, he came to be one of the two or three most important figures in the enormous job of rebuilding the City. But these activities would take a heavy toll on his duties for the Society, and, ultimately, on his career as a natural philosopher. A hint of the scale and diversity of Hooke’s activities as Curator during this first decade of his involvement with the Society, which ends with the start of his Diary in 1672, can be gotten from the fact that Robert Gunther devoted nearly 400 pages in his Early Science in Oxford just to summarizing it. The only way to really appreciate the enormous volume of experiments he performed for the Royal Society and the wide range of phenomena he investigated from his first days as Curator into the mid 1670s, is to read the Journal Book of the Society or Birch’s proxy. Despite the fact that the ephemeral preoccupations of members often determined what experiments might be performed, it is still true that more often than not Hooke’s interests are the Society’s interests, and vice versa. With some notable and sometimes frivolous exceptions, the problems Hooke was thinking about were also those that interested Wren or Power or Petty or continental virtuosi like Huygens. For almost a decade Hooke’s contributions to the Society were so crucial that it probably would have collapsed without him and the experiments he provided. Al-

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though members were supposed to bring in experiments, they rarely did, so that without Hooke’s experiments, discourses, and comments, little of substance would have taken place beyond Oldenburg’s maintenance of correspondence with members well removed from London and with foreign scientists. And that correspondence might well have dried up without Hooke’s contributions to meetings and, of course, Oldenburg’s Transactions, which heavily emphasized foreign communications.27) But by the early 1670s Hooke’s growing obligations as surveyor and his own architectural projects were seriously impacting the time he had for preparing experiments. This is quite clear from the numerous references in his Diary to meetings with contractors, tradesmen, and visits to building sites, but also from evidence, in the Diary, Birch, and in the Society’s Journal Book, of his absence from meetings. In work that began in about 1668, and reached a crescendo in the mid 1670s, Wren had undertaken the task of rebuilding the parish churches of the City of London, an enormous project in which Hooke was deeply involved as Wren’s partner, and without whom Wren could not have assumed such a burden. This work went on for over two decades28) and Wren’s crowning achievement, St. Paul’s Cathedral, begun in 1675,29) was still incomplete in 1710. We find ample evidence that this work was not entirely independent of Hooke’s larger interests in natural philosophy, including his posing the problem of finding the form of an arch which would support any desired weight late in 1670, and there are many such examples of his interest in similar “engineering” problems, and often of his discussing them with Wren.30) The jewel in Hooke’s crown, so to speak, was his law of the spring, “Hooke’s Law,” which he extended to all elastic bodies, including wood and masonry. By 1670, with his activities as surveyor for the City in full swing, Hooke was clearly not prosecuting his curatorial duties with as much diligence as he once had. Having become dissatisfied with Hooke’s performance as early as fall and winter of 1668/9, the Council of the Society decided that it needed an additional Curator, and on November 10, 1670, it resolved that «Mr. Hooke be summoned to attend the next meeting of the Council, to receive their rebuke for the neglect of his office.» He was not present at that meeting and nothing seems to have come of it, even though by 1675 he was giving only cursory attention to these duties, for which he was receiving very little remuneration anyhow.31) Nonetheless, and despite this alienation, there was hardly a period between 1662 and the late 1690s, when Hooke was not providing the bulk of the intellectual leadership for the Society.32) During the next several years, at least up to the end of 1677, both as a result of his work in rebuilding London on his own and with Wren and of the bad blood between himself and Oldenburg,33) Hooke distanced himself perceptibly from the Society. These duties for the City would have limited his participation in any case, as Oldenburg noted in letters to Hevelius and Beckman as early as 1668; writing to the latter he said that «Mr. Hooke, whom you recalled, returns your greetings; at the present time, however, he is so occupied (with others) in the work of rebuilding this city that he can spare almost no time for other tasks.»34) But the combined effects of his duties as surveyor and architect and his problems with Oldenburg, Brouncker, and continental correspondents like Huygens and Leibniz, meant that Hooke was bringing

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in fewer experiments. His frequent absences, or lack of preparation when he was in attendance, made him less a factor at Society meetings until Oldenburg’s death. The year 1677 began as a difficult one in Hooke’s relationship with the Society, as, indeed, the previous three had been. He was reprimanded for his remarks about Hevelius’ work (see below), the president was exerting pressure on him about the Arundel House library, which was in his charge, he had trouble with John Martyn, printer to the Society, about the printing of his “Cometa,”35) and his relations with Oldenburg were at a low ebb: in May he recorded in the Diary that «Oldenburg fled at my sight.» We may assume, then, that Hooke was not entirely displeased when the Secretary died unexpectedly, apparently of a stroke,36) in September, one piece of evidence being that he immediately threw himself back into the life of the Society and even into his job as Curator. During the next five years Hooke is omnipresent, expansive, experimenting, discoursing on everything, again very much the intellectual center of the Society. This despite his other duties, which were near their peak. He had nearly twenty years as a professional scientist (natural philosopher) behind him, and in ingenuity and depth of insight had only his friend Wren – and Boyle, who rarely attended meetings after the early years – as competition, and in addition to being Curator he now became Secretary and a member of the Council. The next two decades would be difficult ones for the Society, but for Hooke Oldenburg’s death and the replacement of Brouncker, for whom he also had little respect, made his own life easier.37) Personally, he was at the height of his powers, his health was, for him, relatively good, and after Oldenburg’s death, he was the essential member of the Society. Absent Hooke, one can imagine that the Society might have collapsed entirely. Such was the situation in 1677, but his euphoria would not last, and Hooke still had opponents on the Council. But if his relations with the Society were never free of turmoil, his growing stature, almost as an elder statesman (despite then being only in his 40s), along with his successful architectural career, led to what must have been a rewarding decade that ended in 1687. Before we get to that decade, however, we pause to look at the relationship between Hooke and Oldenburg, who together gave the Society its reason to exist.

Hooke and Oldenburg, 1675–1677 Hooke’s deteriorating relationship with Henry Oldenburg is a fascinating but thoroughly sad episode in the early history of the Royal Society, involving the two men who were most responsible for its survival during those years;38) sad in that it led to a complete rupture in the relations between them that was embarrassing to all concerned. For Oldenburg had done much more than keep the Society’s correspondence. He had served as a clearinghouse for scientific dialogue involving much of Europe, and actively pursued correspondence with those in other countries he knew to be interested in philosophical questions. That correspondence, collected in 13 volumes by Rupert and Marie Boas Hall, is one of the crucial documents of seventeenth-century

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science.39) If the Society had two main functions, to practice and promulgate the experimental philosophy at home, and to spread the gospel across Europe, it was Hooke and Oldenburg, jointly, who were chiefly responsible for carrying out these distinct missions. As late as the winter of 1674/5 relations between Hooke and Oldenburg, both protege’s of Boyle, were apparently cordial. Oldenburg seems to have carefully and scrupulously promoted Hooke’s discoveries and inventions in the preceding years, including the latter’s supposed detection of the annual parallax of the earth and his new quadrant with telescopic sights.40) But all this would change in the spring of

Fig. 10: Hooke’s drawing of a quadrant employing a Hooke universal joint. From “Animadversions”.

1674/5, beginning with the announcement on 18 February of Huygens’ invention of the spiral balance-spring watch.41) An indignant Hooke was quick to point out that he had invented such a watch many years before (c. 1658) and that it was documented in the files of the Society and in Sprat’s History. 42) Anxious not to offend so important a foreign correspondent as Huygens, the Society cautiously ordered that «. . . Mons. Huygens, notwithstanding [Hooke’s claim], should be thanked for his communication and informed what had been done here; and what were the causes of its want of success.»43) Oldenburg transmitted this information to the Dutchman, saying that the members would «. . . suspend their judgement until they can have the advantage of the figure and a more ample description, principally in the face of Mr. Hooke’s having invented, some years ago, a similar thing, as he believes, which however did not then succeed entirely according to his hopes . . . ».44) Clearly some prejudging was going

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on and Hooke’s own view of the matter was, as he noted in his Diary, that «The Society inclined to favour Zulichems [Huygens].»45) While the details of the horological issues are beyond the scope of this work,46) it is quite clear that Hooke constructed a watch with some kind of spring-controlled escapement around 1658, though it is not clear that it was a spiral spring. At the meeting of 13 January 1663/4, Brouncker had informed the Council that «Mr. Hooke had discovered to himself, Dr. Robert Moray, and Dr. Wilkins, an invention, which might prove very beneficial to England, and to the world . . . » This is evidently a reference to the balance-spring watch, which Hooke said at the time that he had invented five years before. In the late winter of 1664/5 he returned to the question of determining longitude at sea, which either required a clock which could maintain a long-term accuracy at sea in spite of adverse environmental conditions and the roll of the ship, or the use of an astronomical method.47) While Huygens had tried to adapt the pendulum clock to this purpose, Hooke was convinced that this was entirely impractical. On 15 March he announced his solution, which he intended to put in the hands of the president. A year later it is recorded that «Mr. Hooke produced . . . a new piece of watch-work of his contrivance, serving to measure time exactly both by sea and land; of which he was ordered to bring in the description.»48) He would demonstrate the watch on two other occasions in the next five years, but the absence of any reference to these performances in the records of the Society would be at the center of a bitter controversy involving both Oldenburg and Huygens. In the aftermath of the presentation of Huygens’ watch, Hooke quickly decided that Oldenburg had conspired to deliver the secret of his invention to the Dutchman. The crux of the matter was the almost fawning attention given by the Society, and Oldenburg in particular, to Huygens’ announcement. Shortly thereafter, Hooke discovered that Huygens had sweetened the deal, as it were, by offering the English patent for his watch to Brouncker and Oldenburg. He wrote in his Diary for 6 March 1674/5 that he was «At Sir J. Mores [Moore’s]. he told me of Oldenburg’s treachery his defeating the Society and getting a patent for Spring Watches for himself.»49) For Hooke this was the last straw. Three months later he wrote in his Diary, «Oldenburg a raskall for not registering things brought into the Society . . . », and on 10 June noted that he had «reproved Oldenburg for not Registering Experiments,» and commented that «Brouncker took his [Oldenburg’s] part.»50) Moray, whose role (in 1663/4) we have already mentioned, had died in the meantime (1673).51) It is not surprising that Hooke was incensed and it is difficult to feel that Oldenburg acted honorably in the matter, since he clearly knew of Hooke’s priority. Hooke’s indignation was further fed by his discovery, after Oldenburg’s death, that the Secretary had deliberately failed to record his 1668–70 demonstrations. In a letter to Huygens in June 1675, Oldenburg seemed resigned to what he saw as Hooke’s «very peculiar temperament,» commenting (after Seneca), «No great wit without [. . . an admixture of madness] etc.»52) And during the Society’s summer recess of 1675 he was writing increasingly frantic letters to Huygens on behalf of Brouncker in the face of the apparent success of Hooke’s own watch, hoping that Huygens would furnish one which would surpass their Curator’s. On the other side

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of the channel, Huygens was livid with anger and dismissive of Hooke in his correspondence with Oldenburg: «I do not know how you put up with the ill-founded boastings of this man, and whether you have not considered whether, if he had had so useful and important an invention, he would have failed to avail himself of it and put it into effect.»53) Whether one believes that Hooke’s suspicions of Oldenburg were justified or not, especially in view of new details that have recently emerged, the unfortunate episode made Hooke bitter, alienated him from important members of the Society, and caused a number of Fellows to side against him in support of Oldenburg. Indeed there were probably some in the Society whose ill will toward him never abated.54) But it was Moray rather than Oldenburg who originally told Huygens about Hooke’s spring watch,55) even though the latter probably already knew of it. Moray had carried on an extensive correspondence with Huygens, exchanging information, ostensibly with the goal of advancing the experimental philosophy. He seemed to be driven by the somewhat conflicting dual motives of sharing information among philosophers, and the concern that Hooke’s slow pace of publication would allow others to outstrip English science.56) In this case, Moray was at the very least generous in letting Huygens know what Hooke was doing. On the other hand, Hooke’s invention had been already mentioned in Sprat’s History of eight years before,57) as Hooke himself pointed out, and could hardly be considered a secret. In any case, it is difficult to imagine that Huygens was unaware of what Hooke had done 15 years before. At the start of the episode, it could be said that Oldenburg had taken Hooke’s side,58) and to cite an example from a decade earlier, we see him writing to Huygens (7 October 1665) on another subject, that «For the impediments which Mr. Hooke has met with in the working of his [lens grinding] machine, I must first speak with the inventor before describing them to others, several circumstances having escaped me.»59) Through the early 1670s, Oldenburg consistently wrote highly of Hooke and was apparently scrupulous in guarding his (and others’) priority.60) All of this prompted the Halls, Rupert and Marie Boas, to ask «why blame Oldenburg?»61) While admitting that «Hooke had some reason to feel slighted . . . », the Halls excuse Huygens, Moray, Brouncker, and Oldenburg on the grounds that Hooke had never actually executed his idea, and that it was Huygens, years later, who actually produced a balance-spring watch.62) But it is quite clear that Hooke showed a completed watch to the Society in 1668, even though the minutes of the Society, maintained by Secretary Oldenburg, do not mention the event.63) While this has been clear for a long time, the reason for the omission has remained a mystery, and one can still only guess the motive behind it. In all probability the most important revelation in the recently discovered “Hooke Folio,” now in the library of the Royal Society, is the evidence of Oldenburg’s quite deliberate action to delete any reference to Hooke’s presentation. Among many pages which Hooke has

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transcribed from Oldenburg’s minutes, we find the original minutes for the meeting of 23 June 1670 (Fig. 11),containing a reference to Hooke’s watch, which has been crossed out so that it was absent from the Journal Book when Oldenburg’s minutes were transcribed. We know from his Diary that Hooke went through Oldenburg’s papers shortly after his death, and it was probably at this point that Hooke found the original minutes with the Secretary’s redaction, and made off with them.64) We are probably entitled to assume that the earlier omission (1668) was also deliberate, though what Oldenburg’s motive may have been then, nearly five years before Huygens’ watch was announced, is obscure. But Oldenburg’s duplicity, or at the very least, lapse in judgement, is now clear. Ironically, by “lifting” this page from Oldenburg’s catalogued draft minutes, Hooke prevented three centuries of interested parties and scholars from learning the truth, thus weakening his own case. Hooke had long known that Oldenburg had failed to record at least some of his demonstrations, though his ire surfaces only after the question of his priority in the invention of the balance spring watch was raised. But since his most candid comments are found only in the Diary, which began (as we have it) in 1672, this may not mean anything. During the two years preceding the Secretary’s death, he and Hooke were bitter enemies. The public dispute that ensued, not least in the pages of Oldenburg’s Transactions, was deeply troubling for the entire Society. If we now know that Oldenburg’s failure to register Hooke’s demonstration of the balance-spring watch was deliberate, it is difficult to understand why. Apparently a mercenary motive is revealed in the attempt to obtain an English patent for the spring-controlled watch.65) Oldenburg clearly had something at stake in Huygens’ watches turning out to be superior, and perhaps that interest was financial. He was often in financial straights and there is at least a hint that he may have exchanged information for money. He served as a sort of amanuensis for Boyle and was eventually paid for his work as Secretary, but was frequently searching for better employment.66) In passing, we might add that Oldenburg’s role in the controversy between Hooke and Newton was considered by many, including Newton himself, to have exacerbated that situation and perhaps not by accident or neglect. Hooke’s anger finally boiled over in a postscript which he attached to the published version of his Cutler Lecture “A Description of Helioscopes,” printed in October 1675, which concerned the construction of a telescope for solar observations. There he intimated that Huygens’ had learned of his invention of the balance-spring watch from Oldenburg, or at least from Sprat’s History of the Royal Society.67) As we have seen, something of the sort was likely the case, but since Sprat was freely available and since Hooke had failed either to fully develop or patent his invention, the charge is largely without force. On the other hand, Huygens never acknowledged Hooke’s priority or the intelligence he received from Moray. Oldenburg had anticipated Hooke’s broadside when, in describing Huygens’ watch in his Transactions in 1675,68) he implied, though of course he knew better, that Hooke learned of the balance-spring watch from Huygens in the Journal des Sc¸avans.69) Indignant, Hooke responded by appending a postscript to his next Cutlerian Lecture, “Lampas,” accusing Oldenburg of calumny, and dismissing him with «Speque metuque Procul hinc

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Page 83 from the Hooke Folio of 2006, showing Oldenburg’s excision of Hooke’s demonstration, on 23 June 1670. By permission of the Royal Society of London.

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procul ito. Ho.»70) “Lampas,” though nominally published in 1677, had already been printed by the Society’s printer, John Martyn, by October 1676. Hooke would not – as usual, one might say – have the last word, for on 2 November 1676 the Council of the Society ordered the publication of a defense of «Mr. Oldenburg’s integrity and faithfulness to the Royal Society . . . », and Oldenburg published replies to Hooke in his Philosophical Transactions for September and November.71) The readiness of the leaders of the Society to accommodate Huygens at the expense of one of their own, or to choose between their Secretary and Curator, is revealing. It clearly put a higher value on its connections with continental philosophers than on its Curator. In due course, the Council of the Society would again side against Hooke for his comments about both Hevelius and Flamsteed, and in both cases its actions could be seen as motivated more by politics than justice.72) In his Diary Hooke left no doubt about how he felt about the matter. In the entry for 3 September 1675 he notes that he «Writ against Oldenburg,» and a bit later he recorded that «Sir Chr Wren read my papers . . . against Oldenburg and approved».73) Both references probably concern the postscript to “Helioscopes.” In November he «resolved to quit all employments and seek my health.» Full of frustration, Hooke, with some of his friends, founded a “Philosophical Clubb”, which he described as being for “N[atural] P[hilosophy] and Mechanicks.” It was evidently not very successful, though it did meet, off and on. In October of the following year, Hooke again «Resolved to Leave the Royal Society,» wrote of «Great intrigues of Councell,» of the «Grubendolian Councell»,74) and called Croune «a Dog.» It was at this time that the Council was grappling with the question how to deal with Hooke’s attacks on Oldenburg in his postscripts to “Helioscopes” and “Lampas”. The revelation that Oldenburg intentionally suppressed evidence of Hooke’s demonstration of his pocket-watch is damning, and yet there is no evidence that he was generally duplicitous or consistently played favorites until the affair erupted into print and hot tempers overtook reason and good judgement. Nonetheless, the Halls’ view that «It was only after the dispute with Newton and Oldenburg’s subsequent death that Hooke began to blame Oldenburg for having mistreated his reputation in the 1660s . . . »75) is just not in accord with the facts. As early as January 1673/4 he had written in his Diary «Oldenburg treacherous and a villain,»76) and in the spring of 1675, after the first interaction with Newton but nearly 2 12 years before Oldenburg’s death, Hooke was again grumbling about the Secretary. After a meeting on 25 March he wrote in his Diary that he «suspected Hills whispers with Oldenburg», and following the meeting of 8 April he scribbled «Lord Brouncker & Oldenburg, discovered their design.» In the fall he wrote of a «Grubendolian Caball at Arundel House,»77) and the following year saw the two trading attacks in print, as we have already mentioned. No one emerges from this incident without some blame. Huygens had been informed at the time of Hooke’s earlier invention but failed to acknowledge that fact. And when attacked, Oldenburg escalated the public dispute, making the patently ridiculous charge that Hooke had gotten the idea of a balance-spring watch from Huygens, and eventually tried to obtain English patent rights for Huygens’ watch.78) And

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he had deliberately eliminated any mention of Hooke’s watch from the minutes. But it was sadly typical of Hooke, that by failing to follow up on an important invention or discovery, he had made it possible for someone else to take the invention from him, or at least to discover it independently. Specifically he had chosen not to patent the invention in 1660, against the advice of Boyle, Moray and Brouncker, had not developed it further, and had suffered the consequences.79) To the Halls, this «lack of persistence» was a defect in Hooke’s character.80) Such may very well be the case, but as we have already made clear, as Curator he was pulled in one direction and then another, according to the Society’s wishes, or, one might say, whims, and most importantly, the time he had to pursue natural philosophy was greatly compromised by his duties in rebuilding the City. Under the circumstances, we might take it as remarkable that he accomplished what he did.

Hooke and the Society after Oldenburg; 1677–1687 Hooke’s Cutler lecture “Animadversions on the first part of the Machina Coelestis,” challenging Hevelius’ failure to use telescopic sights on his quadrants, and indeed, pointing out they were no more accurate than Tycho Brahe’s of a century before, was published in 1674. The controversy simmered for more than a decade, with Hevelius’ final answer coming in his Annus Climactericus in 1685, just two years before his death. But it caused some discomfiture in the Society, and in January 1676/7 the Council made clear that what Hooke had published “against” Hevelius, «was done without any approbation or countenance» from it,81) again siding against its Curator. In many respects this was an unnecessary dispute, and not only because Hooke was clearly right in arguing that such sights made possible much more accurate observations. Evidently Hevelius was a careful observer with acute vision, so that his data were about as accurate as naked-eye observations could be, but as Hooke well knew, and Hevelius could have been expected to, they could have been greatly improved by using telescopic sights.82) A fateful consequence of Hooke’s assuming the new duties of Secretary in November 1677 was that he resumed a correspondence with Newton that had lapsed three years earlier (in February of 1675/6), with fond sentiments but little commitment. The two had also corresponded briefly after Oldenburg’s death, as Hooke began to assume secretarial duties. Thus, in December 1677 he responded to a request from Newton for some information relating to a correspondence between him and the Jesuit Antony Lucas, who was professor of Theology at Leige.83) Although the letter may have recalled the bad feelings that had existed between the two over their competing theories of light (Chapter 8), this time, between December 1677 and June 1678 Hooke and Newton exchanged a half-dozen quite civil letters.84) Picking up the correspondence again more than a year later, with a specific issue in mind, Hooke began formally: «Finding by our Registers that you were pleasd to correspond wth Mr Oldenburg and having also had the happinesse of Receiving some Letters from you my self, make me presume to trouble you with this present scribble.»85) Then he quickly turned to what was on his mind in this justly famous

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letter of 24 November 1679, asking Newton’s thoughts «of compounding the celestiall motions of the planetts of a direct motion by the tangent & an attractive motion towards the centrall body . . . » This was the first of six letters that would be exchanged between the two through early 1680, consisting of four from Hooke and two replies from Newton, which brought the latter back to the problem of gravitation and planetary motion after nearly 15 fallow years.86) What this correspondence wrought, Hooke would only learn four years later, as De Motu appeared and publication of the Principia approached. As we shall show in Chapter 10, Hooke’s letters caused Newton to reexamine the question of central attraction and elliptical orbits, and without doubt gave him the key to understanding the problem of motion under a central attractive force. It is hard not to see the 24 November letter as one of the most important in the history of science. Just before the annual election in 1680 Hooke was charged for the second time with asking Boyle to accept the presidency of the Society. Though he was duly elected, Boyle again declined the invitation, and after Henshaw also refused, Wren was chosen. This happy occasion apparently caused Hooke to offer «a more sedulous prosecution of the experiments for the service of the Society . . . » for which he was awarded an additional $40 for the year 1681. But while there was indeed a real resurgence in his dedication to Society affairs after Oldenburg died, it is apparent that the Council was concerned over the job being done by both Hooke and Gale as secretaries, and it complained that experiments had not been registered (ironically a charge Hooke had made earlier against Oldenburg!) and that correspondence was not being maintained. In an attempt to revitalize intercourse with the world at large, responsibility for foreign correspondence was shifted entirely to Gale, and Hooke was asked to continue the Philosophical Collections.87) Eventually Hooke’s desultory efforts during five years as Secretary seem to have exhausted the Society’s patience, and at the elections of 30 November 168288) he was voted off the Council and replaced as Secretary in something of a coup; Oldenburg, by contrast, had served unchallenged as Secretary for nearly 14 years. One point of irritation was Hooke’s failure to continue publication of the Philosophical Transactions, or at least a successful alternative, and within two weeks of his removal, the decision to resurrect the Transactions was made.89) While it is clear that anti-Hooke forces were at work, some of the dissatisfaction with his tenure was just political ebb and flow, with Wren departing the presidency in favor of Sir John Hoskins at the same time.90) Moreover, members, often notable ones, were voted on and off the Council regularly, merely to maintain a rotation among the membership; Croune, Gale, Flamsteed, Pepys, Petty, and four others suffered the same fate as Wren and Hooke in 1682. Two years later, Hooke would be returned to the Council along with Pepys, who would become president. Hooke’s tenure as co-Secretary had been five years, first with Nehemiah Grew (1677–79), then Thomas Gale (1679–81), and eventually with Francis Aston, who replaced Gale in 1681 and served for four years. Even after he was replaced as Secretary, Hooke was further chastised, or had his performance questioned, on several occasions during the following year, including 12 December.

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A visible consequence of the reorganization was that he again became noticeably disaffected.91) In February 1682/3 Tyson and Slare were asked to provide experiments at every meeting,92) and in June the Council, still dissatisfied, resolved «that Mr. Hooke shall receive every meeting day [an] order for the bringing in of two experiments at the next meeting-day, together with a declaration by word of mouth of the purpose and design of the experiments . . . and that at the end of every quarter there shall be a meeting of the Council, where his performances shall be considered, and a gratuity ordered him accordingly; and that from this time he have no other salary.»93) Birch records that when Hooke was called in two weeks later (June 20), he «declared his satisfaction therewith, and his resolution to proceed in his office of Curator upon those conditions.» Perhaps it was a relief for him to have his performance placed on a sort of fee for service basis, otherwise it is hard to see how he, the intellectual heart of the Society, and a man of no small ego, could swallow this bitter pill. In view of the fact that he would be found at his death twenty years later to be in the possession of an estate of over $9000, the income was unlikely to have been important. In any case, he did continue to perform his duties, though Papin94) was added as a temporary curator in April 1684 and soon became the Society’s de facto Curator until he left in late 1687 to take an academic position in mathematics at the University of Marburg. Thus while Hooke, who was nearly 50, was still performing experiments, he had major assistance by Papin, who regularly brought in pneumatic experiments, some of which had been carried out in collaboration with Boyle. Even his friend Halley, who was now on the Council, was «desired to bring in experiments at the meetings of the Society in the manner of a curator.»95) Hooke meanwhile had declared his intention «to write an historical account of the experiments he had shown the Society, together with a declaration of the use and consectaries of each, and an idea of natural philosophy built upon them.»96) As he gradually gave up primary responsibility for providing experiments, he spent rather more time reflecting on his earlier performances. He was off the Council again in 1685, then rotated back on the next year. In April 1684 Brouncker died, and later in the year Halley reported to the Society on his visit to Cambridge, where he had been shown by Newton «a curious treatise, De Motu . . . ». Of this, we will have much more to say. The years 1686–1687 saw the presentation to the Society of Newton’s masterpiece, an event which we might assume turned Hooke’s world upside down, but it is precisely this period for which we have none of his thoughts at all, except the guarded ones which were voiced at Society meetings (recall the 8 year hiatus in the Diary which ended in 1688).97) There is no reason to believe that the publication of the Principia was the cause of the suspension of the Diary, if there really was one. One might think it much more likely that Grace’s death was the cause, but the gap, as we have it, is 1683–88, beginning well before the Principia or Grace’s death. A romantic might ascribe it to Hooke’s obsession with the problem of planetary dynamics but there is little to support that either.

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From this point on, Hooke would labor in Newton’s shadow, realizing98) that he had given his rival the key which made the Principia possible, knowing that a new giant strode the earth, and that his own star was setting.99) While he would continue to be a force in the Society for the next decade, younger members like Halley began to dominate its deliberations. These post-Principia years of decline are discussed in Chapter 12.

“Restless Genius:” Hooke as Scientist Hooke missed few meetings of the Royal Society during a period of nearly forty years, attending perhaps 1000 meetings in all – as Curator, Fellow, Council member, and eventually, something of an eminence grise.100) During this long period he carried out experiments, read descriptions of experiments, or discoursed, at nearly every meeting. His interests were perhaps as wide as any man’s has been, a breadth to some extent fostered by the demands the Society put on him, but entirely in tune with his own voracious and omnivorous curiosity.101) It is this diversity that makes summarizing his activities as a natural philosopher in the three decades between 1663 and the 1690s a challenge, as his attention was diverted, time and again, from one interesting idea to an entirely different one, often with the result that a promising lead, once raised, is never followed up on. But in this section we will try to trace his interests as evidenced by his presentations to the Society, focusing on broad themes and especially crucial issues. Our judgement on what is worthy of special note will mostly reflect what the greatest concerns of the time actually were, e.g., planetary motion, pneumatics, the barometer, the problem of longitude, etc. Occasionally, it must be admitted, we will emphasize some notion of Hooke’s primarily or even solely because it foreshadowed future developments, was ahead of its time, or is the first known expression of the idea. Hooke and Newton were both products of their times, but both were bold and original thinkers and rarely followed scientific fashion. If this statement applies somewhat better to Newton than Hooke, it is largely because the latter was often at the beck and call of the members of the Royal Society. Initially Hooke’s experiments and discourses mostly concerned pneumatics, specifically applications of the air-pump. Early thermodynamics, if you like, though the connection of pneumatics with the nascent science of heat and heat engines was barely sensed.102) Hooke was especially interested in the weight of the air, which some argued103) was a chimera, and its springiness when compressed, following his mentor Boyle. These interests extended to the designing of a diving bell and other means of supplying air to divers. He also carried out so-called “Torricellian experiments”104) at Old St. Paul’s and later, the Monument, which he and Wren would construct to commemorate the starting point of the Great Fire (Fig. 12), and where, at least in principle, the effect of altitude on the barometer could be tested (see below). Related issues, such as the anomalous suspension of mercury surfaced occasionally at Society meetings, which frequently featured pneumatic experiments by Hooke and others.

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The Monument, erected to commemorate the place of origin of the Great Fire of 1666. Designed by Hooke and Wren, 1673–76. By permission of the Guildhall Library, Corporation of the City of London.

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Shortly after Hooke assumed the office of Curator, and in a reflection of the Society’s interest in pneumatics, we find the first proposals to put animals, a pigeon to begin with, into “Boyle’s engine”,105) in an attempt to study the role of air in respiration, and in February 1662/3 Hooke put a lamp and a chick in a closed vessel, to see if they would die at the same time. The role of air in combustion or respiration was only dimly sensed at this point, but experiments such as these led Hooke to believe that there was a “nitrous” component to the air which was essential for both106) . This was a germ of a theory of combustion to which Hooke would return from time to time. In all likelihood his interest in this important question was kindled by Boyle, who is known to have been thinking about it at least as early as 1660.107) In January 1663/4 Hooke again spoke of the «nitrous substance inherent and mixt with the air», and showed an experiment in demonstration, and he reiterated the theory again and carried out further experiments almost exactly a year later.108) These included one on combustion in an atmosphere of compressed air, and another in which nitre (saltpeter) was inserted into a closed vessel in which the fire had almost died, with the result that it revived, showing the similarity of effect of nitre and the “nitrous property” of the air. Hooke would elaborate upon this idea and it would be studied in various ways at Society meetings into the 1680s, at least. Recall that he not only subjected small animals to a depleted atmosphere, but, as we discussed in Chapter 4, eventually constructed a receiver that would hold a man, and in 1671 placed himself in it while air was being pumped from it. These experiments of Boyle and Hooke were important in the process of rejecting the Aristotelian view of fire as an element («it seems reasonable to think that there is no such thing as an element of Fire») and it is fair to say that they foreshadowed the discoveries of Lavoisier and Priestley of more than a century later109) On 24 December, 1662 Hooke gave an account of an experiment «concerning the decrease of gravity, by removing the body farther from the surface of the earth upwards.» He got a null result, requiring him to explain the positive result of a trial conducted earlier by Henry Power.110) Hooke would return to his question several times during the next two decades. And at meetings in January and February, he was experimenting with the important question of the force of falling bodies, having devised a device for its measurement (Fig. 13). 111) A number of interesting and important experiments were performed as 1662 drew to a close, which included exploring the «resistance of air to bodies moved through it» using pendulums, the related issue of the behavior of falling bodies in an exhausted receiver, and the motion of bodies shot vertically upward, or dropped, compared with the same bodies fired horizontally, timed with a pendulum. We noted earlier that this question was still being debated as late as 1670, despite Galileo’s Discoursi of 1638. Hooke’s interest in horology, which never waned, was also a major preoccupation of Huygens’, helping foster a somewhat tense and even acrimonius competition between them into the mid 1670s, as we have already seen. A by-product of this was a particular interest in the pendulum (“pendule”) in ways that went far beyond horology. We discussed earlier Hooke’s collaboration with Brouncker on the “seconds pen-

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Fig. 13: Hooke’s device for measuring the “force of falling bodies.” Birch, I, p. 195. By permission of the Royal Society of London.

dulum,” which beat with a period (or half-period) of exactly one second, but Hooke also studied the effect of gravity on the pendulum, as a test of how gravity varied with height, by comparing the period of oscillation at the top of St. Paul’s112) and eventually the Monument, with one on the ground, as he earlier had done with atmospheric pressure. If the results were inconclusive, the theory was sound,113) specifically the conclusion that if gravity were weaker, the pendulum would have a longer period. It was originally Huygens’ idea that the seconds pendulum might be employed to define a “universal measure.” His studies of the physical pendulum, the conical or circular pendulum, and pendula with cycloidal cheeks to accomplish true isochrony, went well beyond Hooke’s, but in a quite different direction. In particular, Hooke employed the circular pendulum as a kind of analogy for planetary motion, recognizing that there was a center-directed force which resulted in circular or elliptical motion, very much like a planetary orbit. He never regarded the analogy as perfect, or more

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than an analogy, but clearly gained important insights into the problem of planetary orbits by analyzing it.114) He went even further by using a compound circular pendulum to demonstrate the motion of two bodies about a common center of gravity, and in August 1666 he showed that the motion of a circular pendulum could be thought of as compounded from the motion of two linear pendulums, vibrating at right angles to each other.115) Perhaps the most interesting and important aspect of Hooke’s study of the circular or canonical pendulum is that we have, in his own hand, his demonstration of its isochrony for orbits of differing size only if the paths of the bob lie on a parabola of revolution.116) This offers one of the clearest insights into his ability to carry out a sustained mathematical argument in demonstration of a mechanical result. Unfortunately Hooke’s argument is far from convincing and raises the question whether he heard of Huygens’ result, and tried to reproduce it. Though from the very different (and faulty) form of the argument, one would think not.117) More interestingly, Hooke speculated, in a lecture on 14 December 1664, about whether our standards of time, based on celestial cycles, might not be variable. He even wondered if the strength of gravity might be variable, noting that the “magnetical properties” of the earth do vary. Thus, «if therefore the gravitation of the earth be magnetical, that may also alter.»118) While little more than conjecture, these speculations nonetheless reveal a subtle and probing intelligence possessed of great physical intuition. On 25 March 1663 we see that «Mr. Hooke was solicited to prosecute his microscopical observations, in order to publish them,»119) and within two years his Micrographia would be in print. We discuss it further below, but it is upon this work that what little reputation Hooke had during the two centuries after his death, rests.120) He entertained the Society during the next five weeks, and many times thereafter, by showing moss, «leeches in vinegar,» a female gnat, viper powder, and in September, he produced «a microscopical observation of the several parts of a fly.» On 1 April he was charged «to bring in at every meeting one microscopical observation at least,» and while this did not happen, microscopy would continue to be an interest of Hooke’s and of the Society, and it would come up from time to time at meetings, often because of a letter from Leeuwenhoek. In the fall of 1664 he was being asked by the members to experiment with the speed of falling bodies, which he did, from the «top of St. Paule’s steeple,»121) where, as we have seen, he also tested the variation of the period of a pendulum with height as well as the “Torricellian experiment,” the effect of height on the mercury column in a barometer.122) It was in March 1664/5 that Hooke announced a solution to the longitude problem, which we assume referred to the spring-regulated watch, that he said he had first constructed over five years before. This means of regulating a compact time piece would have no competition for nearly three centuries. In less than a decade the issue of the balance-spring watch would be the cause of the rupture between Hooke and Huygens and the break with Oldenburg that we have already described.

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In the late 1660s, both before and after the fire, Hooke carried out numerous interesting experiments on magnetism, studying the effects of interposing substances between a magnet and a piece of iron. The unique problems posed by magnetism were a continuing interest of several members in the spring of 1665/6, and Hooke in particular studied the dependence of a loadstone’s attraction on distance (4 April), «in order to find out, whether gravitation be somewhat magnetical.»123) Other experiments with magnetism were carried out, including one which used “steel dust” and a loadstone in the shape of a terrella (essentially a sphere) «which seemed to shew how the load-stone conforms to the earth.»124) Somewhat later, the experiments he used to illustrate the earth’s magnetic field led him to conclude that the earth’s magnetic axis revolved around its spin axis with a period of 370 years, but he acknowledged that the problem needed much more study. Some of these experiments were fundamental, in that they were designed to explicate the basic principles of magnetism, others were purely descriptive, and in other cases the motivation was a practical one: navigation. During the period of almost six months between resumption of meetings after the plague in 1665–6 and the onset of the fire, again Hooke explained his attempts to measure the dependence of gravity on distance, «either upward or downward», and on 23 May he read a paper «concerning the inflection of a direct motion into a curve by a supervening principle», referring in particular to planetary orbital motion. This is the first evidence we have of his interest in that fundamentally important question, which we will explore at length in Chapter 10. Various threads which weave themselves in and out of Society meetings in this period show Hooke’s continued interested in horology, microscopy, magnetism, particularly the earth’s magnetic field, optics, including the devising of machines (“engines”) for grinding mirrors or lenses of elliptical or hyperbolic cross-section. He would never lose his interest in these practical optical questions, which he regularly discussed with Wren. He also retained an interest in human-powered flight, which dated at least to his Oxford days with Wilkins, and was being hounded, as it were, by the Society, to honor his promise to measure the degree, that is, the length of a degree in miles at London, which is obviously a determinant of the circumference of the earth. This was also related to the question of the sphericity or shape of the earth, which was another interest of his.125) Hooke had continuing interests in respiration and combustion, in the role of earthquakes in creating mountains and raising fossils far above the sea, and was still pursuing his and the Society’s interests in pneumatics and astronomy. But beginning in late October 1668, at his urging, and continuing for nearly a year, the Society extensively explored the important question of the laws of motion and the rules of collisions between bodies. As we discussed in Chapter 4, he was very much involved in what was probably the most sustained attack on a single problem in the early years of the Royal Society, although he was mostly relegated to the role of experimentally verifying the theories of Wren, Wallis, and Huygens. In July 1669,126) Hooke electrified the Society with the announcement that he had detected «the parallax of the earth’s orb,» the apparent displacement of a star due to the Earth’s revolution about the Sun.127) This was something of an astronomical

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“holy grail”, to use a much-abused expression, since it would have established for the first time the earth’s motion around the sun. The resulting Cutler lecture “An Attempt to Prove the Motion of the Earth Through Observations” was one of his most important contributions to natural philosophy, though not because he had actually detected stellar parallax. Had he been right, it would have been perhaps the greatest of his discoveries, and he likely went to his grave believing that this was indeed his crowning achievement in astronomy. What he did observe (if anything) could have been just as decisive, if it had been properly understood, but we will likely never know. The lecture itself, read in 1670, but published four years later, led the listener (and finally the reader) through the arguments, pro and con, respecting the Copernican hypothesis, and eventually narrowed the discussion to the problem of measuring the parallax due to the earth’s annual motion. After dismissing earlier attempts to detect parallax using naked-eye observations, and after detailing the many difficulties which hinder an accurate measurement, including refraction, flexure of the instrument, thermal expansion, and so on, he described his zenith telescope, erected at Gresham College, and the way in which each of the difficulties was met by his telescope. The lecture is altogether a tour de force of natural philosophy, as was his zenith instrument itself (Fig. 24), and yet his conclusions were based on the scantiest of data, consisting of observations made of the star γ Draconis on only four dates over the same number of months in the summer and fall of 1669. By way of excusing the meagre data, Hooke blamed «inconvenient weather and great indisposition in my health.» He said that he would have printed the lecture earlier had he not been «diverted by the advice of some Friends» to repeat the measurements «rather than publish it upon the Experience of one Year only,» but that «Sickness hath hitherto hindered me from repeating the Tryals . . . » This episode in some respects epitomizes Hooke’s scientific career. A brilliant attempt to solve a leading problem of the day, that of demonstrating the earth’s motion through space, executed with great care and mechanical ingenuity, ultimately not fully followed through on, and bearing little fruit. Though it must be conceded that Hooke’s complaints about the weather sound thoroughly credible to anyone who has tried to observe from southern England. Hooke would never follow up on these early observations. At the same time, in the summer of 1669, Hooke revisited the circular pendulum as an analogy to elliptic planetary motion, but despite this evidence of interest, the first reference to planetary motion in his Diary does not come until the late summer of 1676, over four years into its writing. In the late winter of 1671/2 Newton presented his reflecting telescope as well as his theory of light and color to the Society, sparking the first controversy with Hooke. It was also the beginning of Newton’s tenuous, sporadic, and somewhat tense relationship with the Society that would culminate in its publication of the Principia 15 years later, and eventually in his long tenure as president. This controversy over the rival theories of Hooke and Newton on light and color continued to create tension between them into 1675. The importance of this episode lies in the fact that it was the first interaction between the two, Hooke the Society’s authority on light and color, and the up and coming young Lucasian

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Professor, and because it caused a rupture which really never healed. This controversy is the subject of the next chapter. In the spring of 1671,128) Hooke and Wren had been asked to come to an agreement over whether a concave sphere or parabola [oid] would focus all rays to a point, and Hooke was reminded again of his promise to measure a degree along the earth’s surface, as well as to further observe the parallax due to the earth’s motion, studies he had talked about for some time. He did perform an interesting experiment which involved sound vibrations in a glass bell, using flour to make the vibrational modes visible. And late in November of the following year he described some observations, clearly of the phenomenon of diffraction, «which seemed to discover some new properties of light . . . »129) hitherto unnoticed, though Grimaldi had actually observed it a decade earlier. In the next couple of years Hooke’s main interests are in optics, mostly astronomical, including his own reflecting telescope, after the design of Gregory, and in magnetism. It is perhaps worth noting here, while recounting of a host of interesting and important ideas that Hooke had or discoveries that he made, that almost none were printed at the time. Some would appear in his Cutler Lectures, which were published between 1674 and 1679, well after they were presented to the Society, others reached print only after his death in the Posthumous Works. Prior to 1674, then, excepting the paper on capillarity and Micrographia of 1665, Hooke had only the Philosophical Transactions130) as a forum for publishing his ideas. Continental scientists read the Transactions, and Oldenburg often mentioned Hooke in his correspondence. Nonetheless, it is interesting to speculate what might have been his reputation if some of these conjectures had become widely known at the time. The summer of 1672 is notable because while the Society was in summer recess from 3 July to 30 October, Hooke began to expand his Diary entries beyond mere meteorological data, providing us the great resource we now have.131) It was in the mid to late 1670s, as already noted, that Hooke was most deeply involved in architecture and construction, to the detriment of his career as a scientist and his job as Curator. Yet it is difficult to say that one career was more important or fundamental to him than the other, nor would it be correct to see them as totally distinct, since in his work outside the Society, he regularly put his physical principles to work in what was essentially architectural engineering. Both offered recognition and reward, and each comported with a different side of his professional personality: the speculative or theoretical, and the practical or technical. In January 1674/5 Huygens announced his invention of a spring controlled watch in the form of an anagram in a letter to Oldenburg, revealing the details a month later. The ensuing controversy (described in detail above) took a toll on both Hooke and the Society itself, and it is not out of the question that this episode may have hastened Henry Oldenburg’s death less than three years later by what was likely a stroke. We know that by 1676–7 both Hooke and Wren were thinking seriously about planetary motion, including the problem of the moon. This issue, central to Hooke’s entire career, of how a theory of planetary motion, which would reproduce Kepler’s

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Laws, might be formulated, and Hooke’s deep involvement in it is the subject of Chapter 10. At the end of February the issue of the possible oblateness of Mercury was raised, with Hooke arguing, insightfully, that this might have resulted when Mercury was fluid enough to be distorted by its rotation. Already embroiled in controversy with Hevelius over telescopic sights, Hooke now tangled with John Flamsteed. He records that at the meeting of 10 May 1677 «Flamsteed told me I spake nothing to purpose.» The latter had just been elected a fellow in February, and already there was tension. The Astronomer Royal132) was notoriously difficult, but he certainly had no monopoly on quarrelsome behavior in these times. There would be yet more trouble with Flamsteed, although it seems to have been more a personality clash than a disagreement over ideas. Ultimately Flamsteed fell out with Halley and Newton as well. In September 1677 Oldenburg died suddenly. We have seen that one consequence was Hooke’s taking over some of the Secretary’s duties, including the correspondence which Oldenburg had established with most of the virtuosi of Europe. His architectural work was peaking in this period, and in particular he was working on the Monument (which he refers to as the “piller” or “column”), which marked the location of the start of the Fire in Pudding Lane. This structure is of special importance because Hooke, probably with Wren, seems to have included in it a zenith tube,133) which would have facilitated several kinds of measurements, and in particular could have aided Hooke in his attempts to measure parallax. Interestingly, however, nothing in Hooke’s writing even hints at this use of the Monument. In particular, there is no suggestion in the Diary of a nighttime visit to it. It was, however, used for other experiments, such as the attempt to measure the difference between the force of gravity at its top and in its basement using two pendula as well as experiments with falling bodies, as evidenced from discussions on 18 April 1678. In the winter of 1677–78 Hooke returned to discussions of barometric pressure, the “springiness” and weight of the air – which were still at issue – and the character of the aether. He gave an articulate, even impassioned, defense of the Society’s labors in attempting to understand the nature and properties of the air, asserting that «an exact and thorough knowledge of [it] is of more concern to mankind than all the other physical knowledge in the world.» The strength of expansion, or spring, of the air, was considered at subsequent meetings, with Hooke showing that the force of the spring of the air was «reduced in proportion to the expansion,» and that «the force necessary to condense the air was always proportionate to the condensation.»134) In the early months of 1678 (1677/8) he led a discussion of the aether and the distinction between it and the air or atmosphere. When in January a skeptical Wren expressed his doubt that such a thing as the aether existed, Hooke claimed that he could «by hundreds of experiments evidence the reality of such a body.» One would like to know what he thought the empirical evidence was.135) A series of experiments was carried out in January showing how the specific gravity and “height” of the air would affect barometric pressure. On the theoretical or explanatory side, Hooke’s arguments were based on an analogy with water pressure in a vessel.136) In continuing discussions which went on into May, he addressed

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the variation of atmospheric pressure with height, the «swimming of clouds in the air» and the fact that their lower surfaces were usually horizontal, 137) revisited the question of the spring of the air, and explained how pressure and specific gravity of the air differed. Altogether a remarkable investigation, based on experiment, of the properties of that elusive medium, the air. Several times in the spring of 1678 Hooke led discussions of sounding the depth of the ocean, which raised the issue of the way a body descended in the sea, some members citing Galileo in support of their argument that since bodies «accelerate their motion continually in a duplicate proportion to the time of their descent,» Hooke’s method of determining depth by timing the ascent and descent of a ball must be faulty. This provided Hooke the opportunity to explain what we call terminal velocity, or as he put it «that there would be in all mediums a certain degree of velocity, which the . . . descending body would never exceed.» He also chided those, apparently Henshaw and Hill, whose conclusions «had been made upon a theory, and not upon experiment; for that experiment would evidence the contrary.» One of the last of Hooke’s published lectures138) was “De Potentia Restitutiva” or “Of Spring” (1678), in which we find his expression of the fundamental law of elasticity, known familiarly as “Hooke’s Law.” (Fig. 14). It is this law that usually comes to mind when laymen, and even most physicists, who ought to know better, hear Hooke’s name. As he stated it in the lecture, «The Power of any Spring is in the same proportion with the Tension thereof»139) or «. . . the Rule or Law of Nature in every springing body is, that the force or power thereof to restore it self to its natural position is always proportionate to the Distance or space it is removed therefrom . . . » Hooke generalized this idea, which he said had its origin 18 years earlier, to all “springy” bodies, that is, metal, wood, stone, etc., so that he saw it as a general principle of elastic bodies, «whether it be by rarifaction, or separation of its parts the one from the other, or by Condensation, or crowding of those parts nearer together.»140) Thus it had the potential to explain how masonry structures supported and transmitted the loads placed upon them. The civil engineer J.E. Gordon has perhaps overstated the situation when he called Hooke’s ideas on elasticity «one of the greatest intellectual achievements in history»141) , but it fully established him as one of the founders, with Galileo and Mariotte, of the science of elasticity. In this same lecture, Hooke also speculated about the structure of matter and the vibrations of its parts, and specifically noted the isochrony of the vibrations of a spring-mass system. Quite remarkably, he also concluded that the “power” stored in a stretched spring was proportional to the square of its displacement.142) Toward the end of 1678 Hooke was again demonstrating his strong and continuing interest in geology, speculating on the origin of veins of gold, and especially on earthquakes. A decade earlier he had addressed this issue in his “Discourse of Earthquakes.” This recurring theme143) had been first explored in Micrographia of 13 years before, but his interest in the history of the earth, and especially “petrified shells”, can be traced to his boyhood on the Isle of Wight. Ellen Tan Drake144) has devoted an entire volume to Hooke’s geology, freeing us from pursuing this important side of Hooke’s science at length; suffice it to say, however, that he has a legitimate

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Figure from Hooke’s published lecture “De Potentia Restitutiva or Of Spring”, from his Lectures and Collections, 1678.

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claim to being a father of geology as a physical science. He was rarely content just to describe marine fossils as curiosities, but would go on to speculate about what kind of forces had raised fossils well above the current sea level and on the effects of the earth’s internal heat or “subterranean fire” in causing these effects, as well as vulcanism. This interest in geology, expressed so early in his career, was never lost, and continued virtually until his death. He also speculated on the connection between the fossilized forms he saw, or knew about, and living forms. The bright comet which appeared at the end of 1680 was observed by astronomers throughout Europe, and Hooke and Newton were not exceptions. In early February, Wren, who was now president of the Society, claimed that Flamsteed’s observations of the comet agreed with his own hypothesis «that comets move in strait lines equal spaces in equal times, but not according to Kepler’s hypothesis.»145) Hooke already had lectured on comets in 1677 and had published the Cutler lecture, “Cometa”, in a collection early the next year.146) Therein he had written that he «supposed the attractive power of the Sun, or other central body may draw the body towards it, and so bend the motion of the Comet from the streight line, in which it tends, into a kind of curve, whose concave part is towards the Sun . . . »147) That is to say, he was closer to seeing comets as obeying Kepler’s laws of planetary motion than perhaps any of his peers. He noted that cometary tails pointed away from the Sun, and concluded that comets were more distant than the moon, based in part on arguments from parallax. Most interestingly, Hooke ventured, in a 1664 lecture (heard by Pepys), that one seen in 1618 might be the very same object, suggesting, that is, that comets might be periodic, thus foreshadowing Halley’s dramatic and much more quantitative prediction about the return of the comet of 1682.148) Following the appearance of the great comet, Hooke again turned his attention to these fascinating and mysterious objects in late 1682, in a lecture read to the Society and published in his Posthumous Works by Waller as “A Discourse of the Nature of Comets.” In this work, he reasons that the cometary tail must shine by reflecting sunlight rather than being “an actual flame,” though he does imagine that comets might be neither solid nor fluid, but a «third sort, that is, such as appear partly by the help of their own Light, and partly by the help of other Light reflected from them . . . ,»149) and concludes that «there may be a Fire or Flame . . . in part of the Heavens far beyond the atmosphere.» He speculates that there must be a solid body «within the cloudy Nucleus» of a comet. Newton, of course, would go well beyond Hooke’s ideas on cometary orbits when he prepared Book III of the Principia.150) In this same work, Hooke also notes that all solid bodies attract each other,151) and finds the cause of gravity to lie in the aether, «the Substance that fills the Cavity of an exhausted Vessel.» Although it is clear from other writings that Hooke takes gravity to be a property inherent in a body, it is not so apparent here. It is also interesting to note that he distinguishes between gravitating bodies and “levitating bodies,” where the motion is continued upwards. While this sounds Aristotelian, Hooke mainly had in mind the phenomenon of Light, that is, radiation from a body such as the Sun. In the Discourse we see some of Hooke the natural philosopher, a subject we take up in Chapter 9.

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Early in 1681 Hooke spoke about light, air resistance, and the projection of a sphere onto a plane. He was still occasionally reporting microscopic observations and corresponding with Leeuwenhoek over such issues as worms in pepper-water, and so on. Toward the end of the year, his interests returned to optics, a consequence of which was a minor controversy between himself and Flamsteed, who thought that Hooke’s method for finding the focus of parallel rays striking a spherical surface incorrect. At the next meeting, Hooke announced that Flamsteed had acknowledged that he been mistaken,152) though Flamsteed evidently would harbor ill feelings over the incident. In December 1681, Hooke was again proposing to measure the dependence of gravity on distance from the center of the earth by comparing precisely calibrated pendula placed at the top and bottom of the Monument,153) returning to an issue he had explored more than 15 years before. His mechanical side is illustrated by his efforts to construct an «engine for describing all manner of helixes upon a cone» and dividing an inch into 100,000 parts, while his analytical side was exhibited in discussions of heat and cold, in which he denied that “particles of cold” issued from a body when warmed. A notable discovery of Hooke’s came in the late winter of 1681/2 when he demonstrated (on 15 March) that an ordinary pane of glass cut off most of the heat from a fire, but little of the light (or for that matter heat from the sun). As he put it, the heat of fire and the sun were «not propagated in the same manner» through a pane of glass. The implications were enormous, but far beyond the ability of anyone to discern for two centuries. There was continuing interest in light, in weights and measures in various countries, and in the measure of a degree, which (as we have seen) Hooke had been continually charged to determine over the years. In June 1681 the Council had offered Hooke an extra $40 «as an encouragement» to deliver on his promise, as it was put, «for a more sedulous prosecution of the experiments for the service of the Society, and particularly the drawing up into treatises several excellent things, which he had formerly promised the world.» This idea, though it may have been Hooke’s, had its desired effect, as he provided a series of discourses and experiments during the following year, though as we have noted, he was now Secretary and on the Council. He spoke of light, the barometer, pendulum clocks, memory, problems in geometry, and more. On July 5, 1682 with Hoskins presiding, we learn that Hooke was desired «with what convenient speed he could,» to «print his discourses and lectures read before the Society; as also a more full description of all those several instruments, which he had shewn that year to the Society, together with the demonstrations of the grounds and reasons and use of them.»154) Most of them remained unpublished at his death. It was later that year (in the November elections) that Hooke’s tenure as Secretary was abruptly terminated. The conflict with Flamsteed simmered for another three years, and in July 1684 the Council, answering Flamsteed’s complaint «that he had been reflected upon by Mr. Hooke in the minutes of the Society,» ordered that «a line should be drawn through the places complained of, and that there should be written on the side, cancelled by order of the Council . . . »155) Yet Hooke was returned to the Council at the end of the following November, and he was one of five selected to audit the treasurer’s accounts.

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Hooke’s interests continued to be wide-ranging. He was still thinking a lot about fossils or “petrified shells” and what they said about the earth’s past, in particular that the earth had been highly modified by catastrophic events, presumably earthquakes, that had thrust rocks far above their original positions in the sea-bed. On 22 December 1686, for example, «he gave several material instances to prove, that there have been very great changes in the earth’s surface, as rows of oistershells found in a cliff in the Alps . . . and the like shells observed by himself at a great hight from the sea in a cliff in the Isle of Wight.»156) A month later he speculated about the effect of the earth’s “vis centrifuga” in determining the shape of the sea surface and suggested that the earth’s axis of rotation might be moveable (Hooke understood precession, of course), and in March of 1686/7 he wondered whether the protrusion of mountains might affect the direction of the earth’s axis.157) This was part of a wider interest in the figure of the earth, the effect of the sun and moon on the earth’s rotation, and so on. If Hooke was thinking deeply about the problem of planetary motion in this period, we have only modest evidence of it, but as we will describe below (Chapter 10), it was in January 1683/4 that Halley raised with Hooke and Wren the question of the motion that would occur in the presence of an inverse-square law of gravitation.158) Dissatisfied with what he learned from his friends, Halley decided to journey to Cambridge to pose the same question to Newton, which he did in August, and perhaps earlier. The rest, as they say, is history. The first hint of what was to come emerged at the meeting of the Society on December 10, when, to quote the Journal Book, «Mr. Halley gave an account, that he had lately seen Mr. Newton at Cambridge, who had shewed him a curious treatise, De Motu . . . »159) What Hooke’s reaction may have been at the time, we cannot know, since we lack a diary for this period and his comments and discourses at Society meetings through the end of 1687, when Birch’s account ends, reveal little, mostly being devoted to what we now call geology and paleontology. Hooke, who would turn 52 in 1687, would carry the dual burdens of Newton’s triumph and Grace’s death into his declining years. His original scientific contributions were mostly behind him, and his architectural duties were also largely completed.160) But, as we will see when we look at his declining years, he was as much involved in the Society as ever, which still met at Gresham. His fertile mind was apparently clear to the end. We look at his post-Principia years in Chapter 12. Newton would remain in Cambridge until 1696, weathering the storms of the Revolution, briefly serving in Parliament, and very rarely attending Society meetings even after moving to London, at least in part because he knew that Hooke would be there.

The Hooke Folio, 2006 Some of the background to the remarkable discovery in 2006 of the “Hooke Folio” now in the possession of the Royal Society is given in Adams and Jardine (2006); these details need not concern us here.161) But the documents bound in this folio are a treasure-trove of information on Hooke and the Royal Society. Gossip aside,162) they

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contain Hooke’s original minutes from the period when he was Secretary, 1677 to 1682, including a significant amount of information missing from the Journal Book of the Society for over 300 years, including papers read to the Society, and so on. There are minutes of a few meetings for which there has been no previous evidence, and there are notes on informal meetings which took place between regular meetings. It contains, as well, minutes he took of meetings in 1691, which are also not in the Journal Book Original (JBO). In contrast to the very well organized Oldenburg, none, or almost none, of Hooke’s raw minutes found their way into the “secretarial draft minutes” from which the scribes produced the JBO.163) We now have them. But in addition, the folio contains notes that Hooke clearly made from Oldenburg’s raw minutes shortly after the latter’s death, consisting of extracts of his own contributions during Oldenburg’s tenure, on which he sometimes elaborates.164) . It took Hooke more than a month after the election at which he was made a Council member to get access to Oldenburg’s papers,165) and there are continuing references in the Diary to his reading the papers, along with various other members, into the spring of the next year. Sometime in this period, Hooke found Oldenburg’s original minutes for the meeting of 23 June 1670, with the passage referring to his balance-spring watch crossed out, confirming his conviction that its absence from the Journal Book was not an accident. Finally, as we have said, the folio contains minutes taken by Hooke at meetings in the summer of 1691, most of which failed to make their way into the Journal Book.166) For the most part, they add only modestly to our knowledge of Hooke’s later years or the activities of the Society in this period, but they fill in important gaps in the record. It is not unlikely that other discoveries will be made as the folio is carefully examined, but as it stands, it is the most important discovery of original documents bearing on seventeenth-century science since the recovery of Hooke’s Diary over a century ago.

Conclusion: Micrographia Hooke’s masterpiece, Micrographia, whose complete title is Micrographia, Or Some Physiological Descriptions of Minute Bodies made by Magnifying Glasses with Observations and Inquiries Thereupon, is clearly deserving of a more detailed examination than we have so far afforded it. It is a work of some 250 pages, an original copy of which now can be had for nearly $100,000. Apparently fewer than 200 copies were printed by Martyn and Allestry, printers to the Royal Society, «at their Shop at the Bell in St. Paul’s Churchyard,» and sold for 20 shillings. It was not financed by the Society. A second edition was published two years later.167) Micrographia is dedicated, first to the King (Charles II), and second to the Society itself, under whose imprimatur the work was published. In his paean to the Society, Hooke apologizes, as it were, for some «Conjectures and Quaeries (which YOUR method does not altogether disallow),» which method avoided «Dogmatising and the espousal of any Hypothesis not sufficiently grounded and confirmed by Experiments.» There follows a 28 page preface in which, returning

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to his Baconian roots, Hooke asserts that «The truth is, the Science of Nature has been already too long made only a work of the Brain and the Fancy: It is now high time that it should return to the plainness and soundness of Observations on material and obvious things.» Tellingly, he remarks that «If I have contributed to the meanest foundations whereon others may raise nobler Superstructures, I am abundantly satisfied . . . ,» thereby foreshadowing Newton’s more famous if grudging acknowledgement to Hooke (and others) of 15 years later. As he did later (see Chapter 9) Hooke alludes to a “certain method,” which he has used in all his inquiries, «which I may on some other opportunity explain.» This presumably is his “philosophical algebra,” an account of which was still wanting at his death. Micrographia is an altogether remarkable account of microscopic observations, accompanied by wonderful drawings (Fig. 6) that are still prized today, but it is also full of speculation on the nature of light and color and on other areas of natural philosophy, including gravity and the nature of the moon’s surface. Bacon, we might guess, would have been uncomfortable with much of it. The entire project was an outgrowth of studies carried out by members of the Oxford club and especially Wren, who himself made wonderful drawings of curiosities seen through the microscope, and whose influence on the slightly younger Hooke’s development is quite clear.168) The work itself is organized into 60 “Observations,” many of them microscopical, involving mites, fleas, cloth, slices of cork, snowflakes, and so on, accompanied by Hooke’s exquisite drawings. The figures, presented in 38 plates, have always been famous, and were republished a century later, with most of the text excised,169) and it is they that kept Hooke’s name alive for biologists and naturalists. But almost none of the Observations is merely descriptive and almost invariably there is elaboration, analysis, even conjecture, over the origin of the forms, if inorganic, or function, if part of an animal, recent or fossilized. Beyond that, however, Hooke addressed a number of somewhat deeper issues which arose in the context of the microscopical observations. Observation VI, for example, involves “small glass canes,” that is, capillary tubes, which, we recall, was the subject of Hooke’s first publication, and which allows all kinds of speculation on the nature of fluids. But we also find him discussing gravity as “natural motion,” to be distinguished from “violent motion,” a very Aristotelian separation. Observation IX concerns “Fantastical Colours,” which he saw in Muscovy Glass, or mica, but quickly makes a transition to structural colors, as in a Peacock’s tail feathers, and to what we now know as interference, caused by flat glass plates in contact, or in soap bubbles. In his attempts to explain the colors that result, Hooke exhibits his commitment to the idea, inherited from Descartes and others, that the colors produced, in refraction at least, occur as a modification of the original white light, which could be restored by further refraction. As we have seen, he still held this view in the early 1670s, when he encountered Newton’s experiments with light and color. But he also speculates on the nature of light, asserting that there is «no luminous Body but has the parts of it in motion more or less,»170) and that it is specifically a “short vibrating motion,” and compares the expanding spheres of light to expanding circles on the disturbed surface of water. Notably, part of the justification lies in the

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fact that «all kinds of fiery burning bodies have their parts in motion . . . » These are among the earliest discussions of light as a kind of wave or vibratory motion. In Observation XVIII Hooke examined the pores or cells in cork, which he noted that no one had seen before, and found the same thing in other plants. He was not in a position to extend this discovery to cells and cell walls in animals, but it represents the first observation of the cellular structure of biological material, in a sense the origin of microbiology. He also studied the microscopic structure of molds, sponges, and seaweed, various plant seeds, hair, before turning, famously, to insects in most of the next 50 pages In the last three sections (“Observations”), Hooke returns to light and specifically the problem of atmospheric refraction, especially near the horizon, and its relation to the variable density of the air, leading to a discussion of its rarefaction and compression. He goes on to explain the phenomenon of scintillation, or “twinkling,” but then concentrates on the atmosphere itself, whether it has a maximum height or thickness, whether the surface between different layers might cause reflection (!),171) speculates about whether the air density decreases with height, and wonders about the generally flat lower surface of clouds as compared to the irregular cloud tops (something we have seen he returned to a decade later). He then examines the effect of refraction on the measurement of planetary and lunar parallaxes, and concludes with some remarks on lunar eclipses. In Observation LIX Hooke describes briefly his observations of the Pleiades asterism and the effect of aperture in making faint stars visible. The final section concerns the Moon, focusing on its shape and the irregularities of its surface. Hooke’s drawing of the crater Hipparchus (see Fig. 23) is the first faithful and detailed representation of a lunar crater and the experiments he performed in an attempt to simulate lunar craters by dropping an object into a mixture of «Tobacco pipe clay and water» were undoubtedly the first of their kind. In the end, «. . . since it would be difficult to imagine whence those bodies should come . . . », he concluded that the craters must have a volcanic origin. This issue was not decided until the middle of the twentieth century. It is also here that Hooke first addresses the universal character of gravity, certainly before Newton, and probably long before him. We will address this question more generally in Chapter 10, but we take note here of his statement that “‘tis not unlikely that there is in the Moon a principle of gravitation, such as in the Earth,» and goes on to explain the Moon’s spherical shape as due to gravity, and extends this idea to the planets and their moons. Altogether one of the remarkable documents of the history of science,172) and while Micrographia did not, as the Principia did or, say, the Origin of Species, establish a new scientific paradigm, it is a wonderful work of natural philosophy, groundbreaking in many respects and thoroughly charming. And we know that both Huygens and Newton were influenced by it. But the Great Fire erupted in the year after its publication, and for the next 30 years, Hooke had more on his plate than almost anyone could handle. For this, and other reasons, he never again attempted a work of this scale.

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Annotations 1) In this Hooke is almost unique, though his situation recalls Faraday’s long association with the Royal Institution in the nineteenth century. 2) See the proceedings of the Oxford, 2003 Hooke conference, Robert Hooke and the English Renaissance(Kent and Chapman, 2005). 3) In modern terms. It seems to do no violence to the historical record to alternatively call Hooke a natural philosopher or scientist. 4) See, for example, ‘Espinasse (1962), pp. 61–63. Glasgow (1885), in Watch and Clock Making says that «About the year 1665, Dr. Hooke invented what is known as the recoil, or anchor, escapement. This was afterwards adopted in a clock made by Clement, a London clockmaker of the time. It should be admitted here that Hooke’s recollection of what occurred forty years earlier might not be any more reliable than Newton’s, which we will later discount, but the difference lies in the evidence from the documents of the Society.» 5) Apparently feeling that a patent would reveal his invention, thus making it possible for others to improve upon it. This question is discussed in various places, including ‘Espinasse (1956), pp. 61–69. Waller, in his “Life of Dr. Robert Hooke,” says that he saw the draft of an agreement between Brouncker, Boyle, Moray, and Hooke, to promote this invention, with Hooke receiving most of the proceeds. See Gunther, VI, p. 11. In his biographical sketch, Hooke describes this as having occurred «Immediately after his Majesty’s Restoration.» 6) The innovation was using a spring to regulate the watch, as opposed to powering it. See Wright (1989) and references therein for details of Hooke’s efforts with the balance-spring watch. 7) Apparently (Jardine, 2000, pp. 268–9) making trips back and forth between London and Oxford for some time. Hooke’s work with Boyle led eventually to one of the few extant monuments to his having lived. Thus, on a plaque marking the location of Boyle’s laboratory in Oxford, we find a reference to Hooke’s discovery of the cell. 8) Boyle, New Experiments (1660). “Mr G”, Ralph Greatorex, was a leading engineer who had been involved in pumping the fens of Southeast England. 9) This important issue has been dealt with in detail by Cohen (1964), Webster (1965), and Agassi (1977). There seems no doubt that Mariotte came to this idea no earlier than 1679, some 16 years after Boyle and Hooke. But Boyle knew of the experiments of Henry Power and Richard Towneley which had been carried out in 1660–61. Their data had been forwarded to Boyle by William Croone, and Boyle quotes Hooke as having said that he had performed experiments in August of 1661 verifying “Mr. Townly’s Hypothesis,” of which he had “lately heard.” In fact, Hooke said that he had made such measurements a year before, but never claimed to have made the discovery himself. Cohen points out that Newton, who was reluctant to grant Hooke any credit at all, acknowledged the

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role of “Hooke and others” in this discovery, rather than Boyle, in Book 3 of the Principia. Newton probably learned of the law by reading Hooke’s Micrographia. On the other hand, it seems clear that Boyle’s experiments on compression of a gas, and those of Towneley on expansion, were independent, with Boyle’s being earlier. Hooke’s role will never be precisely known. See Agassi, and for a somewhat different view, Webster. Cohen’s sound verdict is that «this is a law discovered by Power and Towneley, accurately verified by Hooke, accurately verified again by Boyle (aided in some degree by Hooke), first published by Boyle, but chiefly publicized by Mariotte,» in short the law of Power and Towneley, and of Hooke and Boyle, and – to a lesser degree – of Mariotte. 10) See, for example Maddison (1969), Chap. III. Boyle regularly contributed experiments in the early years of the Society, and had a laboratory in his sister’s house in Pall Mall. 11) He had complained of «distemper of the eyes» since 1655 (Maddison, Ibid., p. 85). See also Gunther, VI, p. 73. 12) On Boyle, there is a massive amount of recent important writing, especially by Michael Hunter and his collaborators. The recent biographies by Hunter (2000, 2009) are definitive. There is no doubt that Boyle set new standards for the actual practice of experimentation, as well as the philosophical basis for it and its interpretation. 13) Published in facsimile in Gunther, Vol. X, pp. 1–50. Keynes thought that the New Atlantis. Begun by the Lord Verulam [Francis Bacon], Viscount St. Albans: And Continued by R.H. Esquire, published in 1660, was a work of Hooke. See Keynes’ arguments in his Bibliography of Robert Hooke, (Keynes, 1960), pp. 2–4. 14) See the Society’s A Guide to the Archives and Manuscripts of the Royal Society by Keith Moore (1995). 15) Not infrequently this resulted from the fact that these problems were intractable given the state of 17th -century science. One thinks of magnetism, for example. 16) The appointment was made permanent two years later. See below. Hooke’s movements during 1661–2 are obscure. 17) One notes that Boyle, for example, was always “desired” or “requested.” 18) These terms are taken from Birch’s transcription of the Journal Book, but are generally faithful to the original. 19) For example, a letter from Moray to Oldenburg in November 1665 commenting on Hooke’s “slackness.” The full passage is «. . . I would hee had any thing hee desires that hee may have no longer excuses for his slackness in making out hypotheses.» CHO, Vol. II, p. 605 (12 November 1665). 20) These periods could be seen, approximately, as 1662–72, 1672–77, 1677–87, and 1687–1703. 21) Waller (1705), p. ix.

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22) Birch, 1, p. 123. It is recorded that «The proposition was received unanimously, Mr. Robert Hooke being named to be the person.» 23) The order of the Society, honoring Cutler, is printed in Birch, 1, 484–5 (11 Nov. 1664). 24) Publication was authorized in 1664 and it was apparently printed in that year, but is dated 1665. 25) The situation is a bit more complex than this suggests, in that Hooke initially lost a controversial election for the vacant Gresham professorship, but after the Society protested, he won the post. See Birch, I, p. 436. Cutler’s intention was to have Hooke lecture on the history of trades, and he was never satisfied with the arrangement by which Hooke became Professor of Geometry, and stopped paying in 1670. 26) It was in that June that Pepys first saw houses in Drury Lane marked with red crosses, indicating plague victims (7 June 1665). Evelyn’s weekly reports of deaths rose from 1000 in mid-July to 5000 in mid-August, and Pepys recorded over 6000 in the last week in August. 27) The Transactions can be readily browsed through JSTOR (www.jstor.org/ journals/). 28) The work on the churches really went on until 1717, although in was interrupted around 1688, but Hooke’s contributions waned in the mid 90s, as did his health. 29) Though Wren worked on designs for it during the previous six years. The first service was held on 5 December 1697, well before the dome was built. 30) Hooke concluded that the proper form for an arch would be an inverted catenary, the latter being the curve taken by a uniform chain hanging from two supports under gravity. He approximated this curve, or rather the surface generated by it, by a “cubico-parabolic conoid,” which is generated by rotating the curve y = ax 3 about the y-axis. The catenary problem was solved by James Bernoulli, Huygens and Leibniz in the 1690s. Hooke’s formulation was apparently used by Wren in the dome of St. Paul’s. For a discussion of the issues involved, see Heyman (1998). In “Helisocopes” Hooke expressed this in an anagram, which has been unscrambled as «Ut pendet continuum flexile, sic stabit contiguum rigidum inversum,» or (Heyman (1998), p. 40) «as hangs the flexible line, so but inverted will stand the rigid arch.» 31) He was promised $80 but this was to be made up of $30 provided by the Society, and $50 from Sir J. Cutler, who in his lifetime (he died in 1693) never paid Hooke. Only after his death was Hooke able to obtain a judgement from Cutler’s estate. Thus Hooke labored for some 30 years, usually receiving payments from the Society for his work as Curator, often grudgingly, but receiving no payment at all for the Cutler lectures, which he regularly gave during this entire period. 32) Which is not to discount the behind-the-scene influence of figures like Boyle and Wren, or Moray and Brouncker, who moved in different circles from Hooke

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and certainly had a large impact on the direction the Society would take. But Hooke was in the trenches, so to speak. 33) And perhaps his growing antipathy for the president, Lord Brouncker. We considered Hooke’s relationship with Oldenburg in a previous chapter. The first clear evidence of a disaffection on Hooke’s part came in 1675. 34) Oldenburg to Beckman, 30 March 1668. CHO, IV, p. 280. 35) Based on three observations of the comet of April 1677 and earlier cometary observations of 1664–5. 36) Hooke reported, on 6 September, that he «heard that Oldenburg Dyed yesterday morning being stricken speechless and senseless.» Oldenburg’s second wife, Dora, died only 12 days after her husband, at about age 25. See M.B. Hall (2002), pp. 299–300. What connection the two deaths might have is unknown, and indeed the only evidence that Oldenburg died in London comes from Hooke’s Diary, showing what an important resource it is. 37) The Society’s presidents during Hooke’s tenure at the RS were: Lord Viscount Brouncker, 1662–1677, Sir Joseph Williamson, 1677–1680, Sir Christopher Wren, 1680–82, Sir John Hoskins, 1682–83, Sir Cyril Wyche, 1683–4, Samuel Pepys, 1684–6, John Vaughan, Earl of Carbery, 1686–89, Earl of Pembroke, 1689–90, Sir Robert Southwell, 1690–5, Charles Montague, 1695–8, Lord Summers, 1698–1703. Note that most, after Brouncker and before Newton, served 2–3 years or so. 38) Though Oldenburg did not receive a regular salary until 1669. 39) The Correspondence of Henry Oldenburg (CHO). 40) In his Cutler Lecture, An Attempt to Prove the Motion of the Earth by Observations (pp. 23–25) Hooke described detecting what he thought was stellar parallax in the summer of 1669. His measurements were, like most of his astronomical observations, somewhat desultory, and his descriptions of the difficulty in keeping his zenith telescope in adjustment leave one with at best modest confidence that he actually measured anything real. The observations he made in the summer and fall of 1669 were only of the N-S departure of the position of a single star. See Chapter 11. 41) In his Diary for this date, Hooke wrote: «Zulichem’s [Huygens’] spring watch spoken of by his letter [to Oldenburg]. I shewd when it was printed in Dr. Spratt’s book.» 42) In his postscript to his “A Description of Helioscopes” of 1676, Hooke noted that Sprat’s History of the Royal Society records «several new kinds of Pendulum Watches for the Pocket, wherein the motion is regulated, by Springs, or Weights, or Loadstones . . . ;» Sprat (1667), p. 247. Hooke’s name is not mentioned, but clearly it is he who is the inventor. In “De Restitutiva,” Hooke speaks of showing his balance-spring watch to Brouncker, Boyle, and Moray. Gunther, VIII, p. 337.

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In the Diary for 1675 one finds the following passages: «At Sir J. Mores. He told me of Oldenburg’s treachery his defeating the society and getting a patent for Spring Watches for himself.» (6 March) «Lord Brounker & Oldenburg, discovered their designe.» (8 April) «Brounker a Dog for belying me to the King.» (29 April) «Oldenburg a raskall for not registering things brought into the society . . . » (3 June) «I reproved Oldenburg for not Registering Experiments. Brouncker took his part.» (10 June) «Oldenburg a Rascall.» (17 June) «Dind with Mr. Boyle. Raild against Oldenburg.» (10 August). «Writ against Oldenburg.» (3 September) «Sir Ch Wren read my papers and against Oldenburg approved.» (25 September). 43) Birch, 3, 190. 44) Oldenburg to Huygens, 11 March 1674/5, CHO, XI, p. 220–3. 45) 18 February 1674/5; Birch, 3, 190. The Diary entry is p. 148, Robinson and Adams (1935). Ironically, it was at this meeting that Newton was admitted to the Society. 46) See, for example, Jardine (2004), pp. 193–202 or Chapman (2005), pp. 175– 182. One needs to be careful in interpreting Jardine’s comments on circular pendula in her chapter “Skirmishes with Strangers,” since Hooke used the circular pendulum, in this case an actual pendulum swinging in a circle or ellipse, as an analogy to planetary motion. See Chapter 10. 47) As is well-known, Galileo proposed using the phenomena of Jupiter’s major moons to determine time at sea, but such observations were hardly practical from a rolling ship. Still, interest in this problem was at least partly responsible for Ole Rømer’s discovery of the finite speed of light in 1675 from the phenomena of Jupiter’s satellites. The other astronomical approach was to use the position of the moon among the stars (lunar appulses) as a clock. 48) Birch, 2, 112; 29 August 1666. 49) Diary I, p. 151. 50) Diary I, p. 163–4. 51) Three years later, Hooke noted that as newly elected Secretary he had viewed the correspondence of the late Henry Oldenburg and «found two letters of Sir R. Moray to Hugens about my watches . . . » Diary I, p. 29 December 1677. 52) CHO, 21 June 1675 (letter # 2684). «He is a man of very peculiar temperament, which must be endured with the more patience because he has a real spirit of inventiveness.» 53) CHO, Vol. XI, pp. 378–381 1 July 1675. 54) It is interesting that Boyle, who was a patron of Oldenburg’s and a mentor to Hooke, seems not to have taken sides. He certainly maintained a close relationship with Hooke. Boyle had by then moved to London, so that we do not have the substantial Boyle-Oldenburg correspondence which might have shed some light on this question.

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55) In a letter to Oldenburg 30 September 1665, Moray asked the secretary to inquire of Huygens «if hee doth not apply a spring to the Arbre of th Balance? and that will give him occasion to say somewhat to you. if it be that, you may tell him what Hook hath done, in that matter & what he intends more.» (CHO) Over a decade later, in his Diary for 29 December 1677, three months after Oldenburg’s death, Hooke wrote: «With Grew and Hill viewd Oldenburg letters to be rejected when I found two letters of Sir R. Moray to Hugens about my watches . . . », Diary I, p. 337. 56) Moray apparently believed that Hooke was too secretive about his discoveries and slow in sharing them with the Society. On the larger issue of sharing discoveries – in the present context, Hooke’s – with correspondents at home and abroad, this is seen as a conscious desire to stimulate further productivity by keeping one scientist apprised of what his competitors were doing. Motives, as is so often the case, can be difficult to ascertain, and often complex. 57) Sprat (1667), p. 247. Hooke also spoke of it in a Gresham lecture in 1664 (Inwood, 2003, p. 189). 58) As the Halls believe (Hall and Hall, 1962a). 59) CHO, II, p. 553. In other places as well, it appears that Oldenburg was scrupulous in guarding priority, and in particular with respect to Hooke. See, for example, a letter to Boyle on 17 March 1665/6 concerning Hooke’s invention of ways to sound the depths (CHO, III, p. 61.) Oldenburg, as the Halls point out in defense of him, managed an exchange between Hooke and Auzout expertly, and defended Hooke’s priority. Hooke, of course, saw the matter differently, for in his view, Oldenburg had not only told others of his discoveries, but failed to register important inventions, allowing others to claim discoveries which he had previously presented or described to the Society. 60) In a letter dated 22 May 1688 describing the operation of the Society, Oldenburg told Thomas Harpur that «Among them [the RS] they keep public Registers; it is the duty of the two secretaries, under solemn oath, to enter in them all those matters which are furnished, observed, and communicated by the Fellows of the Society . . . » 61) Hall and Hall, “Why blame Oldenburg,” Op. Cit. This was certainly not the conclusion of Keynes in his Hooke bibliography (Keynes, 1960, p. 36), nor of ‘Espinasse (1956, pp. 66–70). Finally, see the new evidence against Oldenburg in the “Hooke Folio,” below. Oldenburg was German, and apparently performed minor diplomatic services for his native state of Bremen. He was alleged to have «a peculiar temper which prevented him from agreeing well with others.» Quoted in Powell (1948), p. 168. 62) CHO, Vol. XI, pp. xviii–xix. 63) See the passage quoted in ‘Espinasse (1962), p. 67, from the journal of the Italian Count Magalotti, who described seeing Hooke’s spring-regulated watch

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Chapter 7. Scientific Virtuoso: Hooke 1655–1687 at the Royal Society on 27 February 1667/8. Note also the revelation in the “Hooke Folio” discovered in 2006 (see below). Much later, on 8 March 1674/5, Hooke inserted a drawing of a double spiral spring for a watch in his Diary.

64) A scribe would take Oldenburg’s raw minutes and write them in the Journal Book. So until the Secretary’s death Hooke could not know who was responsible for the omission. In an earlier version of this chapter I had written: «It remains to be seen whether the newly recovered (2006) Hooke manuscript will shed light on this issue.» And indeed it has. In a manuscript filled with interesting details, this is perhaps the most revealing discovery of all. See below. 65) But see ‘Espinasse (1956), pp. 63–65, and also Keynes (1960), p. 36: «It seems, however, from the evidence of correspondence still in the archives of the Royal Society that Oldenburg did in fact betray Hooke’s invention to Huygens.» Finally, the letter from Moray to Oldenburg on 30 September 1665. Huygens gave the Society his rights to an English patent. See Birch, 3, 322; PT, vol. xi, no. 129, p. 749. 66) He hoped, for example, to find a position with Seth Ward, who had become Bishop of Salisbury, and in a letter to Boyle on 24 September 1667, sounded Boyle out on the question of a recommendation. [CHO, III, 480–1]. 67) Sprat (1667), p. 247, where is discussed the regulation of watches «wherein the motion is regulated, by Springs, . . . ». This account was published in 1667. 68) PT, Vol. 10 (1675), No. 118, p. 440–1. This was patently disingenuous given his letter to Huygens of 11 March 1674/5 (CHO, XI, 220–220), not to mention an earlier letter to Huygens on 7 October 1665 (CHO, II, 551–54). 69) Even Oldenburg’s advocates cringe at this knowing sacrifice of the truth. 70) «Go far away from both hope and fear.» In the postscript to “Helioscopes” Hooke wrote that «Of these things the Publisher of the Transactions was not ignorant, and I doubt not but Mr. Hugens hath had an account, at least he might have read so much of it in the History of the Royal Society as was enough to have given him notice of it . . . » Gunther, Vol. VIII, p. 149–150. And in the devastating postscript to “Lampas”, referring to Oldenburg’s attack on him in the PT of October 1675, he accused the Secretary of prevarication and worse, and concluded as follows: «To his upbraiding me with his having published some things of mine; I answer, he hath so, but not so much with mine as with his own desire, and if he send me what I think worth publishing I will do as much for him, and repay him in his own coyn. Lastly, Whereas he makes use of We and Us ambiguously, it is desired he would explain whether he means the Royal Society, or the Pluralities of himself. If the former, it is not so, as I can prove by many Witnesses; if the later, I neither know what he is acquainted with, or what has been imparted or explained to him.» Gunther, VIII, 208.

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71) PT, Nos. 128 and 129. Oldenburg wrote that «the publisher of this tract [the Transactions] intends to take another opportunity of Justifying himself against the Aspersions and Calumnies of an immoral Postscript put to a Book called Lampas, published by Robert Hooke: Till which time, ’tis hoped, the Candid Reader will suspend his Judgement.» PT, No. 128, 25 September 1676, p. 710. In the next number, dated 20 November, Oldenburg elaborated, publishing the Council’s declaration of the same date absolving him. 72) On 24 November 1686 a letter from Hevelius was read, «justifying Mr. Oldenburg against an aspersion of Mr. Hooke, who had represented, that the former had written to Mr. Hevelius more and different things, than he had been directed to do by the Royal Society.» Birch, 4, 504. 73) 25 September 1675. 74) “Grubendol” was an anagram for “Oldenburg,” used by Hooke and others. 75) Hall and Hall, CHO, II, p. xxiii. See also “Why blame Oldenburg,” (Hall and Hall, 1962a). 76) Diary, 28 January 1673/4. 77) Diary, 15 October 1675. 78) One can argue about Oldenburg’s motives in trying to obtain the patent, that is, whether it was for personal gain or not. Huygens apparently desired to share his patent rights with the Society. 79) ‘Espinasse gives a good account of the controversy. Hooke’s version is in the Postscript to his Cutler lecture “Helioscopes.” (Gunther, VIII, pp. 146–152.) 80) CHO, II, p. xx. This was only Hooke’s second year as Curator. 81) The issue was Hooke’s advocacy of the use of telescopic sights in measuring stellar positions. This controversy raged for over a decade, highlighted by Hooke’s “Animadversions on the first part of Machina Coelestis” in 1674, through Hevelius’ “Annus Climactericus” of 1685. Hooke was obviously correct in principle, but when his friend Halley visited Hevelius in Dantzig in 1679, he initially reported that Hevelius was achieving unbelievable accuracy with his open sights. Later, however, Halley indicated that he had been merely trying to assuage «an old peevish Gentleman.» (MacPike, 1932, 60, 65) See Armitage (1966). Hooke eventually answered Hevelius on February 24, 1686, when he read a paper «vindicating himself from some injuries, which he conceived done him by Mr. Hevelius in his Annus Climactericus.» (Birch, 4, 461). 82) As is true of all of Hooke’s writing, the lecture (“Some Animadversions On the first Part of Hevelius His Machina Coelestius”) is full of interest, although it may be thought a little long-winded and repetitious. Hooke’s drawing of a mechanically driven quadrant in his published lecture is a masterpiece of seventeenth-century scientific illustration (his Fig. 15 and our Fig. 23). 83) This was an outgrowth of a controversy between Newton and Francis Linus (variously Line, or Hall), which began three years earlier and which helped

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84) Corresp., II; letters 214, 215, 219, 222, 223, 224, mostly having to do with letters written by Lucas to Oldenburg as Secretary in 1676–7. The correspondence was initiated by Newton shortly after Oldenburg’s death and concerned an experiment by Lucas. The subject was Newton’s theory of color and the spectrum produced by a prism. The four letters written to Hooke by Newton are signed, perhaps perfunctorily: «your real Friend & humble servant», «Your most affectionate & humble Servant,» «Your very much obliged & humble Servant,» and «Your obliged & humble Servant.» In his first letter to Newton, on 24 December 1677, Hooke takes a swipe at Oldenburg: «Oldenburg of late omitting all things done by me.» Newton’s next letter refers to “clamouring” against Oldenburg, not necessarily meaning Hooke, and the correspondence with Lucas (letters 220 and 221 plus two more to Aubrey: 225 and 226) gets increasingly testy. 85) Newton had written Hooke, as Secretary, only three months after Oldenburg’s death, among other things wishing Hooke «much happiness in your new employmt & yt ye R. Society may flourish more by ye labours of so able a member . . . » Newton to Hooke, 11 December 1677, Corresp., 2, 239. 86) There exist in Turnbull (Corresp.) only 12 letters written by Newton during the next four years; clearly his attention was elsewhere. And in the following two and one half years, 26 letters were exchanged with either Flamsteed or Halley out of a total correspondence of 30 letters, again showing what Newton was thinking about. 87) At the Council meeting of 17 December 1679. 88) The elections were always held on St. Andrew’s Day, Nov. 30, unless it fell on a Sunday. 89) In only two months, under Robert Plot, and they were initially published in Oxford. Hooke’s decision to publish his own Philosophical Collections during his tenure as (1677–82) was not, we are unsurprised to learn, well received, and indeed it seems to have been a case in which he let his disregard for Oldenburg cloud his judgement. 90) It is not unlikely that Wren’s departure was at his wish, and that without Wren’s backing, Hooke was voted out. 91) The new Council included continuing members Aston, Colwall, Evelyn, Grew, Henshaw, Hill, Hoskyns, Lowther, Packer, Williamson, and Wren. The new members were Deane, Creed, Holder, King, Meredith, Perry, Petty, Plot, Slare, and Wyche. The old Council, in addition to the continuing members above, had consisted of Croune, Gale, Hooke, Aerskine, Flamsteed, Hall, Pepys, Southwell, Tyson, and Wood. These were the 10 voted off the Council in 1682. Aston had

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been co-Secretary with Hooke, but now shared duties with Plot. Hoskins was the new president. 92) 28 February 1682/3, Birch, 4, 187–8. 93) Birch, 4, 207–8. So while Curator “in perpetuity,” he was no longer regularly salaried. 94) Papin, who assisted Hooke in 1675, worked in Boyle’s laboratory from 1679 to 1679, and in the later year he presened his “steam digester,” which is considered a forerunner of the steam engine despite its modest purpose of digesting bones. After being gone from London for five years, he returned in 1684 as temporary Curator. 95) Birch, 4, 260–1. 96) Birch, 4, p. 229–230; November 24, 1683. Perhaps his “Present State of Natural Philosophy” and/or “The Method of Improving Natural Philosophy,” which we discuss in Chapter 9. 97) Ellen Tan Drake has suggested that the lack of a diary for this crucial period might be blamed on Newton himself. While the disappearance of Hooke’s portrait and instruments can plausibly be ascribed to Newton’s hostility, directly or indirectly, there is no evidence that any part of the Diary fell into the possession of the Royal Society, where Newton’s influence might have led to its suppression. Hooke died intestate, which led to a scattering of his possessions. His books were sold at auction. 98) Or believing, if you prefer. 99) Hooke’s beloved niece, Grace, died in the same year, a double blow from which he probably never recovered. In the later Diary (1688–93) he often speaks of his melancholy. See Chapter 2. 100) At the height of his activity as surveyor and architect, his attendance dropped a little, though more often he was present but had not prepared an experiment. 101) It is the wide-ranging character of his intellect that has caused several writers to draw the comparison with Leonardo da Vinci that we alluded to earlier. 102) We note that Hooke later tried to see if air could be condensed under pressure. 103) Including Charles II, according to Pepys. 104) Referring to the experiments of Galileo’s successor, Evangelista Torricelli, who was one of the first to carry out pneumatic experiments, including what was perhaps the first barometer. 105) Birch, 1, 83. Hooke was named on 5 November and approved the following week. 106) This would be the fabled “Pabulum vitae.” 107) Boyle, New Experiments Physico-Mechanical (1660). See also Pepys’ diary entry for 25 April 1661, describing experiments in which a snake and a chick were placed in “Mr Boyle’s pneumatic engine.”

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108) 4 January 1664/5. Birch, 2, 2. 109) The quote is from Micrographia, p. 105. At a Society meeting on 18 January 1665, in which various comments were made on Hooke’s theory of combustion, Boyle, when asked his opinion, remarked that, to quote Birch (or the Society’s minutes) «four or five years before he had made the consideration of this subject a part of his business, but did not know, whether his present studies . . . would give him leave to review what he had then written.» In his New Experiments, Boyle describes experiments in which gunpowder is ignited in an evacuated receiver. Ralph Bathurst (influenced by George Ent) earlier held some similar ideas, and later, John Mayow would amplify on the ideas of Hooke and Boyle. While Boyle was more interested in the physical properties of the air, Hooke gave considerable attention to its physiological and chemical effects. For elaboration, see Frank (1980). 110) Birch, 1, 163–5. 111) On 21 January and 11 and 18 February. On the latter date, he delivered a discourse on the subject. 112) Specifically, he reported to the Society on 24 August that he had begun to make such experiments, and gave details in a letter to Boyle written the following day. See Birch, 1, p. 461. 113) The period of a pendulum depends inversely on g 1/2 or directly on R, the distance from the center of the earth. An increase of height by, say, 200 ft, would make a difference of about one part in 100,000, which would be unmeasurable. See fn. 153. In principle, this was a much better way of measuring the variation of gravity than by weighing, where the effect would be less than a part in a billion. On the other hand, there was no theory of how the pendulum responded to variations in gravity. 114) The matter is also discussed in Chapter 10. Horrocks had earlier employed the circular pendulum as an analogy to planetary motion. See Pugliese, 1989, p. 194 and n. 32. 115) Birch, 2, 107–8; 8 and 15 August 1666. 116) Requiring that the pendulum fiber be wrapped over a “cheek” in the shape of a cycloid. See, for example, Pugliese (1989). 117) This is Pugliese’s view (Pugliese, 1989). For Hooke’s flawed analysis of the conical pendulum, see Pugeliese, pp. 196–198. The source is a manuscript of Hooke’s, Royal Society Classified Papers xx. 53 (fol. 116). 118) Birch, 1, 505–8. If these ideas of Hooke cannot be said to foreshadow the similar speculations which are indulged in today, they are interesting nonetheless. 119) In July Hooke was «charged to shew his microscopical observations in a handsome book . . . » Hooke’s masterpiece was published in 1665, under the auspices of the Society, printed by the Society’s printer. The Society apparently provided no financial support.

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120) Though in fact, except for abbreviated versions consisting mainly of the plates, published in 1745 and 1780, Micrographia went 271 years without being reprinted. Gunther finally managed to have it reprinted in facsimile in 1938, just after the tercentenary of Hooke’s birth. 121) This, of course, was the steeple of “Old St. Paul’s”, which though in a state of near ruin, would not burn for two years. 122) At St. Paul’s or the Monument, pressure changes of on the order of 1% could be observed. Certainly measurable. Hooke described this experiment in a letter to Boyle, written 8 Sept. 1664. Hunter, et al. (2001), v, 535. At a Society meeting the previous day Hooke said that a column of mercury fell about half an inch between the bottom and “the top of the steeple” at Old St. Paul’s. This would be about a 2% change. 123) As he had done a year earlier. Birch, 2, 75. 124) Ibid, p. 88. 125) In his letter to Newton of 25 May 1678, Hooke asked if he knew of a flat area in Lincolnshire, evidently with a view toward making this measurement. 126) We note that it was in October 1669 that Newton became Lucasian Professor of Mathematics at Cambridge. The five years Hooke had served as Curator up to that point were also the years during which Newton made his first discoveries in mathematics and (perhaps) gravitation, and was establishing himself as the first mathematician of Europe. He had read Hooke’s Micrographia, but Hooke had not yet learned of him, though he would soon become a Fellow of the Society (early 1672). 127) On 22 October 1668 Brouncker had remarked that Hooke, who was present, «had erected a tube to try, whether he could observe to a second minute [a second of arc] the passing of any fixt stars over the zenith, and thence find a parallax of the earth’s orb, in order to determine the earth’s motion.» Birch, 2, 315. But on 15 July 1669 the Journal Book (Birch) records that «Mr. Hooke intimated, that he was observing in Gresham-college the parallax of the earth’s orb, and hoped to give a good account of it.» 128) Specifically, 13 April 1671. Birch, 2, 477. 129) Birch, 3, 63. See also Hall, 1990. 130) By 1674 Hooke had been published in about 14 Philosophical Transactions, though some of these are reports from Hooke to the editor. See Keynes (1960), pp. 56–7. 131) In one of the first entries in his expanded Diary, on 11 August 1672, Hooke writes «fitted my Newton,» apparently a reference to a model of Newton’s reflector that he was constructing. He also mentions experimenting on colors. What role, if any, Newton’s bursting on the scene may have in stimulating Hooke to keep a Diary, is of course unknown. The date of 1 August is the

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result of the (not entirely arbitrary) choice by Robinson and Adams to begin transcribing the Diary with that date. 132) “The King’s Royal Observator,” an appointment he received in April 1675 and held for 44 years. 133) Nichols (1999); Jardine (2002), xii. Hooke seems to have intended that the Monument, whose construction was begun in 1673, the year before the Cutler Lecture was published, should be used for zenith observations. There is, however, no clear evidence, that he did, and indeed he never mentions this aspect of the Monument in his Diary. 134) Birch, 3, pp. 384–5. Of course this was far from being novel, even for Hooke, who had first addressed the problem with Boyle 20 years before. 135) See also Chapter 9. 136) On 20 December 1677, he had performed some ingenious experiments involving measuring the increase in water pressure with depth, and discussed pressure at the bottom of different shaped vessels. 137) Which is a very interesting observation. This is what is now called the “lifting condensation level.” 138) The six lectures, which were published separately, as Lectiones Curlerianae, were collected and published together in 1679. It is telling, no doubt, that none of his other lectures were published in the ensuing 24 years of his life. 139) “Ut Tensio, sic Vis.” 140) Gunther, VIII, pp. 333, 336. 141) Gordon (1978). 142) «Consequently all those powers beginning from nought, and ending in the last degree of tension or bending, added together in one sum, or aggregate, will be in duplicate proportion to the space bended or degree of flexure . . . » And, «. . . a spring bent two spaces in its return receiveth four degrees of impulse . . . ; so bent three spaces it receiveth in its whole return nine degrees of impulse . . . » De Restitutiva, in Gunther, VIII, p. 349–50. 143) Lamentably, Hooke had many of these recurring interests, as he failed to pursue an idea as far as he might, or would have liked to. Whether this was largely a natural predilection, or as seems likely, simply a consequence of the demands of his job as Curator, is difficult to be certain about. Manuel (1968, p. 135) called him a “Don Juan of Science.” Newton, we note elsewhere, had the ability to concentrate on a problem to its conclusion, and to the exclusion of all else. 144) Drake (1996). 145) Birch, 4, p. 67. 146) Lectures and Collections (1678). In the Diary for 27 January 1677/8 Hooke wrote «Finisht Comet papers.» 147) “Cometa,” p. 229–230

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148) In March 1664/5 Pepys recorded in his diary that «. . . Mr. Hooke read a very curious treatise about the late comett . . . proving very probably that this is the very same comett that appeared before in the year 1618. . . » (The Diary of Samuel Pepys, 1 March 1664/5. Halley’s later conclusion that the comets of 1304, 1380, 1456, 1531, and 1607 were one and the same, was published in his Synopsis (Halley, 1704–5). One should add that while Hooke’s conjecture had some empirical basis, Halley’s was based on an orbital calculation. This idea of cometary periodicity may have been anticipated by Pythagoras, Hippocrates, second-century rabbinical scholars, etc. 149) Which, incidentally, is correct, since a comet has a dust tail which reflects sunlight and a gas or ion tail which emits its own light. PW, 165. 150) As well as the conclusion to the semi-popular “Newton’s System of the World.” 151) And later, «By Gravity . . . I understand such a Power, as causes Bodies of a similar or homogeneous nature to be moved one towards the other . . . The Universality of this Principle, throughout the the whole and everything therein, I shall afterwards have more occasion to explain.» PW, p. 176. See Chapter 10, where we quote this again. 152) The controversy began on 26 October 1681 and continued, with interruptions, into February. The question of generating curves – great circles, helices, etc. – on planes, cones, and so on, was an important interest of Hooke’s in this period. After several related demonstrations by Hooke, Flamsteed objected on 15 February to Hooke’s method of generating a parabola. As Birch has it, Flamsteed «. . . cavilled against the method shewn by Mr. Hooke . . . ». Eventually, after seeing Hooke’s method again, «the president [Wren] declared to the Society, that it was true and certain.» (Birch, 4 p. 100, 101, 118, 122, 129.) There is no evidence that they ever reconciled. 153) The height of the Monument, about 60 m, is on the order of one part in 105 of the earth’s radius. The pendulum at the top would swing more slowly, again, by about 1 part in 105 . This would be detectable in about 104 oscillations, i.e., a few hours or less. But the periods of the pendula would have to have the same period when at the same distance from the center of the earth, to within better than one part in 105 . In other words, they would have to be watched for synchrony for at least several days. One would have to consider temperature differences between the top and bottom. Very difficult. 154) Birch, 4, 154. 155) 23 July 1684; Birch, 4, 318. Flamsteed was one of seven members of the Council present at the meeting. Hooke was not on the Council in 1683–4, but was returned in November 1684 and Flamsteed was voted off. 156) Birch, 4, 513. 157) Hooke’s wonderful physical intuition is again exhibited here. In the last chapter we will indulge ourselves a bit with a list of some of Hooke’s prescient ideas, which taken out of context, and with modern developments to measure them

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Chapter 7. Scientific Virtuoso: Hooke 1655–1687 against, seem so astonishing. No more than brilliant guesses, or conjectures, but brilliant nonetheless.

158) Halley was then living in the northern suburb of Islington, about two miles from Gresham. This visit would evidently been for a meeting of the Council and Society, which occurred on January 9, 16, and 23, with Halley (and Hooke) present each time. 159) In November, after receiving a copy from Newton through E. Paget. See Chapter 10. 160) Bethlehem or “Bedlam” Hospital, the College of Physicians, and The Monument were all completed in the late 1670s. The work on Ragley Hall, Willen Church, and Montague House (see Stoesser, 2006) was finished by about 1680. Between 1676 and 1693 Hooke did repairs on Westminster Abbey and the school, and other projects are recounted in the later Diary. 161) Perhaps the whereabouts of these documents during the 300 years since Hooke’s death will eventually emerge. Their discovery in 2006 came about as the result of an estate-sale. 162) Including some sniping at Boyle. Jardine (Adams and Jardine, 2006) says «we all believed that the one person Hooke never quarrelled with was his old patron . . . ,» [Boyle], but there are in fact several places in the Diary in which Hooke expressed exasperation with Boyle. 163) Which were evidently in Oldenburg’s possession at his death. See Adams and Jardine (2006). As currently bound (by Derham?) they are somewhat scrambled chronologically, which creates only the most modest difficulty. 164) Short of a handwriting analysis which might date them, the presence of the minute page in Oldenburg’s hand makes the assignment of these notes of Hooke’s to 1677–8 very probable. The Folio is available on the Society’s website, in original and transcribed form. 165) Diary, 24 Dec. 1677 and 27 Jan. 1677/78. On the latter date a trunk containing «19 bundells, 1 Letter book, 1 pocket book . . . » was received. Hooke, of course had two motivations, to secure the archives of the Society, and to uncover what he saw as Oldenburg’s duplicity. 166) They record seven meetings which took place between 3 June and 29 July 1691. At this time, the Society was meeting through early August, before adjourning until October. The secretaries during this period were Richard Waller and Thomas Gale. 167) Evidently the Society’s influence, and in all probability the obvious marketability of Hooke’s wonderful drawings led the printers to undertake the risk of publishing it. 168) In his preface, Hooke acknowledged that he was following in «the footsteps of so eminent a person as Dr. Wren, who was the first that attempted any thing of this nature; whose original draughts do now make one of the Ornaments

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of that great Collection of Rarities in the King’s Closet.» Jardine’s suggestion (Jardine, 2002) that the drawings of insects are by Wren has little to recommend it. Nothing in the record suggests this, and there are exquisite, detailed drawings of fossil specimens seen under the microscope that are known to be by Hooke, and that most likely were made by the same individual. See the interesting study of a Hooke drawing of a “kettering stone” in Micrographia in Hull (1997). Wren’s talent as a draftsman may have exceeded Hooke’s, but Hooke’s was great nonetheless. Hooke’s countryman Henry Power published observations with the microscope in 1661 (Chapman, 1996). 169) The copper plates survived and were reprinted in 1745 and 1780 with much reduced text, as Micrographia Restaurata. 170) Micrographia, p. 54. 171) What we think of as “an impedance mismatch.” 172) Pepys said, of the Micrographia, that it was «the most ingenious book that I ever read in my life.» (Diary, 21 January 1665).

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Chapter 8

And All Was Light: Hooke and Newton on Light and Color Late in 1671, with the first decade of his service to the Society drawing to a close, Hooke was the Society’s acknowledged expert on light and color. He was just embarking on some of his most important architectural projects and in the coming decade would publish several of his Cutler lectures, displaying for the world to see his breadth of interests and sheer virtuosity. It was at this point, with Hooke at the top of his game, that the young Isaac Newton, not quite 30, offered the first installment of his thoughts on light and color to the Society in a letter which Oldenburg read on 8 February. His remarks, which caused an immediate sensation, followed closely on the heels of the presentation to the Society of his reflecting telescope, his “coming out” as it were.1) Newton’s discourse posed a direct challenge to Hooke’s views, many of which Newton had encountered in Micrographia five or six years earlier, and to his authority.2) The essential part of Newton’s theory, which was based on careful experiments performed in Cambridge during the previous half-dozen years, was that light was heterogeneous, that it «consists of rays differently refrangible,» and that if a ray of a particular color was singled out, a second refraction produced no change in color. This challenged the accepted view, held by Hooke among others, that dispersion, the appearance of colors when white light passed through a prism, was «nothing but the effects of a compounded pulse or disturbed propagation of motion caused by Refraction».3) The colors were “generated” by a mechanism Hooke first proposed in Micrographia.4) in which the transverse vibrations or pulses were distorted or “qualified” by refraction. The implication of this view was, as Hooke claimed, that further refraction could restore already refracted light to its “primitive whiteness.”5) Hooke further asserted that all colors can be obtained from only two primary colors. Defending his hard-won status as much as his ideas, Hooke responded to Newton’s results forcefully but tactfully, saying that he remained unconvinced by Newton’s arguments for both his theory of color and his corpuscular theory of light. In his review of Newton’s theory, Hooke reiterated that «white is nothing but a pulse or

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motion, propagated through an homogeneous, uniform, and transparent medium: and . . . colour is nothing but the disturbance of that light . . . » While accepting much of the phenomena Newton described, and even claiming to have done many of the experiments, Hooke said that «as to his [Newton’s] hypothesis of solving the phenomena of colors thereby, I confess, I cannot see yet any undeniable argument to convince me of the certainty thereof.»6) Further, he would be «very glad to meet with one experimentum crucis from Mr. Newton . . . for the same phenomena will be solved by my hypothesis, as well as by his . . . »7) Treating Newton’s theory as an “hypothesis,” he would not be understood «to have said all this against his theory . . . for I doe most Readily agree wth him in every part thereof, and esteem it very subtill and ingenious, and capable of salving all the phaenomena of colours; but I cannot think it to be the only hypothesis.»8) All in all this was a calm and reasoned, not to say valid, or even very quantitative, critique of Newton’s ideas, just as Hooke had been asked to provide (along with Ward and Boyle). He certainly can be accused of having missed the significance of Newton’s demonstrations, and it was definitely not his finest hour as a natural philosopher, but he had not gratuitously provided an unsolicited criticism, nor were his remarks immoderate; in Thomas Kuhn’s view they were «most judicious.»9) Indeed, they reflect the sober judgment of one who believed that his long history of experimenting and thinking about light and colors gave him grounds for his criticism. For his part, the Cambridge Don’s initial response was restrained: «. . . having considered Mr Hooks observations on my discours, [I] am glad so acute an observer hath said nothing that can enervate any part of it.»10) As for a reply, «You shall very suddenly have my answer,» wrote Newton. Seeking at this point, at least, to avoid controversy, Secretary Oldenburg suggested to him that when he did reply to Hooke, as well as to the Jesuit Ignace Gaston Pardies who had also criticized Newton, he might choose not to mention them by name. 11) Newton’s eventual answer came almost four months later in a letter to Oldenburg read to the Society on 12 June 1672, and when it was printed in November12), the identities of those he was answering were not revealed. Of this reply, Westfall observed that «The critique [Hooke’s] must have rankled more than he let on . . . Instead of receiving the answer “suddenly,” Oldenburg had to wait three months; and when it arrived, its tone was rather less unruffled.»13). Newton met Pardies objections with notable restraint,14) but Hooke was another matter, for when the long and heated reply finally came, it was apparent that he had ruminated over Hooke’s arguments with growing anger.15) Westfall characterized the response as «viciously insulting – a paper filled with hatred and rage»:16) «The first thing that offers it selfe is lesse agreable to me & I begin with it because it is so. Mr. Hook thinks himselfe concerned to reprehend me for laying aside the thoughts of improving Optiques by Refractions. But he knows well yt it is not for one man to prescribe Rules to ye studies of another, especially not without understanding the grounds on wch he proceeds. Had he obliged me by a private letter on this occasion . . . »17)

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What Hooke had said was that he was a little «troubled that this supposition should make Mr. Newton wholy lay aside the thoughts of improving telescopes and microscopes by Refractions . . . » Newton’s harsh reaction hardly seems commensurate to the objection. The background of this dispute, which was really a side issue, and the source of the admonition of Hooke’s to which Newton refers, was the former’s earlier proposal for the employment of compound lenses, which in his case consisted of two lenses (one a flat slab) with a refracting “liquor” in between. Hooke thought that this would allow the use of lenses of larger aperture, achieving better definition and light gathering power. At the time, Newton also thought that the problem of chromatic aberration could be solved («I despaired not of their improvement by other constructions») but later did in fact despair of a solution and in the Opticks of 1704 purported to prove that an achromatic lens was impossible.18) Hooke’s response to Newton’s angry letter, though read on 15 February 1672, was never printed, and when he composed a response designed to mollify Newton, perhaps at the urging of some officers of the Society, it may never have reached him.19) In it, Hooke said that he «. . . had not thereby understood that somewt that I had sayd in my first paper had given offence to one that I had noe thought much lesse any Designe to disobleige . . . », and that he was «. . . soe far from imagining that Mr. Newton should be angry that I cannot yet believe that he is or will be soe for any concerne in a philosophicall Dispute wherein certainly if any where a freedome & liberty of Discoursing and arguing ought to be Tollerated.» Might the future of the relations between the two have been different if Newton had seen this message? Or were the two fated to clash, as Westfall suggests? Probably so, given Newton’s personality, Hooke’s assumed status as the authority on the subject, and his constant striving to be taken seriously as a natural philosopher.

Hooke’s Theory of Light As is the case with most of Hooke’s natural philosophy, his theory of light and color is neither highly developed nor very detailed. Although supported by geometrical arguments, it was not really quantitative. The earliest exposition of his ideas was in Micrographia, followed by his critique of Newton’s discourse in 1672, and then in his lectures on light of 1680–2.20) Although ostensibly devoted to his observations with the microscope, much of the early part of Micrographia is devoted to natural philosophy in general or to such diverse issues as capillarity and the nature of heat. But more than 30 pages are given over, at least to some degree, to problems of light and color. Hooke discusses what we know as interference, which he was probably the first to describe in detail and the first to provide a plausible explanation for, but most of this section of Micrographia was devoted to the nature of propagation of light, and how dispersion, or colors due to refraction, originate. The two fundamental issues on which Hooke disagreed with Newton were 1) light as undulatory, according to Hooke, or corpuscular, in Newton’s view,21) and 2) the nature of white light and the way in which colors resulted from the refraction

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of white light. Hooke believed that light traveling in a medium represented a «short vibrating motion,» «exceedingly quick,» that it propagates in straight lines or rays, that in a homogeneous medium, «every pulse or vibration will generate a sphere, which will continually increase . . . just after the manner (though indefinitely swifter) as the waves or rings on the surface of the water . . . », and that «all the parts of these Spheres undulated through an Homogeneous medium cut the Rays at right angles.»22) He attributed refraction to the fact that one medium «propagates the pulse more easily and weakly, the other more slowly, but more strongly», though he thought that light traveled more easily in glass than in air. Hooke was firmly committed to a vibratory theory of light and employed that idea in his explanation of the appearance of color under refraction. He had accused Newton of adopting an “hypothesis” with respect to the corpuscular nature of light, but of course his wave theory is no less hypothetical. We might take these positions as only “working hypotheses,” given the impossibility of testing them in the seventeenth century, but both Hooke and Newton showed strong commitments to their opposing views. Hooke speaks of the “orbicular pulse” which represents the direction of the vibration, which is, in space, perpendicular, that is, transverse, to the direction of propagation. But when light is incident obliquely on a medium, the orbicular pulse is oblique to the “Lines of Radiation,” i.e., rays,23) and it is this that results in dispersion, or the production of colors from white light. He believed that white light is fundamental and uncompounded and that color results when white light is disturbed by refraction: «. . . Blue is an impression on the Retina of an oblique and confus’d pulse of light, whose weakest part precedes, and whose strongest follows. And . . . Red is an impression . . . whose strongest part precedes, and whose weakest follows.»24) It is interesting, however, that while the two principal colors, “Scarlet and Blue” are produced by the process of modification of white light, the “intermediate” colors «arise from the composition and dilutings of these two,» which, one could argue, is only one step away from Newton’s theory, that white light is such a composition. Hooke does go to some length to show how his theory of refraction differs from Descartes’ «exceedingly ingenious Hypothesis.»25) In his 15 February (1671/2) letter to Oldenburg, commenting on Newton’s “Excellent Discourse”, Hooke had said that he accepted Newton’s experiments, and «was not a little pleased with the niceness and curiosity» of them. But he added that «though I wholy agree with him as to the truth of those he hath alledged, as having by many hundreds of tryalls found them soe . . . », he nonetheless could not accept the “hypothesis” used to explain them. He went on to reiterate that «For all the expts & obs: I have hitherto made, nay and even those very expts which he alledged, doe seem to me to prove that light is nothing but a pulse of motion propagated through an homogeneous, uniform and transparent medium: And that Colour is nothing but the Disturbance of yt light by the communication of that pulse to other transparent mediums, that is by the refraction thereof: that whiteness and that whiteness and blackness are nothing but the plenty or scarcity of the undissturbd Rayes of light;

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and that the two colours . . . are nothing but the effects of a compounded pulse or disturbed propagation or motion caused by Refraction.»26) This statement from a consummate experimentalist is perplexing. Newton’s experiments clearly showed that Hooke’s view of color was wrong and he stubbornly stuck to his inadequate theory in the face of empirical evidence It is unclear what insight we should take away from this episode, other than, perhaps, that we cannot expect anyone, however talented, to be totally rational or consistent.

Newton’s Theory In his initial communication to Oldenburg, Newton claimed that «Colours are not Qualifications of Light, derived from Refractions, or Reflections of natural Bodies (as ’tis generally believed,) but Original and connate properties, which in divers Rays are divers. Some Rays are disposed to exhibit a red colour and no other; some a yellow and no other . . . » Furthermore, «To the same degree of Refrangibility ever belongs the same colour . . . » and «The species of colour, and degree of Refrangibility proper to any particular sort of Rays, is not mutable by Refraction . . . » Finally, «. . . the most surprising and wonderful composition was that of Whiteness. There is no one sort of Rays which alone can exhibit this. ’Tis ever compounded, and to its composition are requisite all the . . . primary Colours, mixed in a due proportion.» Newton stated 13 propositions concerning color and went on to describe some experiments which demonstrated the validity of his theory, establishing in particular that «when any one sort of Rays hath been well parted from those of other kinds, it hath afterwards obstinately retained its colours.»27) In his response, Hooke said that he failed to see why «all these motions, or whatever els it be that makes colours, should be originally in the simple rays of light . . . »,28) indeed, «noe more than that all those sounds must be in the air of the bellows which are afterwards by differring stoppings & strikings produced . . . », thereby confusing the medium with the message, as it were. While accepting most of the propositions, at least in some modified form, he was quite unwilling to agree with the most fundamental of them, that «Light is a confused aggregate of Rays imbued with all sorts of Colors . . . » Hooke did concede that he could entertain the idea that «the white or uniforme motion of light» might be «compounded of the compound motions of all the other colours, as any one straight and uniform motion may be compounded of thousands of compound motions, in the same manner as Descartes explicates the Reason of the Refraction,» but he saw “noe necessity of it, » making a false analogy between a kinematic and a physical problem, but one that he certainly could be excused for making. In the meantime he had been conducting his own experiments on light and colour, including what we know as interference and diffraction,29) . and continued experiments designed to test Newton’s ideas. For example, on 18 April 1672, Birch records that «Mr. Hooke was ready to make an experiment by a prism, viz. to destroy all colours by one prism, which had appeared before through another: but there being not sun, as was necessary, the experiment was deferred.»30) By late May, Hooke’s experiments were confirming New-

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ton’s, so that «rays of the light being separated by one prism into distinct colours, the reflection made by another prism doth not alter those colours,» but even then he was not ready to concede that «light consists of different substances or diverse powders, as it were . . . » And he acknowledged in a paper read to the Society on 19 June that his experiments seem at first «much to confirm Mr Newtons Theory of colours & light;» but «yet I think it not an Experimentum crucis, as I may possibly shew hereafter.»31) Hooke was urged to «make more experiments of the same nature.» While Hooke’s clinging to his theory may seem stubborn, his attitude seems to have been at every point conciliatory, the best evidence, other than a total lack of acrimony, being the draft of a letter to Lord Brouncker, in which he said of his comments on Newton’s work that «if there be any thing therein that any ways savors of incivility or reproach I doe heartily begge his pardon and assure him twas innocently meant.»32) But among other things, Newton strenuously objected to Hooke’s use of the word “hypothesis” as applied to his ideas, which he had verified through experiment. He also objected to Hooke’s observation that he had said that light was a “body,” though he went on to defend that idea in the letter to Oldenburg and even claimed that Hooke ought to find it attractive. With somewhat more restraint, he attacked Hooke’s idea of light as some kind of wave motion, gave a detailed critique of Hooke’s ideas about the way in which colors resulted from refraction, and rejected his surprising notion that there are only two primary colors. The exchange, via Oldenburg, clearly defined two views of the nature of white light and how colors were produced by refraction, and if we see Newton’s arguments as obviously stronger, that was certainly not apparent to Hooke. In any event, there was little in Hooke’s critique that ought to have offended Newton, and Westfall’s view that Hooke’s observations were “irritatingly patronizing,” seems a bit forced. It is interesting that six letters from Newton to Oldenburg in the next two months reveal little agitation. Andrade, admittedly a Hooke partisan, wrote that «The whole matter might have dropped if Oldenburg had not, as always, done his best to stir up controversy: had he, on the other hand, exercised a little tact, and dropped a few soothing words rather than incitations to strife, bitterness between two men who essentially respected one another would probably never have arisen.»33) And the late Bernard Cohen argued that the controversy «in good measure was a result of Oldenburg’s intercession.»34) Finally, to Westfall, «the handling of Newton’s first letter tends to confirm Hooke’s suspicions that Oldenburg egged him on.»35) Hooke certainly believed that Oldenburg, who was in constant correspondence with Newton, had intentionally exacerbated the tension between the two of them, and Newton came to believe the same thing.

Debate after 1672 Hooke would never lose his interest in light, which he still regarded as his province. Although he was mostly silent in the immediate aftermath of the controversy with Newton, in March 1674/5 he was again elaborating on his wave or vibratory theory

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of light and color, likening it to sound, as against Newton’s theory. He continued to discourse on the subject, and talked about «an inflection of light differing both from refraction and reflection . . . » which is «made towards the superficies [surfaces] of the opacous body perpendicularly.»36) This description of the phenomenon of diffraction, which Hooke discovered independently, and which Newton may have learned of from Hooke,37) would also generate some fireworks, with Newton claiming that it was only a form of refraction and pointing out that in any case others had seen it before Hooke. In the meantime Huygens had also been mulling over Newton’s theory of light and color, and offered his own critique of it in letters to Oldenburg.38) Neither the Society’s decision to test Newton’s theory, nor Huygens’ observations upon it, sat well with Newton. In 1673 he asked Oldenburg to strike him from the rolls of fellows of the Society, though he did not pursue the issue, and indeed, in early 1675 he came to a meeting and duly signed the register, making him officially a member. More than three years would elapse without any contact between Hooke and Newton, although they apparently were both at a meeting of the Society on 18 February 1674/5, and Hooke records speaking with Newton about polishing speculum metal, in his Diary for that date. In December of the following year, four years after the first exchange, Newton responded to attacks by Francis Linus, as well as to the comments of Hooke and Huygens, by delivering a long manuscript on light and color to the Society. The paper, consisting of an “Hypothesis” and a “Discourse,” was read by Oldenburg in five parts between 9 December and 10 February 1675/6.39) In a letter to the Secretary, Newton prefaced the paper by remarking that he had «formerly purposed never to write any hypothesis of light & colours, fearing it might be a means to engage me in vain disputes: but I hope a declar’d resolution to answer nothing, that looks like a controversy (unles possibly at my own time upon some by occasion) may defend me from that fear.»40) Newton began by saying that he would not make any hypothesis about the aether and its role in the propagation of light, not thinking it necessary «to concern my selfe whether the properties of Light, discoverred by me, be explained by this or Mr Hook’s or any other Hypothesis capable of explaining them . . . »41) Further on he discussed Hooke’s discovery of diffraction, noting others who had observed it as well, but certainly giving Hooke credit. Hooke was, however, unimpressed, and after hearing the first part of the “Discourse” on 9 and 16 December, noted «that the main of it was contained in his Micrographia, which Mr. Newton had only carried farther in some particulars.»42) Five days later, Newton had not only learned of Hooke’s somewhat incautious comments but had already penned a reply, via Oldenburg (20 January), saying that «As for Mr Hook’s insinuation yt ye summ of ye Hypothesis I sent you had been delivered by him in his Micrography, I need not be much concerned at the liberty he takes in yt kind.»43) Much of the controversy had to do with the interference phenomenon that is now generally known as “Newton’s Rings,” though it was discussed much earlier by Hooke in Micrographia, but Newton was also at pains to point out, again, the differences between his and Hooke’s understanding of reflection and refraction.

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The result of this new exchange, indirect though it may have been, with Oldenburg as intermediary, was to rekindle the old animosity of four years before. Oldenburg would be dead in a little less than two years, but Hooke’s bitter feelings toward him, which had been simmering for some time, were about to burst into the open, the issue being the balance-spring watch. The rift between Hooke and Oldenburg was growing at this time, and Hooke felt that the Secretary was trying to exacerbate the ill will between himself and Newton. Ironically, this alienation prompted Hooke to write a very conciliatory letter to Newton,44) hoping to heal the rupture that he felt the Secretary had fomented. He wrote Newton on the day the latter’s heated reply was read to the Society, 20 January, and the Diary suggests that he wrote him immediately after the meeting, hoping to heal the rupture. In Newton’s more than cordial reply to this letter,45) he mentioned having called at Hooke’s lodgings only to find him out. And it was in this letter that Newton penned the famous line: «If I have seen further it is by standing on ye shoulders of Giants,» making it clear that Hooke was one of those giants. This almost friendly exchange of letters between brought a sort of peace and established a basis for Hooke’s correspondence with Newton after Oldenburg’s death in 1677. Eventually they reached a sort of truce through these letters of January and February of 1675/646), of which, however, Westfall has noted that «Sentiments too lofty drift away from human reality. A lack of warmth was evident on both sides. Neither man endeavored to institute the philosophic correspondence both professed to want, and their basic antagonism remained undissolved.»47). Their relationship would never be less than tense and ripe for misunderstanding. Newton had certainly carried the day, but not only because his theory provided the beter interpretation of his, and later Hooke’s, experiments.48) He had shown his intolerance of criticism and the anger that controversy with him could generate. Nor would this be the last time that his rage would quell discussion of opposing ideas. During the next decade or so the relationship between the two, if tenuous and distinctly lacking warmth, was free of direct acrimony, even if this was in part because of Newton’s touchiness. Newton’s paper was a tour de force of experimental natural philosophy, and would form a substantial part of the Opticks when he finally published it over a quarter century later, with Hooke barely in the grave. It is, therefore, representative of the Newton of the Opticks, characterized by careful and quantitative measurement, but mostly qualitative argument with relatively little mathematics (other than geometry). In the end, Hooke’s mostly qualitative and intuitive understanding, contrasting so strongly with the detailed arguments of his rival, left him fighting a rear-guard action with at best some rather plaintive objections. The victor in this contest was never in doubt. Hooke returned to light in 1680–1682 in lectures which were published two decades later in the Posthumous Works.49) Then, after nearly a decade in which his attention had turned elsewhere, he responded in February 1689/90 to the publication of Huygens’ Trait´e de la lumiere, in a discourse «tending to vindicate his notion of

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Light published in his Micrographia, in answer to that Theory thereof lately published by Mr Hugens.» In two decades, Hooke’s views had undergone little change. Both Hooke and Huygens were continuing to advocate something that could be called a wave theory of light, and at least Huygens may have been influenced by another advocate, Father Pardies.50) Although Hooke was defending what he had written on light a quarter-century earlier, many of Huygens’ ideas were not much more recent, some probably having arisen in response to Newton’s theory of 1671–2. Against Huygens, Hooke reaffirmed his belief that light traveled “easier” through glass «wherein he agreed with Mr Des Cartes in his Dioptricks», to quote the minutes.51) Huygens’ contrary view had been foreshadowed by Fermat, who had employed the minimal principal that bears his name to correctly derive the law of refraction. Huygens’ device of secondary wavelets was a very powerful innovation that allowed him to treat double refraction, a phenomenon that in turn led him to the discovery of polarization of light. The resulting Trait´e was a much more substantial and mature work than the theory of light given by Hooke in the Micrographia, or for that matter in the Posthumous Works. Nonetheless, seventeenth-century optics was mostly concerned with finding out what the phenomena of light and optics actually were, rather than in developing a theoretical structure or description. Fermat’s principle is an exception, as are Huygens’ wavelets, but even in Newton’s Opticks, the science is mostly an empirical one. Thus we have Newton’s experiments on color, his and Hooke’s study of interference, Hooke’s study of diffraction, and Huygens’ discovery of polarization of light. Hooke ‘s discourses on light in the early 1680s were thoroughly qualitative and actually deal with a wide range of issues only peripherally related to the propagation, reflection, and refraction of light, something that Waller apologized for when he published the “Lectures on Light” in the Posthumous Works.52) He discusses sunspots and the structure of the Sun (concluding that it must be a solid body), the fact that the Sun supplied heat as well as light, why the Sun has not diminished in size over time, vision, the nature of fire, comets, the inverse-square law, and so on. He does devote some space to the important issue of his “pulse” or “wave” theory of light. And among other things, he declares that «heat . . . is nothing but the internal Motion of the Particles of Body, and the hotter a Body is, the more violently are the Particles moved . . . » In this, he and Newton would agree. Hooke’s interest in light and optics would continue to the end of his life, although his comments became increasingly retrospective. This fascinating episode does little credit to Hooke as a scientist. In the face of clear experimental evidence he maintained that his own theory could equally well fit the data, which was clearly false, and that Newton’s theory was only a gloss on his Micrographia, which was equally untrue. It may be that he was too busy to carefully read what Newton had written, as indeed he implied, but that is not impressive as a defense. Despite Hooke’s moderate tone, Newton’s exasperation is unsurprising, yet his intolerance of criticism produced a reaction disproportionate to Hooke’s refusal to bow to his arguments. . . Historical “what ifs” are rarely fruitful, but . . . As for Newton, he lost no time in publishing his Opticks in 1704, on the heels of Hooke’s

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death the previous year.53) In this work he too speculated widely, and often on issues such as the cause of gravity and the nature of heat, far removed from the central topics of light and color. To the extent that two separate styles are apparent in the two works, the Principia and the Opticks, the mathematical physicist and the experimenter, we note that though published later, much of the Opticks was written in the decade or so before the Principia, and relied heavily on his own optical lectures of many years before, Of course Newton revised both works almost up until the time of his death, so that this chronology may be irrelevant, but that two traditions radiate from Newton is fairly clear, at least as measured by how they were received by the eighteenth century, that of the Principia influencing mathematical physicists like Euler and Laplace, and that of the Opticks, guiding such figures as Benjamin Franklin, and perhaps even Michael Faraday and Ernest Rutherford.

Annotations 1) It was evidently the first to be constructed, but far from the first proposed. Newton got his idea from James Gregory’s Optica promota, but the concept of a reflecting (“catadioptrical”) telescope was considerably older, perhaps going back to Leonard Digges in the sixteenth century. On the other hand, the particular design, which we call “Newtonian,” was original. Rupert Hall wrote, probably with good cause, that «It is doubtful that any scientifically useful reflector was made in the seventeenth century.» Hall (1992), p. 118. 2) Hall (1992), pp. 50–53, especially p. 53. Keynes printed Newton’s notes on Hooke’s Micrographia (Keynes, 1960, pp. 97–108. See also Buchwald and Cohen (2001), p. 3. When Newton wrote in 1665 that optics was a subject «more proper for mathematicians than naturalists,» he may have been referring to Hooke. Ibid, p. 52. 3) Hooke to Oldenburg, 15 February 1671/2 (Corresp., I. p. 110). This was Hooke’s response to the first part of Newton’s hypothesis of light. 4) Micrographia, pp. 62–3. 5) It is interesting that in his “Lectures on Light,” delivered in 1680–2, nearly a decade after the exchange with Newton, Hooke had little to say about this contentious issue, implicitly conceding that Newton was correct. 6) Hooke to Oldenburg, 15 February 1671/2. Newton’s letter to Oldenburg was dated 6 February and was quickly published in the Philosophical Transactions [6 (1671/2) 3075–87, No. 80]. 7) Hooke’s answer occupies nearly five pages in Birch (vol. 3, pp. 10–15). Note that Hooke is speaking of “saving the phenomena,” rather than arguing for a unique, perhaps “true”, explanation. 8) Note Hooke’s emphasis on “saving the phenomena,” rather than providing a unique explanation.

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9) Though to Marie Boas and A. Rupert Hall, they were «most ill judged.» 10) Newton to Oldenburg, 20 February (Corresp., I, 116). 11) Corresp., I, 159. 12) PT, No. 88, p. 5084, 18 November 1672. 13) Westfall (1980), p. 241. 14) Of Pardies, he wrote that «As to the Reverend Father’s calling our doctrine an hypothesis, I believe it proceded only from his using the word that first occurred to him . . . » (Newton to Oldenburg, 11 June 1672; Corresp., p. 171). Huygens also thought that Newton should be content to have his theory regarded as an hypothesis: «Nevertheless the thing could very well be otherwise, and it seems to me that he ought to content himslf if what he has advanced is accepted as a very likely hypothesis. The more so since even if it were true that the rays of light were, by their origin, some red, others blue, etc. there would still remain the great difficulty of explaining by the mechanical philosophy what this diversity of colors consists of.» Huygens to Oldenburg, 17 September 1672, CHO, IX, 247–51. 15) Newton to Oldenburg, 11 June 1672. Corresp. I, 172–188. 16) Westfall (1980), p. 247. 17) Corresp., I, 172. 18) «Seeing therefore the Improvement of Telescopes of given lengths by Refractions is desperate; I contrived heretofore a Perspective by Reflexion, using instead of an Object-glass a concave metal.» Opticks, Book one, Part I. Hooke mentioned the compound lens in the preface to the Micrographia, and publicly at the meeting of the Royal Society on 18 January 1671/2. Newton described a compound lens of similar construction between 1666 and 1668. See Bechler (1975). 19) Letter to the president, Lord Brouncker, after 11 June 1672. Corresp. I, pp. 198–205. 20) In the Diary for 11 November 1680, Hooke says «Read lectures of light.» 21) Newton’s theory of the way light propagated directly challenged Hooke’s. Newton’s strongest defense of his corpuscular theory was in the Opticks, where he defended that position against the wave theories of Huygens and Hooke. In the Queries which conclude the work, Newton also committed himself to the idea that matter itself was corpuscular, that matter consists of small particles, and that their motions are responsible for «a great part of the Phaenomena of Nature», and in particular that their motion constitutes heat. 22) Micrographia, pp. 56–7. This seems reminiscent of Huygens’ principle, that every point on a wavefront is the source of a spherical expanding wavelet. 23) Micrographia, p. 59. Alternatively, » the pulse is made oblique to the progressive.»

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24) Ibid, p. 64. 25) A good analysis of Hooke’s ideas can be found in Sabra (1967), pp. 251–264. 26) Hooke to Oldenburg, 15 February 1671/2; Corresp. I, p. 110. 27) All of these passages are in Corresp., I, 92–102. 28) Hooke to Oldenburg, 15 February 1671/2; Corresp. I, 110–114. 29) Interference: 14 and 28 March (Birch 3, 29); Newton’s Rings, 4 April (Birch 3, 410; diffraction: 7 March (Birch, 3, 19). On diffraction: Birch, 3, p. 194 (18 March 1675); PW, pp. 187–190, Micrographia, p. 221. Francesco Maria Grimaldi (1618–63) is usually given credit for being the first to describe diffraction. 30) Birch, 3, 43. This result, had it been successfully demonstrated, would have contradicted Newton’s theory and experimental results. The brief description of the experiment carried out on 24 April suggests that Hooke managed to obtain the result he desired: «Mr. Hooke shewed two experiments of colours with a couple of prisms. By the one it appears that one prism took off the colors, which the other had produced.» Ibid, 31. En passant, it is worth noting that we sometimes forget that there would not be any effective artificial light sources for nearly two centuries. 31) Birch, 3, 53; Corresp., I, 195. 32) There is no evidence that Hooke actually was allowed to read this longer reply to Newton’s answer: Westfall (1980), p. 247 n. 34); Corresp. I, p. 203–4. 33) E.N. da C. Andrade, in the introduction to Turnbull (1959–61), pp. xxi–xxii. The quote is on pp. xxi–xxii. 34) Cohen (1961). 35) Westfall (1980), p. 273. 36) See fn. 30. 37) On this point see Hall (1990). 38) Huygens to Oldenburg, Corresp. I, 283, 285–6. 39) Newton to Oldenburg, 7 December 1675; Corresp. I, 362–386. For elaboration, see Chapter 7 of Westfall’s Never at Rest, especially pp. 267–271. Also the endnotes in Turnbull’s Corresp. I, 386–392. Hooke’s Diary comment is of no help: «a Discourse of Mr. Newtons read about Light.» (9 December 1675/6). 40) Corresp, I, 360–1. 41) «An Hypothesis explaining the Properties of Light discoursed of in my severall Papers.» Corresp. I, 362–386. Also Birch, 3, p. 248ff. 42) Birch, 3, 269. Hooke made very much the same comment on Newton’s theory of planetary motion. Everything we know of Hooke suggests that he really believed these assertions. 43) Corresp., I, pp. 404–406.

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44) Hooke to Newton, 20 January 1675/6. Corresp. I, pp. 412–3. In his Diary for that date he wrote «A letter also of Mr. Newtons seeming to quarrel from Oldenburg fals suggestions,» and a few lines later, «Wrot letter to Mr. Newton about Oldenburg kindle cole.» This was the first of 16 letters between the two. This exchange of letters in January-February 1675/6 was prompted by Hooke’s concern that Oldenburg may have misrepresented his comments on Newton’s optical theories. Hooke wrote, referring obviously to Oldenburg, that «you might have been some way or other misinformed concerning me and this suspicion was the more prevalent with me, when I called to mind the experience I have formerly had of the like sinister practices.» and that «. . . the collision of two hard-to-yield contenders may produce light [,] yet if they be put together by the ears of other’s hands and incentives, it will produce rather ill concomitant heat which serves for no other use but . . . kindle cole.» The sentiment Hooke expressed, of public controversy producing more heat than light, has been called the “kindle-cole” principle, or the “Hooke-Newton-Merton” principle, and expresses the idea that scientists ought to avoid airing their disagreements in public. Or, as Bernward Joerges put it, «the distorting effects of public . . . polemics among men of science.» (Joerges, 1990). Hooke went on to praise Newton’s work, saying that «. . . you have gone farther in that affair much than I did . . . » and that there was no «more able person to inquire into than yourself, who are every way accomplished to compleat, rectify, and reform what were the sentiments of my younger studies, which I designed to have done somewhat at myself, if my other more troublesome employments would have permitted, though I am sufficiently sensible it would have been with abilities much inferior to yours.» It was in the 6 February letter to Hooke that Newton uttered his famous «If I have seen further it is by standing on ye sholders of Giants.» (Corresp., I, 416). Some have seen this as an insult, but this was surely not the case. 45) Corresp., I, 416–7. Manuel has provocatively described the exchange this way: «Here were two former country boys, now men of genius at the height of their powers, aping the manners of Restoration courtiers – flattering each other, overpraising, scraping and bowing, . . . » Manuel (1968), p. 143. It was in the 6 February letter to Hooke that Newton uttered his famous «If I have seen further it is by standing on ye sholders of Giants.» (Corresp., I, 416). Some have seen this as an insult, but this was surely not the case. 46) Hooke to Newton, 20 January; Newton to Hooke, 5 February. Corresp., I, 412, 416. 47) Westfall (1980), p. 274. 48) What we do not address here is that Newton’s theory was supported by substantial mathematical argument, something that was not true in Hooke’s case, in this matter or in others. The geometrical arguments Hooke offers in Micrographia are basically qualitative. 49) These included 11 November 1680, 4 May 1681, and 3 May 1682.

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50) See Sabra (1967), pp. 195–7, and elsewhere. 51) Journal Book for 19 February 1689/90. 52) «Instead of proceeding farther in the Method he had proposed to himself, of explaining how the Rays or Pulses of Light from Luminous Bodies are Reflected, Refracted or Inflected . . . which several Subjects I suppose he design’d to treat of, though I do not find that he ever did . . . being diverted by other intervening Subjects, which carried his Thoughts other ways . . . » Waller, PW, 128. 53) In July 1694 the Society asked Newton if he would «please to Communicate to the Society in order to be Published his Treatise of Light and Colours . . . » (Journal Book, 4 July 1694).

Chapter 9

The Nature of Things Themselves: Robert Hooke, Natural Philosopher «There is no means in the World for the attaining of the true Knowledge of things more certain . . . than the accurate Observation and strict Examination of them by Trials and Experiments.» “Discourse of Comets,” 1682

Introduction Despite the fact that Hooke was one of the important natural philosophers of the seventeenth century,1) very little has been written on his philosophy per se, as distinct from his discoveries in natural philosophy, that is, his 40-year practice of experimental philosophy. Given Hooke’s general obscurity, we should not be very surprised that his philosophical thinking has been neglected, but at least as strong a reason is that in his busy life there was little time for the contemplation that might have led to more systematic and abstract thought about natural philosophy and how philosophical (or scientific) knowledge was to be acquired and understood. And finally, while Hooke may have debated such issues with friends over coffee, he was by nature of a rather practical bent. Nonetheless, very few if any of his speculations and discoveries were simple or naive, that is, unconnected to other phenomena or to some larger idea. Like Galileo before him, Hooke understood the implications of his own discoveries and those of his contemporaries. The only notable exception to this statement would seem to be the mathematization of natural philosophy carried out by Newton when Hooke was in his 50s. The sparseness of the record is further exacerbated by the fact that much of what we have of Hooke’s reflections on natural philosophy are in the form of lectures, generally with another subject in mind, for example, light or comets. The result is that while interesting in view of his importance to the origins of modern science, Hooke’s writing on the subject is neither particularly deep or revealing, not least because much

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of it dates from the years around 1680, by which time his style of natural philosophy had been on display in the Royal Society for nearly two decades. It relied heavily on Bacon, but with a strong tempering influence from Descartes, much of this filtered through his friend and mentor Boyle, though, surprisingly, this influence, which was undoubtedly important, is barely acknowledged. Hooke’s lecturing and writing on these issues had neither the depth nor the breadth of Boyle, who was much more a philosopher than he, but by the same token, Hooke was much more of a “scientist” than his friend.2) Boyle’s leisure, moreover, afforded him the luxury of reflecting at length on natural philosophy and to preserve these thoughts for posterity. Hooke’s writings and lectures on natural philosophy represent a ringing defense of his Baconian ideals, but we should not forget that Bacon had been revered by the Society since its inception, and much of what Hooke wrote can be seen as elaborating upon what was a consensus. No one better exemplified this method, however, nor was anyone as influential in showing its power. It too would begin to wane in influence, but it is nonetheless very revealing of Hooke’s vision of how the natural world was to be understood.3) Hooke absorbed these Baconian ideals while he was apprenticing in Oxford, and put them into practice with Boyle and as the Society’s Curator. In the ensuing years, he showcased them using the Society as a forum, and as one of its intellectual leaders helped perpetuate its Baconian leanings through the 1680s. We shall see below, however, that Hooke realized the dangers of undirected experimentation, and we often see him appealing to the authority of Descartes, who despite his devotion to Bacon, still influenced him. In this chapter, our strategy in studying his natural philosophy will be to study, for the most part chronologically, his discourses and lectures, rather than to look at specific issues or questions, e.g., his ideas on matter, motion, force, space, time, and so on. For the most part, this is dictated by the material we have to work with.

Hooke’s Natural Philosophy Although we can construct a picture of Hooke as a natural philosopher by looking at his career as an experimental scientist, as indeed we did in Chapter 7, we can learn as much, perhaps more, by studying his musings on the subject, the most directly relevant being his “Present State of Natural Philosophy” and “The Method of Improving Natural Philosophy,” which were published after his death by Waller, but were apparently composed in the first decade of his service to the Society, perhaps as early as 1666.4) As we have already suggested, Hooke’s writings about natural philosophy rarely stray far from a specific problem, experiment, or observation, and we note that in “Improving Natural Philosophy,” Hooke has in the back of his mind the nature of comets and their orbits, prompting him to offer a long series of Queries concerning the aether, the atmosphere, clouds, rainbows, and so on. But he turns to the more general question of method, or as he thought of it, a “philosophical algebra,” as a means of answering these Queries:

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«After the Queries have been thus propounded . . . the next thing will be to consider what Materials are to be got for the solving of them, and answering our Doubts, what Histories and Observations from abroad, and what Experiments, Observations and Tryals at home will be necessary to be obtained and made . . . »5) The succeeding paragraphs in this discourse deal with sense experience and how to register and quantify it, how to augment the evidence of the senses with instruments, how to collect and cull experimental data, and how to «reason and deduce» from them. What results is a sort of manual of experimental philosophical practice, focusing on the detailed properties of bodies, how one body affects another, and on changes and transformations which may be observed, emphasizing «great Care and Judgement . . . in exactly determining the Quantity, Quality, Time, Place, Space, and several other Circumstances . . . that all things may be reduced to some Certainty of Number, Weight, and Measure . . . »6) Following an enumeration of the “Operations of Bodies” and how such operations or effects are made evident to the senses,7) Hooke elaborates at length on these effects and their origins, examining how a property is modified in different states of a body, how a particular property is manifested in several bodies, how properties are combined or separated, how they transform from one into another, and so on. These he sees as providing ways of discovering the “Methods of Nature.” If Hooke’s idiosyncratic style defies easy summary, the examples he chooses to illustrate are always of interest and constitute a kind of catalog of interesting problems in seventeenthcentury natural philosophy. Hooke is at pains to emphasize the importance of “registering,” that is, taking careful, detailed notes on each experiment performed, cautioning one to avoid «augmenting the Matter by Superlatives, nor abating it by Diminutives,» or «accommodating it to this or that Author’d Opinion; avoiding all kinds of Rhetorical Flourishes, or Oratorical Garnishes . . . » Drawings are important to the process of registering, but, significantly, appeal to authority is not. All in all, quite good advice.8) For Hooke, the comparison of the works of man, i.e., the practical arts, with those of the natural world, offered several opportunities for discovering the latter, «by observing and comparing the Production of Art with those of Nature,» that is, considering products of the crafts or trades as analogies to the workings of nature. These include «. . . observing and comparing the Natural and Artificial ways of producing the same Effects, . . . observing where and by what means Art causes Nature to deviate or alter its usual Course, . . . observing and comparing the Natural and Artificial ways of producing the same Effects . . . by observing the differences between the Products of Nature and those of Art . . . » and so on.9) In the second part of his “Philosophical Algebra” Hooke promised to explain how one ought to proceed «from Axiomes to Experiments, and from Experiments to Axiomes . . . [which is] indeed the Business of the Philosopher.» This nuanced and balanced view of scientific discovery is very promising, but, Waller, in the role of editor, informs us that, «. . . as to the reasoning part of his Philosophick Algebra,»

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his promise was never fulfilled.10) Hooke was content to show «the way of making use of the Penus Analytica, of raising Axiomes, and more general Deductions from a sufficient Stock of Materials collected according to the Method of this first part . . . »11) In other places, however, Hooke does elaborate upon these issues, requiring us to summarize his thinking at some length. On scientific truth, for example, he said, in his “Lectures on Light,” read in early 1680: «For as in pure Geometry nothing is to be let pass for a Truth, whose Cause and Principles are not clearly shown by the Progress of Reasoning, and the Process of Demonstration: So in Physicks Geometrically handled, nothing is to be taken for granted, nor any thing admitted for a true Conclusion, that is not plainly deduced from self-evident Principles, and those founded upon the immediate Objects of Sense disintangled from all the Fallacies of the Medium and Organ.»12) In a subsequent lecture on light, apparently read to the Society on 11 November 1680,13) Hooke addressed the «true Method of coming to the Knowledge of all the Operations of Nature,» which, is to observe the effects, and then to deduce «from what Causes those Effects proceed.» Therefore, «whoever goes the other way to work, and begins a priori to this first of the Cause, and then to deduce the Effects from it . . . begins at the wrong end.»14) He likened the works of nature to a great Labyrinth, «which is already built and perfected . . . and bounded by impenetrable Walls; and there are no new Passages to be made, other than what are already fixt: He therefore that shall think immediately to fly and transport himself over these Walls, and let himself in the very middle and inmost Recess of it, and thence think himself able to know all the Meanders and Turnings, and Passages back again to get out; will find himself hugely mistaken and puzled in finding his way out again . . . The most of our Philosophers that have hitherto written . . . have begun from some inward part of the Labyrinth, having made some small Entrance, and have thence thought they knew the whole Fabrick, and to have found the way out again by the help of their Memories, neglecting or despising the Clew, the Compass, the Circumferenter, and the Chain, whereby to observe Measure . . . And have thereupon feigned a way, and have made to themselves a Labyrinth, and have presently given you a Design of the whole. But alas, this Labyrinth was in their own Mind, and not of Nature’s making . . . »15) Hooke returned to the same theme, though somewhat less metaphorically, in his “Discourse of Comets,” of November 1682, defending the “Synthetic method” against the “Analytic way,” and in “A Discourse of Earthquakes” he elaborated:

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«The methods of attaining this end [a true and certain knowledge of the Works of Nature] may be two, either the Analytick, or the Synthetick. The first is the procceding from the Causes to the Effects. The second from the Effects to the Causes: The former is the more difficult, and supposes the thing to be already done and known, which is the thing sought and to be found out; this begins from the highest, most general and universal Princples or Causes of Things, and branches itself out into the more particular and subordinate. The second is the more proper for experimental inquiry, which from a true information of the Effects by a due process, finds not the immediate Cause thereof, and so proceeds gradually to higher and more remote Causes and Powers effective, founding its Steps upon the lowest and more immediate Conclusions.»16) On the other hand, despite this ringing endorsement of the experimental philosophy, Hooke argued forcefully for the importance of theory in guiding experiment and observation, acknowledging, as he did in Micrographia, that he was departing somewhat from the Baconian method so dear to the Society: «I mention this, to hint only by the by, that there may be use of Method in the collecting of Materials, as well as in the use of them . . . that there ought to be some End and Aim, some pre-design’d Module [i.e., model] and Theory, some Purpose in our Experiments, and more particular observing of such Circumstances as are proper for that Design. And though this Honourable Society have hitherto seem’d to avoid and prohibit preconceived Theories and Deductions from particular, and seemingly accidental Experiments; yet I humbly conceive, that such, if knowingly and judiciously made, are Matters of the greatest importance.»17) Clearly Hooke understood the hazards and futility of unguided experimentation.

Light; Matter, and Motion In the first lecture on light, of 1680, which took place the better part of a decade after he and Newton had clashed over light and color, Hooke explored the propagation of light through space and in matter, and tackled the question of the existence of a vacuum in nature. He was inclined to side with Descartes, who equated body with extension. Either there must be a vacuum, he wrote, «which impugns the very ground of the Cartesian Principles,» or an infinite fluid. After also exploring Aristotle’s ideas about light, he offered his own theory, which he described as a sort of mechanicalgeometrical reformulation, or explanation, of Aristotle. Light to Hooke was some kind of motion of the body or medium, which, despite Rømer’s observations of the satellites of Jupiter, he thought was infinitely swift.18) He described the action of light as being «so near of Kin to that of a Spirit», but equivocated, saying that «after all this

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we may prove it to be purely corporeal, and subjected to the same Laws that bulky, tangible, and gross Bodies are subject to.»19) In another lecture on light, presented according to Waller, «about May, 1681»,20) Hooke ends the lecture with the claim that it is the power of light that is «the Power of Celestial Bodies by which they Act upon, and attract each other; and by which all the Primary Planets that move about the Sun are regulated in Velocities, Distances and Motions, whether circular or Oval.» There follows the promise that «. . . from the true stating of this Power, and the Effects of it on Bodies at several Distances, all the Theory of Astronomy will be deduced a Priori, with Geometrical Certainty and Exactness; and consequently the Tables and Numbers will be easily adapted, which will tend to the Perfection of that Noble Science.» Whether Hooke thought that he could supply the Theory which would lead to the “perfection” of astronomy is not clear, nor can we guess how he intended to establish the relation between gravity and light hinted at above. This lecture was read a year or so after the exchange of letters with Newton on the motion of a body experiencing a centripetal force (Newton’s later term) due to gravity, which we discuss in the next chapter. In that correspondence, Hooke sticks much closer to what he knows. In the same lecture, Hooke comments on motion, saying that the observable properties of motion are quantity, quality, and power. By the quantity of motion, he wrote, «I understand only the Degrees of Velocity existent in a certain Quantity of Matter.» And, «By the Power, I mean the Act or Effect it produces upon other Bodies, in agitating or moving them.» He then assured the listener (or reader) that «In the Consideration of every one of . . . [the observables], I shall endeavour to reduce the Theory to Calculation and Mathematical Exactness; without which, all other ways are but Random Guesses.» But while we are a bit startled to hear him say that «. . . Heat, as I shall afterward prove, is nothing but the internal Motion of the Particles of Body . . . »21) and perhaps marvel at the clarity of his defense of that position, alas, we again look in vain for the promised «Mathematical Exactness.»22) In his “Discourse of Comets,” Hooke says that the two powers «which cooperate in effecting the most of the sensible and insensible Effects of the World,» are Body (or matter) and Motion; they are the «Whole of Realities,» the female and male principles of Nature, and the «immediate Product of the Omnipotent Creator.»23) Hooke’s “Body” is essentially equivalent to our “mass”, because it is independent of shape. Motion «may be increased or diminished in any assignable Quantity,» but «the natural Ballance of the Universe is reciprocal to the Bulk or Extension, or to the Quantity of the other Power, Body.» Hooke further took matter and motion (or body and spirit) to be primitive quantities, given their meaning by “the Omnipotent”: «It may possibly be demanded, what is Matter, and what is Motion? To which I can only answer, That they are what they are; Powers created by the Omnipotent to be what they are, and to operate as they do . . . and these are those which we call the Laws of Nature; which though at first glance they seem wholly unsearchable and incomprehensible, yet God has

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planted in Man a Faculty by which, I conceive, he has a Power of understanding and finding out, by and according to what Order, Rule, Method, or Law, they act, and produce the Effects that are produced by them. And this I conceive to be that which we call Natural Knowledge . . . »24) Evidently for Hooke, Man has an innate capacity or power which effectuates his understanding of the natural world. A bit later in the lecture, Hooke looked to the first chapter of Genesis for confirmation of his hypothesis of the existence of the two great principles, Matter (=Mater; female principle) and Motion, as exemplified in gravitation and light, the former being embodied, as Hooke saw it, in the division of the Waters from the Waters. His aim, he said, was to show «that nothing of what I have hitherto supposed, does any ways disagree with Holy Writ, but rather, that it is perfectly consonant to that, as well as it is to Reason, and the Nature of things themselves.»25) We could desire no clearer statement of the way natural theology and natural philosophy were seen to stand side-by-side in providing understanding of the natural world. In a further lecture on light read in the spring of 1682, Hooke was concerned with the propagation of light instantaneously in successive brief pulses [ my term] through the fluid which fills the «whole Expansum of the Ethereal Matter», and attempted to show why the impediment to motion of bodies through it should be “inconsiderable.”26) The same idea is expressed in his later “Discourse of Comets,” in which he says, speaking of the aether, that «The vast Expansum of the World, that is, the whole Interstice between the greater globular Bodies thereof, is a Body exceeding fluid, and so fluid as hardly to be able to hinder the Motion of any Solid through it . . . » But it is by means of this fluid that «the Motion of Light is propagated outwards . . . with unimaginable celerity: And also the Gravitation or Motion of descent from all imaginable Distance . . . of all solid Bodies, is caused and produced by the like Radiating Lines or Orbicular Pulses reversed, with an unimaginable Celerity and prodigious Power.»27) Here we see Hooke’s commitment to the aether, its role in the propagation of light and even gravity. Of course we expect no one to be perfectly consistent or invariably true to principle, and Hooke was no exception. For example, his theory of air as consisting of «vapours and exhalations» dissolved in the aether, the «grand or universal menstrum,» was not entirely compatible with his Baconian principles.28) When Thomas Henshaw objected, during discussions of Hooke’s theory in January 1677/8 that (quoting from Birch), «it was not very evident that there was any such thing as an aether, much less was it understood what it was, and what properties it had . . . », Hooke responded, as he did later to Wren, «that by multitudes of experiments he could make it very evident, first, that there was such a body: secondly, what many of the properties of that body were . . . »29) In the seventh section of the “Lectures on Light,” as Waller collected them, evidently the content of a “long” lecture given on 21 June 1682,30) Hooke addressed time, memory, and the Soul, for he considers memory to be «nothing else but a Repository of Ideas formed partly by the Senses, but chiefly by the Soul it self . . . », and

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supposes that «there may be a certain Place or Point somewhere in the Brain of a Man, where the Soul may have its principal and chief Seat.» This leads to a consideration of each of the senses and how sense impressions are received, and eventually, what thought is, which Hooke says is «partly Memory, and partly an Operation of the Soul in forming new ideas.» At one point Hooke discusses the infinite divisibility of space and time, and suggests that our sense of what a short time interval may be is relative to the pace of our own lives and not absolute, noting that the rapid movement of a fly’s wings may not seem rapid to the fly. Similarly, he imagines a body resolved into the «thousand thousandth Part of the least sensible Space», observes that «the bigger a Body is, the slower is its Vibration,» and conjectures that «there may be yet beyond the reach of our Ears infinite shriller and shriller Notes.»31) Finally, discussing “small Creatures” he notes that «it does seem that Nature has as it were ballanced Gifts bestowed upon them by some other Means adapted more particularly to each of their Constitutions.» This sense that animals have somehow become adapted to their environments is amplified in his “Lectures on Earthquakes” which, however interesting and far-seeing, we do not explore here.32) In the concluding section to the “Discourse of Comets,” the section that Waller has titled “Of Comets and Gravity,” and from which we have already quoted, Hooke speculates extensively about gravity, including its universality and its origin. It is interesting that he considers «its working within the Body of the Earth below its Surface,» but says that «no one I have met with seems to me to have hit upon a right Notion concerning it . . . » This, in a lecture which according to Waller was given in late 1682, two years after the exchange with Newton that we recount in the next chapter in which he has a clear (and correct) idea of how gravity varies in this situation. He hints at the «various degrees at several Distances» with which gravity acts, «not asserted by any Person whatsoever,» but does not reveal the answer.33) Hooke’s defense of the method he understood to be proper for the investigation of nature was unequivocal. He was heavily influenced by Bacon and Descartes, as we hear from his own mouth, but he arrived at his own personal synthesis, one that we see manifested in his informal comments at Society meetings and in his more formal lectures. We can imagine that these discourses on natural philosophy were influential within the Society, buttressed as they were by the virtuoso performances at meetings in which he displayed numerous applications of their principles, and yet, except for the very early Micrographia and the Cutlerian Lectures, none of these thoughts were published in his lifetime. In the Society only Boyle was more expansive on these issues, but it would be Boyle’s prodigious and more systematic published writing, along with his much more illustrious reputation, which defined natural philosophy in England in the first quarter-century of the Society, that is, the last half of the seventeenth century.

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Natural Philosophy and Newton As the 1670s drew to a close, Hooke’s mostly Baconian method, while still clinging to its place as the secure foundation of natural philosophy, was beginning to be pushed aside. There was increasing discussion of the new developments in mathematics, and when the Principia appeared in the next decade, a new vision began to take hold, one which was completely compatible with the experimental philosophy of Bacon, Boyle, and Hooke, but one which would result in a fundamental mathematization of nature. If commentators have argued about what his method actually was in the nearly three centuries which have passed since Newton, it is nevertheless true that from Hooke to Newton we see an unmistakable shift in outlook which would leave Hooke behind. With that in mind, it is worth spending a few moments on Newton as a natural philosopher. If nothing else, it provides some hints into the “revolution” in natural philosophy which Newton brought about, and why Hooke’s views passed out of favor. Newton’s natural philosophy has stimulated a vast body of scholarship and writing, including a recent and important collection by Jed Buchwald and Bernard Cohen.34) Newton’s Mathematical Principles of Natural Philosophy can be seen as establishing for the eighteenth century the character of natural philosophy, in the largest sense of that term. As with Hooke, one can distinguish between what Newton wrote about the philosophy of nature, which is to be found in the Principia, the Opticks, and here and there in his extensive correspondence, from natural philosophy as he practiced it. The latter is displayed in his mathematical and physical papers, most of which can be found in Whiteside’s monumental Mathematical Papers of Isaac Newton, and, above all, in the Principia. But Newton actually wrote very little about natural philosophy, so that his philosophy, fundamentally, is his method and its application. It is that framing of nature in mathematical terms, the possibilities of which were glimpsed by Galileo and carried forward by Descartes – however flawed the uses to which he put it – which was in the end carried out by Isaac Newton.35) In a discussion of Book II of the Principia, George Smith, echoing Bernard Cohen, asserts that the “Newtonian style” consists in proceeding by a series of successive approximations from the simplest idealization toward to a more complex and realistic one. Most of his examples are from Newton’s treatment of motion in resisting media. As Smith puts it, «Newton’s genius as a physicist . . . was one of recognizing evidential pathways, paved by mathematically derived if-then principles, that offered a potential for vast, sustained step-by-step empirical inquiry.»36) One of Newton’s great strengths was his ability to carry a theoretical development far enough to make actual calculation possible, usually through a variety of approximations, thus grounding it in or testing it against empirical results. To Michael Blay and others the main aim of the Principia is to deal with the transition from the discontinuous to the continuous, notably in the effect of the action of gravity on an orbiting body. If so, Newton was better suited than anyone else to do this, given his mastery of the techniques of quadratures and tangent methods, that is, the integral and differential calculus. Other notable features of the Principia

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which derive directly from Newton’s mathematical discoveries, and obviously related to each other, are his widespread use of infinite series and perturbation methods.37) As for Newton himself, he gave perhaps the clearest summary of his philosophy, or at least his method, in the conclusion to the Opticks, in words that are not so different from Hooke’s – indeed seem to echo them – except in the emphasis on mathematics: As in mathematics, so in Natural Philosophy, the Investigation of difficult Things by the Method of Analysis, ought ever to preceed the Method of Composition. This Analysis consists in making Experiments and Observations, and in drawing general Conclusions from them by Induction, and admitting of no Objections against the Conclusions, but such as are taken from Experiments or other certain Truths. For Hypotheses are not to be regarded in experimental Philosophy. And although the arguing from Experiments and Observations by Induction be no Demonstration of general Conclusions; yet it is the best way of arguing which the Nature of Things admits of, and may be looked upon as so much the stronger, by how much the Induction is more general . . . This is the Method of Analysis: And the Synthesis consists in assuming the Causes discover’d, and establish’d as Principles, and by them explaining the Phaenomena proceeding from them, and proving the Explanations.38) The “Rules of Reasoning in Philosophy” which begin Book III of the Principia offer a further statement of how Newton would balance experiment and hypothesis, though he does not use this word until the final sentence. In the end it is a stirring defense of the experimental philosophy. Newton notes that the qualities of bodies are known to us only by experiment, and that «We are certainly not to relinquish the evidence of experiments for the sake of dreams and vain fictions of our own devising.» He concludes by saying (in Rule IV), that In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.39) Finally, «This rule we must follow, that the argument of induction may not be evaded by hypotheses.» This seems very clear, and one might say, Baconian, but in the Preface to the first edition of the Principia, Newton wrote that «it has seemed best in this treatise to concentrate on mathematics as it relates to natural philosophy. The ancients divided mechanics into two parts: the rational, which proceeds rigorously through demonstrations, and the practical.» Further, «. . . rational mechanics will be the science, expressed in exact propositions and demonstrations, of the motions that result from any forces whatever and of the forces that are required for any motions whatever . . .

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And therefore our present work sets forth mathematical principles of natural philosophy. For the basic problem of philosophy seems to be to discover the forces of nature from the phenomena of motions and then to demonstrate the other phenomena from these forces.»40) These views are not contradictory, but there is certain a tension between them. A mathematical description of observed phenomena provides a model, that is, a hypothesis, which, to be sure, must be tested against the phenomena, but a hypothesis nonetheless. The essential departure of the Principia from what came before it consists in Newton’s postulating forces between particles, usually attractive and most often inverse-square or proportional to distance, to explain the phenomena at issue. As Westfall pointed out long ago, this made possible the mathematization of dynamics in which Newton was interested. To matter and motion, he added force.41) The eighteenth century often saw the models of the Principia and the Opticks as distinct and different, and to a great extent the followers of the methods of the Principia were continental. Cohen makes the point that in studies of electricity in particular, most of the references to Newton were to the Opticks, not the Principia.42) The Opticks at least seemed more Baconian, not least because of Newton’s statement in Book III that «the main business of natural Philosophy is to argue from Phaenomena without feining hypotheses, and to deduce causes from effects . . . »43)

Conclusion Being a natural philosopher did not, of course, mean being a mathematician. Boyle, for example, was not much of one and his writing is mostly devoid of mathematics. Hooke had evidently absorbed the traditional mathematics of his time, and indeed taught it as Professor of Geometry at Gresham College, but, as we have suggested, showed little interest or creativity in pure mathematics, and seems not to have much appreciated the infinitesimal mathematics of Wallis, Newton, Leibniz, and Sluce. Indeed, one has to look very hard to find any explicit mathematics in Hooke’s writing, 44) although its absence is mostly explained by the fact that most of his published work derives from public lectures or discourses to the Society, giving it a. semipopular nature.45) As a natural philosopher, Hooke’s influence was largely limited to his lifetime. His impact on eighteenth-century natural philosophy, for example, was minimal, a statement which applies both to practice and to theory, for reasons that have little to do with what he actually did or said, and much more with changing fashions, the power of Newton’s method, and the fact that much of his writing was published posthumously. Much the same could be said of Huygens, many of whose works reached print decades after they were written. But if Hooke’s musings on natural philosophy break little new ground (though we have already noted some flashes of brilliance), they do provide almost the only insight we have into how he thought philosophical inquiry should be carried out, and provides a context for our discussions of his science.

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Annotations 1) One is tempted to add “as usual,” and much of the interest in Hooke and Newton as contemporary natural philosophers lies in the extraordinary differences between them. 2) On the other hand, the case can be made, as Michael Hunter has (Hunter, 1999), that Boyle was the «founder of experimental science in the modern sense.» Various factors may have kept Boyle from accomplishing more in his life-long experimentation, including poor eyesight, generally poor health, a stroke in 1670, a certain fastidiousness, his very intense religiosity, and his devotion to alchemy and magic. But as a model and advocate for the mechanical and experimental philosophies, he had no peer. Boyle’s ideas could be considered as having been summed up in “A Free Enquiry into the Vulgarly Received Notion of Nature,” of 1686, which is broadly contemporaneous with Hooke’s more modest writing on the subject. 3) A view he apparently first expressed, anonymously at age 25, in The New Atlantis, and one he never shed. The New Atlantis. Begun by the Lord Verulam [Bacon] and Continued by R.H. Esquire. Wherein is set forth A PLATFORM OF MONARCHICAL GOVERNMENT, etc., which purports to be a continuation of Bacon’s New Atlantis of 1626, is signed “R.H. Esquire” Although it seems likely that “R.H.” was Hooke, the attribution is certainly not without controversy. Andrade, for one, did not accept it. 4) PW, pp. 3–70. Although there are references to contemporary events which allow this dating, there is no way to know whether these writings were added to over time or not. 5) PW, 5. 6) “The Method of Improving Natural Philosophy,” PW, p. 44. 7) Hooke lists 29 ways nature may work on pages 43 and 44. The next 17 pages represent elaboration of these ideas. 8) On “registering,” see also Shapin and Schaffer (1985). 9) PW, pp. 57–61. 10) Waller, PW, p. 65. Hooke made such a promise as early as Micrographia. Waller’s comments as editor, inserted at this point, which raise the issue «of what Use, if not Necessity, Theories and pre-conceived Hypotheses are (contrary to the opinion of some Learned Persons) in order to the making of more proper Observations and ordering more convenient Experiments . . . » (p. 65), very clearly refers to some of Hooke’s comments on the subject in other places. 11) PW, p. 61. 12) PW, p. 73. 13) In the Diary (Diary I) «Read lecture of light.» There was a meeting that day, but Birch says nothing about the lecture. I have not consulted the Journal Book.

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Waller, in PW, says «read about Michaelmas,» which is September 29, but the Society did not return from its summer recess until Nov. 4. 14) PW, pp. 83–4. In this passage, Hooke interjects «as a great Man has done, or at least would be thought so to have done . . . ,» referring to Descartes. He added that «when he came to the ultimate and most visible Effects, he found himself . . . that he was much at a loss and unable to get out, and extricate himself.» 15) PW, p. 84. 16) Waller, PW, p. 330. It is interesting to compare this with what Newton had to say about the analytic and synthetic ways. For example, see Centore (1970), p. 21, fn. 14. See also our comments on Newton, below. 17) “A Discourse of Earthquakes,” in PW, R. Waller, ed (1705), p. 280. Also Drake (1996), pp. 160. The “Discourse” as published by Waller is a collection of lectures by Hooke presented between 1668 and 1700 (Rappaport, 1986). Altogether an excellent statement of the idea that experiments are “theory-laden.” 18) Only about four years before (1676). Cassini had the discovery in his grasp, but apparently abandoned the idea and it was picked up by Rømer, his assistant. Hooke’s argument with Rømer seems to have been that if we lack a decent theory of the motion of our moon, we cannot have much of a theory of Jupiter’s moons. Perhaps this hearkens back to his preference for chronometers over astronomical methods of determining longitude, but he might have been expected to have enough familiarity with the issues to understand Romer’s arguments. In any event, the finite speed of light was not widely accepted until well into the eighteenth century. 19) It is interesting to note that Hooke had taken Newton to task for describing light as a body in his lectures on light in 1671/2 (Newton to Oldenburg, Corresp. I, 92–102; PT 6 (1671/2), pp. 3075–87. Hooke’s comments are found in Hooke to Oldenburg, Corresp. I, 110–114; also HCO. 20) Evidently 27 April and 4 May 1681; See Birch, 4, p. 82, 84. «Mr. Hooke read another discourse about his theory of light.» 21) And «Heat is a property of a body arising from the motion or agitation of its parts.» Micrographia, p. 37. Newton expressed a similar view in his Opticks of 1705. Lucretius had been known since the fifteenth century and atomism had a number of adherents in the seventeenth century, including Pierre Gassendi. 22) We have noted elsewhere, however, that the nature of these discourses for the most part prevented “mathematical exactness.” Had Hooke prepared the text for publication, which he did not, we might hope that he would have been quantitative. 23) PW, 172. One should note that there are serious pagination problems in this portion of the Posthumous Works, which is printed in facsimile in Waller (1705). 24) PW, 173.

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25) PW, 175. In this discussion, Hooke considers the Greek, Hebrew, Arabic, and English versions of the creation story in Genesis. 26) Evidently 3 May 1682. PW, pp. 136–7. 27) PW, 171. Earlier (p. 165), he calls this fluid «the quite fluid Aether.» 28) As pointed out by Centore (1970), for example. 29) January 1677/8; Birch, 3, 370–1. 30) PW, p. 138. Birch, 4, p. 153. 31) Is this not remarkable? Could such speculation have been influenced by Galileo’s showing that there are stars in the heavens not visible to the unaided eye? 32) See especially, Drake (1996), Chapter 6, «Hooke’s Theory of Evolution and Attitude Toward God and Time.» For example, in his “Discourse on Earthquakes,” Hooke wrote the following: «We will, for the present, take the Supposition to be real and true, that there have been in former times . . . divers Species of Creatures, that are now quite lost, and no more of them surviving upon any part of the Earth. Again, That there are now divers Species of Creatures which never exceed at present a certain Magnitude, which yet in former Ages of the World, were usually of a much greater and Gygantic Standard . . . we will grant also a supposition that several Species may really not have been created of the very Shapes they now are of, but that they have changed in great part their Shape, as well as dwindled and degenerated . . . We will further grant there may have been, by mixture of Creatures, produced a sort of differing in Shape . . . from the true Created Shapes of both of them.» (PW, p. 435). See also extensive comments in Drake, 1996. 33) PW, 178. 34) Buchwald and Cohen (2001). 35) See Westfall’s “Background to the Mathematization of Nature,” Westfall (2001) for a fuller study of this issue. 36) Smith (2001), p. 288. 37) Blay (2001). On perturbation methods, see M. Nauenberg, “Newton’s perturbation methods for the three-body problem and their application to lunar motion.” 38) Opticks, p. 404–5. 39) Motte/Cajori translation (Cajori, 1947), p. 400. In the new translation by I.B. Cohen and Anne Whitman (1999), the passage is on p. 796. There is no essential difference between the two translations. 40) Ibid, Cohen and Whitman, pp. 381–2. In the Motte/Cajori translation (Cajori, 1947), it is rendered thus: «I have in this treatise cultivated mathematics as far as it relates to philosophy . . . the ancients considered mechanics in a twofold respect; as rational, which proceeds accurately by demonstration, and practical . . . In this sense

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rational mechanics will be the science of motions resulting from any forces whatsoever, and of the forces required to produce any motions, accurately proposed and demonstrated . . . I consider philosophy rather than arts and write not concerning manual but natural powers, and consider chiefly those things which relate to gravity, levity, elastic force, the resistance of fluids, and the like forces . . . and therfore I offer this work as the mathematical principles of philosophy ...» It is worth adding that we are reading Newton, who in this case was writing in Latin, in modern translation, while Hooke wrote almost entirely in English and we read his words exactly as he wrote them. 41) Westfall (1971), p. 143. 42) I.B. Cohen, preface to the Opticks (Dover, 1979), pp. xvi and l. See also Franklin and Newton (Cohen, 1956). 43) Opticks (Dover, 1979), p. 379. 44) There are some notable examples, for example a paper on cubic equations in the Royal Society’s Classified Papers, Vol. XX, No. 81. Another is his copy of a paper by L’Hospital on the calculus, which, in fact, has on occasion been misinterpreted as Hooke’s own. 45) Of Newton we hardly need to add to what is obvious, that he was a major contributor to seventeenth-century mathematical progress, involving the calculus, infinite series, calculus of variations, numerical methods, etc., and that his masterpiece is densely mathematical.

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Chapter 10

The System of the World: Hooke and Universal Gravitation, the Inverse-square Law, and Planetary Orbits Introduction: Hooke and Planetary Dynamics Of all the problems which occupied Hooke’s fertile mind over the four decades of his scientific career, the most important was without question planetary motion, despite the fact that his contributions are not yet generally acknowledged. It was, of course, a problem which Kepler necessarily left unsolved, and even in the early 1660s one which no one knew how to approach. In the two decades between 1665 and 1685, Hooke may have occasionally lost interest, perhaps because he thought he had already solved it, or because he was simply too busy to give it much attention, but in those years it was almost always on his mind. It is an issue that brought Hooke and Newton into serious conflict, and was, of course, what led Newton to the Principia. The role that the Royal Society played in this important episode is interesting and a bit complicated. Hooke first lectured on gravity on 21 March 1665/6, on the heels of the speculations in Micrographia (described below) and just a week after the Society resumed meeting after an eight month hiatus because of the plague. In that lecture he described experiments on gravity that he carried out during that interval, in Surrey. Although they were inconclusive, the discourse provided the opportunity to talk, or think, about gravity, and in particular about whether it was in some sense “magnetical.” Hooke’s interest in gravity, we can be sure, never waned, especially its role in planetary dynamics. It was something he talked with Wren about on many occasions, and eventually Halley joined the conversation. To get a bit ahead of ourselves, it was Hooke’s correspondence with Newton at the end of 1679, that proved to be crucial. Starting ostensibly as an inquiry from its new Secretary to the Lucasian Professor at

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Cambridge, it quickly became a personal exchange that would have the greatest consequences for both men. The silence which followed that year-long correspondence was broken only in 1684 when Halley told the Society of his visit to Cambridge and the «curious treatise» which Newton had shown him. And eventually, of course, the Society, through Halley’s efforts, brought the Principia into print. Hooke was removed as Secretary in the middle of this period, but in any case there were no contacts between Newton and the Society between 1680 and 1684. We have almost no information on how much time Hooke may have been devoting to the problem in these years, other than a series of lectures he delivered in late 1682 on comets. Furthermore, the Diary begins running out in 1682 and there is little evidence in the Journal Book of any special interest during the next two years. In October 1679 Hooke’s Diary records in its typically laconic way that he had «Dind with Sir Christopher and Lady Wren, about seeing monument [“the” Monument], and Gresham College about Elliptick motion,» and that he was «At Bruins coffee house with Sir Chr. Wren about planetary catena and coyled cone for Celestiall theory . . . »1) In spite of these laconic and obscure comments, we can see clearly that Hooke was mulling over the problem of planetary motion and discussing it with Wren, barely a month before he initiated the now famous exchange with Newton.2) We will see in due course that there is simply no doubt that at this point he had a better understanding of the problem than Newton, but also than anyone else, including Huygens in particular. In several places in the Diary, as well as in conversations with Wren, Hooke intimated that he had the solution to this challenging problem, which had lain unsolved for more than two generations. If we cannot know precisely what Hooke meant, it is quite clear that he believed that he had all the elements of a solution, may well have thought his solution was complete, or, at worst, that all that was needed was the time to work it out. On the other hand, it certainly was not uncharacteristic of Hooke to gain some fundamental insight into a problem and then fail to pursue it to a conclusion. From a modern perspective, and taking into account Hooke’s abilities, we know that a full solution, the deduction of Kepler’s Laws of planetary motion from a theory of attraction between the Sun and a planet, which is what Newton would do, was far more difficult than Hooke could have imagined, and, in fact, beyond him. The two most important elements of a solution which Hooke did bring to the table were the knowledge of what he called «direct motion by the tangent & an attractive motion towards the centrall body,» which we should recognize was the crucial insight, and the nature of the force law. He might be forgiven for thinking that these ingredients actually constituted a solution, rather than simply a starting point. When he arrived at the inverse-square nature of gravity is not certain, but there is no firm evidence that it was before late 1679, though 1677 is a very real possibility. What is on the record is that in the course of his correspondence with Newton, Hooke suggested (on 6 January 1679/80) that «the Attraction is always in a duplicate proportion to the Distance from the center Reciprocall.»3) There is no reason to believe, despite the myths, that Newton could have made this assertion.

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But the problem had bothered Hooke for more than a decade, at the very least since a meeting of the Royal Society on 23 May 1666, when he commented that he often wondered «why the planets should move about the sun according to Copernicus’s supposition . . . » He then elaborated on this commonplace remark by noting that «a solid body, moved in a fluid . . . must persevere in its motion in a right line . . . But all the celestial bodies, being regular solid bodies, . . . and yet moved in circular or elliptical lines, and not strait, must have some other cause, besides the first impressed impulse, that must bend their motion into that curve.»4) In this same lecture, after discussing the effect of variable density, Hooke advanced another cause: «. . . the second cause of inflecting a direct motion into a curve may be from an attractive property of the body placed in the center; whereby it continually endeavors to attract or draw it to itself. For if such a principle be supposed, all the phaenomena of the planets seem possible to be explained by the common principle of mechanic motions . . . » Hooke believed that this insight, coupled with a knowledge of the nature of the “attractive property,” would lead to a solution. We might recall that he had already expressed the germ of universal gravitation in Micrographia the year before, so that this can be seen as part of a program, not an isolated shot in the dark. In these early comments in the spring of 1666, Hooke went on to make an analogy between planetary motion and that of the conical or circular pendulum,5) one he would use frequently in the future. He noted the similarity to planetary motion, but also the obvious difference, which is that the «conatus of returning to the center», which Newton would later call the centripetal force, increases rather than decreases with distance.6) He saw this analogy as a key to understanding planetary motion, and indeed the conical pendulum exhibits quasi-elliptical motion which depends on the initial conditions and illustrates the role of an attractive central force. The force law, as we have noted, is quite different, and the force is directed to the center of the orbit rather than to a focus. Finally, Hooke demonstrated these ideas before the assembled Society members using the circular pendulum as a model. These lengthy comments of Hooke’s represent the first time that the Kepler problem was addressed by anyone in a serious and plausible fashion. According to the traditional account, Newton had discovered the inverse-square nature of gravity in 1666, but had laid it aside and by 1679 had not thought about the problem for many years. In fact, there is little reason to believe Newton’s claims, other than that he had given the problem little thought. But we could hardly fail to note that it was in that same spring or summer of 1666, with the plague abroad in the countryside and while Hooke was speaking of planetary motion to the Society, that Newton, at Woolsthorp, and likely under his mother’s apple trees, perhaps even with the moon in the sky as the tales of Conduitt and DeMoivre tell us, supposedly discovered that an inverse-square gravitational force extending to the moon could result in a centrifugal force that would balance gravity.7) That much happened during

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that summer we can be reasonably certain, but again there is not a shred of evidence, other than Newton’s testimony years later, that either then, or during the next decade, he understood the universal character of gravity, or that he took gravity as an inversesquare force. And as would become evident 13 years later, he clearly lacked Hooke’s understanding of the importance of the center-directed force. In this period Newton was enamored of what Kollerstrom has called a «quasialchemical [a]ether theory of gravity»8) , in which gravity was seen, to quote Westfall, as due to «the descent of a subtle invisible matter which strikes all bodies and carries them down.»9) This was not entirely unlike the Cartesian vortex theory of the kind he eventually rejected in the Principia. He did deduce that the “conatus recendendi”, the force causing a planet to recede from the Sun, depended on 1/r 2 , but this is more revealing of his confusion than understanding. Little is known of the attention, if any, that he gave to the problem between 1666 and 1679, in the course of a long and halting journey toward a solution, as he became perhaps the premier mathematician of Europe, but at best his efforts were desultory, frequently interrupted by other studies, many of them not in physics at all. Indeed, we have it in his own words, this time contemporaneously, that he had not thought about the problem at all. The aether-flow or aether-gradient theory of gravity that he would hold until after 1680 did not offer any obvious way to the kind of solution which would finally emerge. But what did begin was a slow convergence of the very different paths that Hooke and Newton were to take, that would lead to the encounter of 1679 and eventually the Principia.10) In his Cutler Lecture “An attempt to prove the Motion of the Earth through Observations,” published in 1674, Hooke clearly expressed clearly, for the first time,11) the universal character of gravity: «. . . That all Coelestial Bodies whatsoever, have an attraction or gravitating power towards their own Centers, whereby they attract not only their own parts, and keep them from flying from them, as we may observe the Earth to do, but that they do also attract all the other Coelestial Bodies that are within the sphere of their activity; and consequently that not only the Sun and Moon have an influence upon the body and motion of the Earth, and the Earth upon them, but that (Venus) also (Mercury, Mars, Saturn, and Jupiter) by their attractive powers, have a considerable influence upon every one of their motions also.»12) We discuss Hooke and universal gravitation below, but clearly the understanding that all bodies possess gravity is an essential ingredient of a model of the solar system. After again speaking of what we would call tangential (inertial) motion and a centripetal tendency toward the center,13) and of the decrease of gravity with distance, he reiterated, in this lecture, his belief in the connection between planetary motion and the circular pendulum: «He that understands the nature of the Circular Pendulum and Circular Motion, will easily understand the whole ground of this Principle, and will know where to find direction in Nature for the true stating thereof.»14) It is on the record then, in stark contrast with Newton’s later claims, that in the mid-1670s Hooke understood (or believed in, if you prefer) the universal character of

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gravitation, and thought that each body attracts all others with a force that decreases with distance. Combining the principle of inertia of Galileo and Descartes with the insight that there must be a central attraction to «bend the motion» into a curve, Hooke could reasonably believe that he had the essential elements of a theory of planetary motion, despite our recognition of the fact that he had no means to calculate the position of a planet in its orbit, or to prove Kepler’s laws. Beyond this farseeing but admittedly qualitative understanding of the problem of planetary motion, however, we mostly have to guess what Hooke meant by his claim to have solved (or “perfected”) it, as he did in 1679, or by the promise in his lecture on light of 1681 of a solution «with Geometrical Certainty and Exactness.»15) It is worth making the distinction, however, especially in view of the evidence (see below) that Hooke did achieve or at least approach a geometric or graphical solution that might have met this standard of “certainty and exactness,” between this sort of geometric construction, which might show that the orbit resulting from a central force would be an ellipse, and an analytical solution which is at least implied by Book I of the Principia. We cannot say with certainty that Hooke was not the first to accomplish the former, though we know that the latter was beyond his reach. Hooke left several accounts, vague though they may have been, of his attempts to formulate a solution,16) especially between 1676 and 1679, which, as we have already learned, was a critical period in his life, as he assumed secretarial duties for the Society after Oldenburg’s death and his architectural practice was at its peak. On 22 August 1676 he had written in his Diary that he had «Invented planetary Line on hyperbolicall consect the velocity about one asymptote and planet in the other», but three days later noted that «I examined planetary line found it not satisfactory,»17) and almost a year later, on 16 August 1677, he recorded that while at the Crown with Wren he had «Discoursed about the theory of the Moon which I explained.» On 20 September, the two were discussing the lunar theory again: «To Sir Chr. Wren at Paules, met him at Gresham, to Jonathans, Discoursed with him about [lunar] theory. he affirmd that if the motion were reciprocall to the Distance the Degree of velocity should always be as the areas, the curve whatever it will.»18) And as noted already, in October and November 1679 Hooke discussed «elliptick motion» and «celestiall theory» and «central attraction,« with Wren. Clearly he was grappling with the problem, though without much success we can assume. It was his deep engagement with the problem in the fall of 1679 that induced Hooke, as Secretary, to write Newton, opening the crucial correspondence with him. We will show that this epistolary exchange, presumably much to Hooke’s chagrin, provided Newton with the key that he needed, which was that instead of a Cartesian balance between the centrifugal force due to the orbital motion and the centripetal force of gravity, the problem should be understood in terms only of inertial “motion by the tangent” and the centripetal attraction. Hooke may or may not have been the first to fully understand orbital motion as compounded of a tangential velocity and a

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center-directed force, but it was he who played the role of enlightening Newton on the matter. As it happened, however, Newton had other interests in early 1680, and we know that he was preoccupied with alchemy during the next four years, almost to the exclusion of everything else.19) Of his claim that he quickly achieved a solution, if a faulty one, in 1680, which is what we hear from his own mouth, we are entitled to be skeptical, though it is entirely possible.20) Ironically, both Newton and Hooke were seriously distracted at this point by other interests or obligations. The problem might well have been solved by someone else. Although Hooke frequently spoke with Wren about planetary motion in what were likely wide-ranging conversations, little seems to have come of these talks (and later, those with Halley). The same might even be said, on Hooke’s side at least, of the exchange of letters with Newton as Hooke’s interest in the problem seemed if anything to wane during those crucial years after 1682. To be sure, he had less to gain from the exchange than Newton, but at the very least he might have sensed a serious competitor. Did he misjudge Newton? If he did lay the problem aside,21) one would like to know why. Nothing that Hooke published, before or after this period, gives us any hint that he had the mathematical tools required to solve the problem of motion under gravity with anything like Newton’s rigor.22) A good geometer he may have been, though we have relatively little to go on even there except that he was Gresham Professor of Geometry for most of his professional life. We have seen, however, that he had a sound grasp of the “physics” of the problem. This gives us some insight into what he thought a solution would consist of, since he later seemed to be certain that the solution lay in what he told Newton. But Newton was in a position to see the problem as one involving integrating the equations of motion, or the force law, to use modern terminology,23) something which would have been entirely foreign to Hooke. In his “Discourse of Comets,” read to the Society beginning in October of 1682, but only published in 1705 by Waller in the Posthumous Works,24) Hooke acknowledges that he has no empirical evidence that gravity decreases with distance from the earth, but says that he nonetheless believes that this is the case,25) and then immediately notes that, if so, the path of a projected body is elliptical rather than parabolic! In his words: «For I shall in my following Discourses plainly shew, from the theory thereof, that there is necessarily a Difference, and that the Power of Gravity does decrease at farther and farther Distance from the Center of the Earth, and consequently that the Line of a projected descending Body is not truly Parabolical, but Elliptical, though it should be made in vacuo, where the Impediment of the Medium could make very little or no Alteration.»26) This is a thoroughly remarkable assertion if you think about it, although someone with Hooke’s knowledge of the laws of Kepler, and who also believed that gravity was an inverse-square force, might not have had a difficult time guessing, as it were, that one implied the other.27) It is, in fact, the very same claim that Newton made to a surprised Halley when he rode up to Cambridge to see the Lucasian Professor almost two years later, in May or August of 1684. Hooke has extrapolated from Keplerian

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elliptical planetary orbits to the assertion that the path of a projectile near the Earth’s surface is elliptical, and only approximately parabolic.28) We doubt that Hooke had a proof to support his arguments, but Newton may also have claimed more in 1684 than he could actually demonstrate, which is indeed what Westfall believed. The crucial difference is that when Newton finally attacked the problem with all his resources, he effectively solved it in not much more than two months. But in a way this statement of Hooke’s is more astonishing than the already remarkable claim that an inverse-square center-directed force in the solar system implied elliptical orbits. He has intuited what Newton would later prove, that a body propelled near the earth’s surface would behave essentially as though the mass of the earth were concentrated at its center, meaning that the orbit would be an ellipse. He doesn’t explicitly say this, of course, and no one could do so before Newton, but this is what Hooke’s claim implies. There is much of interest in this work (the “Discourse of Comets”), however, not only the material on comets per se, which is descriptive and long-winded, but in Hooke’s ideas about the cause of gravity (and of magnetism and electricity as well), which he finds to be something he calls “Globular Motion” which is transmitted to the aether, and which in turn causes the descent of bodies toward the center of the Earth.29) This is not so different from Newton’s early aether theory. Especially interesting is the way Hooke speaks of a “propagated pulse”, “in Lines radiating” from the center, and “Vibration towards and fromwards the Center.”30) Nonetheless, we search in vain among this and other of his works for the “geometric certainty and exactness” he promised, or the quantitative rigor of the Principia, or even De Motu, and wonder how much mathematics, if any, underlies those speculations. True, they were usually delivered orally to the Royal Society, and only a few such presentations, mainly of a mathematical nature, ever had that kind of detail, as we have noted earlier. But in its discursiveness, the “Discourse of Comets” is more natural philosophy than physics, to draw a distinction the seventeenth century would not have made. But whatever Hooke had actually done, thought he could do, or imagined a solution would actually look like, what he could not foresee was that it would be Newton who would accomplish it, and that when revealed, it would be so profound and far-reaching. Newton had been silent since the 1679–8031) exchange between the two of them in which Hooke had the upper hand, and in 1684 Hooke had no reason to expect a solution from that quarter. In that, he misjudged his competitor.

Halley and Newton Unfortunately we have no Hooke diary for the crucial five years leading up to 1687, so that as we seek to understand Hooke’s efforts to address the problem of planetary motion, our resources are mostly limited to some of his lectures from 1682–5 collected by Waller in Posthumous Works,32) minutes of Society meetings, which turn out to be surprisingly unhelpful, and Halley’s letter to Newton, written in 1686.

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As Halley told it, he «came one Wednesday to town, where I met with Sir Christ. Wren and Mr. Hook . . . » This would have been either the 16th or 23rd of January 1683/4 for a meeting of the Council and the Society, and he used the occasion to meet with Wren and Hooke, perhaps at Jonathan’s where they often were to be found. Then, Halley continued, «. . . falling in discourse about it, Mr Hook affirmed that upon that principle [the decrease of centripetal force with the square of the distance] all the Laws of the celestiall motions were to be demonstrated, and that he himself had done it; I declared the ill success of my attempts; and Sr Christopher to encourage the Inquiry sd, that he would give Mr Hook or me 2 months time to bring him a convincing demonstration therof, and besides the honour, he of us that did it, should have from him a present of a book of 40s. Mr Hook then sd that he had it, but that he would conceale it for some time that others triing and failing, might know how to value it, when he should make it publick; however I remember.»33) Wren had tried his hand at a solution as well, for, as Halley reported, «he himself very many years since had had his thoughts upon making out the Planets motions by a composition of a Descent towards the sun, & an imprest motion; but that at length he gave over, not finding the means of doing it.» Wren also told Halley that «Mr Hook frequently told him that he had done it, and attempted to make it out to him, but that he never satisfied him, that his demonstrations were cogent.» Thus, while we know little about the nature of Hooke’s supposed “demonstration”,34) we do know that Wren, who knew Hooke better than anyone else and who was no mean mathematician himself, remained unconvinced. A half year later, with nothing forthcoming from Hooke, Halley journeyed to Cambridge to pose the problem to Newton in August of 1684,35) with the result which Westfall described so richly in Never at Rest.36) As is almost too well known, Newton immediately responded to Halley’s question about the orbit that would result from an inverse-square attractive force, that it would be an ellipse, though he claimed to be unable to locate the demonstration.37) Newton’s story was that he subsequently located the proof, found it faulty, and worked it out properly, the result being De Motu,38) which is what Edward Paget brought to Halley in November. The latter quickly returned to Cambridge to learn more about the treatise, to urge Newton to continue his researches and, presumably, publish them in the Philosophical Transactions. De Motu was only a first step toward the Principia, and was still cast in language that Newton would abandon in the final work, but what an enormous distance he had spanned between the end of 1679 and 1684, or more astonishingly, perhaps, between August and November of 1684! At the Royal Society meeting of 10 December 1684, 39) Halley described De Motu, the contents of which must have stunned Hooke when he learned of them, and it cannot have taken him long to get a look at it. Newton had granted him five full years (1679–84) to solve the problem himself, while he, Newton, concentrated

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on theology and alchemy. His interest in the comets of 1680 and 1682 show that he was not completely given over to the alchemical arts, however, and we can imagine him mulling over what he had learned from Hooke about dynamics and the nature of gravity during that time. But Hooke’s attention was also elsewhere. As Curator, Secretary until 1682, still involved in surveying, supervising construction, and especially his own architecture, he probably just did not have the time. In the minutes of meetings for this period we see him presenting or commenting on a wide range of problems, with little evidence of any special preoccupation or consuming interest in planetary motion. Whether he had already done all he was capable of when he presented the “Discourse of Comets” in the fall of 1682, and genuinely thought he had the problem solved, we cannot say with certainty. But then no one, before Newton, had a clear idea what a solution would actually consist of.40) We will explore below the consequences of the exchange of 1679–80, alluded to above and prompted by Hooke’s innocent (?) question to Newton, but it obviously clarified the latter’s thinking about centripetal and centrifugal forces. The comet of 1680 probably also played a critical role, especially in forcing Newton to re-think his aether theory of gravity, which made gravity depend on the surface area of an object. The comet of 1682, eventually to be known as “Halley’s comet,” also was crucially important because its orbit is retrograde, raising truly thorny questions for advocates of vortex theories. But Halley’s ride up to Cambridge provided the final, direct impetus that set Newton on his way toward De Motu and the Principia.

Huygens Before going on to the detailed ideas of Hooke and Newton on gravitation, it may be useful to take notice of Christian Huygens’ own efforts. Newton and Huygens were interested in many of the same problems, both in dynamics and mathematics, and Newton admired Huygens as much as he admired anyone.41) Moreover, many of Huygens’ ideas on gravitation preceded those of both Hooke and Newton, and if we include the issue of centrifugal force in this discussion, Huygens influenced both men. Then again, both Huygens and Newton were influenced by Hooke’s Micrographia. Huygens would never fully appreciate the conclusions of the Principia, most of all Newton’s conception of gravity. Not long before his death he wrote that he esteemed Newton’s «understanding and subtlety highly» but considered «that they have been put to ill use in the greater part of this work, where the author . . . builds on the improbable principle of attraction,»42) that is, action at a distance. As early as 1659 Huygens had established the equivalent of the v2 /r form of centrifugal force in circular motion (though obviously expressed in different terms), which he took as a tendency away from the center that counteracted gravity, though the full development of his theory appeared only posthumously in 1703,43) the year that Hooke died. He seems still, in 1659, to have considered circular motion to be a special, natural, even absolute, class of motion, as, of course, did the Aristoteleans.44) There was clearly a tendency opposing centrifugal force which resulted in circular motion, but Huygens

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hoped to understand gravity as an effect of motion rather than the cause of it, employing a model in which Cartesian vortices in a plenum of subtle matter could account for the attraction of one body for another. Hooke himself at least briefly entertained a similar view. Thus, if in 1659 Huygens’ understanding of gravitation was ahead of Newton’s (who was then only 17) and Hooke’s (who was 24), the fact that much of his work was only published after his death meant that his actual influence was less than it might have been.45) On the other hand, he was a regular correspondent of the Society through Oldenburg, and not infrequently in town and at meetings, so that his ideas gained a greater currency than the published work might suggest.46) He was also an honored member of the French Academy, which carried out discussions of gravity beginning in August 1669, involving himself, Roberval, Mariotte, and other luminaries.47) He and Newton met on at least three occasions, including a famous ride into London from Hampton Court sharing a carriage in 1689 when Newton was in Parliament. Hooke and Huygens also met on several occasions,48) or at least were present in the same room, mostly at Society meetings, yet there is no evidence that any real connection was made, not least because of their competing claims in pneumatics and over the balance-spring watch. The one remarkable exception to this was very early on when the two of them worked, side by side as it were, trying to reproduce Huygens’ “anomalous suspension” (Chapter 4) in London.49)

Hooke and Universal Gravitation In Hooke’s earliest published comments on gravitation in Micrographia, while discussing telescopic observations of the moon, he observed that: «it being very probable that the Moon has a principle of gravitation, it affords an excellent distinguishing Instance in the search after the cause of gravitation, or attraction, to hint that it does not depend upon the diurnal or turbinated motion of the Earth, as some have somewhat inconsiderately supposed . . . ; for if the Moon has an attractive principle, whereby it is not only shap’d round, but does firmly contain and hold all its parts united . . . and that the Moon is not mov’d about its Center, then certainly the turbination cannot be the cause of the attraction of the Earth; and therefore some other principle must be thought of, that will agree with all the secundary as well as primary Planets.»50) This position, that gravity might be due to the earth’s diurnal rotation, which Hooke attributes to Descartes and to Hobbes, was at some point held by Huygens as well.51) Hooke’s argument here is that if the Moon has gravity, but doesn’t rotate, then the Earth’s gravity cannot be due to its rotation. His argument is logically defensible, but notably faulty, since his view that the Moon does not rotate on its axis is quite mistaken, and a rather elementary error.

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But this is a fascinating passage, for several reasons. Hooke has concluded that the roundness of the moon suggests that it, like the earth, possesses gravity, and indeed that is why it is round. Underlying this is the very early conjecture that gravitation is universal, possessed by «all the secundary as well as primary Planets,» which, as we saw above, he followed with an unequivocal statement, nearly a decade later, in the 1674 Cutler Lecture “An Attempt to Prove the Motion of the Earth.” At the end of that lecture Hooke elaborates on what Ofer Gal sees as the three stages of “Hooke’s Programme,”52) in a fascinating passage in which he talks about the mutual gravitational influence of one body on another, reiterates the law of inertia, and speaking of gravitational attraction writes that «. . . these attractive powers are so much the more powerful in operating, by how much the nearer the body wrought upon is to their own Centers. Now what these several degrees are I have not yet experimentally verified . . . »53) Earlier we saw that in his 1674 work on parallax, Hooke committed himself to the idea that gravitation was universal, that is, a property of all bodies. In the fall of 1682, in the wake of the great comet of 1680, Hooke again discoursed at length on gravitation. These lectures, delivered, «soon after Michaelmas», were published by Waller as “A Discourse of the Nature of Comets” after Hooke’s death.54) However influential the lectures were at the time, and whether Newton may have gained something from them, they reached print only two decades later. Still, they are among the most important of Hooke’s writings. Speaking of the “roundness” of the Earth, Hooke says that he takes «this Roundness to be as convincing an Argument as any, to prove that there is a like Power in every Globular Celestial Body, as there is in the Earth.»55) This conclusion, hinted at earlier, that celestial bodies are round because of their gravity is, needless to say, a truly remarkable, and, of course, correct claim.56) It constitutes an excellent example of the clarity and sophistication of Hooke’s thought, and express very clearly his concept of universal gravitation. For example, he says that «By Gravity then I understand such a Power, as causes Bodies of a similar or homogeneous nature to be moved towards one another, till they are united, or such a Power as always impels or drives, attracts or impresses Motion into them . . . The Universality of this Principle, throughout the whole and every thing therein, I shall afterwards have more occasion to explain . . . »57) A bit further on is the very clear statement that «this Power of Gravity is not only placed in the Earth, but . . . there is the like Power in every Globular Body in the Universe, whether Sun or Fixed Star, Planet primary or secondary . . . »58) Clearly, by any fair reading, universal gravitation springs from these writings of Hooke in 1665, which, of course, Newton read.59) In the face of the failure of his own and others’ sporadic attempts to measure the decrease of gravity with altitude, Hooke remarked that «It cannot, I suppose, be expected that I should try or shew Experiments at Distances sufficient . . . »60) to

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establish the law of decrease, though this was based on failure to detect such an effect, rather than an understanding that it would be difficult to measure, in principle. Yet he was not reluctant to speculate upon or to justify by analogy, a dependence of attraction on distance that he could not measure. In these lectures he began by only saying that gravity «does act with various Degrees at several Distances . . . which Degrees I shall also endeavour to state . . . ,»61) Empirically he had no evidence for the inverse-square character of gravity, but he had already taken that speculative leap as early as January 1679/80 (see below), and perhaps earlier, and would return to it at the end of the discourse. After noting that gravity is directed toward the center of the attracting body,62) that it extends to great distances, «even indefinitely,» and, again, that all celestial bodies possess gravity, which draws objects toward their centers and determines their spherical shape, Hooke began to ruminate on the cause of gravity. He speculated that this was due to internal vibrative motion in a body which «does communicate or produce a Motion in a certain Part of the Aether . . . in Lines radiating from the center . . . ».63) The application of this model led to a theory of how the power of gravitation diminishes with distances, with Hooke again announcing that he would «shew with what proportioned Power it acts upon Bodies at all Distances both without and within the Earth.» Indeed, «For this Power propagated, as I shall then shew, does continually diminish according as the Orb of Propagation does continually increase [that is, its area], as we find the Propagations of the Media of Light and Sound also to do . . . And from hence I conceived the Power thereof to be always reciprocal to the Area or Superficies of the Orb of Propagation, that is duplicate of the Distance . . . »64) Thus, while Hooke had held the view that gravity decreased with the square of the distance for at least three years,65) in this lecture he has gone further and advanced an argument to justify that conclusion by analogy with the spreading of light and sound. Moreover, «this way of working at a distance, by means of the internal Motion of the Particles of the Body» was not unusual in nature, and indeed «the Motions of several Bodies at a distance, are caused by the internal Motion of the founding Body; and that this Power of moving is every way propagated by the ambient Medium . . . »66) Thus these passages bear on an important issue which goes beyond the question of the detailed cause of gravitation, and that is whether gravity is an innate or inherent property of bodies or somehow results from the medium in which they reside. It seems clear from these statements of Hooke that he does believe that it is a property of the bodies themselves, and that the aether is only responsible for transmitting the force. Apparently internal motions in a body generate gravity which propagates through the aether. But Newton was adamant on the subject. In a letter to Bentley, written 17 January 1692/3 he wrote, speaking of the view of gravity as «essential and inherent to matter,» «Pray, do not ascribe that notion to me.»67) As many have pointed out,

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it was rather Roger Cotes, in his preface to the second edition of the Principia, who took gravity to be one of the primary qualities of a body and endorsed the idea of action-at-a-distance, which was anathema to Newton. Newton, as we know, claimed to have been committed to the inverse-square law since 1666,68) and in a discussion of his priority 20 years later, asserted that Wren had come to the same supposition [as himself] «about 9 years since», specifically saying that he was «. . . almost confident by circumstances that Sr Chr. Wren knew ye duplicate proportion wn I gave him a visit,» i.e., some time in 1677.69) This was by way of saying that Hooke probably got the idea from Wren, who in turn might have had it from Newton himself.70) Again, nothing supports any of this except Newton’s authority, and given his consistent disparaging of Hooke’s influence on him, it should be given little weight.71) Or to be a shade more generous, his claims were at best based on a generous recollection of events which occurred a decade earlier. On the question of how and when those two companions, Wren and Hooke, adopted inversesquare gravitation, and who taught it to whom, we will never have a definitive answer, except that Hooke alone is on the record no later than 1679. 72) These lectures that make up the “Discourse of Comets” are also interesting to the extent that they shed light on progress in Hooke’s understanding of planetary motion, coming as they do about three years after the 1679–80 correspondence with Newton. But the problem of cometary motion was still seen as quite distinct from that of the motion of the planets, and even the discussion of gravity, as interesting and important as it is, fails to address planetary motion. Further, as we have already noted more than once, lectures delivered to the Society were usually rather popular in nature and of a quite different character from the quantitative arguments of both men in that earlier exchange, to which we now turn our attention.

Hooke and Newton, 1679 The exchange of letters between Hooke and Newton which began at the end of 1679 has been described in detail by all of Newton’s biographers.73) It is one of the most fascinating episodes in the history of science, and it is generally recognized to have been a crucial episode in Newton’s scientific career because it focused his attention again on the problem of planetary dynamics after a decade or more in which he apparently had given it little thought. And while he once more laid the problem aside, when prompted a second time, in this case by Halley almost five years later, he was ready to attack it with all of his considerable energy and concentration. Hooke did much more than merely raise the issue, of course, and indeed the manner in which he framed the problem, as involving motion by the tangent and an attraction toward the center, forced a critical rethinking on Newton’s part. It is surely not too much to say that in this exchange Hooke gave Newton the key to understanding the dynamics of motion under gravity. If only the first step, it clearly started him on the path toward the Principia. One can speculate whether there would have been a Principia without Hooke’s intervention, but with little profit. But as Whiteside wrote, «We may appreciate in hindsight how exceedingly fortunate it was for Newton that Hooke pressed

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him so strongly to conceive of “planetary” free fall as generated continuously by a central-force deviation from an instantaneously uniform, rectilinear path tangential to the orbit . . . »74) In a real sense, Hooke, very reluctantly, played midwife to the Principia. Although it might be argued that there is not much new to be said on the issue, each generation views the same facts in slightly different ways. In particular, a view of the Hooke-Newton controversy espoused by Westfall but supported only by the later testimony of Newton himself, today deserves less credence.75) And with the importance of Hooke’s “Laws of Circular Motion” paper (see below) now clear, one may very well arrive at somewhat different answers from those that have been reached before. For these reasons we will revisit this crucial exchange, which consists of eight letters, five from Hooke and three from Newton, between November 1679 and December 1680. A few other letters bear on the issue, especially six between Halley and Newton in the period May-July, 1686.76) The correspondence on dynamics began with the letter from Hooke to Newton on 24 November 1679, ostensibly renewing contact between the Society and Newton following Oldenburg’s death77) . After a few opening remarks, Hooke quickly got to the point: «For my part I shall take it as a great favour if you shall please to communicate by Letter your objections against any hypothesis or opinion of mine, And particularly if you will let me know your thoughts of that of compounding celestiall motions of the planetts of a direct motion by the tangent & an attractive motion towards the centrall body.»78) We don’t know what Hooke’s motive was in asking this question of Newton, to establish his own priority, or to find out what Newton knew, or even to gain some insight from Newton, though that seems the least likely possibility. Newton’s reply came only four days later, and he may have soon regretted his haste. After pleading preoccupation with «Country affairs»,79) he let Hooke know that he «. . . had for some years past been endeavouring to bend myself from Philosophy to other studies . . . » «Perhaps,» Newton said, «. . . you will incline ye more to believe me when I tell yt I did not before ye receipt of your last letter, so much as heare (yt [that] I remember) of your Hypothesis of compounding ye celestial motions of ye Planets, of a direct motion by the tangt to ye curve & of ye laws & causes of springyness . . . And having thus shook hands with Philosophy, & being also at present taken of wth other business, I hope it will not be interpreted out of any unkindness to you or ye R. Society that I am backward in engaging myself in these matters . . . » In concluding the letter, he again pled ignorance of what was current in London and abroad: «If I were not so unhappy as to be unacquainted with your Hypothesis above-mentioned (as I am with almost all things which have of late been done or attempted in Philosophy) I should so far comply with your desire as to send you what Objections I could think of against them if I could think of any . . . But yet my affection to Philosophy being worn out, so that I am almost as little concerned

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about it as one tradesman uses to be about another man’s trade . . . I must acknowledge my self avers from spending that time in writing about it wch I think I can spend otherwise more to my own content . . . »80) After the perfunctory comment on “springyness”, Newton picked up on a different point. Hooke had written about Flamsteed’s supposed confirmation of his own discovery of the stellar parallax due to the Earth’s orbital motion, and Newton offered in reply a way of demonstrating the Earth’s diurnal motion. He argued that a body dropped from a large height would fall to the east of the point directly below its original position, «describing in it’s fall a spiral line . . . quite contrary to ye opinion of ye vulgar who think that if ye earth moved, heavy bodies in falling would be outrun by its parts & fall on the west side of ye perpendicular.»81) The argument was accompanied by a drawing which showed the object spiraling to the center of the Earth (Fig. 15), a point which Hooke immediately jumped on.

Fig. 15: Newton’s drawing from letter to Hooke, 28 November 1679, showing a body spiraling to the center of the Earth.

Hooke replied in a letter to Newton dated 9 December, and after the usual pleasantries and acknowledging that Newton was correct in saying that the body would fall to the east, he informed Newton that the path of the body would be «nothing att all akin to a spirall but rather a kind [of] Elleptueid.»82) If the body could move freely through the Earth, the path would be an ellipse, or if there were resistance, it would be a decaying ellipse ending at the center (Fig. 16). Furthermore, the body would actually, at the latitude of London, fall to the south-east.83) Hooke ended by saying that he could «. . . adde many other conciderations which are consonant to my Theory of Circular motions compounded by a Direction motion and an attractive one to the center.»

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Fig. 16: Reconstruction of Hooke’s drawing of the descent of a body toward the center of the Earth in letter to Newton, 9 December 1679. Yale U. Manuscript, Koyr´e (1952, 1965) and Pugliese (1989).

Newton’s reply, again four days later, though (disingenuously?) dismissing the problem as «being of no great moment» begged Hooke’s pardon for troubling him with «this second scribble,» acknowledged that the object would fall «more to ye south then east if ye height it falls from be any thing great.» He then argued that the path of a body inside the earth would not be a spiral to the center, but rather «if its gravity be supposed uniform» it would «circulate with an alternate ascent & descent made by it’s vis centrifuga & gravity alternatively overballancing one another.» The accompanying figure (Fig. 17) makes it not entirely out of the question that Newton actually computed the path that the object would take, given the admittedly unrealistic assumption that gravity was constant. That in itself is thoroughly remarkable.84) In what was effectively the last important letter in this six-week exchange, Hooke wrote to Newton three weeks later (6 January) to point out that if one assumes that the attraction is always «in a duplicate proportion to the Distance from the Center Reciprocall, . . . that the Velocity will be in a subduplicate proportion to the Attraction and Consequently as Kepler Supposes Reciprocall to the Distance».85) But he qualified this by saying that in fact he did not really believe that the inverse-square attraction would persist to the center, rather that «the more the body approaches the Center, the lesse will it be Urged by the attraction.» This is an important result which Newton first established quantitatively in the Principia.86) We could be excused for marveling at how close, intuitively, if not quantitatively, Hooke was to an understanding of the problem. But is this kind of qualitative result as far as he got? Is this what lay behind his frequent claims to his close friends Wren and Halley that he had solved the problem? We examine this question below. There is one more remarkable aspect to this letter of Hooke’s. In an offhand way, he notes, in connection with Newton’s drawing, which the latter prefaced by saying

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Fig. 17: Newton’s revised drawing from letter to Hooke, 13 December 1679.

«if its gravity be supposed uniform,» that this is simply the result that one would get by having a ball rolling on the interior of a conical surface.87) This astonishing remark reveals a remarkable understanding of particle dynamics, again, whether intuitive and qualitative, or quantitative. And these two comments taken together, one providing the analogy with motion on a conical surface, the other suggesting that gravity should decrease toward the center of a spherical object, show clearly, once and for all, that Hooke was capable of deep insights into dynamical problems. This exchange might well have led directly to the Prinicipia, but it turned out not to be sufficient to cause Newton to lay aside his other preoccupations (notably alchemy), and it would be more than four years before Halley’s visit to Cambridge unleashed the lion.88) Newton, in any event, was not to be denied. Though he told Hooke that his «affection for philosophy» had worn out, we shortly find him in enthusiastic correspondence with Flamsteed on the motion of the late comets. The problem was not yet consuming him, as it would eventually, but it had clearly taken hold. His

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arguments during the period 1680–82 are mostly geometrical rather than dynamical, but by the end of 1684 (Gregorian), following the visit by Halley, his interest is clearly in planetary orbits and those of their satellites and he is beginning to vigorously pump Flamsteed for data. His program seems now to be quite different. And in little more than a year and a half, the Principia was born. That the correspondence with Hooke was critical to the path Newton took toward the Principia is hardly debatable.89) Although Newton heatedly denied any significant contribution from Hooke in two letters to Halley in the summer of 1686,90) the letters implicitly acknowledge his debt. For if we take Newton, who said he had not thought about these questions for some time, at his word when he claimed to have established that elliptical orbits implied an inverse-square force in the winter of 1679/80, and only a matter of weeks after the exchange with Hooke, that would seem to clinch the case for Hooke’s influence. We have no hint of Hooke’s reaction to De Motu, which he first heard about in December 1684, nor to the Principia, which was presented to the Society at the end of April 1686, but about which he must have been hearing from Halley. It seems likely that he might have perused De Motu somewhere in this time period, perhaps in early 1685.91) The hiatus in his Diary between 1682/3 and 1688, again is to be regretted, and the lacuna of 1684–87 is especially lamentable.92) From the minutes of Society meetings we see Hooke speculating about light, and in the process rehashing some of his old ideas. He is still interested in navigation, the pendulum and the possibility of measuring the variation of gravity with height using it, telescopic sights, various mathematical projections onto curved surfaces, water pressure, the density of ice and refraction, superheating and cooling, the Zodiacal light, shells found in the earth, the figure of the earth, and so on. The diversity of ideas and experiments was all too typical of Hooke. Some of it is mere recapitulation, and increasingly Hooke was turning to questions of changes in the earth, the meaning of fossils, and so on. We have seen that he was in conversation with Wren and Halley about the problem of planetary motion, but there is little evidence of any special interest in the issues that were consuming Newton, or any sense of urgency.

Hooke’s “Laws of Circular Motion” It would be easy to argue that if indeed Hooke grasped the central idea of the dynamics of motion under a central attraction much earlier than Newton and eventually provided his rival with the key to solving the larger problem of planetary motion, his own attempts to obtain a solution were thoroughly inadequate. Newton, as a leading mathematician of the age, was supremely equipped to formulate a problem mathematically once he grasped the physics of it, while Hooke’s understanding was more intuitive and qualitative. As far as we can tell Hooke had given the problem much more thought than Newton during the fifteen years leading up to 1680 and had a deeper understanding of it when the correspondence with Newton began. Notwithstanding which, his frequent assertions that he had solved the problem, or could solve

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it, were not convincing to his contemporaries, and have been only slightly more convincing in recent times. Yet it now seems probable that Hooke did indeed achieve at least a partial solution to the very problem Halley posed to Newton in 1684, and it is not out of the question that he succeeded in obtaining a geometrical proof that an inverse-square force implied an elliptical orbit, possibly earlier than Newton. That is, he not only believed that the orbit of an object under an inverse-square gravitational force would be an ellipse, as he claimed in 1679 and 1682, but may have been able to establish that fact around the same time as Newton, that is, no later than 1684–5.93) Combining this admittedly somewhat speculative view with knowledge of the aid Hooke gave Newton in 1679, it is not hard to see why Hooke might claim Newton had stolen the idea from him. Yet even in light of the “Circular Motion” manuscript discussed below, we cannot be sure what Hooke actually accomplished, and it is clear that he could not have matched De Motu, much less the Principia. Much of what we have said about the Newton-Hooke correspondence could have been written 25 years ago, or even 60, but an unpublished manuscript apparently dating from 1685, first treated seriously by Patri Pugliese94) , provides us with the concrete example of Hooke’s dynamics that has long been looked for, and much more importantly, with a model of how he may have “solved” the problem in question, namely that under certain circumstances a central attractive force would yield an elliptical path. The manuscript evidence we have of this serious and credible attempt by Hooke to quantitatively solve the problem seems to date from September 1685,95) suggesting that it might be his attempt, after learning about De Motu, to answer Newton’s challenge. This brief but enormously important document bears not only on the question of Hooke’s veracity96) in claiming the solution to the problem of planetary motion as his own, but on the larger issue of his ability as dynamicist. Now in the Trinity College Library at Cambridge, the manuscript, entitled “The Laws of Circular Motion,”97) (Fig. 18) analyzes circular motion in a familiar way, in terms of a many-sided polygon approximating a circumscribed circle (Fig. 19): «. . . in the time of a [gravitational] puls the body has moved from h to a, which subtends a part of the circle and at (a) hath Received a motion in the Ray ao which is equall to ad, the body therefore which hath now a compound motion is moved in the diagonall ab of the Rhobeoeid acbd, which is equal to ac = ha, It shall therefore at b arrive at the circle & describe the subtense ab.»98) It can be shown that this is equivalent to the statement that the center-directed force is proportional to v2 /r . But Hooke then shows geometrically how elliptical motion would result from the central attractive force. The example he gave was of a force proportional to the distance from the center, rather than an inverse-square.99) Of Hooke’s calculation, Pugliese says that «Hooke claims, but certainly does not demonstrate» that the path is elliptical, a conclusion on Pugliese’s part which may be technically correct, though we know that the curve generated this way, in the limit of small increments, is indeed an ellipse.

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Reproduction of a page from Hooke’s manuscript “The Laws of Circular Motion,” showing his construction of an elliptical path of a body under a force proportional to the distance. Trinity College, Cambridge, Ms O.11a1 (fol. 6r). Reproduced by permission of the Master and Fellows of Trinity College, Cambridge.

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Fig. 19: Reconstruction of Hooke’s “proof” of elliptical orbits. From Nauenberg (1994a).

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The most detailed analysis of this handwritten manuscript is by Michael Nauenberg,100) who remarks that the graphical construction given by Hooke is similar to that used by Newton in De Motu, and that it represents the mathematical formulation [Nauenberg’s italics] that Hooke had long promised.101) Although, as we have said, it is entirely possible that Hooke had seen De Motu by 1 September 1685, the date on the manuscript, it is clear, as Nauenberg asserts, that Hooke’s argument is not only consistent with what he had said and written in the previous 20 years, but if similar to Newton’s, is also quite different in its details.102) It is of course possible that the argument given in the manuscript was formulated well before its date of 1685. It should be noted again, however, that even if Hooke carried through a geometric proof that an inverse-square force yielded elliptical orbits, that was far from what Newton did even in De Motu, in establishing Kepler’s Laws. The essential part of the proof is Hooke’s graphical demonstration (Figs. 18 and 19) that «the vertices of the resulting polygonal orbit lie on an ellipse.»103) The two critical issues which surround this proof are first, that it treats the case of a force proportional to distance from the center, and second, its date and originality. It is limited to the case of a linear force, and while no similar calculation is known for the crucial case of the inverse-square force, such a proof would be not terribly more difficult, and it does not require a great leap of faith to suppose that such a proof by Hooke once existed. As the case of by far the greatest interest, it seems improbable that he would not have at least made the attempt. It also seems unlikely that he would have continued to make the claims he did if he had been unable to complete the proof.104) Between 1681 and 1684 (and perhaps earlier), Hooke was explicitly claiming a solution to the problem of planetary motion. We know that he showed Wren a proof which left the latter unconvinced. Recall also that in the context of Wren’s wager Hooke claimed that he was withholding his solution so that others might realize the magnitude of the feat involved. If that is not entirely convincing, it is also not out of the question and perhaps not inconsistent with his personality. In any case, it was easier to dismiss this as a bluff before the discovery of the contents of the 1685 manuscript. Whether “The Laws of Circular Motion” and the elliptical construction contained in it resulted from a hasty attempt by Hooke to carry out what he had earlier boasted of, perhaps after getting a peek at De Motu, as is clearly possible, or whether it was merely a writing out of a proof he had possessed for several years, cannot be resolved. At the very least, Hooke seems to have arrived at a proof of elliptical orbits independently of Newton, if only for a force proportional to the distance from the center. One can argue whether it offers a rejoinder to Pugliese’s view that Hooke «. . . does not seem to have ever come to a full appreciation of the magnitude of the step from his ideas to Newton’s achievements,»105) but Hooke does not seem to have been much given to self-delusion. It may be that it was precisely because he recognized the profundity of Newton’s proofs, when he saw the Principia, that he did not make his efforts public.106)

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All we can say with certainty of this paper is that it is consistent with his claims. One can speculate that this document is the concrete embodiment of these claims, and thus might have an earlier date. There is not a shred of evidence for this other than Hooke’s assertions, which at least, and unlike Newton’s, are contemporaneous, but there are some hints. We now know from his repeated claims that he thought he had solved the problem. We also know that he clearly believed that an inverse-square force led to an elliptical orbit (and that a linear force did as well).107) Finally, not only was his approach to obtaining an elliptical orbit given in “Laws of Circular Motion” somewhat different from Newton’s in De Motu, but more importantly, the problem he addressed was quite different. If he had simply read De Motu and then copied or reproduced Newton’s proof, he surely would have treated the crucial problem of the inverse-square force rather than the rather academic case of a force proportional to the distance. This almost establishes that we are looking at an original proof which was independent of De Motu.108) Even if it is quite tentative, this conclusion puts Hooke’s accomplishments in a new light.

Newton, Gravitation, and the Kepler Problem, 1665–1987 Newton’s ultimately successful attempts to solve the Kepler Problem have been exhaustively studied, and are documented in such classics as Herivel’s The Background to Newton’s Principia, by Whiteside in several places, and in papers written by Bernard Cohen, Sam Westfall, Alexandre Koyr´e, and many others.109) We discuss it here merely to provide a context for Hooke’s own efforts. In addition to those bearing directly on the solution of the Kepler problem, a number of other important manuscripts survive which show the evolution of Newton’s dynamics more generally. Among these is an undated manuscript of which John Locke had a copy which may date from as early as 1680 or as late as 1684 (more likely the latter), which is the date of De Motu,110) the “curious tract” referred to by Halley. De Motu exists in at least five versions, all similar. It would evolve into the Principia in less than three years and is thus the first glimpse at what was to be. But since Hooke had goaded Newton into again turning his attention to the problem as early as the winter of 1679–80, he may have made important first steps toward its solution then.111) The full title, De Motu Corporum in Gyrum, may be translated as Herivel did, as “The Motion of Revolving Bodies.” In roughly 5000 words, Newton formulates the problem, introduces the term “centripetal force” for the first time, states the law of inertia (which he described as «the force innate in a body by reason of which it endeavours to persist in its motion along a straight line») as an hypothesis, and proceeds to prove four theorems, including the law of equal areas, the proportionality of the centripetal force to v2 /r , and the harmonic law («the squares of the periodic times in ellipses vary as the cubes of the transverse axes).»112) As Herivel points out, Newton’s understanding of the need for a center-directed force had changed so radically since 1679 that centrifugal force is not even mentioned. Newton, it seems

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Fig. 20: Frontispiece to the first edition of Newton’s Principia, 1687.

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reasonable to say, had Hooke to thank for this evolution. Whiteside, as we have seen, was of this opinion. The period of intense, almost superhuman concentration which produced the Principia so soon after De Motu, and so beautifully described by Westfall,113) was by no means devoted to the Kepler problem alone, but it was this problem, or more generally the problem of motion of a body under gravitational attraction, including its application to the problem of cometary orbits, that represented the crucial test of his method. Newton’s most extensive comments on gravitation are to be found in Book III of the Principia, “The System of the World.” There he reiterates his earlier discovery that the gravitational effects of a spherical mass are as if the mass were concentrated at its center, a discovery that can be seen as crucial to Newton’s further progress in dynamics.114) He also discussed parabolic cometary orbits, the tides and precession of the equinoxes, and offered an extensive theory of the moon’s motion. Ironically, if Hooke played a critical role in Newton’s path to the Principia, his claims of priority may have come close to derailing the entire project in the spring of 1686, when Halley informed Newton that «Mr Hook seems to expect you should make some mention of him, in the preface . . . »115) A difficult position for Halley, friend of Hooke’s, but in awe of Newton and mid-wife to the Principia.

Conclusion The fateful exchange of 1679 changed the lives of both men. This is not to say that Hooke’s query and the embarrassment Newton may have experienced at being corrected by Hooke, alone created Newton the dynamicist. Other factors were crucial, including the comets of the early 1680s, over which Newton puzzled for some time, and of course his mastery of mathematics. It is clear that between late 1679 and 1684 Newton was giving some thought to the problem of motion of bodies under the sun’s attraction, stimulated by the exchange with Hooke. This was very far from his major interest, as he worked on a history of the church, on the prophesies, and continued his interest in alchemy. And based on the volume of his writings on theology and alchemy in this period – the better part of a decade starting in 1676 – labeled by Westfall as “Years of Silence,” Newton cannot have devoted a great deal of time to the problem which made him immortal. Yet between the professed ignorance of 1679 and De Motu of 1684 is an enormous gap, which he must have slowly and sporadically closed.116) For this we have Robert Hooke to thank. Did Hooke ever admit, if only to himself, that the achievement represented by the Principia was beyond him? Perhaps he did not, as Pugliese has claimed. Thus his comment on meeting Newton at Edmond Halley’s residence in Islington on the fifteenth of February 1689, about which he wrote grimly that Newton «vainly pretended claim yet acknowledged my information. Interest has no conscience. A posse ad esse non valet consequentia.» And earlier, as Halley was bringing the Principia into print, he noted in a lecture on earthquakes that Newton’s treatise “now in the Press” was bringing to completion the work he would have revealed in his lectures «upon the

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motions and influences of the Caelestial Bodies,« «if it had been thought fit.» Hooke clearly was not prepared to face the truth. John Aubrey, in his Brief Lives, wrote of the Hooke–Newton exchange in words that Hooke no doubt would have relished: «Mr. Hooke sent, in his next letter, the whole of his Hypothesis, scil. that the gravitation was reciprocall to the square of the distance: which is the whole coelastiall theory117) concerning which Mr. Newton haz made a demonstration, not at all owning he receiv’d the first Intimation of it from Mr. Hooke. Likewise Mr. Newton haz in the same Booke printed some other Theories and experiments of Mr. Hooke’s, without acknowledging from whom he had them.» Aubrey had earlier written similar words to Anthony Wood, claiming that Newton had gotten his ideas on gravity and planetary motion from Hooke, but we know that Hooke played an important role in composing the letter.118) As late as July 1693, six full years after the publication of the Principia, a copy of which he owned at his death, Hooke wrote in his Diary that he had «asserted my invention of Coelestiall Motions.» We know what Newton did, and in many respects we know the process by which he reached his results. But what of Hooke? Only in the last two decades has it become clear what he was capable of, and while it did not and could not have led to De Motu, much less the Principia, it was not inconsiderable. It is surely correct to say that up to at least 1680 he not only understood the centrality of the problem, but that he alone had a program for solving it. Before De Motu there is no evidence that anyone other than Hooke embraced the center-directed inverse-square law of gravitation119) or its universal character. No one seems to have tried to go beyond Kepler and actually attempt to show how, dynamically, elliptical orbits come about, before Hooke. If the “Circular Motion” manuscript represents, as it appears to, his own ideas, then we know, for the first time, something of how far along he got before being overtaken by Newton.

Annotations 1) Diary I, 18 and 21 October 1679. 2) 24 November; see below, especially fn. 73. 3) Two days earlier he had written in his Diary that he had «pefect [ed] theory of heavens». 4) Birch, 2, 91. Register Book, iii, p. 114. Hooke also speculated that an increase in the density of the interplanetary medium could keep a body from moving off along a tangent, as did Newton somewhat later. See, for example, Pugliese (1989).

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5) This, as we have seen, is a pendulum which is allowed to move in three dimensions, rather than only in a plane. If the angle from the vertical is constant, the motion is circular. Hence it is best called a “conical pendulum,” since the motion is circular only given the correct initial velocity. It may have been a Hooke invention, though such a simple and evocative device could hardly have a single discoverer. Huygens showed that the conical pendulum was isochronous if the vertical distance from the point of support to the bob √ was constant in De Vi Centrifuga. That is, the period T is given by T = 2π h/g, where h is the vertical distance. Hooke apparently showed, or at least guessed, that for the conical pendulum the period is independent of the size of the path only if the circular motion of the bob is confined to a parabola of revolution: «Mr. Hooke had demonstrated, that the bullet of the circular pendulum, if it can be always kept rising or falling in a parabola, will keep its circular motion in the same time; yet he had not demonstrated, that the diameter of the parabola from the point of contact in the curve to the vertex of the diameter is equal to that portion of the curve from the said point of contact to the vertex of the same curve, plus half the latus recturm or plus double the focus of the parabola.» Birch, 2, p. 153. Despite repeated requests (7 and 14 March 1666/7, 28 March and 4 April 1667), Hooke never provided the proof. On Hooke, Huygens, and the conical pendulum, see Pugliese, 1989. 6) Perhaps in an attempt to improve the analogy with planetary motion, Hooke made the surprising decision to take the conatus directed toward the center to be proportional to the distance squared, though he understood that this was not the case. 7) Westfall (1980), Chapter 5. We note that Hooke was discussing the problem in terms of «direct motion by the tangent, and of another endeavour tending to the center,» to use Birch’s words, while Newton was, following, or perhaps “paralleling” Huygens – Westfall’s term – in balancing gravity and centrifugal force. Much later Newton coined the term “centripetal” for the tendency toward the center that Hooke was talking about. There is a very real difference between these positions, i.e., whether gravity balanced centrifugal force, or whether it simply provided the centripetal tendency (to use Newton’s term) that disturbed the inertial motion. On 11 July 1667 Hooke further commented that, according to Birch, «he had a theory, which would solve all the unequal motions of the planets . . . » 8) Kollerstom (1999). 9) Westfall (1980), p. 91. 10) Even if that slow convergence was only a product of the way their paths sporadically crossed in the 1670s.

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11) Though his statements about the Moon’s “principle of gravitation” nearly a decade earlier in Micrographia (referred to above) barely fall short of a statement of universal gravitation. See below. 12) «An attempt to prove the Motion of the Earth from Observations,» Cutler Lecture, 1670, published in 1674 and reprinted in Gunther, VIII, pp. 27–28. 13) Corresp. II, p. 297, 24 November 1679. 14) “An Attempt to Prove the Motion of the Earth,” p. 28. 15) See Chapter 9. 16) Hooke comments on the problem of planetary motion on eleven occasions in the Diary (Diary I), between 1674 and 1680. 17) Diary I, 22 and 25 August 1676. 18) Diary I, p. 314. 19) Dobbs (1991), Westfall (1980). 20) Newton acknowledged as much in a letter to Halley, written 14 July 1686: «This is true, that his Letters occasioned my finding the method of determining Figures, wch when I tried in ye Ellipsis I threw the calculation by [,] being upon other studies & so it rested for about 5 yeares till upon your request I sought for yt paper . . . » Corresp, II, 444. 21) The record is largely silent on the issue after the 6 January letter to Newton, in part because the Diary begins to get very sketchy before the end of 1680, but even the posthumously published lectures from the period 1680–82 shed little light. Yet, see his “Laws of Circular Motion” paper, below. 22) We have already noted that one reason for this is that his published work, a major exception being the Micrographia, is largely based on lectures, mostly to the Royal Society. This left little room for quantitative development. While the geometrical argument in his “Laws of Circular Motion” (see below) is impressive, one notes with some dismay his comment in his Diary on 8 July 1693, that «I masterd Logarithms.« (Gunther, X, p. 257). 23) Which is not to say that this is what Newton actually did in the Principia. 24) He continued on the 8th , 15th , and perhaps 22nd November. 25) And, as we shall see, had already gone beyond this in the 1679–80 exchange with Newton to assume an inverse-square force. 26) “Discourse of Comets,” PW, p. 182. 27) Technically, elliptical orbits do not imply a 1/r 2 force, and a 1/r 2 force implies that the orbits are conic sections, i.e., ellipses if the objects are bound together. 28) This is much more complicated than it might seem. Hooke has had to intuit that gravity in the vicinity of the earth’s surface obeyed an inverse-square law depending on the distance from the center of the earth, which involves the implicit

Annotations

29) 30) 31)

32) 33)

34) 35)

36) 37)

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assumption that the effect of all the mass of the earth is as if it were concentrated at the center, something Newton would prove later (Book I, Proposition LXXI). This is reminiscent of the early Newton. See Kollerstrom (1991). There is perhaps a hint of field theory here, not to mention a sense of gravity as dynamic, propagated radially in pulses. Most of the letters from Newton in this period, as compiled by Turnbull (Corresp.) concern the comet of 1680, in which almost everyone was interested, but particularly Hooke and Flamsteed. There are only 11 letters from Newton in Turnbull between the exchange with Hooke and Halley’s visit, a period of four full years. Especially the comments on gravity in his “Discourse of Comets,” PW, pp. 167– 185. He concluded with «Sr Chrisopher was little satisfied that he could do it, and tho Mr Hook then promised to show it him, I do not yet find that in that particular he has been good as his word.» Halley to Newton, 29 June 1686; Corresp. II, 441–2. The context was Newton’s threat to suppress Book III of the Principia in the face of Hooke’s claims that his contribution to Newton’s understanding had not been acknowledged, and Halley’s attempt to smooth Newton’s ruffled feathers. Although Halley attributes to Hooke the term “centripetal” force, it is not at all clear that Hooke actually used it in the conversation in question. Halley disclosed that he had found that Kepler’s Third Law would result from an inverse-square force, or in Halley’s words: «having from the consideration of the sesquialter proportion of Kepler, concluded that the centripetall force descreased in the proportion of the squares of the distances reciprocally . . . » Halley’s proof would have been restricted to circular oribits. Including whether it may have resembled the geometric argument contained in his “Circular Motion” manuscript, discussed below. Herivel (1965) thought that Halley may have gone earlier, possibly in May, 1684, and that this was the visit which revived Newton’s interest in dynamics. This would conform more readily with the two-month deadline set by Wren in January. Herivel (1965), p. 97. Westfall (1980), pp. 404–408. This is how Newton described it: «his [Hooke’s] letters occasioned my finding the method of determining Figures, wch when I had tried in ye Ellipsis, I threw the calculation by being upon other studies & so it rested for about 5 yeares till upon your request I sought for yt paper, & not finding it did it again . . . » Newton to Halley, 14 July 1686 (Corresp., II, 444). DeMoivre’s famous description was as follows: «In 1684 Dr. Halley came to visit him at Cambridge . . . the Dr. asked him what he thought the Curve would be that would be described by the Planets

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supposing the force of attraction towards the Sun to be reciprocal to the square of their distances from it. Sir Isaac replied that it would be an Ellipsis, the Doctor struck with joy & amazement asked him how he knew it, why saith he I have calculated it, whereupon Dr. Halley asked him for his calculation without any further delay, Sir Isaac looked among his papers but could not find it, but he promised him to renew it, & then to send it to him . . . » (MS 1075–7, University of Chicago Library). As we have noted, it is by no means clear that Hooke could not have made the same claim that Newton made to Halley. In fact, he essentially did. It merely required combining the knowledge that the planets moved in elliptical orbits with the conviction that gravity was an inverse square force. He might even have claimed that he had «calculated it,» and indeed he made such claims. 38) Herivel (1965), gives the text of De Motu, and an English translation. 39) See Birch, 4, 347. 40) That is, the orbit in the form of the radius vector as a function of t or θ, as we would now require. For example, Proposition XXXI of Book I. 41) Huygens and Newton had a rather testy exchange in 1673, through Oldenburg, over Newton’s theory of color, but it never reached the level of animosity that characterized the comments that Newton directed at Hooke. 42) Quoted in Bell (1947), p. 89. 43) The results were published in his Horologium Oscillatorium of 1673, a copy of which Hooke had in his library at his death. De Vi Centrifuga was published 30 years later, and eight years after his death. Hooke takes note of the work in his Diary for July 1673. 44) Bell (1947), p. 121. 45) Though Newton’s thinking was not so different before about 1682. 46) For example, John Keill, Savilian Professor of Astronomy at Oxford, among others, gave his ideas currency and provided missing proofs of his theorems. See Bell, Ibid, p. 117. Keill was deeply involved, on Newton’s side, in the priority dispute with Leibniz. 47) J.B. Duhamel, Regia scientiarum academiae historia (Paris, 1698); noted in CHO, p. 63, n. 1. 48) Including a remarkable one recounted in Chap. 12. 49) June-July, 1663; see, particularly Shapin and Schaffer (1985), pp. 249–52. 50) Micrographia, p. 246. 51) PW, p. 201–2. On the causal connection Huygens saw between centrifugal force and gravity, see, for example, Yoder (1988), chapter 3. 52) Gal (2003). 53) Gunther, VIII, 28.

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54) PW, pp. 149–190 (though p. 149 is labelled “194”). As compiled by Waller, the lectures run to about 35,000 words, which might be delivered in about 5 hours. Thus 5–10 lectures at minimum. The Journal Book (Birch) records lectures on the subject for 25 October, 8 and 15 November, 20 December, and 14 February (1682/3). The treatment of gravity is mainly on pages 176–185. Michaelmas, honoring St. Michael, was traditionally September 29, coinciding very nearly with the autumnal equinox, hence an equinox celebration. The Michaelmas term at British universities is, and was, the fall term, beginnng about Michaelmas. The Royal Society would usually resume meetings, after a summer hiatus, around Michaelmas. In 1682 they began again on 25 October and Hooke read the first part of a discourse on comets, prompted by the bright comet of 1680 and 1681. 55) “Discourse of Comets,” PW, p. 177. Hooke, of course was right; while the small bodies of the solar system are irregular, gravity has moulded the large bodies into approximate spheres. 56) Should one be reminded here of Aristotle’s arguments about the sphericity of the Earth, it is clear that Hooke’s understanding of the physics of the problem is very different. In “A Discourse of Comets” Hooke advances the argument that if they did not possess gravity, the parts of rotating bodies like the Sun and Jupiter, would be dispersed by their rotation. PW, p. 178. 57) PW, P. 176. 58) PW, p. 178. 59) A fact which Westfall came close to conceding as early as 1967 (Westfall, 1967). 60) PW, 178. 61) PW, p. 178. 62) Though he does argue that «the perpendicular of Gravity will not always point to the center of the Earth,» because of its rotation (to which an exclamation mark might be added). PW, p. 181. 63) See fn. 30. Of course gravity is mediated by the aether. 64) PW, pp. 185. 65) Corresp., II, p. 309. As noted below, Newton thought that Wren knew this is 1677, and if true, Hooke would have as well. 66) PW, p. 184. 67) Works of Richard Bentley, London, 1938, Vol. 3, pp. 210–11. Cited in Cajori (1934), p. 633. 68) Aside from his recollection of 50 years later, the evidence comes mostly from the Waste Book. See Herivel (1965), Chapter II. 69) Corresp., II, pp. 433, 435. Newton to Halley, 27 May and 20 June 1686.

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70) Kollerstrom (1999) interprets a Halley letter to Newton (Corresp. II, p. 442) as carrying the implication that Wren did not confirm Newton’s claim. Whether that interpretation is warranted or not, nothing Halley or Wren, or for that matter Hooke wrote, suggests that Wren was ahead of Hooke in arriving at the inversesquare nature of gravity. Yet they exchanged ideas on the subject regularly over coffee. 71) We should note that in the second edition of the Principia (1713), in the Scholium to Proposition IV, Theorem IV, Newton does acknowledge Hooke, along with Wren and Halley. 72) The evidence against Newton’s story lies in his treatment of gravitation in the intervening period. See Kollerstom (1991) or Wilson (1989), for example. Though, to be fair, the lack of any evidence in support of Newton’s claims only makes them improbable, and does not rule them out. 73) The total of fourteen letters betwen Hooke and Newton after Oldenburg’s death consist of six from the fall of 1677 to the spring of 1678, and eight between 24 November 1679 and 18 December 1680. Of the latter, the first six constitute the exchange over dynamics: Hooke to Newton, 24 November 1679; Newton to Hooke, 28 November 1679; Hooke to Newton, 9 December 1679; Newton to Hooke, 13 December 1679; Hooke to Newton, 6 January 1679/80; Hooke to Newton, 17 January 1679/80. There are two more letters from almost a year later: Newton to Hooke, 3 December 1680 and Hooke to Newton, 18 December 1690. (Corresp. II. We have alluded to this correspondence in several places. Two of these letters, Newton to Hooke, 28 November 1679, and Hooke to Newton, 17 January 1679/80, were reproduced in facsimile by Gunther, X, 52–55. (Corresp., II, letters #235–241, 243). See n. 2, above. 74) Whiteside (1967–90), VI p. 11, n. 32. 75) Whiteside (1991), Kollerstrom (1999), and the earlier works by Lohne (1960) and Patterson (1950). 76) Corresp., II, pp. 431–447; letters 285–291; see n. 35. 77) Gunther published the 28 November and 17 January letters in facsimile in Vol. X of his Early Science in Oxford (pp. 52–55). 78) Corresp., II, p. 297. 79) He had buried his mother in June of 1679 and had just returned from Lincolnshire when he received Hooke’s first letter. Westfall (1980), pp. 339–340. 80) Corresp., II, p. 300, 302. In evaluating this statement, one should weigh in the balance the relative care with which Newton seems to have used centrifugal force in 1664 (Brackenridge and Nauenberg, 2002, p. 88ff.) 81) There is some tension between Newton’s professed desire not to get involved with philosophical matters and his bringing up the issue of the earth’s rotation on a falling body. He cannot have been totally surprised that Hooke wanted to pursue the point.

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82) To wit: «Your Deserting Philosophy in a time when soe many other Eminent freinds have also left her . . . Seems a little Unkind yet tis to be hoped her allurements may sometimes make you . . . alter your resolutions . . . » Corresp., II, pp. 304–6. Hooke may have later regretted those generous words. Newton’s argument was that since the body was above the surface of the earth when released, it had a greater velocity toward the east than the point directly below on the surface, and thus advanced on the earth, falling to the east. Hooke pointed out to Newton that there was a southerly deflection as well, and Newton acknowledged that that was indeed the case. We now know that if the rotating earth is viewed as an inertial system, there is a centrifugal force which has a southerly component as well as one perpendicular to the earth’s surface. The Coriolis force will deflect the resultant southerly motion to the west (in the northern hemisphere). But the Coriolis force also acts on the much larger velocity component toward the center of the earth, causing a resultant easterly deflection. So the object will fall to the east of the perpendicular, and indeed, to the SE, as Hooke argued. It is unclear how he arrived at this conclusion. See also the discussion by Lohne (1960). It might be further noted that a plumb line suffers a similar deflection due to the centrifugal force. But there remains a very small southerly deflection due to the Coriolis force. 83) We might note that Hooke showed less interest in the proof of the earth’s diurnal motion than in the details of the path under gravity. In the matter of the earth’s motion, he was more interested in the motion of the earth about the Sun, which he thought he had established by observing stellar parallax. Hooke’s real issue was with the spiral path, though he elaborated Newton’s drawing into «sume few revolutions.» Hooke considered a body at the equator, falling in the equatorial plane, but allowed to fall in a gap between the upper and lower halves of the earth, so as not to encounter matter, and drew its motion in what we would call an inertial system, i.e., a system not rotating with the earth. The resultant path, assuming «. . . that the gravitation to the former Center remained as before . . . would resemble An Elleipse» returning to its original point. Quite evidently Hooke meant varying as the inverse-square of the distance, in which case he was right, but others have thought he meant constant gravity. Indeed Newton may have. Hooke had the body spiralling to the center only if the medium offered some impediment. In Newton’s reply, quoted in the text, he said that «if gravity be supposed uniform . . . » If he really thought gravity inside the earth was constant, he was quite wrong, but it is not clear whether he did or not. He went on to add, of gravity, that «if it be supposed greater nearer ye center . . . » the curvature would be greater closer to the center and «the increase of gravity in ye descent may be supposed such yt ye body shall by an infinite number of spiral revolutions decend continually till it cross ye center by motion trascendently swift.» Neither

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the assumption of constant gravity or «greater nearer ye center» was correct, but given those assumptions he obtained something like the correct orbit. In Hooke’s rejoinder three weeks later, he agreed generally with Newton’s curve for constant gravity, but reiterated his original supposition that gravity is always an inverse-square force and that the velocity will be «as Kepler Supposes Reciprocall to the Distance.» This incorrect statement seems to expose the qualitative or intuitive nature of Hooke’s arguments. He saw this giving rise to something like an elliptical path, with the two turning points (nearest and furthest from the center) opposite each other, though he did not provide a figure. He went on, however, to deny that there «really is such an attraction to the very Center of the Earth . . . » and argued instead that «. . . on the Contrary I rather Conceive that the more the body approaches the Center, the lesse will it be Urged by the attraction . . . » This is, as we note in the text, remarkably prescient. Concerning Hooke’s incorrect statement of Kepler’s second law, Cohen, apparently correctly, has argued that Hooke simultaneously held incompatible understandings of the second law, this one and the correct one (Cohen, 1980). 84) It should be said that not everyone agrees that Newton’s very small figure was anything other than a qualitative solution. Whiteside wrote that «it is evident that we should not lay too great an emphasis on the precise shape of Newton’s roughly sketched fall curve.» Whiteside (1967–80), VI, p. 10, n. 29. 85) 6 January 1679/80. Corresp., II, p. 309. For comparison, consult what Wren told Hooke two years earlier, on 20 September 1677; Diary I, p. 314. 86) Book I, Proposition LXXIII. 87) Newton assumed gravity to be constant, and a ball rolling in a circular path on the interior surface of a cone has a constant centripetel force, which is the radial component of the normal force. As Hooke put it: «Your Calculation of the Curve by a body attracted by an aequall power at all Distances from the center Such as that of a ball Rouling in an inverted Concave cone is right and the two auges will not unite by about a third of a Revolution.» Corresp. II, 309. 88) See Westfall. 89) Though Ofer Gal has written a book which has a very different take on these issues and the same is the case in his contribution to the Hooke 2003 symposium (Gal, 2002, 2003). I do not find all of his arguments unconvincing, in particular details of the discussion of his relationship to Kepler in Gal (2003). See also Brackenridge and Nauenberg (2002). 90) Newton to Halley, 20 June and 14 July 1686. Corresp., II, letters 288 and 290. Among other things, Newton wanted to defend himself against Hooke’s later claim that he had shown his ignorance of the inverse-square nature of gravity when he assumed it constant in the letter of 28 November 1679. Newton heatedly wrote to Halley that «in my answer to his first letter I refused his correspondence, told him I had laid Philosophy aside, sent him only ye experiment

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of projectiles to sweeten my Answer, expected to heare no further from, could scarce perswade myself to anwer his second letter, did not answer his third, was upon other things, thought no further of philosophical matters when his letters put me upon it, & therefore may be allowed not to have had my thoughts of that kind about me so well at that time.» (Corrresp., II, p. 436). Very self-serving, one might say. Halley’s reply of 29 June (Corresp. II, pp. 441–3) described the meeting of the Society at which the Principia was presented, and Hooke’s reaction. 91) As we mentioned in Chapter 5, the Journal Book (Birch) entry for the meeting of 10 December 1684 notes that «Mr Halley gave an account, that he had lately seen Mr. Newton at Cambridge, who had shewed him a curious treatise, De Motu . . . ». Hooke may have first seen it somewhere around this time, though some have argued, as did Lohne, that he «only gradually became aware of contents of the work Newton was composing. But from the fall of the year 1686 we can see him [Hooke] feverishly active to assert his claims of priority.» Lohne (1960). 92) The Diary begins to thin out in 1679 and, as we have it, at least, terminates four years later. There seems to be no obvious way to relate this hiatus to anything going on in his scientific life, other than his assumption of the duties of Secretary and his launching of his Philosophical Collections. It is tempting to draw a connection between this gap and the impact of De Motu, but evidence is totally lacking. If these, along with his other duties for the Society and his still vigorous architectural practice are what kept him from writing his Diary, it is not surprising that he failed to make further progress on the Kepler problem. Even in 1679/80, Hooke’s references to the correspondence with Newton are perfunctory, consisting of «Letter from Newton . . . » on 1 December, «Sent letter to Newton . . . » on 9 December, and «Read Newtons letters to Boyle at Garways . . . » on Christmas Eve. Two days before he wrote Newton on 6 January he does scribble «perfect Theory of Heavens,» in his Diary. 93) By 1687, of course, Newton’s proof had a rigor that Hooke could not even approach, and furthermore, it was only part of a grand system, if perhaps the centerpiece. 94) Pugliese (1989). 95) Which date is found on the manuscript. It could have been “back-dated” of course, though nothing we know of Hooke suggests that that is likely, or the date could have been already on a page that Hooke re-used. Alternatively, it could have been jotted down sometime after the manuscript was written, or in any case, the argument may have existed for an unknown period of time prior to September 1685. Tentatively, we have little choice but to take it at face value. 96) Veracity is probably not the issue here. Rather, it is a question of whether Hooke had achieved what he thought he had.

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97) Now in the collection of Hooke material in the Wren Library at Trinity College, Cambridge, Ms 0.11a.1/16. Pugliese (1989), p. 201. The manuscript consists of seven pages, and includes a diagram, reproduced in both Pugliese and Nauenberg (1994a); Ms 0.11a folio 6r. Nauenberg (1994a, p. 346) gives a transcription of the text in the figure. 98) Ibid, fol. 4r. The passage is quoted by Pugliese (1989). 99) This, and the inverse-square force (1/r 2 ), are two of a rather small number cases of integral exponents which can lead to elliptical orbits. 100) Nauenberg (1994a, 2006). 101) In Newton’s case, the force on a moving body was taken to be proportional to the distance it would recede from the center if it continued along its tangential path (in some short time interval). Also Hall (1957). An almost identical approach was employed by Huygens as early as 1659. See Yoder (1998). 102) See, for example, Nauenberg (2003). 103) Whether Hooke “proved” that the resulting orbit was an ellipse is difficult to determine unequivocally, since, among other things, we do not know whether we have a complete proof. Nauenberg shows how Hooke could have carried out such a proof and that certain constructions in the diagram in the manuscript are consistent with such a proof. One suspects that a good geometer like Hooke would not settle for a curve which resembled an elllipse. Hooke’s description and the diagram from the Trinity College manuscript suggest that he invoked a “pulse” theory of the action of gravity, i.e., that it was not just a mathematical device that would be followed by a limiting process that led to a continuously acting force. 104) On the other hand, perhaps it was the failure of such an attempt that explains why no proof ever surfaced and why Wren was unconvinced. It is worth emphasizing that while Nauenberg has shown what Hooke could do, and in fact did do in the case of a force proportional to the distance, the only evidence that Hooke might have done the same for the inverse-square force lies in his repeated claims that he had solved the problem. The views of Ofer Gal on Hooke’s and Newton’s constructions are different from Nauenberg’s. See Gal (2002). Nauenberg is mostly correct, but the issue cannot be further elaborated here. 105) Pugliese (1989), p. 204. 106) Halley’s argument (Corresp. II, 442) was just the opposite, that if Hooke was waiting for others to fail, in order to appreciate the value of his discovery, that no longer applied after De Motu. 107) But it is also true that Hooke made the mistake, in the letter of 6 January, of claiming that «as Kepler supposes» the velocity (in circular motion (?)) under an inverse-square force, is «Reciprocall to the Distance». He makes this a consequence of the fact that «the Velocity will be in a subduplicate proportion to

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the attraction (proportional to the square root). That is, since v2 is proportional to the force, F, which itself is proportional to 1/r 2 , v ought to be proportional to 1/r . The fallacy is that the force F is proportional √ to v2 /r or, alternatively, v2 is proportional to r F. Then v is proportional to 1/ r .» Newton did not reply to this letter, which ended their correspondence on dynamics. 108) Although the date on the document is the better part of a year after De Motu was presented to the Society, there are at least two reasons for believing that Hooke had not seen De Motu before he offered his “proof,” or at least that he was giving an independent argument. They are, first, that Hooke’s arguments are his own, typical of his reasoning and seemingly not informed by a reading of De Motu, and second, that based on the lack of discussion of De Motu at Society meetings, it may very well be that its detailed contents were not made available. Hooke was no longer Secretary and may have had no special access to correspondence or other documents. Perhaps trumping these theoretical arguments, however, is that in a letter to Newton on 29 June 1686, Halley wrote, referring to De Motu «. . . since which time is has been entered upon the Register books of the Society as all this past Mr. Hook was acquainted with it . . . ». Corresp., II, 442. In Problem 2 of De Motu, Newton posed the following problem: «Given a body revolving in the ellipse of the ancients, there is requird the law of centripetal force directed to the center of the ellipse.» The result is «directly as the distance.» But the approach is entirely different. Herivel (1965), p. 281. 109) For example, Cohen (1999), Whiteside (1970, 1989, 1991), Koyr´e (1955). 110) Whiteside (1991), Wilson (1989). 111) Nauenberg in “Newton’s early computational method for dynamics” (Nauenberg, 1994a), Brackenridge and Nauenberg (2002), and Nauenberg (2006), have attempted to reconstruct the process by which Newton arrived at the orbits he drew in his second letter to Hooke. Their analysis is very interesting and very possibly correct, but speculative. Nonetheless, the mathematical imperatives are such that there a very few ways for Newton to have arrived at his result, assuming that he had a method, and that the argument wasn’t merely qualitative. As to when Newton first either obtained Kepler’s Second Law or showed that elliptical orbits resulted from inverse-square forces, Cohen calls Newton’s claim, made around 1718, that he had done the latter in 1677 (conveniently before the correspondence with Hooke), as “bogus history.” Cohen (1980), pp. 248–9. 112) Herivel (1965), p. 282, Brackenridge (2001) in Buchwald and Cohen (2001), pp. 105–115. 113) Westfall (1980), pp. 404–408, and all of his Chapter 10. 114) This result was first established in Book I, in Propositions LXXI and LXXV, and restated in Book III, Proposition VIII. 115) Halley to Newton, 22 May 1686. Corresp., II, 431.

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116) Of course there is but circumstantial evidence that Newton gave any thought at all to the problem in those five years, consisting mostly of his clear interest in the comets which appeared in those years. The alternative is that De Motu was the product of only two, or at most five, months effort. 117) That is far from the “whole celestial theory,” as we know, but then Hooke contributed much more than just the force law. 118) Aubrey to Anthony Wood, 15 September 1689; Corresp., III, pp. 40–44; especially notes 1–9 pp. 43–44. See also Chapter 12. 119) Wren, as we have seen, was a “co-conspirator;” no doubt they discussed precisely these issues over coffee.

Chapter 11

The Omnipotence of the Creator: Robert Hooke, Astronomer Even though Hooke was probably England’s most important astronomer between Galileo’s contemporary Thomas Harriot and the first Astronomer Royal John Flamsteed, his role in astronomy is not generally recognized.1) His activities as an astronomer and astronomical instrument maker were uniquely diverse by comparison with those of his contemporaries, both because he was a somewhat sporadic observational astronomer who made discoveries with the telescope and discoursed on them to the Royal Society, but also because he was also a recognized authority on optics, an adept designer of and fabricator of astronomical optics, and an original designer of mountings for quadrants, telescopes, and other instruments. The Journal Book is full of accounts of Hooke’s designs of grinding machines for lenses and mirrors, and his mechanical designs are displayed for all to see in his published Cutler Lectures.2) This represented a convergence of his talents as an optician and instrument maker with his other interests in natural philosophy, notably light and color on the one hand, and planetary motion on the other. Although the telescope as a scientific instrument was only a half-century old in 1660, the latter half of the century saw planetary astronomy advance rapidly. This progress followed the consolidation of the Copernican theory in the early 1600s and advances which took place in optical technology throughout the century. The decade before the Restoration, in particular, saw significant advances in optics and telescope design simultaneously on the continent and in England.3) There was continuing interest in celestial cartography, much of which was independent of the telescope, increasing speculation on the nature and origin of the Moon as the process of mapping its surface and naming lunar features accelerated, and the planets, of which still only seven were known, were a prime focus of attention. Naturally, there was especially high interest in the known outer planets Mars, Jupiter and Saturn (especially the latter’s rings),4) and applied astronomy took on great importance because of the problem of determining longitude at sea or in distant places, usually employing either the earth’s moon or the moons of Jupiter. The latter part of the seventeenth century was

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blest by the appearance of several bright comets, which played an important role in the development of planetary dynamics. Hooke’s most important English astronomical predecessors in England were Thomas Harriot (1560–1621),5) who anticipated Galileo in some of his discoveries, having made the first drawings of the moon and having independently determined the period of rotation of the Sun using sunspots, and Jeremiah Horrocks (1619–40) who predicted, contra Kepler, the transit of Venus of 1639, and Samuel Hartlib (c. 1600– 1662).6) Hooke’s most important astronomical contemporaries were Flamsteed and Halley – the first two Royal Astronomers – in England, Huygens in the Netherlands and Paris, G.D. Cassini, who also spent much of his time in Paris, Guiseppi Campani in Rome, Johannes Hevelius (Johann Hewelke) of Dantzig, and Bologna’s Riccioli. The latter was a pioneer in selenography, discovered the binary character of Mizar, and, following Langrenus (van Langren, Dutch) gave names to most lunar features. Huygens, of whom we have had much to say already, advanced the technology of the refracting telescope in the late 1650s, was the first to understand the nature of Saturn’s rings, and discovered its large moon, Titan. Cassini used Campani-built telescopes to discover the rotation of Mars in 1666 (independently of Hooke), the division in Saturn’s rings which bears his name, and four more of Saturn’s moons. Hevelius was a notably acute and patient observer who employed large quadrants without telescopic sights (hence the controversy with Hooke), but used telescopes in planetary (especially the moon7) ) and solar observing. His names for some of the northern constellations survive. Flamsteed, a younger contemporary and sometime antagonist of Hooke, is noted for, among other things, his “Historia Coelestis,” a map of the heavens not improved upon for decades. His name survives in the “Flamsteed numbers” for stars that are still in use, he provided cometary positions to Halley and Newton, and regularly predicted lunar appulses and occultations, which were published in the Philosophical Transactions. “Stellar” astronomy in the century was mostly restricted to mapping and cataloging and to observation and discovery of binary star systems. Only the barest attention was paid to what we recognize as non-stellar galactic and extra-galactic objects such as the Orion nebula. Although the latter may have been discovered in 1610, Huygens noted it in 1656 and Hooke mentions «that small milky cloud» when describing the sword of Orion in Micrographia.8) Most of Hooke’s well-known astronomical contemporaries were more systematic observers than he, who was much more than just an astronomer and had heavy demands on his time. In this respect Hooke was very much like Huygens, who made important discoveries in astronomy while his primary focus was elsewhere. For Hooke, astronomy, though a life-long love, was usually harnessed to some larger issue or project in natural philosophy. Much of his observing was incidental to the task of testing optics or driving mechanisms or in pursuit of other questions such as timing or parallax. Thus, as was the case with his experimental program, Hooke had periods of intensive observing, followed by intervals with little evidence of astronomical activity as his interests were diverted elsewhere or as his other duties prevailed.

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Telescopes and Optics Hooke’s contributions to optics, lens and mirror figuring, and telescope design and construction were major, if not actually decisive. In this he was influenced by Wren and by older contemporaries like Sir Paul Neile and Dr. Jonathan Goddard, but also by his association with Richard Reeves (fl. 1641–1679)9) of Long Acre, perhaps the premier optical instrument maker of his time, and later Christopher Cock.10) Aside from his work as surveyor and architect, it was horology and practical optics that brought Hooke most strongly into contact with instrument makers like Reeves. He was constantly working on devices for grinding mirrors and lenses with non-spherical shapes, often in concert with Wren, and sometimes in competition with him. These attempts, which were regularly reported to the Society, were motivated by the goal of reducing the aberrations which plagued 17th optics, seriously compromising image quality. He actually built, possibly for the first time, a reflecting telescope of Gregory’s design, which ideally would employ parabolic and elliptical mirrors, though this may have only been an attempt to improve on the instrument that Reeves attempted, or, perhaps, to upstage Newton.11) In any event, Birch records (quoting the minutes for 5 February 1673/4) that «Mr. Hooke produced a new kind of reflecting telescope, differing from that of Mr. Newton in this, that the observer looked directly at the object erected.»12) He even experimented with mirrors made from glass, noting how a concave lens could be used as a mirror, and made a step toward coating a concave glass surface with a reflective coating, such as mercury. The experiments with the Gregorian reflecting telescope bore little fruit, which, indeed, was the case with any form of the reflecting telescope in this period, Newton’s not being an exception. The spherical mirrors commonly in use required large radii to reduce aberrations. While it was possible to figure spherical mirrors fairly precisely, the means of evaluating paraboloids and other shapes didn’t exist, and it was almost the time of Herschel, a century later, before a satisfactory solution to the problem of speculum metal was reached. Hooke made optics for many astronomers, and not a few dilettantes, though much of his observing was done with large “glasses” owned by others such as Boyle. None of his lenses survive with certainty. Most of the accounts of Hooke’s work with grinding and polishing engines date from the mid 1660s to the mid 1670s. For example, the Journal Book reports that on 10 June 1669 he «produced the model of another engine contrived by himself, so as to work a glass into any elliptical or hyperbolical figure assigned, by two motions, one upon the centers, the other upon a flat.» He discussed the problem again in January, and once more a year later, when he actually produced the grinding machine. At about this time Flamsteed expressed his concern to Brouncker that Hooke was not sharing his discoveries in lens grinding and polishing with the question: «why burns this lamp in secret?»13) And in the fall of 1670 Flamsteed was further frustrated at his inability to get Hooke’s help in mounting an objective that the latter had provided him, eventually telling Collins that «I would not trouble him further in that business, who, I perceive, is full of employment.»14) Frequently, it must be said, the utility of

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his designs was seriously compromised by an inability to fully execute them given the technology of the day. Although Hooke’s mechanical and theoretical ingenuity contributed in important ways to the advancement of telescope technology, and despite his extensive experience in grinding lenses and mirrors, and while he thought he could reduce chromatic aberration by employing a liquid-filled lens, neither he, nor any of his contemporaries was able to take the important step of conceiving and constructing an achromatic doublet, something that was only accomplished three-quarters of a century later by John Dolland. In the preface to Micrographia, Hooke discussed how “longer” objectives, that is, of greater focal length, «such as would bear a bigger aperture,» would produce better image quality, something he reiterated later, effectively announcing that greater apertures yield better resolution.15) He also expressed his understanding of the role of aperture in determining limiting magnitude, noting, while talking about going to a 36-foot glass, and even larger, that «for the discovery of small stars, the bigger the aperture be, the better adapted is the Glass.» He notes that a typical thirty-foot glass  will have an aperture of not much over two inches (perhaps up to 3 12 ) while a sixtyfoot glass will allow a three inch aperture, a consequence of the high focal ratios (relative aperture) required to keep aberrations in check in these days of pre-achromatic refracting telescopes which employed a single objective of spherical figure. In a typical refractor of Hooke’s time, the focal ratio might be greater than f /100, hence paraxial rays. Hooke also speaks about aperture stops, first introduced by Huygens. Hooke experimented with pendulum-driven equatorial clock drives for quadrants and telescopes, which represented an important application of his original discoveries in horology, which had also included astronomical timing. His well-known invention of the universal joint may have been motivated by this work on drives for observing instruments. Some of this is described in the two Cutler Lectures “Some Animadversions on the first Part of Hevelius[’] Machina Coelestis” of 1674 and “A Description of Helioscopes and some other Instruments,” published two years later. The rest is buried in the Journal Book of the Royal Society or in Birch’s transcription of it. A particularly interesting mechanism is illustrated in the “Animadversions” and described in detail in the body of the text (Fig 22). It shows an equatorial quadrant (Frontispiece) which is regulated by a conical pendulum and utilizes a worm and gear driven backwards,16) a situation which is very difficult to achieve. On the same plate (Fig. 10) he illustrates an altazimuth quadrant, rotated by use of a universal joint. Incidental to the working of these quadrants were some of his innovations in the means of producing finely graduated measurement scales, which allowed an accuracy at the level of arcseconds, the resolution of his telescopic quadrant sights. In fact Hooke designed and constructed a whole host of precision measuring devices, including a new type of sextant, etc, though of course he was not alone in these efforts. For years Hooke engaged in a dialogue, which sometimes became acrimonious (see Chapter 7), with Johannes Hevelius over the use of telescopic sights on quadrants

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for measuring celestial positions. Hooke was unquestionably right, and it may seem to us that there should have been no controversy, especially since Hevelius used telescopes for other purposes, but such was not the case. The Polish astronomer doggedly maintained his position, something which frustrated Hooke and eventually motivated the Cutler Lecture, “Animadversions.” This episode exhibits an aspect of Hooke’s personality, in which continued frustration in getting an idea across finally results in an intemperate outburst. Hooke was one of the pioneers of an admittedly qualitative and speculative wave theory of light and an independent discoverer of interference and diffraction, but the relation of the latter to optical resolution was an unexplored topic which required a theory that would not surface for well over a century, and the role of aperture in determining resolution (see above) was only dimly understood in the late seventeenth century, though as we have seen, Hooke was not completely in the dark. 17) .

Hooke As An Observer In all likelihood, Hooke’s interest in astronomy had its genesis in his boyhood on the Isle of Wight, where we can imagine he may have developed an interest in the heavens. We know that his imagination and his interest in natural history were stirred by the invertebrate fossils he found there, and the darkness of the sky on this sparsely populated island must have given an awesome immediacy to the night sky. But if we do not know how much he brought with him to Oxford, his initiation into astronomy as a science apparently was at the hands of Seth Ward there when he was in his 20s. By 1658, age 23, he had become an expert on pendulum clocks and was already interested in their use in astronomical timing, and as with all of his contemporaries, in their use in determining longitude. When reporting his apparent invention of the anchor escapement in 1656–7, he cited Riccioli’s (Ricciolus’) Almagestrum, making it clear that he was working on clock-driven telescopes. Horological issues played an important role in Hooke’s professional life, as we have seen, including the controversy over the spring-regulated watch which poisoned his relationship with Huygens. Most of these applications were motivated by either astronomical timing or the driving of astronomical instruments, usually quadrants. Hooke’s Diary is replete with references to optics, including means of generating lenses and mirrors of complex shapes, and to telescopes and other equipment, but observations are few and far between, usually of the planets, comets and eclipses, often with Halley. At best Hooke observed systematically only for short periods at a time, when a particular issue interested him, as with the nature of comets or his attempt to measure the stellar parallax due to the Earth’s motion, or when an eclipse or lunar appulse was predicted. As is true of the work as a whole, references to observing in the Diary are quite brief and laconic. The notoriously bad English weather and seventeenth-century London’s pollution no doubt played a part, but on one clear day after another in the early 1670s, Hooke records no observations. He was, of course, already overextended, busily preparing experiments for the regular weekly

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meeting of the Royal Society and heavily involved in supervising rebuilding the City after the fire. Most of the information we have on Hooke’s observing comes from Micrographia (1665), published under the aegis of the Society, from his Cutler Lectures, published between 1674 and 1678,18) from Diary entries, and, occasionally, from the Journal book. We also find, in Flamsteed’s correspondence, the Astronomer Royal’s attempts to get Hooke to provide him observations. What Hooke did not do was to indulge in lunar or celestial cartography, as did some of his continental contemporaries, or generate systematic predictions of appulses, eclipses, and the like, as did Flamsteed. Hooke is frequently found observing lunar eclipses19) or transits of Mercury, with Halley and others, but in the absence of a sustained observing program, we typically find that if he has priority in a discovery, and such cases are relatively few, it is just barely so, and usually the phenomena were discovered independently or later pursued in a way Hooke did not. Examples include the rotation of both Mars and Jupiter. Often what is of greater importance is the role that his astronomy played in his practice of natural philosophy, exemplified by the resulting lectures such as “Cometa,” “Helioscopes,” “An Attempt to Prove the Motion of the Earth Through Observations,” and “Animadversions.” In that sense he recalls Galileo, though the Italian had the advantage of being almost the very first telescopic astronomer. Although Micrographia was subtitled «. . . Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries thereupon», and much of it is indeed devoted to discoveries with the microscope, it is, as we have seen, full of speculations on the nature of light and color, including diffraction and interference, optics, and even universal gravitation and pneumatics. There is a lengthy, and remarkable, section on the effects of atmospheric refraction and the motion of the air on the color of the sky, the image of the sun near the horizon, scintillation as it affects images of the stars and planets, and so on20) . But as the work draws to a close, Hooke eases into a discussion of telescopic observation, and considers how to determine if the Moon’s orbit is an ellipse. Interestingly, and somewhat perplexingly, while quoting the accepted moon-earth distant as about 60 earth semidiameters, he argues from the geometry of lunar eclipses that it might fall to as little as 25 earth radii «much lower then any Astronomers have hitherto put it.»21) Perhaps the most interesting part of this discussion at the end of Micrographia is Hooke’s description of the surface of the Moon, accompanied by a drawing of the crater Hipparchus (Fig. 23) made in 1664 using a 30-foot glass (Figs. 21 and 22). While his ideas about vegetation on the Moon and comparisons to the Salisbury plain may seem a bit quaint, his speculations on the origins of the craters are quite interesting. He first considers the possibility of impacts but then rejects this hypothesis in favor of vulcanism, finding it «difficult to imagine from whence those bodies should come.» Remarkably, this leads, in short order, to the speculation «that there is in the Moon a principle of gravitation, such as in the Earth.»22) This is, of course, the germ of universal gravitation, expressed at about the same time as Newton claimed to have come by it, according to convenient recollection of decades later. It is known that

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Fig. 21: Sixty-foot telescope erected in the courtyard of Gresham College.

Newton carefully read the Micrographia, since we have his notes on it, and as we argued in the previous chapter, there is little reason to doubt Hooke’s priority. Commencing when Hooke became Curator of experiments at the Royal Society in late 1662, there are scattered reports by him of astronomical observations to be found in the Society’s Journal Book (or in Birch), usually, but not always, when a notable event, like an eclipse or the appearance of a comet, occurred. The first reference to his observing in the Journal Book comes on 15 April, 1663, when he proposes to observe the satellites of Jupiter, probably with the view of harnessing them to the task of determining longitude, which had been of interest since the time of Galileo. In August he reported counting 85 stars in the Pleiades with a 12-foot (focal length) telescope, an observation that found its way into Micrographia two years later, in the form of a drawing of the asterism in which 78 stars are recorded. In March of 1664 he was assigned to the Astronomical and Optical Committee of the Royal Society, some indication of where it was thought his interests lay, although he was put on several

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Plate from Hooke’s published lecture “Animadversions on the first part of the Machina Coelestis . . . ” showing an equatorial quadrant driven by a canonical or circular pendulum.

other committees as well. In January 1664/5 he was asked to bring in his observations of the partial lunar eclipse of 21 January, and when the first number of Oldenburg’s Philosophical Transactions was published in March 1664/5, there was a comment on an observation by Hooke, on 9 May 1664,23) of «a small spot in the biggest of the three obscurer belts of Jupiter,» and the revelation that by following it, he had deduced the planet’s rotation.24) Hooke, among others, also followed the comet which appeared in the winter of 1664,25) and was asked to print his account of it.26) His attempts to measure its parallax yielded a negative result, confirming its great distance. Much later (1678) he would describe these observations and those of the comet of 1677 in his Cutler Lecture “Cometa” (see below).

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Fig. 23: Hooke’s drawing of the lunar crater Hipparchus, from Micrographia.

The plague would intervene in 1665, interrupting Society meetings for eight months and scattering members. During part of that period Hooke was experimenting in Surrey, just outside London, and may have done some observing then, since two weeks after meetings resumed, on 28 March 1666, he announced the discovery, from watching what we call albedo features on Mars, that it too rotated, with a period of about 24 hours;27) Mars was then less than a month past opposition. Cassini arrived at the more precise period of 24h 40m (compared to the modern figure of 24h 37m) in the same year. On 20 June 1666 Hooke expressed interest in determining the parallax due to the Earth’s annual motion “to seconds.” These potentially crucial observations,

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carried out three years later, are described below. He also commented on a new spot he had observed on Jupiter, seen with Boyle’s sixty-foot glass. There was also a partial solar eclipse on 22 June 1666 (2 July Gregorian), which Hooke observed with some others, and observations of Saturn made a week later (it too was just past opposition, which is less relevant in Saturn’s case) were published in the Transactions in July.28) Clearly he was regularly observing in these years, and indeed had become one of the important astronomers of Europe, along with Hevelius, Cassini, and others, only to have his life, and that of those around him changed forever, as the Great Fire broke out in September. The greatest effect on Hooke was that it threw him into the enormous job of helping rebuild London, a job that would occupy him for two decades. Perhaps no one, even Wren, played a more important role in that process than Hooke. What that meant for his astronomy was that there was even less time for a coherent observing program. We can speculate about what his contributions might have been, but he would never again devote as much time to observing as he had done during the first half of 1666. The following March, in response to a report of observations from Paris, Hooke noted that «the air had been for a good while so thick about London, that he had not been able to see» the stars in question, but in fact, his already somewhat fitful observational program was at low ebb. His fertile mind was ranging widely over natural philosophy, exploring magnetism, pneumatics, even physiology, and eventually mechanics (1668), but astronomy seems not to have been a priority. There are no references in the Journal Book 29) to observations by Hooke for over two years, until 15 July 1669, when he created a sensation by telling the Society that he was observing, at Gresham, «the parallax of the earth’s orb . . . » Five years later, when his Cutler Lecture, “An attempt to prove the motion of the Earth through Observations,” was published, he reported that he had made observations with a zenith telescope specially built for this purpose at Gresham College between July and October, 1669. In the end he only made four measurements, because of «Inconvenient weather and great indisposition in my health,» though to be fair, the need to make repeated measurements to reduce systematic and other errors was not generally appreciated in the 17th century. Moreover, while we don’t know what Hooke’s health was like in 1669, we know from the Diary that it was not good three years later. We explore Hooke’s attempts to measure parallax more fully below. In March 1669/7030) Hooke described observing occultations of stars by the moon that had been computed by Flamsteed, using a six foot telescope, These are the first observations reported by him, other than the attempt to measure parallax, in a four year period going back to before the Fire. That April it was suggested that he undertake some observing to verify other of Flamsteed’s calculations, and the following March31) he records observing another appulse (or “congress of the moon” with a star). This was a grazing occultation, and it suggested to Hooke the existence of a lunar atmosphere. Again, in January 1672/3 he was provided with Flamsteed’s predicted lunar appulses for the upcoming year with the expectation that he would observe them. There was, as we have said, a great interest in these events as well as lunar eclipses because of their use in determining longitude at sea. Hooke himself

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never showed much interest in calculating ephemerides, and his attempts to solve the problem of planetary motion theoretically had not yet begun. Some of the impetus for observing in this period came from frequent letters to secretary Oldenburg from Hevelius and Cassini, often resulting in Hooke’s being directed to observe the same phenomena. But while Cassini was discovering new moons of Saturn in late 1673, Hooke was preoccupied with other matters, including the controversy with Newton over light and color, and, of course, his architectural work. In October 1674 his “Animadversion on the first part of Hevelius his Machina Coelestis”32) was published, criticizing Hevelius’ use of “naked” rather than telescopic sights and describing his own designs for the equatorially driven quadrant. We examined some of the consequences of this controversy earlier. The Diary begins, as noted earlier, in March 1671/2 with mostly meteorological data. The first significant astronomical entry in the Diary, dated 1 September 1672, concerns Mars: «Slept ill all night and observed Mars with speculum, but not so good.»33) Evidently he was testing a reflecting telescope, perhaps his Gregorian. The following day Hooke notes that he «Made instrument for eclipse of starrs by the Moon.» This is the level of detail (or lack thereof) that one comes to expect from the Diary. The few observations Hooke mentions during the next two years are mostly perfunctory, e.g., «viewed [Venus] and [Jupiter] with Harry.»34) More interesting are his comments on a lunar eclipse on 1 January 1674/535) appended to his Cutler Lecture “Helioscopes,” observations of a lunar appulse on 1 March of the same year, and a comment on the «strange inequality in the reflective propertys of the Moon» on 22 December 1675, the day after a lunar eclipse, of which Hooke wrote that he «Went not to bed, but saw Eclipse. Observed nothing.» Despite occasional observations of greater interest, it is clear that Hooke had nothing approaching a sustained and continuous observing program. Even discoveries that he could call his own, e.g., the rotation of Mars and Jupiter, were not followed up on. On 17 June 1676 Hooke recorded that he had «discoverd a spott in the Sun,» which was a distinctly unusual occurrence for the seventeenth century36) and at the end of July he was showing sunspots to Boyle. We can speculate that this was near sunspot maximum,37) and it was, indeed almost exactly three full cycles of 22 years after the Harriot/Galileo/Scheiner discoveries of 1610–12. The 7 November 1677 transit of Mercury, which, perhaps because of weather, does not seem to have been observed from London, provoked an interesting discussion during February and March, centering on the observation by Gallet in Avignon that Mercury was oblate. Hooke suggested it was due to the planet’s rotation, though it was objected that because it was solid, rotation would have no effect on it.38) As it turns out, Mercury is not oblate, a point made by Flamsteed. This is because of Mercury’s slow rotation, which was only confirmed in the twentieth century, but Hooke’s argument made sense. Hooke also observed the lunar eclipse of 19 October 1678 with Aubrey. It was in the fall of 1682 that Hooke was relieved of his duties as Secretary of the Royal Society and was voted off its Council along with Wren. The short five-year period of his Secretaryship, which began with Oldenburg’s death and the subsequent reshuffling of the Society’s leadership, saw the three important comets

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which prompted his two major works on these objects, his critical correspondence with Newton in 1679–80 which would never have taken place had he not been Secretary, the suspension of publication of the Transactions, and finally the shakeup that replaced Hooke and Wren. During the next two years we have no evidence, from the Diary, Society minutes or the Transactions, that Hooke had any kind of coherent observing program, even though other demands on his time were easing at the time. Indeed it appears that his interest in astronomy per se had waned, though an important reason may have been his eyesight, which we know was declining. In the next decade, as he was approaching 50 (and Newton was sequestered in Cambridge writing the Principia), Hooke was still doing some observing, often because his friend Halley came to Gresham to observe with him, as on 31 March 1686 when they observed an occultation of Jupiter by the Moon, and just about a year later when the two of them observed a partial solar eclipse, on 1 May 1687. It would be interesting to know what Halley may have told him of what Newton was creating in those years. Post-Principia, the later Diary, which covers a portion of the years 1688–93, contains few references to observing, and these are mostly of eclipses, which are naked-eye events and which did not put great demands on his compromised vision. He observed a partial solar eclipse with Halley on 3 September 1689, and two weeks later recorded the timing of the lunar eclipse which followed, in his Diary.39) Possibly the last recorded observation was a failed attempt to see a lunar eclipse on the night of 12 January 1692/3.40) By this time he was nearly 60 and having more trouble with his sight, especially in his right eye. The Diary continues for a further seven months without any reference to astronomy and he would be dead within the decade. In summary, aside from the important attempt to measure parallax, Hooke’s contributions to the history of observational astronomy consist primarily in 1) his detection of the rotation of Mars and Jupiter and discovery of Jupiter’s “Great Red Spot,” and 2) the way in which the comets of 1677, 1680–1, and 1682 motivated his speculations on their physical nature, their orbits about the Sun, and the nature of gravitation. His interest in longitude no doubt lay behind some of his lunar observations, often with Halley, who had an even stronger interest, but Hooke believed, rightly, that timing with a stable spring-controlled clock would be the answer. Although he was among the first to observe a binary star system, γ Arietis, in 1664, we find only the slightest hint of interest in non-stellar objects such as nebulae and clusters.

Comets The big astronomical event of 1677 was the appearance of a comet in the morning sky for a little over a week in late April, the comet having made its closest approach to the Earth on the 17th .41) This comet, which Hooke had heard about the day before his first observation on the 21st, provided the stimulus for his speculations into the nature of comets and their motions and formed the basis for his “Cometa,” composed in the fall and winter and published in April 1678.42) Observations by Cassini, Hevelius,

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and Flamsteed were published in vol. 12 of the Transactions as well. Hooke, and then Flamsteed, had begun observing the comet nearly a week before their continental counterparts. The former’s observations, as they appear in “Cometa,” provide less useful data on the position of the comet than the others, but are far richer in that he devoted over 50 pages to the nature of comets, using as illustration both the present comet and that of 1664–5. Hooke, in other words, was far from just being an observational astronomer. Halley eventually computed the comet’s orbit, approximating it by a parabola. In “Cometa”, Hooke ruminates on gravitation as he had 13 years earlier in Micrographia, noting that just as the Sun attracts the Earth and planets, «each of those again have a respect answerable, whereby they may be said to attract the Sun . . . » Thus, it would seem, bodies exert forces on each other, that is, they occur in pairs.43) He attempts to explain why the “blaze” or tail of the comet is driven away from the sun even as the comet itself is attracted toward the Sun. He makes a qualitative attempt to deduce the orbit of the comet, using an estimate of the comet’s distance and assuming Kepler’s second law, which led him to ask if it might be identical with the comet of 1618 that Kepler had observed. This was one of the first suggestions that comets might be periodic.44) The timing of Hooke’s “Cometa” turned out to be somewhat unlucky, as the Great Comet of 1680 appeared in November of that year. His first observation was on the morning of 22 November and he records seeing it on nearly 20 occasions through 10 February.45) This comet would become one of the most famous in the history of astronomy because of the role it played in Newton’s Principia, and Newton’s calculation of a parabolic orbit for it. In January Cassini claimed “such a comet” had occurred 300 years before.46). The comet reappeared in December in the evening sky, apparently as early as the 10th (still before perihelion, which according to the later computations of Newton and Halley occurred on 18 December), though it took some time before it was recognized as the same object, and indeed Hooke was not fully convinced two years later.47) After another bright comet appeared in August 1682 (“Halley’s Comet”), Hooke was prompted to gather his records of the earlier comet together and to again deliver a major discourse on these wonderful and unpredictable objects, which he began on 25 October, although it was not published until two decades later as “A Discourse of Comets,” in his Posthumous Works.48) The work detailed his observations of both comets, but also allowed him to indulge in extensive speculation about the nature of comets, the source of their light, their paths or orbits, and of the nature and cause of gravity, emphasizing its universal quality. Although Hooke did speculate about cometary orbits, the question of periodicity, and so on, his interests went well beyond mere astronomy into the physical nature of comets and their place in natural philosophy, which was the reason we examined his views on comets in Chapter 9.

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Stellar Parallax We have said that the detection of stellar parallax was in a sense the “holy grail” of ancient astronomy. The absence of any detectable parallax due to the Earth’s motion around the Sun was troublesome and often used by opponents to refute the heliocentric theory (the noted astronomer Riccioli was one skeptic). The obvious rejoinder, that the fixed stars must be very distant (argued quantitatively by James Gregory in his Geometria on the basis of their relative brightness compared to the Sun49) ), didn’t really settle the question. So, in the late 1660s, Hooke began to consider the possibility of actually measuring stellar parallax and thereby proving once and for all the motion of the Earth. He was undoubtedly better prepared than anyone else to attempt such a measurement because of his knowledge of astronomy, optics, and mechanical design and construction. In the spring of 1674, while discoursing on the design and construction of very accurate quadrants, he argued – against the authority of French astronomers – that parallax should «perhaps amount to a quarter of a minute,» hence easily measurable. Whether this was his own estimate, the result of his attempts to measure parallax, or merely a matter of deferring to Kepler’s guess, we cannot say. Hooke’s thinking on the subject, and his description of the efforts he made to eliminate all sources of error in his observations, are elaborated in the Cutler Lecture, “An Attempt to Prove the Motion of the Earth Through Observations,” which we touched on briefly in an earlier chapter. Although he had been talking about measuring parallax as early as 1666, on 15 July 1669 Birch records that «Mr. Hook intimated, that he was observing in Gresham college the parallax of the Earth’s orb . . . » Somewhat less conclusively, the Journal Book records a year later, in a passage we have already quoted, that «Mr. Hooke reported to the society, that he had already found so much, as to suspect some parallax of the earth’s orb, and conceived, that it would be more sensible half a year after.» In the spring of 1671 he was “exhorted” by the Society to continue his observations of parallax, «concerning which he said, that he thought indeed he should find a parallax, unless it be said, thatt there may be a variation in the perpendicularity.»50) In February 1673/4 we find that the Society ordered that Hooke’s first Cutler Lecture, on parallax, be published.51) As noted, the published lecture was based on only four observations made over a period of less than four months in the summer and fall of 1669. It is clear from the passages quoted above that Hooke had some justified misgivings about the quantity and quality of his data, and that he intended further measurements. He excused himself by noting that bad weather and his health «hindered me from proceeding any further with the observation that time.» He waited five years before publishing this first of his Cutler Lectures, evidently hoping, but failing, to obtain more data. At some point he decided to go ahead with the evidence he had, scanty though it was, although in his Diary for 5 January 1677/8,52) he «resolvd . . . to make some coelestall observations of parallax . . . » further suggesting that he felt a need to improve on his earlier data. At the outset of the published lecture, Hooke admits his unease at the failure of astronomers to detect any parallax due to the Earth’s motion and mentions that it had «hitherto somewhat detained [him] from declaring absolutely to that Hypothesis

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[the Copernican] . . . »53) On the other hand, he points out that claims, by Riccioli and others, that there was no parallax, were faulty because they failed to realize that the resolution of the eye was only about a minute of arc, while estimates of what the parallax ought to be, by Kepler, for example, was a third or a quarter of that.54) Hooke addressed the problems of warping, shrinkage, thermal expansion, and flexure, and how they might be addressed, as well as the issue of atmospheric refraction. He erected a 36-foot zenith telescope in a tower at Gresham (Fig. 24), realizing the structural advantages of a solidly mounted zenith instrument as well as the advantage of eliminating refraction. His complex measuring engine, or “mensurator,” was very carefully designed to allow measurements with a precision of on the order of a few arcseconds or less. The accuracy of the observations depended on making sure everything was properly aligned on each occasion, and Hooke went to great lengths to ensure that this was the case. Perhaps nowhere else in his writing is his mechanical ingenuity and patient attention to detail so well demonstrated.55) Hooke selected the bright star γ Draconis, which passed nearly through the zenith at the latitude of London, and observed its passage overhead between 6 July and 21 October, 1669.56) This interval of 107 days corresponded to nearly the same number of degrees in the Earth’s orbit. Initially, on 6 July, the star passed 2 12 north of the zenith, according to Hooke, and by the last observation, this had been reduced to 1 48 (“or 50”). These observations, which showed a consistent and decreasing displacement in one direction, were taken as vindication of his technique and the soundness of the zenith instrument itself, and he concluded that what he had observed was the parallax due to the Earth’s motion around the Sun, thus establishing the Earth’s annual motion. He extrapolated from his observations to a parallax of 27–30 seconds of arc, which is about 40 times the largest known value, but is of the same order of magnitude as another effect of the earth’s motion, stellar aberration.57) In trying to understand what Hooke observed, if anything, we have to consider what he might have been measuring. He clearly could not have succeeded in his goal of measuring stellar parallax, which is well under an arcsecond even for the nearest star, and for γ Draconis would have been 0.02 arcseconds, not measurable even today by direct means.58) This leaves stellar aberration, discovered by James Bradley in 1725–9, also using γ Draconis. The signature of stellar aberration is entirely different from parallax, being due to the direction and magnitude of observer’s velocity through space relative to the direction to the star, rather than to the Earth’s position in its orbit. Most importantly, it affects all stars in a small region, say a telescope field, equally, which is not true of parallax. That is to say, it does not depend on the distance to the star as parallax does. Clearly, had Hooke accumulated sufficient data, he could have ruled out parallax as the cause of the displacement he observed. Hooke’s choice of a star near the zenith eliminated refraction and had mechanical advantages (reducing flexure, allowing use of a plumb bob to determine verticality). And since the ecliptic pole was (and is) in Draco, not far (about 15◦ ) from the star in question, the observer’s motion through space was nearly perpendicular to the direction to the star. If Hooke’s intention had been to detect stellar aberration, which of course it was not, his choice of γ Draconis would have maximized the effect of the

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Fig. 24: Hooke’s zenith telescope erected near his lodgings in Gresham College. From Gunther , VIII.

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Earth’s motion. On the other hand, the fact that the star did not pass exactly through the zenith and that Hooke’s telescope was not precisely vertical, makes interpretation of his results difficult. The later use of Polaris by Jean Picard and John Flamsteed also virtually eliminated the need for a refraction correction, since it is essentially at the same altitude all the time, and the interpretation of their results is more straightforward. Hooke’s claims prompted others to try to measure parallax. Picard in 1680 and Flamsteed in 1689 found that Polaris’ position varied by about 40 annually, but in a way contrary to what would be expected if it were due to parallax.59) Hooke’s first observation, on 6 July, was apparently made a little after 2200 hours, and the star passed «northwards of the Zenith point,» which was the case in all four measurements. In October, the observation was made, surprisingly, in the daytime, at about 1517 hours, well before sunset.60) Since Hooke admits that he was not concerned that his zenith telescope was pointed precisely at the zenith, the exact path of the star by Hooke’s zenith cannot be reconstructed. But it is certainly true that the closest approach of γ Draconis to his zenith could have been shifted to the south by a few tens of seconds of arc due to the Earth’s motion. This was well within Hooke’s ability to measure optically, but whether his instrument was sufficiently stable, or could be re-calibrated as he thought was the case, we cannot know. Hooke notes that between observations «there had been wrought a considerable change in the Perpendiculars . . . » of as much as a minute of arc. He adds that «with all these difficulties I was forced to adjust the Instrument every observation I made, both before and after it was made . . . » It is apparent that he went to great lengths to correct for humidity, temperature, settling, wind, and so on, but how successfully we can only guess. In any event, his parallax telescope and the precautions he took to insure measurements accurate to a few seconds of arc represent a triumph of seventeenth-century ingenuity. In the end, we cannot be sure what Hooke observed, and could be excused for being appalled that he went to press with such meager data. While the magnitude of the observed displacement is quite consistent with stellar aberration, it is not clear that the motion Hooke observed with his zenith instrument is. That he concluded he had detected parallax and then wrote a substantial tract based on four observations may give us pause, and indeed he expressed «an extraordinary desire to have made other observations with much more accurateness then I was able to make these, having since found several inconveniences in my Instruments, which I have now regulated.» Nonetheless, the “Attempt to Prove the Motion of the Earth . . . ,” is immensely interesting and revealing of the care which Hooke took in attempting this difficult measurement. In his mind, he had for the first time established the Earth’s annual motion, believed in by many, but heretofore without any empirical evidence. He was wrong, of course, though if he indeed detected stellar aberration, that in itself would have been the proof needed. As an aside, in his Cutler lecture Hooke speculates in passing about the apparent sizes of the stars, compared to the distances he thinks he has measured, noting that ratio seems to be similar of that of the Sun to the diameter of its orbit, from which he concludes that the stars are of a similar size to the Sun.

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Conclusion If Hooke is a major figure in the history of astronomy, it was nonetheless largely a sideline for him, and his efforts, especially in observation, were somewhat fitful and episodic. He did make important discoveries and certainly influenced contemporaries, including his friend Halley and their sometime mutual enemy Flamsteed. His contributions to optical design and fabrication and to the design of driving mechanisms for quadrants and telescopes were significant, as was his championing of the higher resolution which could be obtained by using telescopic sights on a quadrant. In the end, it is probably his failed attempt to measure parallax, an endeavor which combined his gifts in natural philosophy with his mechanical ingenuity and attention to detail, displayed in an underappreciated classic of scientific writing, which best illustrates Hooke’s abilities as an astronomer.

Annotations 1) Some exceptions are Nagajima (2001, 2006) and Allan Chapman, “Robert Hooke’s Telescopic Observations of Solar System Bodies,” Hooke 2003 Symposium. Also Chapman’s England’s Leonardo (2005). 2) “An Attempt to Prove the Motion of the Earth Through Observations” (1674), “Animadversions on the First Part of Hevelius’ Machina Coelestis” (1674), and “Helioscopes” (1676). 3) Henry Powers, 1664: «Of all the Inventions, none there is Surpasses the Noble Florentine’s Dioptrick Glasses. For what a better, finer gift could bee in this world’s aged Luciosity; To help our Blindness so as to devize a paire of new and Artificial eyes, By whose augmenting power we now see more than all the world has ever known before.» 4) Neither Mercury nor Venus offered much to the astronomer in the seventeenth century. 5) Harriot was a contemporary of Galileo and Kepler, and corresponded with the latter. His works were recovered only in 1784. His patron was the Earl of Northumberland. He died and was buried in the same area of the City as Hooke and, like Hooke, his Monument was destroyed, in Harriot’s case, by the Fire. 6) Remember that Hooke was born less than 5 years after Kepler died. 7) Embodied in his famous Selenographia of 1647. 8) In Micrographia, p. 242. 9) See Wright (2000), for example. Reeves appears several times in Pepys’ Diary. Huygens took advantage of the opportunity to visit Reeves shop when he visited

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London in 1661 (and also skipped the coronation of Charles II on 23 April 1661 in order to observe the transit of Mercury). See also Nicholson (1965). 10) Cock’s name appears frequently in both diaries, especially the early one. 11) Simpson (1992), pp. 84–88. 12) Birch, III, p. 122. Birch records that «Mr. Hooke produced a new kind of reflecting telescope of his own contrivance . . . This was performed in a way propounded by Mersennus, and repeated in Mr. [James] Gregory’s Optics; but was thought to hve been never actually done before.» Richard Reeves, London’s most accomplished optician, attempted to build a Gregorian telescope. The main difficulty seems to have been that of polishing a speculum metal mirror, but the issue of non-spherical surfaces was also a large one. Reeves also built Boyle’s 60-ft telescope, which was intended for Hooke’s use, and worked with Wren and Hooke on their compound microscopes. Gregory described his telescope in his Optica promota of 1663. Whiteside described Gregory as «the only one of Newton’s British contemporaries who could match him in mathematical breadth and profundity.» (Whiteside, 1967–80, p. xiii) See Simpson (1989, 1992). 13) Gunther, VI, p. 358. 14) Flamsteed to Collins, 1 December 1670. Gunther, VI, p. 370–1. 15) Micrographia, p. 241–2. The effect of aperture on limiting magnitude is clearly described as well. 16) Allan Mills, John Hennessey, and Stephen Watson have given a detailed analysis of Hooke’s design, including the worm and gear driven backwards. See “Hooke’s design for a driven equatorial mounting,” Mills, et al. (2006). Hevelius was not a stranger to telescopes, himself. 17) As we noted in Chapter 7, even though Hevelius seems to have been a meticulous observer with keen eyesight, a bit of experience with telescopes, which he had, should have made the validity of Hooke’s position clear. 18) In particular his “On Helioscopes”, and “An Attempt to Determine the Motion of the Earth Through Observations.” 19) There was no total eclipse of the Sun visible in or near London during the period covered by Hooke’s diaries. There was an annular eclipse in 1621, eclipses visible in Ireland and Scotland at mid-century, and a good total eclipse, visible in London, in 1715. In an appendix to “Helioscopes,” Hooke appended an observation of a lunar eclipse on 1 January 1674/5, noting that he timed it with his balance-spring pocket watch. 20) Including a discussion of the way in which the path of a ray of light is continuously curved as it propagates through air of continuously varying density, the cause of the flat undersurface of clouds, the occurrence of “counterfeit suns” or “sun-dogs,” etc.

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21) This clearly could not be right, given the fact that the angular size of the moon changes by only about 10%. But Hooke says that this is but a conjecture that «must be determin’d by such kind of Observations as I have newly mention’d.» (p. 240). One wonders how Hooke came to this conclusion. 22) Micrographia, p. 245. 23) Reported as 19 May in Birch (I, p. 3). 24) PT, 1, 3 (1666). Hooke recounted that the spot moved half of Jupiter’s diameter, “east to west,” in two hours, implying a period of rotation of perhaps 8–10 hours, though he seems not to have derived a number. This account, of an observation made 9 May 1664, followed a similar report by Campani, who also observed shadows of the satellites on the planet. Jupiter, of course, rotates west to east, so Hooke was in error, perhaps forgetting he was using an inverting telescope. Cassini arrived at a figure of 9h 56m, almost identical to the modern value, and published it in 1665. Cassini also discovered an “inequality” in the rotation of Jupiter of up to 16 minutes, related to the distance between Earth and Jupiter. The final step, that this was due to the finite speed of light, he was unwilling or unable to take. See, for example, J.D. North, “The satellites of Jupiter from Galileo to Bradley,” in The Universal Frame, London, 1989. It was Rømer who took that step, in 1676 (I.B. Cohen, “Rømer and the First Determination of the Velocity of Light,” Isis 32 (1940) 327–79. Rømer’s discovery was published in the Philosophical Transactions in 1677, but Hooke, like Cassini, seems to have been unwilling to admit the finite speed of light. 25) November to March. Hooke records seeing it on 23 Dec. 1664. 26) Birch, I, p. 19. 27) On the other hand, since Mars was then at opposition and it was not a particularly good one, the observations were probably made shortly before the meeting. Given the rather mediocre quality of the instruments Hooke had at his disposal, it is likely that he used the prominent feature “Syrtis Major,” for that determination. These observations required a somewhat sustained program, since at a given time of night, Mars only rotates about 8◦ from one night to the next, meaning that a week to a few weeks would be required to derive a figure for the rotational period. 28) “A late Observation about Saturn . . . ,” PT 1, 14 (2 July 1666) 247. 29) Using Birch as a proxy. This is still three years before the start of the Diary as we have it. 30) Indeed one day before the beginning of 1670 in the Julian calendar then in effect, 25 March. 31) The observation, of a graze of ζ Arietis, was made 4 March 1670/71. On 6 May he observed another Flamsteed-predicted occultation. 32) To be read as “Hevelius’ Machina Coelestis,” or “Hevelius’s . . . ”

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33) Mars and Saturn were near each other in the evening sky during this time, and Saturn’s rings should have been nearly edge-on. 34) Diary, 1 April, 1673 (11 April Gregorian). 35) Which he observed with Jonas Moore, Collins, Brouncker, and perhaps Petty. 36) The “Maunder minimum,” from about 1645–1715. Only a handful of sunspots were observed between 1660 and 1680, indeed in the entire 1645–1715 period. As another indication of low solar activity, apparently no Aurora were seen from London between 1645 and 1708 (Fagan, 2000). The last 20 winters of the century were extremely cold, part of the “Little Ice Age” which had prevailed, off and on since 1316. Frequently the Thames froze over in the latter part of the seventeenth century. 37) Which is thought to have been in 1674, though there are observations from the fall of 1671, reported in the Philosophical Transactions, including by Hooke, and reports from one sunspot cycle earlier, in April 1660. The 1671 observations, which caused something of a sensation, may have been somewhat before maximum. We should note that if Hooke writes in his Diary that he observed some phenomenon, we usually have no way to know whether he had been informed of it beforehand or whether it was a Hooke discovery. That usually comes out if Hooke speaks of it before the Society. 38) Birch, 28 February, 1677/8. Hooke apparently understood that even a solid body could be distorted by its rotation. This idea is consistent with his discussions in Micrographia on how gravity determines the shapes of the planets and with his ideas on elasticity, expressed in his “De Potentia Restitutiva”, i.e., “Of Spring.” We touched on this issue in context in Chapter 7. 39) Diary, pp. 146 and 149. The lunar eclipse was on the night of 18–19 September. 40) The Diary entry for 12 January says «This night cleer; by the last helick noe Eclipse seen.» The eclipse actually occurred on the night of the 11th . 41) As calculated by Halley. 42) For example, Diary, 22 and 29 April 1678. 43) An idea enshrined, with precision, in Newton’s third law or axiom. 44) Pepys, in his diary, noted that he had heard Hooke lecture at Gresham College on 1 March 1664/5, and that «Mr. Hooke read a curious Lecture about the late Comett . . . proving very probably that this is the very same Comett that appeared before in the year 1618, and that in such a time probably it will appear again.» Pepys (1972), VI, p. 48. See also Chapter 7. 45) These observations are in PW, pp. 153–8. 46) This was an understandable confusion with what became known as “Halley’s Comet,” and which appeared in 1682. Four cycles of Halley’s Comet would indeed be about 300 years, but the comet of 1680 has a period of something like 9000 years.

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47) PW, p. 154. 48) PW, p. 150. Other parts delivered on 8 and 15 November. Hooke’s first observation of the Comet of 1682 was on 16 August, and he saw it on another 10 occasions up to 10 September, just before perihelion on 15 September. 49) Had it been possible to estimate how much brighter the Sun is than a typical star (1010 times), then, on the assumption that the stars were Suns, one could estimate their distance (about 105 Earth-Sun distances), and hence that the parallax due to the Earth’s motion would be at best a few arc seconds. 50) The issue here was evidently whether the direction of the Earth’s spin axis was constant. 51) The lecture had been read four years earlier. As we have said, this is really a quite wonderful work, which describes the astronomical issues involved, but also Hooke’s zenith telescope and how he mounted it in his rooms at Gresham College. See Gunther, Vol. VIII, pp. 1–28. 52) Perhaps a New Year’s resolution, despite the fact that the New Year was still often celebrated on 25 March in this period. In his Diary, Hooke takes little notice of either date. 53) A bit later Hooke says «. . . supposing all the fixt stars as so many Suns . . . », something usually credited to Bruno nearly a century earlier. 54) In the absence of any substantial knowledge of the distance to the nearest stars, no accurate estimate was possible, although attempts were made. 55) See especially Gunther, VIII, pp. 17–23. 56) The latitude of Gresham was about 51◦ 31 , meaning that γ Draconis passed a little over 2 “north” of the zenith, ignoring aberration, which is just what Hooke observed. In other words, his telescope was pointed very close to the zenith. His observations were made on 6 and 9 July, 6 August, and 21 October. With no real knowledge of the magnitude of the parallax, Hooke first tried an interval of three days, detecting no displacement. He next waited a month and there had been a change of 6 , the final measurement was six weeks later, when a further change of nearly 20 in the same direction was found. Five years elapsed before the lecture was published, and, as we have seen, Hooke was exhorted in 1671 to continue his measurements, but there is no evidence that he did. 57) With the benefit of hindsight, we might think that Hooke should have made a differential measurement, comparing one star with another nearby. Of course if the stars were all at about the same distance, and that wasn’t known one way or the other, one would expect a null result from a differential measurement. Or if what Hooke observed was indeed stellar aberration, a differential measurement would have given a null result and there presumably would have been no Cutler Lecture. 58) The resolution of Hooke’s 36-foot telescope, which probably had an aperture of around 6 inches, might have reached one arcsecond. It would have had a lot of

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chromatic aberration, but the high relative aperture would have reduced other aberrations. It probably magnified 75–80 times, quite enough to take advantage of the resolution of the objective, depending on imperfections and aberrations. Bessel first measured stellar parallax in 1837–40, a century and a half after Hooke’s attempts. 59) At the equinoxes, for example, stellar aberration would displace Polaris in the vertical plane, or up and down in altitude, something one would not find in a measurement of parallax. As with γ Draconis, Polaris’ parallax would have been undetectable in any case. A half-century later, Halley and James Bradley attempted to use the same star, γ Draconis, to detect parallax. The effect they discovered, of the same order of magnitude as Hooke’s, but showing an annual pattern different from parallax, and affecting all stars in a small neighborhood similarly, was eventually recognized by Bradley as stellar aberration, due to the Earth’s motion through space as well. This effect is about 1 part in 10,000 (the ratio of the earth’s orbital speed to the speed of light) or 20 seconds of arc. The largest known parallax is about 0.77 , more than 25 times smaller, and well below what was possible to measure accurately in the seventeenth century; that of γ Draconis is about 0.017, unmeasurable directly even today. Parallax was finally detected by F.W. Bessel in 1838. An engaging book on the subject is Hirshfeld (2001). 60) Leading him to comment at length on the uniqueness of the observation of stars with a telescope in the daytime. It must have been a crisp, dry, early fall afternoon in London for this to be possible. A typo affecting the time is possible.

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Chapter 12

The Last Remain: Hooke After the Principia, 1687–1703 Introduction During the last 15 years of his life Hooke struggled under Newton’s long shadow and was facing rapidly declining health, and yet was sill vigorous enough to continue as a major intellectual force in the Society. But despite all the recent writing on Hooke, one could be excused for thinking that he had died in 1684, or perhaps 1687, for very little has been written on those last fifteen or so years. There are reasons for this, of course, not the least of which was the publication of the Principia in 1687, a watershed that has diverted attention from Hooke’s last years, indeed from Hooke in any form. That is far from the whole story, and yet, after that monumental work it often seems there is little room for Hooke, or for that matter, anyone else. Newton, the giant, is striding the stage, revolutionizing natural philosophy, shaping the scientific revolution, eventually ruling the Royal Society with an iron hand. As we noted much earlier, this received view is actually somewhat anachronistic, since the deliberations of the Society during the decade of the 1690s hardly reflect the existence of the Principia,1) as the significance of what Newton wrought only slowly came to be understood. There is, however, not much doubt about how the tide was running. Hooke’s way of doing natural philosophy was beginning to yield to a mathematization of nature which would characterize much of the eighteenth century, especially in mechanics. A second reason why little attention has been given to Hooke’s final years is that as he passed 50 his own energies, physical and intellectual, were beginning to wane. In 1687 he had suffered the dual blows of the publication of the Principia and the death of his beloved niece and mistress Grace Hooke. And although he was only 52 in that fateful year, his health, which had never been robust, was on the verge of the steep decline which would characterize his last years, and his eyesight was becoming much worse. By the late 1690s he was clearly suffering from the disease that would kill him, variously speculated to be diabetes or congestive heart failure.

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He was depressed, or at least melancholy, as he repeatedly reports (cries out?) in the very private writings of the later Diary.2) All of this foreshadowed the end of his active intellectual life. Except for some papers in the Transactions,3) which appeared sporadically during this period, Hooke published very little in the last two decades of his life. His printed works, other than Transactions, all date from no later than 1680, and few of the unpublished lectures collected by Waller in his Posthumous Works (1705) were delivered much after that date. Superficially, however, Hooke’s life went on much as before. He rarely missed a meeting of the Society and almost always had something to contribute. He served on the Council nearly every year in the 1690s and in his final decade he was shown growing deference by members, being something of an elder statesman, but also, perhaps, increasingly a subject of pity. While he was still seeing Wren on a regular basis, their meetings now took place only about once a week. This contrasts sharply with the period of the first Diary, when they literally saw each other almost daily, but both were now entering their seventh decade and their architectural partnership was over. Wren continued to struggle with St. Paul’s and other projects which left him little time for Society affairs. When the two of them did meet, it was often at a building site, but Man’s coffee-house was another favorite spot. Wren was still vigorous in body and mind, and moving in elevated circles (he had been knighted twenty years before) while his friend Hooke was increasingly tired and lonely.4) Sir Christopher would outlive him by almost exactly two decades. Although Hooke was still seeing Boyle with some regularity as the 1680s drew to a close, it was also less frequently than before, since Boyle’s health, long problematic, was now in serious decline, and he would die in 1691. Hooke would meet his old mentor Dr. Busby weekly, often dining with him, and he also saw Pepys frequently either in his own rooms or at Pepys’ home. His regular haunt was Jonathan’s in Exchange Alley, where he drank coffee with his friends every day, more often than not twice daily (except Sundays). If he did have insomnia, as certainly was the case in the years of the early Diary, it is hardly surprising given the presumed consumption of caffeine. He was seeing Halley at least weekly, always at Jonathan’s, and following a meeting of the Society, he would invariably repair there with Halley and Hoskins and whoever else came along. Jeremy’s was also a frequent meeting place, and sometimes Hooke would join the more privileged members of the Society there, as on 21 November 1688, when he rode with Henshaw and met Wren, Sir Joseph Williamson, and Lord Carbery, who was then president of the Society. The week before, on 15 November, recounting a session at Jonathan’s with Paggin, Houghton, Ashby, Copley, Spence, and Currer, Hooke penned a cryptic, perhaps ominous “The last remain” in his Diary.5) Seemingly a comment on human mortality, but perhaps we read too much into it. As we seek to build a picture of Hooke’s last decade and a half, there are a number of Hooke manuscripts, letters, and other fragments, scattered in various collections, at the Royal Society, in Oxford, at Trinity College, Cambridge, and so on, which will reward further study. Of potentially the greatest interest are approximately one hundred unpublished fragments, drawings, and completed manuscripts in the

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Royal Society’s Classified Papers, Vol. 20. Many of these fascinating manuscripts consist of lectures delivered before the Society and only briefly referred to in the Society’s Journal Books. These papers, which cover the whole of Hooke’s career with the Society, including many relevant to Hooke’s later years, await the attention of scholars.6) As we saw in previous chapters, Hooke’s early Diary allows us to form a fairly good picture of him from his late 30s into his mid 40s. But while it touches very briefly on the 1679–80 exchange with Newton,7) there is nothing on the crucial years of the mid to late 1680s (1680–88). In the later Diary (Diary II, Sloane MS. 4024) we again have a window on his daily activities during his mid to late fifties, despite lamentable gaps. But we find relatively little of scientific interest in these hasty jottings, which only whet our appetite for more information, and which, in any case, cease in 1693. Are there other Diary fragments lying in an attic somewhere? The chances are slim, though the recent discovery of a large cache of Hooke manuscripts and notes8) has raised the possibility that important new insights into his life and career may await scholarly sleuthing. This “Hooke Folio” has already yielded some important discoveries, and may hold some yet-undiscovered secrets, along with routine matters and some gossip.9)

Hooke and Newton Hooke’s first look at De Motu (see Chapter 10) or his realization of the scale of the Principia when it was presented to the Society in 1686, must have struck him like a bombshell. He learned about the shorter work on Halley’s report in November 1684, and while it is not known when he read it, it is difficult to believe that he failed to take advantage of the chance to examine it late in 1684/5. But we have no evidence one way or the other. Without a diary for the period, we cannot know his reaction to this “first draft” of the Principia, or, two years later, the work itself, though we can guess that he was devastated by what he saw. Nowhere in the 24 months of the later Diary, which begin in late 1688, or in the Society archives, do we find an evaluation by Hooke the scientist of Newton’s work, such as he would have routinely provided in past years. A very pregnant silence. Hooke’s frequent charges of plagiarism against Newton, while no doubt sincerely felt, had little force. If Newton’s determination not to credit Hooke despite the crucial insights into planetary dynamics which were provided him lends some weight to the charge, a quick look by Hooke at the copy of the Principia that he had in his library should have told him that whatever he had accomplished, whatever help he given Newton, the contents of the work were forever beyond him.10) It is hardly surprising that Hooke’s charges angered Newton and, given what we know of him, incited feelings of retribution. That Newton was less than generous in the matter is obvious, but this was hardly unusual for him. In the end, it is hard to escape the conclusion that the final bitter break was inevitable, given the personalities of the two principals, their history of acrimonious exchange, and Hooke’s sincere feelings that the prize he thought was to be his had been won by another.

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On 15 February 1688/89 Hooke’s Diary records (in a passage we quoted earlier) «At Hallys met Newton; vainly pretended claim yet acknowledged my information.» And at a meeting of the Society 11 days later he vigorously defended his contributions to natural philosophy, arguing, with some truth, that his «. . . Discovery of the Cause of the Celestiall motions to which neither Mr. Newton nor any other has any right to Lay Clayme . . . » ought to be sufficient to silence his [Hooke’s] critics. Following an appearance by Newton at a meeting of the Society in July of 1689, Hooke remarked in his Diary that «Newton and Mr. Hamden came in, I went out.»11) Clearly Hooke was in no mood to concede either the magnitude or originality of Newton’s achievement. He was still thinking, sporadically at least, about gravitation, planetary motion, and related problems in dynamics, perhaps in an attempt to salvage something from this episode with Newton. On 16 September 1689 he noted that he had «demonstrated equall motion in parabola,» possibly his attempt at the brachistochrone problem. Nine days later he says he «calculated velocity of falling bodies», which mystifies us a bit,12) and in November he announced that he has «perfected Theory of gravitation.»13) Again, we have no clear idea of what he had in mind, but he may have been still working on the proof sketched out in the “On Circular Motion” manuscript at least four years earlier (see chapter 10). Alternatively, he may have been studying the cause of gravity, as he also had earlier. But there are few comments of this kind in the Sloane diary. In particular, if he is attempting to wade through the recently published Principia at this point, he gives no hint of that in the Diary. In the remaining two years of his extant Diary, there are very few references at all to Newton, the most notable following a dinner with his old mentor Dr. Busby: «D with Dr. Busby: Dr Hickman there; sayd Newton the veryest knaue [knave] in all the Ho:[. . . ]»14) Two years after the publication of the Principia Hooke’s friend John Aubrey had tried to make the case to Wood that Newton had failed to acknowledge Hooke’s contributions. He concluded, in this familiar passage: «This is the greatest discovery in nature that ever was since the world’s creation. It never was so much as hinted by any man before. I know you will do him right.» What he then added is probably echoed by any who have tried to decipher Hooke’s cramped handwriting: «I hope you may read his hand. I wish he had writt plainer, and afforded a little more paper.»15) As already noted, in the early post-Principia period one would be hard pressed to find any evidence in the minutes of the Society that this revolutionary work existed. Not only are there no references to it in the Journal Book, and few to Newton in this period, there is little change in the nature of the business at Society meetings. Halley himself introduced a more quantitative, mathematical tone when he was present, and some of this involved lunar theory, which in part depended on the Principia.16) But the change was marginal, not fundamental, and Newton, even after he moved to London in 1696, rarely attended meetings.

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1687–1703 Even in the absence of Newton’s triumph, Hooke’s situation would not always have been easy. When he was elected to the Council on St. Andrew’s Day 1689, he commented in his Diary that «The gang trd utmost effort, but faild.» But in the decade or so after the Principia, Hooke was a continuing force in the Society, attending most meetings (they would be held in Gresham College until well after his death) and holding forth on a wide range of topics. He was still, after three decades, one of the intellectual leaders of the Society, even though his contributions were declining.17) And as elections approached in 1688 he even talked with Halley about putting himself up for Secretary again.18) Neither Boyle nor Wren attended meetings in this period (if silence is any indication). As we have seen, Boyle’s fragile health was worsening, and in a letter written to Le Clerc in May (1689) he said that his «want of health has, for this great while . . . [has] confined me to my lodgings . . . » and wrote of his «age and sickness» in appealing to friends and visitors to allow him some space to «range his Papers & fill up the Lacunae of them.»19) His eyesight, poor for a long time, was worse. His sister Katherine was also very ill, and indeed she preceded him in death by precisely one week, in December 1691. Wren was consumed by the work on St. Paul’s, Hampton Court, Whitehall and Windsor, and when he spoke at the meeting of 24 January 1699/1700 and again two years later on 18 February 1701/2, it was the first clear evidence of attendance in a decade.20) But he continued to be active in Society affairs, as when he served on a committee in an attempt to have Bishop Stillingfleet’s library given to the Society,21) and was frequently on the Council in the decade before Hooke’s death in 1703. But only occasionally did he offer an experiment. Throughout the later Diary, which concludes, unceremoniously, on 8 August 1693, precisely three weeks after Hooke’s 58th birthday, we see continuing evidence that he had not completely given up his architectural and construction activity, for almost daily he is settling accounts with tradesmen, working at Westminster on the school and the Abbey, at Aske’s Hospital in Hoxton, doing work for Southwell, and so on. These outside duties, which is hardly a fair description considering that he derived by far the greater part of his income from them, were winding down, but he was apparently still relatively vigorous at the start of this last decade of his life, and if the absence of complaints is any indication, his health was tolerable, despite an illness in the winter of 1690/91, prompting Aubrey’s comment to Wood that «we were afraid we would loose him.»22) This was almost squarely in the middle of the hiatus in his second Diary, and may explain it. Hooke had been elected to the Council in 1686, was off in 1687, and there were no elections in 1688.23) He was again elected in 1689, and was on the Council in at least 8 of the next 11 years. He was awarded a Doctor of Physic degree24) «by a warrant of archbishop Tillotson,» in December 1691, an act which gave him added prestige and a new title.25) On 17 February 1691/2, two months after the awarding of the degree, he was referred to as “Dr Hook” for the first time in the minutes, and thereafter he is always “Dr Hook”.

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As early as 1688, when he was in his mid50s, we see Halley gradually beginning to replace him as the lifeblood of the Society, but Hooke continued to provide much of the substance of the weekly meetings almost to the year of his death. Admittedly, many of his contributions are recapitulations of what he had formerly read, or are further elaborations of topics he has always been interested in. For example, the Journal Book records that on 15 May 1689 «Mr Hook read a farther Discourse about his Hypothesis of the changes that have happened in the Earth’s Surface, being chiefly a recapitulation of what he had formerly produced on that subject . . . » An editorial comment by the Secretary, perhaps, but Hooke’s interest in earthquakes and how they must have changed the face of the earth was a continuing one which he explored in a number of original directions. In January 1686 he had lectured on fossils, how they came to be petrified deep in the earth, and found high above the sea.26) He addressed this issue on several other occasions, including 16 November 1691 when he talked of a fossil «sea horse or Hippopotamus» and described the interstices in nautiloids. He had suggested in 1688 that earthquakes occurred every 8 years, were implicated in plague outbursts, and were possibly caused by comets. In July 1690 he was interested in the effects of earthquakes at sea, prompted by an event which had occurred in the Leeward Islands, and in the relation between very high tides and earthquakes (January 1691). Beginning in May 1693, he attempted to understand fables and myths from antiquity in terms of real catastrophes which might have occurred in the earth such as volcanoes and earthquakes. Examples were the fables of Phaeton and of Python and Ovid’s the Rape of Prosperpine. He was among the first to suggest that the content of myth might consist of metaphorical allusions to actual events. He drew others into this discussion, including the President, Sir Robert Southwell, Hunt, Halley, and Hoskins. This interest in changes in the earth extended to its cooling and the idea that the earth was decaying, becoming less productive. In July 1694 the Journal Book records that «Doctor Hook read a Discourse tending to prove that there is an annuall alteration in the Poles of the Earth . . . », though how he reached that conclusion is unclear.27) At a subsequent meeting he discussed Whiston’s New Theory of the Earth, and in 1701 he again talked about earthquakes as well as fossilized or “petrified” trees. Not even Steno could be said to have spoken as clearly and presciently on the question of changes wrought in the earth by its internal heat.28) This was perhaps the one issue that Hooke pursued continuously and creatively in his declining years, and, as suggested earlier, it would not be a stretch to call Hooke the first geologist in the modern sense. On other matters, Hooke talked about the zodiacal light, «subtle parts of the atmosphere left behind» (the aurora), Chinese characters, using gunpowder to raise weights, how water bugs stay on the surface of the water, penetration of salt or oil of vitriol into the pores of water, the figure of the earth under the action of vis centrifuga, the antiquity of natural philosophy, the shape and orientation of sails, climate, bird migration, the “petrifying” quality of water as it washes over stones, illumination of a microscope field, the velocity of water flowing from a vessel, sounding the ocean, measuring salt concentration in the ocean, the tower of Babel, his air barometer for use at sea, range finding devices, his idea to have a 29-hour day, magnetism,

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the presence of seas on the moon, equal time descent of water along an “inverted parabola,” and so on. Altogether a remarkable diversity of interests, and if few of these ideas were fundamental, who in the late seventeenth century could say what was fundamental and what was not? Hooke’s frequent return to ideas or inventions from the past included. a discourse on 19 February 1689/90 «tending to vindicate his notion of Light published in his Micrographia, in answer to that Theory thereof lately published by Mr. Hugens . . . ». The Micrographia, of course, had been published a quarter-century earlier. He continued at the next meeting, and also commented on Huygens’ notions about the cause of gravity. In 1691 he spoke of his discoveries with telescopes and microscopes and in July 1693 he read a letter from the 77 year old John Wallis to William Molyneux containing a proposal for observing parallax due to the earth’s annual motion, which Hooke was convinced he had detected 24 years previously.29) The Journal Book records that «Dr Hook asserted the way propounded by Doctor Wallis to be Inferior to the way that he himself had made use of for that purpose . . . and therefore wondered what should be the Doctor’s reason for now publishing this way, after 40 years of Concealment of it as he pretends.» In that same month, on 19 July 1693, the day after his birthday and shortly before the Diary ends, we find «I read and took minutes; also read my Cutler Lecture» and on the following Wednesday (the 26th ) he «Corrected last sheet of Mays Transactions.»30) In November he read a discourse «about the Improvements to be made in Naturall Philosophy by Microscopes . . . » and followed that in December by again speaking of the use of telescopes in observing parallax. He returned to the subject one more time on 26 July 1699 when he read a discourse «of his Observation [of] Parallax and variation of the fixt stars &c to vindicate his works» and two weeks later read a further discourse «in Vindication of his Astronomical works». Little was new in all of this, as Hooke strove to protect his priority, and we know that in fact he had not successfully observed parallax (Chapter 11), and that no one would for over a century.31) Hooke was still occasionally offering an experiment or describing one he had recently performed. One of a very few examples was the measurement of the speed of sound in July 1689, using the travel time from the Tower to Gresham, though his result of 143 yards/sec was off (as given in the minutes) by more than a factor of 2!32) He also described new ideas or inventions, including a sextant-like device equipped with a plumb line for use at sea when a horizon was not visible, and in between 1690 and 1695 an ingenious sea barometer which employed both an alcohol and an air thermometer, devices to measure speed through the water, as well as leeway, and another «to tell Exactly the distance saild upon every Tack . . . ». In 1690 he described instruments to be carried to the East Indies for measuring the strength of gravity. His fertile mind was still active. Tantalizingly, Huygens was present at the Society meeting of 12 June 1689, when Hooke spoke of the cause of gravity and of birefringence (double refraction). Also there was Isaac Newton, in one of his rare appearances – no doubt because Huygens was also there – who offered his own ideas on double refraction. Both Hooke and Halley also held forth on the “atoms” of salt, so we know that at this remarkable

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meeting, in the late spring of 1689, all four were present, virtually in Hooke’s rooms in Gresham College. This would be the last meeting of the Society that Huygens would attend and one of only a handful that would be graced by Newton’s presence prior to Hooke’s death. But Hooke’s laconic Diary is of little help to us. He casually writes: «Royal Society met, shewd Expt of making branched Mochus: Hugens, Newton, Fazio [Fatio de Duillier]: there with Pif and Wall [Pitfield and Waller]at Jon. then wth Sr J. Hosk[ins] one houre solus . . . Mr Henshaw well pleasd with my Experiment of Mochus . . . Hally arguing against change of Polarity.»33) An equally remarkable passage in the second Diary is one in which we find Hooke describing a meeting at the premises of the instrument maker Thomas Tompion, after which he wrote in his Diary for 30 March 1693 that he «Met Mr Zulich [Huygens] at Tompions, but knew him not.» It takes the breath away. To those who stubbornly cling to the idea that Hooke not only never passed up a chance to point out his priority in an idea or invention, but actually laid claim to the ideas of others – a canard which we can now dismiss absolutely – we offer the following modest counterexample: in December 1691, after considering whether condensing air might turn it into water, Hooke spoke of an object-glass Huygens had given to the Society, but «he forbore to Describe the manner of using it, as reserved til Mr. Hugens himself should be present.» And a decade later, in July 1701, Hooke gave a rave review of the Huygens’ Cosmotheoros; the Journal Book recorded that «Dr Hook read a lecture wherein he gave a great Character of Huygen’s late book called Cosmotheoros but differed from him in his opinion that the moon was not inhabited.» The Dutch scientist had died in 1695 and, as we know, Hooke had less than two years to live. On the subject of priority, we note, as others have, that Hooke could usually, or perhaps, invariably, point to a Journal Book entry to support his claims. Of course there were often times when such a claim, based on a simple observation or conjecture, some real but limited insight, as in the case of Newton and the Principia, was without much foundation. Some have argued, not entirely without justice, that Hooke regarded any idea he ever had as permanently his own, whether he pursued it or not. Just as Halley began to take on Hooke’s mantle as intellectual center of the Society in the early 1690s, he proposed to go to sea on an expedition to measure magnetic variation and to determine longitudes, so that from 1694 or 1695 until he departed in October 1698 his attendance at meetings was sporadic. During much of this time it fell to the aging and failing Hooke to provide substance to the meetings; an appearance by Halley in March 1696/7 was unusual. He was gone much of the next three years, including the famous aborted first voyage, exploring the South Atlantic, eventually returning in August 1700. Back at meetings in the fall, he was now addressed as Captain Halley, as opposed to the generic “Halley” that had been used for nearly 25 years.34) During much of this long period, as the Society suffered through a series of aristocratic presidents who rarely attended meetings, Sir John Hoskins was almost always in the Chair.35) Other regulars in the early 90s besides Hooke were Southwell, Evelyn, Sloane, often Henshaw and Hunt, and, of course, Halley. Later Hill,

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Houghton, and others. But meetings seem to have been very intimate.36) As was very much the case in these early years of the Society, even, in this case, after more than 30 years of existence, the substance of meetings was often quite slim, still mostly consisting of anecdotes, hearsay, and speculation, an example being Henshaw’s venturing in May 1689 that «the eyes of a flye do contain almost all the Brains thereof.» But often Hooke could be counted upon to address an issue of importance, as when, on 9 January 1688/9, he discoursed about scriptural wisdom, «therein shewing, [in the words of the Secretary] that the Design of the scriptures being not so much to teach Natural Philosophy, as to shew the wisdom and power of God in making the world as it is . . . Accordingly he shewed that the escplication of the Creation [was] to the common apprehensions of Mankind . . . » Yet there was very little physical science or mathematics, and even less during the year Halley was at sea in 1698–1700. Interestingly, Hooke took minutes of six meetings during June and July 1691 (the Secretary at the time was Waller) giving us further information on his participation in his late 50s. We know this because the draft minutes were found in the newly recovered “Hooke Folio.”37) There are no records of these meetings in the Journal Book, obviously because Hooke failed to provide them to the scribes. This period falls in the hiatus in Hooke’s later Diary, so we find no insight there into either why he was acting as secretary or why the minutes failed to find their way into the Journal Book.”38) His health (see above) is a possible reason, as might be his preoccupation with the illness of his friend Boyle, who was in serious decline and would die in a few months. While the last 15 years of Hooke’s life were not entirely happy ones, and in spite of his eclipse by Newton and the slow decline in his reputation abroad, he enjoyed the experience of finally coming to be an honored member of the Society which had so often treated him as little better than hired help. Quite noticeable is the deference with which his remarks are increasingly treated in the Journal Book. And a meeting rarely passed without his holding forth on some topic – which is, of course, how we know he was present, since, unlike the Council meetings, no attendance was taken. On 29 January 1700/01, for example, his comments are quoted on six separate occasions. Only rarely do we find from reading the Diary that he attended a meeting despite there being no evidence from the Journal Book that he contributed to the day’s discussion. Although his absences from meetings were infrequent in this period, this was at least in part because they were held near his rooms in Gresham. But in those last 15 years, Hooke attended over 300 meetings, between 20 and 30 a year, all the way through the summer of 1702, excepting, again, only the years 1691–1692. As late as 1699 he attended at least 26 meetings, and even in 1700 and 1701 he managed 18 meetings each. But the next year he was present only 8 times (again, if we are correct in taking silence to mean absence) and in any case, his involvement was in clear decline. Still nominally Curator, though apparently no longer salaried, Hooke now rarely offered a new experiment. Increasingly, as we have said, his discourses were retrospective, recounting earlier demonstrations or inventions, and Waller admits that «. . . the later part of his Life was nothing near so fruitful of Inventions as the former . . . » And that though he intended to «perfect the Description of all the Instruments he had

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at any time contriv’d . . . by reason of his increasing Weakness and a general Decay, he was absolutely unable to perform it . . . » Hooke was elected to the Council for the final time in November 1700. What might be thought of as his final Transaction was printed in No. 269, in 1700/01, but though it concerned Hooke’s marine barometer, it was authored by Halley.39) He was present on 18 March 1701/2 when Halley «shewed a table which he had calculated to shew the Elements of the Motions of all the Comitts . . . and it is designed for discovering if the same Comet does return again &c . . . ». In 1702 he was rarely able to drag himself to meetings, and when on 24 June he spoke further on earthquakes, it was possibly the last Society meeting he attended. In the elections of November of that year, just four months before his death, he received no votes for the Council, a clear recognition of his impending death. Three months later, on 3 March – the day he died and a meeting day – we read that «Mr Hunt related, that Dr Hook being dead, he [Hunt] had received some of the Society’s books from his Friends.» There is no evidence that Hooke suffered significant mental decline in his sixties, but his health, which was always questionable, utterly failed him, as Waller described in this famous passage: «He had for several Years been often taken with a giddiness in his Head, and sometimes great Pain, little Appetite, and great faintness, that he was soon very much tir’d with walking or any Exercise. About July 1697 [he was 62], he began to complain of the swelling and soreness of his Legs, and was much over-run with the Scurvy, and about the same time being taken with a giddiness he fell down Stairs and cut his Head, bruis’d his Shoulder, and hurt his Ribbs, of which he complain’d often to the last. About September he thought himself (as indeed all others did that saw him) that he could not last out a month. About which time his Legs swell’d more and more, and not long after broke, and for want of due care Mortify’d a little before his Death. From this time he grew blinder, that at last he could neither see to Read nor Write . . . . Thus he liv’d a dying Life for a considerable time, being more than a Year very infirm, and such as might be call’d Bed-rid for the greatest part . . . »40) Despite this account of Waller’s, who saw him nearly every week, it is nevertheless true that 1696 and 1697 were very active years for Hooke, at least as measured by his participation in the Society, and the same can be said of 1699. Indeed, he attended more meetings in 1697 than any year in this post-Principia period, but by that time he probably had few other diversions and may not have been going out much. If he was seriously ill in September 1697, he made some sort of recovery before the Society resumed meeting in late October after its late summer recess, missing only one meeting the rest of the year. He did not have far to go, and one can imagine him struggling from his rooms to the weekly meeting, despite his infirmities, perhaps with the aid of some other member like Harry Hunt or perhaps Waller. The last meeting he attended may have been in the early summer of 1702, but the following February

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we find «The V.P. desiring Dr Hook to restore the Glasses which the Society had of Mr Huygens; the Dr returned them . . . » and two weeks later «Dr Hook desired the Society to lend him the book lately presented by Dr. Cheyney. It was accordingly lent him for a week.» Exactly a week later, he died (Waller again): «. . . at last his Distempers of shortness of Breath, Swelling, partly of his Body, but mostly of his Legs, increasing, and at last Mortifying, as was observ’d after his Death by their looking very black, being emaciated to the utmost, his Strength wholly worn out, he dy’d on the third of March 1702/3, being 67 years, 7 months, and 13 days old.»41) «His Corps was decently and handsomely interr’d in the Church of St. Hellen in London, all the Members of the Royal Society then in Town attending his Body to the Grave, paying the Respect due to his extraordinary Merit.» So Robert Hooke died in his 67th year, intestate,42) and was buried under the south aisle of the church of St. Helen Bishopsgate, close by Gresham College, where he lived for nearly 40 years. His effects were sold at auction, and the more than $8000 found in a strong box in his rooms in Gresham College went to his nearest relative.43) Thus his apparent intention to settle his large estate upon the Royal Society never came to pass, probably through the utter misery of these last days.44) As his health rapidly failed, it is fair to say that he did not go serenely to the grave; Waller describes his temper in these last days as «melancholy, mistrustful, and jealous.» Even his good friend Sir George Copley (“Cop” of the later Diary) saw him as a miser in his last days.45) In his life of Hooke, Waller wrote that «all his Errors and Blemishes were more than made amends for, by the Greatness and Extent of his natural and acquired Parts, and more than common, if not wonderful Sagacity, in diving into the most hidden secrets of Nature, and in contriving proper Methods of forcing her to confess the Truth.» And after listing Hooke’s inventions, theories, and discoveries, Waller concluded that «For these, his happy Qualifications, he was much respected by the most learned Philosophers both at home and abroad: And as with all his Failures, he may be reckon’d among the great Men of the last Age . . . » Thus passed from the scene Robert Hooke. He could not be said to stand comparison with either his friend Boyle or his nemesis Newton, though for very different reasons. But few could, and if Hooke was no Newton, Newton was no Hooke either.

Annotations 1) The almost slavish obsession with Newton’s activities in a period when the implications of the Principia were not generally understood, reeks of presentism. 2) BM Sloane MS. 4024 (Diary II). 3) Depending on how one counts, only three or six, in the 15 years following the Principia. See Keynes (1960), pp. 56–58.

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4) Despite, I think, a circle of friends gathered around Gresham College. 5) Gunther (1935), p. 73. 6) These deserve much closer attention than they have heretofore been given. I thank Michael Hunter for urging me to comment on this vast and jumbled “treasure trove” of material which includes a number of unpublished lectures referred to elsewhere in this chapter. Some items are merely abstracts, transcriptions or translations of works Hooke was studying. Also included are letters, a few astronomical observations, even a Gresham lecture. Some of the earlier material may bear directly on the question of Hooke’s efforts to solve the problem of planetary motion. A list of these papers published in Keynes (1960) is not without errors. See also Hunter (1989), p. 333. 7) See, especially, Chapter 10. 8) Currently available for study at the Royal Society, already digitized and available online. The discovery (2006) might justify such a hope. This large collection of handwritten notes (635 pages) on meetings of the Society, including some which fill in lacunae in the Society’s archives, add significantly to our knowledge of the period and Hooke’s role in it, and probably contain some surprises not yet ferreted out. 9) See Chapter 7. 10) One could speculate, unprofitably to be sure, about what might have happened had Newton openly and graciously acknowledged Hooke’s crucial role. But that would not have been possible for Newton. 11) The passage in his Diary for 3 July reads, «. . . dispute about Newton, of Leibnitz fallere fallentens. Newton & Mr Hamden came in, I went out . . . » (Gunther, X, p. 133). 12) By this time Newton had already treated the descent of bodies under gravity in a resisting medium. Principia, Book II. 13) Gunther, Vol. X, p. 163. What Hooke meant by that we cannot know. Had he managed to complete a proof he started in 1685, perhaps earlier, when it is known that he demonstrated elliptical orbits under an attractive central force proportional to the distance? 14) Gunther, Vol. X, p. 184. 15) For Aubrey’s further claims, see Chapter 12. 16) Newton’s lunar theory proved inadequate, so that Halley was forced to go to the historical record and identify long-term periodicity in the moon’s motion. 17) Hooke did not publish anything really new after 1688. Recall, however (Chapter 6), that only four numbers were published from 1688 to 1692. In all, he only had 21 papers published in the organ of the Society, in nearly forty years (Keynes, 1960, pp. 56–7). 18) Diary, 27 November 1688. Gunther, vol. X, p. 76. The passages reads: «Hally here: of Sir J. Hoskins: Mr Henshaw of leaving the Society: of my ingaging for

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the Sec and Curator.» Hooke’s friend Richard Waller served as secretary from 1687 until 1709, along with Gale and Sloane. 19) Maddison (1969), p. 177. 20) Based on the absence of his voice from the Journal Book as well as from Hooke’s regular lists of members present 21) Little (1975), p. 211, 22. 22) Aubrey to Wood, 22 January 1691; in Tylden-Wright (1991). 23) Judging from the Minutes and the Journal Book. This, of course, was the summer and fall of the “Glorious Revolution.” 24) A “Lambeth doctorate”, awarded him by his friend Archbishop Tillotson, which entitled him to put M.D. after his name. 25) It was in that same month that Boyle, friend, mentor, and patron, died, age 64. 26) An issue he first explored almost 20 years before. 27) And one wonders what he thought the implications for his measurement of parallax might be. 28) An almost exact contemporary of Hooke, Steno repudiated science before he reached 30 (in 1667). 29) It was Molyneux’s son, Samuel (1689–1728) who helped Bradley discover stellar aberration. See chapter 9. 30) Gunther, X, pp. 260, 262. 31) In the previous chapter we noted that Flamsteed had definitively observed the same phenomenon a decade earlier, also without knowing what he was seeing. But it might have given Hooke pause if he had considered it carefully, since it could not have been stellar parallax. 32) One speculates that this may have been a slip of the pen on Hooke’s or the Secretary’s part. 33) Gunther, Vol. X, p. 128. 34) Here, of course, we refer to the words of whomever was taking minutes for the Journal Book; Gale and Waller were the secretaries throughout this period. 35) Hoskins had been President for one year, 1682–1683, following Wren. 36) To the extent that Hooke’s lists are complete, there appear to have been no more than about a dozen or so present, and sometimes fewer. 37) HF (2006) 623–634. 38) As Adams and Jardine (2006) have noted, “record-keeping was clearly not one of Hooke’s many and varied talents. 39) This was not untypical of the Transactions, which were the responsibility of the Secretary and hence were often only reports of what someone had done or discovered.

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40) “The Life of Dr. Robert Hooke, in Waller, PW, p. xxvi; Gunther, vol. VI, pp. 63–4. 41) Ibid 42) As did Newton, who was showing of senescence at the time of his death in 1727. 43) Elizabeth Stephens. The estate amounted to a total of $9,580. See Drake (1996), p. 57. 44) There were many expressions of regret on the part of friends and other Society members that this fortune, of which apparently none had known, had not been dedicated to the Society or to other good works, which had apparently been Hooke’s intent. In this, as in so many other matters, Hooke’s intentions were left unrealized. 45) Inwood (2003), p. 409.

Epilogue Introduction To those for whom labeling is helpful, the period in which Hooke lived and worked is the “early modern” period and the birthplace of the “scientific revolution.” It is generally understood that the modern world itself springs from developments in philosophy and science (natural philosophy) during this period. But however we see that transformation, we now know, if we did not already, that Robert Hooke was one of the most important contributors to it. And yet when we assess his achievements, which are of the very highest order, we sometimes expect too much of him, or judge him by standards that we might not apply to his contemporaries. This fate has probably befallen Hooke most of all because of the inevitable comparison with one of the few genuine giants, Isaac Newton, but also, surely, because of Hooke’s status as essentially a transitional figure. If he was a flag bearer in the march toward the institutionalization of science, if he was one of the very first professional scientists, if not the very first (other than university dons), if he was one of a handful of figures who created a revolution in natural philosophy, he was also captive of his past, most especially in the way in which he did science, or, one might say, in the way he was forced to do science. But whatever Hooke did, almost none of it could have happened without the Royal Society of London. There is hardly a better example than Hooke’s of a career that was shaped almost entirely by the times and the culture in which he lived, and in his particular case, the opportunity and the straight-jacket provided by his employment by the Royal Society on the one hand, and the fire that pushed him into surveying, construction, and architecture almost at the start of his career as a scientist, on the other. Unlike Wren, Hooke avoided choosing between the two, natural philosophy and architecture. But if one marvels at Hooke’s achievements, it is hard not to wonder what he might have accomplished under different circumstances or if he had made, or had been able to make, different choices. Though, as we suggested at the outset, he might very well have ended up a country parson, dabbling in astronomy. Some have seen Hooke as a failed genius because of what they think he might have done. Indeed, he might well have left fewer projects unrealized if he had not chosen to bear the dual burdens of Curator of the Society and a major role in the rebuilding of London. But in many respects it was not a choice, and beyond that, one

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suspects that both careers brought enormous satisfaction to him. So the focus ought to be on what he accomplished, rather than what he might have done. Hooke was the quintessential experimental philosopher, with great technical skills and a wide-ranging curiosity, whose own inclinations were heavily reinforced by his job as Curator for the Royal Society. And yet he also speculated widely and, one might say, daringly, his expertise in geometry often being the foundation for his quantitative arguments. These theoretical insights were almost always superior to those of his colleagues in the Society, and rarely was he content to settle for a qualitative description of some phenomenon. And in evaluating his contributions, we should not merely look at what he did, that is at his experiments and discourses, but also at the influence his practice of natural philosophy had on the course of science in England (and on the continent) into his 50s. Hooke’s understanding of what were the important problems in natural philosophy was much better than that of almost all of his contemporaries, and that was certainly true of his interest in planetary dynamics. But he never developed the mathematical skills that would have made it possible for him to fully solve them, and this is especially true of the case of planetary motion. It is that fact that allowed the much deeper and more supple genius of Isaac Newton, as distracted as he was by the other issues with which he was obsessed, not only to solve the most important of these problems, but to revolutionize natural philosophy in the process. Hooke was only in his late 30s when the new techniques of analysis were being discussed in letters to and from Henry Oldenburg, many of them read at Society meetings or published in the Philosophical Transactions. We do find, here and there, interest in these ideas,1) but there is little evidence that he fully realized their importance or had any inkling of the direction in which Newton and others would ultimately take them. There is indeed a limited sense in which the division of natural philosophy (physics) into experimental, and theoretical or mathematical realms, can be traced to the mathematization of nature carried out mostly by Newton, even though those predilections certainly existed earlier in the century; one only has to think of Bacon and Descartes. But this fork in the road is dramatized by the fact that Newton was fully as successful in experimental as in mathematical natural philosophy. If Hooke’s transitional role in the scientific revolution, coupled with Newton’s triumph (if that is the correct word), helps explain his long descent into obscurity, there is nothing unique about what has frequently been the lot of those with one foot in the past and the other in the future. Hooke stood on the shoulders of Bacon and Descartes, and as Newton himself suggested, Sir Isaac stood on Hooke’s (and others). But in his maturity, the influence of both Bacon and Descartes was waning, and in dynamics, at least, the mathematicians were winning out. Hooke’s remarkable and diverse insights advanced natural philosophy on several fronts in the 1660s and 70s, but the ground was slipping out from under him as the 80s dawned and he approached 50. In these later years, his most important contributions were to geology where his qualitative speculations could more easily bear fruit. His lectures on natural philosophy per se, which date from around 1680, are full of important ideas, but for a variety

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of reasons, notably the fact that they were published over 20 years after their delivery, they were not in the long run influential. But if Hooke became a victim of changing fashions in natural philosophy, he also never was his own man in the way Boyle, or Huygens, or Newton were, and in contrast to the latter’s sinecure in Cambridge, he had to earn his living as a surveyor, architect, and contractor, at the same time performing paid services for the Royal Society, which represented only a fraction of his income.2) The result of this lack of independence, was, as we have seen, that the attention he could devote to any problem was limited and sporadic. No less important was the fact that by nature or because of the strictures of time, he seems not to have been inclined to systematic attack on a problem, whether narrow or broad, with the result that his insights and hunches rarely became proofs or demonstrations, and his discoveries were often pursued only fitfully.3) Huygens, also a spiritual prot´eg´e of Descartes, did a much better job of changing with the times than Hooke did, yet he too was being left behind.

Legacy Clich´e though it may be, Newton’s legacy is the modern world, and it is not for nothing that we speak of the “Newtonian world-view.” But if we cannot say the same of Hooke, such is also the case for every other figure of seventeenth-century science. Hooke is one of those countless figures in the history of science who were renowned, famous, or sometimes infamous, in their times, but who today receive little notice. In his case it could be argued that his becoming fashionable is as much a chronological accident as it is a result of a new understanding of his place in seventeenth-century science. But reputations ebb and flow, fads and fashions come and go, and Hooke is now, finally, getting his “due.” Since the time of Newton it has been rare for an empirical scientist, especially in physics, to receive the laurels that have been routinely bestowed on the brilliant and original theorist – a Maxwell, say, or an Einstein. Or a Laplace, and of course, Newton himself.4) Whether the explanatory power of theory validates this tendency is a matter for another time and place, but the trend is undeniably real. For the most part theory, even wrong theory, has had a staying power that experiment has not. Needless to say, this distinction between experimentalist and theorist would have been foreign to the seventeenth century, and as late as the nineteenth century major theorists like Maxwell and Kirchoff were comfortable in the laboratory as well. Nor is the distinction so narrowly drawn in other scientific fields as in physics. But in spite of Newton’s optical experiments and the importance of alchemy to him, and despite his devotion to experiment as the heart of natural philosophy, it is in his mathematics and mathematical physics that his real legacy lies. His influence, or if one prefers, that of the Principia, was especially strong in the eighteenth century, as figures like the Bernoullis, Euler, D’Alembert, Laplace, and Lagrange followed in his footsteps. Hooke possessed an extraordinarily inventive mind and a curiosity about all things, and, we have claimed, understood better than most of his contemporaries

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the fundamentally quantitative character of natural philosophy. One is constantly impressed by the cogency of his analysis of phenomena brought before the Society. Of him, one might say that he saw the trees rather than the forest, but having said that, we should note that the diverse phenomena he studied: mechanics, pneumatics, magnetism, light, gravitation, and so on, would not succumb to unification in his time. Even Newton’s great synthesis was limited to dynamics, as he somewhat plaintively noted in the last sentence of the Principia. Hooke’s own judgement was that he had made 500 inventions and discoveries, a number that is not implausible for such a rich career, spanning forty years. Some of his earliest discoveries came with the microscope, including the cellular structure of plants, but in the work in which he described this and many other discoveries, his Micrographia, he also speculated at length about the nature of light in passages which exerted an important influence on both Newton and Huygens. There Newton learned of Hooke’s ideas about color, the “wave” or pulse theory of the propagation of light, and most importantly, Hooke’s earliest statement of something like universal gravitation. Hooke’s advocacy of light as a wave phenomenon, in opposition to Newton and in this case siding with Huygens’, eventually set the stage for Young’s wave theory of more than a century later. Hooke was an independent discoverer of the phenomenon of diffraction, which is a consequence of the wave properties of light, though he had no way to know that, and as early as Micrographia, he had described the interference phenomenon we unjustly call “Newton’s Rings.” His theory of colors motivated Newton’s experiments which, of course, showed that Hooke was wrong, but his interests in light manifested itself in applied optics, in which he combined his understanding of the laws of optics with mechanical ingenuity to produce engines for grinding lenses and mirrors, the camera obscura, refracting telescopes for use by himself and others, telescope drive mechanisms, and the reflecting telescope. Hooke’s interest in optics naturally led into astronomy, which, however, suffered from his crowded life, full of diverse interests and we might say lack of focus, so that he never observed systematically nor left behind any mass of valuable data. Still, he discovered the rotation of Mars and Jupiter’s great red spot, made important observations of comets from the 1660s to 1681 and wrote lengthy discourses based on those observations, observed sunspots, which were rare in the century, and made one of the first telescopic observations of a binary star system. These are modest contributions, which might have been made by almost anyone, but then the same could be said of Galileo, and we should remember that even in 1670 the solar system posed fundamental and unsettled questions, and there was not yet total unanimity on the truth of the Copernican theory. Potentially Hooke’s most systematic and profound observations were with his zenith telescope in the courtyard of Gresham College, which he used to make what he probably went to his grave thinking was his most important discovery in astronomy, the long sought-for proof of the earth’s motion about the sun. He was mistaken in thinking he had observed parallax, but he was the first to make a credible attempt to establish the earth’s motion through space, being defeated by the smallness of the effect.

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Hooke’s contributions to the science of pneumatics were important, if not especially profound. He built Boyle’s first successful air pump for him and was one of the discoverers of, or at least provided important confirmation for, “Boyle’s Law.” He may have been the first to subject himself to a partial vacuum and report on the experience. But despite nearly a half-century of experiments in England and on the continent, by Hooke himself, Boyle, Huygens, Mariotte, and others, progress was limited. Nonetheless, pneumatics, early thermodynamics, was a continuing interest of natural philosophers in the last half of the century, leading to, among other things, the steam engine and steam technology. Pneumatics is also illustrative of the many issues of verification, witnessing, and the reliability of experimentally derived information which arose inside and outside the Royal Society, and to which Hooke contributed. Hooke was by no means alone in his interest in the pendulum in all of its ramifications, but he, along with Huygens, surely made the most of it. Much of that interest had to do with horology, which had very mundane and practical implications, including the possibility of personal profit, and was at the heart of the problem of determining longitude. This issue, of longitude, was driven by the enormous expansion of trade and exploration on the high seas in the sixteenth and seventeenth centuries, and its solution promised to bring renown if not wealth. Hooke knew that the pendulum clock could not function accurately at sea, despite Huygens’ optimism, and this motivated his experiments with a spring-controlled watch as early as 1658. However, as we noted earlier, the problems of long-term accuracy at sea were only solved by John Harrison in the middle of the eighteenth century, so that the use of astronomical methods, mainly making use of the moon, prevailed even after Newton’s death. More generally, Hooke’s contributions to the design of timekeeping apparatus represented an intersection of his interests in mechanical devices, the timing of physical events and the question of isochrony, and his interest in a means of reliably determining longitude at sea. But the pendulum had much wider implications. Hooke, Huygens, and Newton were all interested in the conical or circular pendulum, for different reasons. Hooke’s case is perhaps the most interesting for the way in which he saw it as an analogy for planetary motion. But he also employed the pendulum to investigate the decrease of gravity with height, and, in principle, the geographical variation in gravity. Although Huygens provided a solution to the problem of the lack of true isochrony in the simple pendulum, using cycloidal cheeks, it was a problem Hooke attacked as well. Hooke was among the first to assume that gravity was an inverse-square force, and seems to have beaten both Newton and Huygens to that conclusion.5) While Huygens and the young Newton argued from the inverse-square form of the centrifugal force, Hooke, correctly, saw orbital dynamics in terms of a center-directed, centripetal force, and in one place at least, based his deduction of the inverse-square law on the increase of the area of a sphere with distance (Chapter 9). Probably as early as 1665, and certainly earlier than Newton, Hooke believed that gravity was universal. And it was he who clarified Newton’s thinking on the dynamics of planetary motion in 1679, which we have seen pushed Newton toward the Principia. In the derivation of a description of planetary motion from inverse-square gravity, the prize belongs entirely

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to Newton, of course, and Hooke’s vision of what a solution might consist of was far more modest than the result that Newton achieved in the mid 1680s. Yet what little we know of Hooke’s actual attempts to solve the problem suggest that he had reason to think that he had the solution, or was near it, as he often claimed. Hooke’s important contributions to the early science of geology are beyond the scope of this work, and have been thoroughly dealt with by Ellen Tan Drake and others. But his interest in the problems of fossils in rocks high above the sea and the changes wrought in the earth by earthquakes and vulcanism, was one of his continuing preoccupations, commencing in his childhood, and never waning. He must be counted one of the fathers of geology. A similar, if more tentative claim, can be made for Hooke as one of the precursors of evolution in geological and biological processes. The twenty years Hooke devoted to surveying, building codes and practices, and architecture, were in a way peripheral to his life as an experimental natural philosopher, and yet they were not. No doubt Hooke’s success in the mechanical arts, specifically architectural engineering, was a direct outgrowth of his understanding of forces and how materials respond to them. This took concrete form in his buildings, of course, but in his famous Cutler lecture De Potential Restitutiva of 1678, he explored the theoretical basis for it. He also undoubtedly advised Wren on questions of the design of arches and masonry construction, at least implicitly playing a role in the design of the dome of St. Paul’s. Newton triumphed over Hooke by his greater ability and opportunity to focus on a problem to the exclusion of everything else and by his facility in translating physical ideas into the language of mathematics. In that sense, and despite the time he spent in experimentation, Newton was one of the first theoretical physicists. But beyond that, and perhaps because of his mathematical skills, one can argue that he had a better grasp of the “larger picture,” of the connection between problems which might have appeared to be dissimilar or unrelated.6) In an entirely different sense, however, his achievements were a working out of his view of a physical world shaped by a very immediate creator. Hooke in his day was lionized by some, dismissed by others. He had great friends and great enemies, and to a considerable extent the same ambivalence prevails today. There are many reasons why he is known more for unfulfilled promises and unfinished ideas than for completed studies, the most important being the distractions of his exceptionally busy life. But his inability or reluctance to cast problems in the mathematics of the day is a major one. A hint or two from Hooke was enough to put Newton on the track toward the Principia, superb mathematician that he was. Hooke has an importance far beyond his role in the life of Isaac Newton; the idea that he merely shines by reflected light from the author of the Principia is no longer tenable. Nevertheless, it is not a great stretch to say that perhaps his greatest contribution, for better or worse, was in his impact on Newton. Such has been the lot of other fine minds – indeed the same might be said of Halley. Hooke did influence Newton, primarily in the controversies over light and color, and of gravitation and planetary motion. But he also swayed Newton by simply being an irritant, serving, on

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the one hand, to motivate him, and at the same time reinforcing his natural tendency to shrink from the world. In much of what he did, Newton had to take Hooke into account, whether he wanted to or not.

Conclusion Hooke was involved in the creation and/or evolution of important areas of natural philosophy, including microscopy, cell biology, pneumatics and thermodynamics, astronomy, planetary theory, and geology. He could not be said to have brought any of them to maturity, but no one could have achieved that in the seventeenth century, except in dynamics. Yet there is another, albeit hazardous way, of looking at Hooke as a natural philosopher, and that is to survey some of his brilliant guesses and conjectures about phenomena which are now familiar but were unknown in his time. This may be presentism at its worst, or best, but is nonetheless revealing of the fertile scientific mind that was Hooke’s. If we have so far resisted addressing his “legacy”, it is because our interest has been in his own time and on his own scientific efforts rather than on his present influence and reputation or how his discoveries affected the course of scientific discovery in the eighteenth and later centuries. That is as it should be, but it may nonetheless be useful to examine that legacy, and indeed, or one might say, his prescience. We have earlier recounted some of his discoveries, such as diffraction, interference, “Hooke’s Law” of elasticity, as well as his early ideas on centripetal force, universal gravitation, and his arguments in support of gravity’s inverse-square nature. We have several times noted his speculation on geological processes such as earthquakes and vulcanism, on fossilization and evolution. But what may fascinate a modern observer, beyond these insights, which are remarkable enough, are what amount to his hunches, lacking any empirical support (or any prospect of it), but the product of a creative mind with wonderful physical intuition. These include the wave nature of light, the possibility that the earth’s magnetic axis might shift and that that might be revealed in its rocks, the presence of a component in the air responsible for combustion and respiration, heat as internal motion in an object, the effect of mountains on the earth’s rotation, and alterations of the earth’s poles. We are further astonished to see him speculating about the possibility that gravity might change with time, or that the weight of an object might increase when it is magnetized. These observations might make us think of Aristarchus. Few if any of these ideas bore fruit because there was no theoretical structure that could contain them, no experiments or observations that could be carried out to test them, and, of course, because most of what Hooke wrote and discoursed about was forgotten anyhow. Hooke’s way of doing natural philosophy was passing out of favor, and that, as much as anything, explains his modest influence on the succeeding centuries.7) He did unquestionably exert a major influence on Newton, but in the last analysis it may be argued that the Royal Society itself, which Hooke served so well and for so long, and which might not have survived without him, is his greatest legacy. The Society would successfully adapt to the changing fashions in science, despite at various times

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being seen as a plaything for privileged dilettantes, and today stands as one of the world’s leading scientific organizations. Hooke’s death, which brought to an end his wretched and protracted physical decline, would not be the final indignity. The combined forces of Newton’s ire8) and, more importantly, the success of his method, consigned Hooke to obscurity for over two hundred years, even extending to the loss (discarding?) of the Society’s painting of him. All of his major buildings were pulled down, and while he was buried with honors in the church of St. Helen Bishopsgate, near Gresham and his haunts in Cornhill. In the nineteenth century his bones were evidently disinterred with others and consigned to a mass grave in north London. Finally, the IRA finished the job of eliminating any hint of a memorial to Hooke when it destroyed the stained-glass window in St. Helen’s that had been erected in his honor.9) And yet, as we have already seen, if one looks carefully at the “Wren” churches in the northeast part of the City, which was Hooke’s responsibility after the fire, one can clearly see the Hooke style at work.10) With the large structures he designed long-since leveled along with Gresham College itself, his instruments and portrait lost, it is there, and to the “Fish Street pillar” that we must look for his memorial, though outside London, Ragley Hall in Warwickshire and St. Mary Magdelene Church in Willen, Buckinghamshire (Fig. 25) still keep his architectural legacy alive and give an imposing concreteness to his life. And finally, after three full centuries, Hooke has finally been memorialized by a plaque in the floor of the nave of Westminster Abbey,11) not far from similar tributes to Churchill, Disraeli, Shakespeare, John Harrison (chronometer), and Paul Dirac (quantum mechanics), among others. This memorial (Fig. 26), near that of his mentor Dr. Busby, in a space he walked many, many times, while honoring his larger achievements, is also a recognition of his work on the Abbey, his attendance at Westminster School, and his friendship with Dr. Busby. It says, simply, “Robert Hooke, 1703.”

Annotations 1) Including a copy of a work on indivisibles by L’Hospital in the Classified Papers of the Royal Society, Vol. 20. 2) Certainly no more than a quarter of it, since he had nearly $9000 at his death, and his income from his positions as Curator and Gresham Professor could not have yielded more than about $4000 over 40 years. 3) It is worth recalling Hooke’s advice from the preface to his Cutler Lectures of 1674, which he clearly embraced in his life, «to be diligent in the inquiry of everything we meet with.» 4) There are exceptions, to be sure, including, for example, Faraday, Rutherford, and Fermi. 5) See Chapter 10. As we have noted before, it is difficult to tell, on any particular point, whether Hooke instructed Wren, or vice-versa, or whether they may have arrived at an idea together, over coffee.

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Fig. 25: Hooke’s Willen church, in Buckinghamshire, built for Busby. Photograph by the author.

6) The mathematical structure of a problem being the key to that insight. Ofer Gal (Gal, 2002) argues that Hooke and Newton had very distinct programs, which is quite obviously true. 7) This is not the place to explore the extent to which Hooke’s experimental practice did become the model for natural philosophers in England and Scotland during the next century and a quarter. Mathematical physics, building upon Newton, flourished in central Europe (France, Switzerland), in the hands of

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Euler, Laplace, Lagrange, etc., but the foundation of the industrial revolution in England and Scotland had a much more practical character. One thinks of Davy, Watt, Joule, Faraday, and so on. The latter half of the century, dominated by Thomson (Kelvin), Maxwell, Stokes, and others, is a different story. 8) We surmise, without real evidence. 9) In the very recent past, the staff at St. Helen’s were only dimly aware that someone of note, by the name of Robert Hooke, had been buried there. A wooden screen of Hooke’s in the Merchant Taylor’s Hall in Threadneedle street was also lost when the building was destroyed during the Blitz 10) See also Chapter 1. 11) Dedicated on 3 March 2005, the 302nd anniversary of his death.

Fig. 26: Memorial to Robert Hooke in Westminster Abbey, dedicated 3 March 2005. Courtesy of Michael Cooper.

Bibliography The reader interested in a “complete” Hooke bibliography should consult the 39-page bibliography in Cooper and Hunter (2006). Frequently used citations: Birch, Birch (1756). Diary I, Robinson and Adams (1935). Diary II, Gunther, Vol. X (1935). Classified Papers, Classified Papers of the Royal Society of London. CHO, Hall and Hall (1965–86). Corresp.; Turnbull, et al. (1959). DSB, Dictionary of Scientific Biography, 18 vols., Scribners, 1970–90. Gunther, Gunther (1930–38). HF, Hooke Folio (2006), Royal Society. Journal Book, Journal Book of the Royal Society. Lectures and Collections, Hooke, 1678. Micrographia, Hooke, 1665. Reprinted in facsimile by Gunther (1630–38), Vol. XIII (1938). Reprinted by Dover, with preface by Gunther, 1961. Record of the Royal Society of London, Morrison & Gibb, 1940. Register Book, Register Book of the Royal Society. Opticks. Newton’s Opticks, 1704, etc. (Dover, 1979). Sprat, History of the Royal Society, Sprat (1667). PT, Philosophical Transactions. PW, Waller (1705). P. Ackroyd, 2000. London, The Biography, Anchor. Adams, Robyn, and Lisa Jardine, 2006. “The Return of the Hooke Folio,” Notes. Rec. Roy. Soc. 60 (2006) 235–9. Adamson, Ian, 1978. “The Royal Society and Gresham College, 1660–1711,” Notes Rec. R. Soc. Lond. 33, 1–21.

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Index 1645 group, 2, 34, 36, 39–40, 223 Accademia dei Lincei, 39 Accademie del Cimento, 39 aether, 58, 75, 109, 112, 141, 150, 155, 162, 168, 171, 173, 176, 195 air pump, 4, 49, 58–59, 64, 82–83, 101, 245, 262 alchemy, 50, 82, 160, 170, 173, 181, 189, 243, 255 Andrade, E.N. Da C. xiv, 1, 8, 13, 140, 146, 160, 252 anchor escapement, see escapement anomalous suspension, 49, 58, 101, 174 Aristotle, 153, 195 Arundel House, 20, 29, 41, 52–53, 61, 68, 91, 97 astronomy, see Hooke, astronomy Aubrey, John, 8, 9, 13–16, 18, 26, 28, 30, 33, 39, 65, 126, 190, 202, 213, 230–231, 238–239, 252, 257, 261, 263 Bacon, Francis, 38, 42, 116, 119, 150, 156–157, 160, 242 – New Atlantis, 42 Baconian, xviii, 34, 38, 54, 67–8, 116, 150, 153, 155, 157–158 balance spring watch, 70, 78, 92–95, 97, 105, 115, 118, 121, 123–124, 142, 174, 207, 214, 221, 245 Bathurst, Ralph, 34, 40, 128 Bedlam (Bethlem) Hospital, see Hooke, architecture Birch, Thomas, xiv, xvii–xx, xx, 26, 28–29, 39–41, 52, 55, 61–63, 69, 84–85, 89–90, 100, 114, 119, 128–129, 131, 139, 155, 160, 191, 195, 199, 205–206, 209, 216, 221–222 Bishopsgate, 5, 10, 248, 251 Boyle, Robert, xiv–xvi, xix, 2–5, 7, 10, 13, 15–18, 21–22, 24, 27, 29–30, 34–35, 37, 39–42, 45, 48–51, 53, 56–61, 65, 71, 73, 76–77, 82–84, 91–92, 95, 98–101, 103, 118, 119–124, 127–130, 132, 136, 150, 156–157, 159–160, 199, 205, 212–213, 221, 228, 231, 235, 237, 239, 243, 245, 252–254, 256–260 – A Free Inquiry into the Vulgarly Received Notion of Nature, 160 – alchemy, 50, 82, 160

266

Index

– – – – –

Boyle’s Law, 4, 82, 118, 245, 254 correspondence, xix, 58, 60–61, 122–124, 128–129 health, xv, 17, 228, 231 invisible college, 40, 83 and Royal Society, 4, 30, 37, 41, 45, 50, 53, 56–57, 65, 73, 77, 91, 99–100, 119, 122, 128, 231 – New Experiments and Observations Touching Cold, 4, 10, 60, 82, 118, 127–128, 253 – New Experiments Physico-Mechanical Touching the Spring of the Air, 4, 83, 253 Bridewell hospital, see Hooke, architecture Brouncker, Viscount Lord, President of RS, 13–15, 21, 26, 30, 37, 40–41, 45, 50–51, 54–55, 59–60, 64–65, 82, 90–91, 93–94, 97–98, 100, 103, 118, 120–122, 129, 140, 145, 205, 223, 262 Busby, Richard, 2, 4, 9, 17, 24, 81, 228, 230, 248–249 calculus, the, 76, 157, 163 Cambridge University, 15, 17 – and Newton, 29, 51, 68, see also Newton Campani, Giuseppi, 204, 222 capillarity, 24, 46, 58, 84, 86, 108, 137 carbon dioxide, 59 Cassini, G.D., xv, 53, 76, 161, 204, 211–215, 222 – Mars, 211 – Jupiter, 222 – Saturn, 213 Charles I, 34, 40 Charles II, 4, 9, 18, 26, 36, 41–42, 48, 58, 62, 115, 127, 221, 257 Chelsea College, 49, 53, 62, 68 chemistry, 46, 50, 82 Christ Church College, Oxford, 2, 9, 81 Clement, William, 81, 118 coffee houses, 4–5, 11, 15, 17–18, 20–22, 24, 27, 29, 69–70, 80, 149, 166, 196, 202, 228, 248, 254–255, 259, 262 College of Physicians, see Royal College of Physicians Collins, John, 21, 30, 54, 205, 223 collisions, 53–56, 64, 106, 147 “Cometa”, see Hooke, Cutler Lectures Comets, xv, 10, 50, 112, 131, 143, 149–150, 152, 154–156, 166, 170–171, 173, 175, 177, 181, 189, 192–193, 195, 202, 204, 207, 210, 213–215, 232, 244, 257, 259, see also Hooke, astronomy Cook, Allan, 71, 77, 254 Cooper, Michael, xiii, xiv, xvi, xviii–xix, 14, 19, 250, 252, 254 Cornhill, 5, 7, 8, 20, 29, 51 Cromwell, Oliver, 37, 40, 41

Index

267

Croune, William, 36, 41, 55–56, 97, 99, 126 Cutler Lectures, see Hooke Cutler, Sir John, 21, 29–30, 53, 87, 120 De Motu, see Newton “De Restitutiva”, see Hooke Descartes, Rene, 54–55, 58, 62, 116, 139, 150, 153, 156–157, 161, 169, 174, 242–243 Diary, see Hooke, Diary; also Pepys, Evelyn diffraction, 108, 139, 141, 143, 146, 207–208, 244, 247, 256 Digby, Kenelme, 37, 41 eclipses, 10, 48, 75, 79–80, 117, 207–208, 212, 214, 221; see also Hooke, astronomy, Halley Ent, George, 34, 128 escapement, anchor, 81, 117–118, 207 escapement, verge, 81 Espinasse, Margaret, xiii, xiv, 1, 8, 14, 26, 70, 118, 123–125, 255 Evelyn, John, 25, 37, 40–41, 73, 120, 126, 234, 255 – diary, 25, 63 – post-fire plans, 31, 52, 89 Euler, Leonhard, xviii, 144, 243, 250 Fermat, Pierre de, 60, 143 Fire, xiii–xvi, xix, 3–7, 22, 24, 41, 45, 49, 51–52, 60, 71, 86, 89, 101–102, 106, 109, 117, 208, 212, 220, 241, 248 Flamsteed, John, 3, 15, 58, 74–76, 99, 112, 126, 131, 193, 203, 204, 205, 208, 213, 215, 219, 239, 256 – and Halley, 76, 220 – and Hooke, 97, 109, 113, 131, 179, 212, 220, 222 – and Newton, 126, 181–182 Gale, Thomas, 74, 78, 99, 126, 132, 239 Galileo, Galilei, 39, 57, 64, 75, 103, 110, 122, 127, 149, 157, 162, 169, 203–204, 208–209, 213, 222, 244 geology – Hooke, see Hooke, geology – Steno, see Steno Glanvill, Joseph, 38, 62 – Plus Ultra, 53, 62 – Scepsis Scientifica, 38, 42 Goddard, Jonathan Dr., 34, 37, 40–41, 49, 205 Greatorex, Ralph, 82, 118 Greenwich Observatory, 7, 58, 70 Gregory David, 78, 80

268

Index

– Astronomiae elementa, 80 Gregory, James, 21, 64, 108, 144, 205, 216, 221, 262 Gregorian telescope, 108, 144, 205, 221, 262 Gresham College, 87, 89, 107, 114, 129, 132, 159, 166, 169, 209, 212, 214, 216–218, 223–224, 231, 233–235, 237–238, 244, 248, 251, 258, 263 Gresham, Thomas, 253 Grew, Nehemiah, 21, 30, 65, 66, 69, 99, 123, 126 Grimaldi, Francesco Maria, 108, 146, 256 Grubendol (Oldenburg), 97, 125 Gunther, Robert, xiv, 1, 8, 18–19, 27–29, 79, 89, 129, 196, 256 Haak Theodore, 20, 34, 39 Halley, Edmond, xvi, xix, 3, 16, 20, 27, 71, 73–77, 79–80, 100–101, 125, 132, 229– 230, 232–234, 236, 246 – Astronomer Royal, 204 – Board of Longitude, 74 – Clerk, RS, 71, 74 – dating antiquity, 76 – eclipse cycles, 75, 79 – and Flamsteed, 76, 109, 204 – comets, 214–5, 223, periodicity of (Halley’s Comet), 112, 131, 173, 215, 223 – and Hevelius, 125 – and Hooke, see Hooke, 7, 10, 13, 15, 17–18, 20–21, 68, 74, 77, 80, 132, 170, 172, 180, 182, 189, 193, 199–201, 207–208, 214, 220, 228, 231 – longitude, 75–76, 79, 214, 234 – lunar theory, 80, 238 – and Newton, see Newton, 17, 109, 126, 171, 178, 182, 189, 192–193, 196, 198 – and parallax, 225 – planetary motion, 114, 170, 172, 180, 182, 193 – and Principia, 68, 71, 166, 189 – religion, 79, 261 – and Saros, 75, 79 – St. Helena, 74, 76 – and transactions, 76 – visit to Cambridge, 29, 68, 100, 114, 166, 170, 172–173, 177, 181, 183, 193–194, 199 – voyages, 78, 234–235 Harriot, Thomas, 39, 48, 203–204, 213, 220 Hartlib, William, 34, 39–40, 204, 256 Henshaw, Thomas, 27, 37, 40–41, 65, 69, 73, 99, 110, 126, 155, 228, 234–235, 238 Hevelius, Johannes, xv, 20, 29, 50, 58, 67, 86, 90–91, 97, 98, 109, 125, 204, 206–207, 212–214, 220–222 Hobbes, Thomas, 16, 37, 39, 42, 174 Holder, William, 18, 126, 147

Index

269

Hooke, Robert – aether, 109, 155 – air, 109; pressure, 129; springiness of, 4, 101, 109; condensing, 248 – air-pump, 4, 82–83 – air resistance, 103 – anchor escapement, 81, 117–118, 207 – animal experiments, 53 – anomalous suspension, 49 – architecture, xiv, xvi, 5, 10, 22, 24, 30, 48, 70, 90, 108–109, 132, 169 213, 231, 246, 248 – churches, 7, 10, 31, 69, 120, 248 – monument, 70 – astronomy, 2, 203–25, 244 – binary stars, 204, 214, 244 – comets, see comets – devices, driven equatorial mounting, 206, 210, 221 – eclipses, 79, 208, 213–214 – Jupiter, 50, 195; rotation of, 60–61, 208, 210, 213–214, 220, 222; great red spot, 60, 61, 210, 214, 244; Galilean satellites, 209 – Mars, 52; rotation of, 52, 204, 208, 214, 222 – moon, 208, 211 – observing, 207–214 – sunspots, 213, 223 – and Aubrey, John, 8, 26, 230 – and Bacon, Francis, xviii, 116, 150, 156–157 – balance-spring watch, 70, 82, 92, 94–95, 97–8, 105, 108, 118, 121, 123–125, 221 – barometer, 28, 101, 105, 109, 127, 129 – and book collecting, 14 – and Boyle, xvi, 2–4, 17–18, 82, 84, 92, 119, 150, 156 – Boyle’s Law, 4, 109, 118–119 – and Brouncker, 14, 121 – and Busby, 2, 17, 228, 230 – capillarity, 24, 46, 58, 84, 86, 108, 137 – the cell, discovery of, 116–118 – centripetal force (center-directed force), 168, 190 – changes in the earth 232 – character, 13–14, 17, 21, 98, 119, 130, 207 – Charles II, 18, 115 – Chelsea College, see Royal Society – Christ Church College, see Oxford – churches, see Hooke, architecture – “Classified Papers”, see Royal Society – Cock, Christopher, 205 – coffee houses, 8, 10, 21, 27

270

Index

– collisions, 53–55 – “Cometa”, see Cutler Lectures – comets, 50, 112, 210, 214–5, 224 – periodicity, 112, 131, 223 – College of Physicians, see Hooke, architecture – combustion, 103, 128 – conical pendulum (circular pendulum), see pendulums – correspondence, xvi, 15, 64, 66, 67 – with Newton, 29, 98–99, 177–181 – as Secretary, 70 – with Boyle, 58–59, 128–129 – as Curator, 10, 24, 49, 56, 63, 65–66, 84–87, 89–90, 97, 100–101, 103, 108, 113, 127, 129, 209 – and Cutler, Sir John, 21, 53, 87, 120 – Cutler Lectures, xiv, 21, 108 – “An Attempt to Prove the Motion of the Earth Through Observation”, 106–107, 168, 175, 212, 216 – “Animadversions on the First Part of Hevelius His Machina Coelestis”, 98, 125, 206, 210 – “Cometa”, 50, 91, 112, 130, 208, 210, 214–215 – “A Description of Helioscopes”, 95, 97, 124–125 – “Lampas”, 95, 97, 124, 124–125 – death, 76, 236–237, 248 – degree, measurement of, 56, 106, 108 – and De Motu, 172, 181, 187, 201, 229 – “De Restitutiva”, xv, 90, 110–111, 121 130, 247 – and Descartes, 116, 139, 150, 153, 156, 161, 169, 174, 242 – Diary, xvi, xvii, xviii, 1, 15–16, 18–22, 27, 29, 45, 100, 108, 121, 207, 229; early diary, 18, 27, 67, 129, 199, 213; Sloan (later diary), 18–20, 230 – diffraction, 108, 141, 146, 208 – direct motion by the tangent and central attraction, 166–168, 178, 191 – “Discourse of the Nature of Comets“ 50, 112, 149, 154–156, 170, 173, 175, 177, 195, 215 – “Discourse of Earthquakes” 110, 152, 162 – Doctor of Physic, 231, 239 – Drake, Ellen Tan, 110 – drawings, see Micrographia – dynamical manuscripts, xiv, xvi, xix – Espinasse, 124 – earth, shape of, 106 – earthquakes, 232, 247 – eclipses, see astronomy – elasticity, 109, 130, 223, 246 – elliptical orbits, 170–171; proof of, 183–186, 190, 200

Index – – – – – – – – – – – – – – – –

– – – – – –

– – – – – – – – – – – – – – – –

271

estate, 25, 127, 240, 248 evolutionary ideas, 162 experiments, 45, 54–55, 73, 101, 146 eyesight, 214, 231 falling bodies, 104–105 Feingold, Mordechai, 14 elected Fellow (FRS), 59, 87 Fire, 6, 89, 117, 212 and Flamsteed, 97, 109, 113 Folio, (“Hooke Folio” 2006), xvi–xix, 27, 29, 94, 96, 114–115, 123–124, 132, 235 fossils, 114, 246 Gal, Ofer, 175, 194, 198, 200, 249, 256 Garraway’s, (Garaway’s) 8, 20, 29 Geology, 110, 114, 232, 246 Grace, see Hooke, Grace, 16–17, 19, 114, 127, 227 gravity, 156, 165–202, 175, 195, 198, 245 – cause of, 112, 174, 176, 190, 197 – inverse-square force, 166, 176–177, 190, 197 – variation of, 60, 103–106, 113, 128, 131, 175–176 – universal, see universal gravitation Greenwich Observatory, 58 Gregorian telescope, 64, 108, 205, 221 Gresham College, 18, 51, 87 Gresham Professor, 17, 76, 89, 120, 159, 170 Hall, A.R. and Marie Boas, 123 and Halley, Edmond, 15, 18, 17, 21, 75, 77, 79–80, 114, 228 – observing, 214 – planetary motion 172, 193, 196 health, 4, 17, 20–21, 24, 25, 30, 56, 66, 77, 214, 227, 231, 235–236 heat, nature of, 161 and Hevelius, 97–98, 109, 124, 207, 221 “Hooke’s Law”, see “De Restitutiva” horology, 46, 103, 106, 117 housekeepers, 15–16, 26 and Huygens, 49, 70, 78, 90, 93, 97, 105, 234 income, 248 interference, 146, 208 inverse-square gravity, see gravity Jonathan’s, 172, 228 Jupiter, see astronomy Kepler problem, see planetary motion Kepler’s Laws, 198, 200 Kuhn, Thomas, 136 laws of motion, see collisions

272 – – – – – – – – – – – – – – – – – – – –

– – – – – –

Index

“The Laws of Circular Motion”, 178, 182–184, 192, 199–201 Lectiones Cutlerianae, 130 “Lectures and Collections”, 130 “Lectures on Light”, 142–145, 155 and Leeuvenhoek, 105 legacy, 243–247 and Leibniz, 70 lens grinding, 56, 106 library, 14 light and color, 57–58, 116, 135–148, 233 longitude, 75, 81, 105, 245 lunar theory, 169 lunar craters, origin, see Micrographia magnetism, 106, 247 Mars, see astronomy mathematics, 159, 163, 170, 248 “mathematical exactness” 154 measuring the degree, see degree memorial, 10, 248 Micrographia, xv, 1, 28, 87, 88, 108, 114, 128–129, 132–133, 147, 156, 160–161, 165, 208–209, 221, 233 – the cell,117 – light and color, 116–117, 141, 143–145 – lunar craters, origin, 117, 208 – Micrographia Restaurata, 133 – microscope, drawings, 47, 116 – moon, 117 – and Newton, 57, 144 – Pleiades, 117 – Refraction, 116–117 – Telescope aperture, 206 – universal gravitation, 117 – wave theory of light, 116 microscopy, 22, 46, 87, 105, 113, 116 Montague House, see Hooke, architecture the Monument (piller), 7, 10, 101–102, 109, 113, 129–131, 248 – experiments at, 7, 11, 104, 109, 113, 129–131 matter and motion, see Hooke, natural philosophy natural history, 48 – and fables, 232 natural philosophy, 33, 90, 118, 149–163, 233, 242 – matter and motion, 153–154 – “The Method of Improving Natural Philosophy”, 127, 150, 160, – “The Present State of Natural Philosophy”, 127, 150

Index

273

– “synthetic vs analytical way“, 152, 161 – “New Atlantis”, 119, 160 – and Newton, xvi, xviii, 17–18, 57–58, 70, 85, 98, 100, 107, 114, 118–119, 129, 165, 177, 189, 227, 229–230, 233, 235, 246 – on light and color, 107, 135–148 – correspondence with, 126, 142, 147, 169, 171, 177–181, 196 – and gravity, 178–181, 197 – on planetary motion, 178–182 – Newton, influence on, xviii, 182, 187, 246 – “Newton’s” rings, 141, 146, 244 – Newton’s theory of light and color, 57–58 – nitrous component in air, see combustion – and Oldenburg, xv, 13, 21, 91–8, 114, 123–125, 142 – death of, 91, 109, 121; impact on Hooke, 3, 37, 65–66, 70, 86, 91, 93, 98, 99, 109, 121, 123, 126, 178, 213 – “Of Spring” see “De Restitutiva” – optics, lens and mirror grinding, 10, 205–206 – at Oxford, 2, 5, 9, 10, 28, 81, 106, 207 – and Boyle, 81, 118, 150 – and Oxford group, 2, 3 – and Papin, Denys, 100 – parallax, 56, 76, 106–107, 121, 129, 211–212, 216–219, 224–225, 233, 244 – pendulums, 245 – conical, 104–105, 107, 122, 128, 167–168, 191, 206; isochrony, 105, 191 – pendulum clocks, 81, 207 – pendulum driven quadrant, 206 – variation of gravity using, 128 – pendulum clocks, 81 – and Pepys, 14, 18, 223, 228 – philosophical algebra, 116, 150–151 – “Philosophical Clubb”, 97 – Philosophical Collections, 66, 70, 126, 199 – Philsophical Transactions, 66, 99, 129 – plague, 89 – planetary motion, 29, 108, 114, 146, 165–167, 169–173, 178, 182–183, 186, 191– 192, 245 – pneumatics, 57, 83, 101, 103, 106, 127, 245 – portrait, loss of, 4, 9–10, 15 – Posthumous Works, 26, 108, 142–143 – Principia, 19, 100 – Ragley Hall, see architecture – rebuilding London, xiii, xix, 7, 22, 52, 89 – Reeves, Richard, 205 – refraction, 116–117, 135, 138–139

274

Index

– registering, 151 – reputation, xiii–xv – and Royal Society, xiii–xvi, 3, 24, 33, 45, 65–67, 69, 73, 80–81, 84, 86, 91, 99, 101, 113, 213 – “Classified Papers”, see Royal Society – council of, 66–67, 117, 213, 231 – Curator, see Curator – Royal Society politics, 65, 67, 99, 113 – St. Helen’s Bishopsgate, 237, 248, 250 – St. Paul’s, experiments at, 59, 101, 104, 120, 129 – science, Hooke’s, 101–133 – and scientific revolution, 6, 242 – seconds pendulum, 50, 59, 103, see pendulum – Secretary, 66–67, 98–99, 113, 122, 126, 166 – sextant, 76, 206, 233 – siblings, 9 – on the soul, 155–156 – sound, 108 – sounding the sea, 48 – space and time, 156 – “Of Spring” see “De Restitutiva” – status, 37, 85 – stellar aberration, 63–64, 217, 225 – Stevens, Elizabeth (niece), 240 – Sunspots, see astronomy – surveying, xix, 5, 14, 24, 27, 31, 48, 90 – telescopes and quadrants, 10, 206, 209–210 – telescopic sights, 98, 109, 125, 207, 221 – tercentenary (1935, 2003), xiv, xvii – terminal velocity, 110 – thermometry, 50 – and Tillotson, John, 13, 18, 231, 239 – “Uc tensio, sic Vis, “ 130; see De Restitutiva – universal gravitation, 31, 117, 131, 168, 174–177, 192, 208, 244–245 – universal joint, 92 – on vacuum, 153 – Waller, 8, 14 – wave theory of light, 116, 135, 138, 145, 155, 244 – Webster, Charles, 119 – wealth, 41 – Westfall, R.S., 136 – Westminster Abbey, 10, 132, 231, 248, 250 – Westminster School, 2, 9, 10, 17, 81, 278 – and Wilkins, 2, 3, 9, 17

Index

275

– Wilkins Lecture, 1, 8, 31 – Willen Church, see architecture – and Wren, xvi, 2, 7, 10, 18, 21–24, 30, 114, 132, 228, 248 – planetary motion 166, 169, 172, 196 – architecture, 90, 212 – youth, 1–2, 8 – zenith telescope, 107, 217–218 – zodiacal light, 232 horology, 24, 103, 106, 205–206, 245 Horrox (Horocks), Jeremy, 3, 48, 79–80, 128, 204 Hoskins, John, 21, 27, 65, 69, 73, 99, 121, 228, 232, 234 Howard, Charles, 52, 61 Howard, Henry, 53, 61 Hunter, Michael, 10, 39, 42, 119, 160, 238, Huygens, Christian, xv, 13, 16, 20, 46, 50, 62, 63, 71, 89, 120, 123, 159, 220, 243, 245 – anomalous suspension, 49, 58, 64, 174 – astronomy, 204, 206 – balance spring watch, 70, 82, 92–95, 97, 108, 121, 124–125 – centrifugal force, 173, 194, 245 – collisions, 54–55, 62, 106 – conical pendulum, 105, 191, 245 – dynamics, 200 – gravity, 166, 173–174, 194 – cause of, 233 – and Hooke, 67, 90, 93–95, 97, 105, 121, 166, 173–174, 207, 234 – horology, 103 – Horologium Oscillatorium, 194 – light and color, 141, 142 – longitude, 78, 245 – and Micrographia (influence of), 87, 117, 173, 244, 252 – and Newton, 141, 145, 173–174, 194 – pendulum clock, 59, 93, 245 – planetary motion, 191 – polarization of light, 143 – on the Principia, 173 – and Royal Society, 59, 92–93, 95, 233–234 – Saturn, 204 – secondary wavelets, 143 – seconds pendulum, 49–50, 59, 113 – universal measure, see seconds pendulum – verge escapement, 81 – wave theory of light, 143, 244

276

Index

institutionalizing science, xv, 241 inverse-square law of gravity, 22, 114, 143, 159, 166–167, 170–172, 176–177, 180, 182–183, 186–187, 190, 192–193, 197, 198, 200–201, 245, 247 invisible college, 34, 39–40, 83 Jardine, Lisa, xiii, 10, 13, 31, 122, 132–133, 239 Jeffery, Paul, 11, 31 Jupiter, 10, 48, 50, 60–61, 75, 122, 153, 161, 168, 195, 203, 208–210, 212, 213–214, 222, 244 Keill, John, 194 Knibb Joseph, 61 Lagrange, xviii, 243, 250 Laplace, xviii, 144, 243, 250 Latitudinarianism, 38 Leeuwenhoek, 46, 76, 105, 113 Leibniz, xv, 13, 55, 76, 120, 159 – calculus, 194 – and Hooke, 16, 67, 70, 76, 86, 90 Lely, Peter, 2 Little Ice Age, 61, 223, 256 Lister, Martin, 67–68 Locke, John, 9, 16, 76 – De Motu, 187 – and Newton, 187 London, xvi, 2, 6, 10, 20, 31, 45, 52, 60, 207, 212 – Fire, 89 – plague, 89 longitude, problem of, 41, 46, 48, 57, 74–76, 78–81, 93, 101, 105, 161, 207, 209, 212, 214, 234, 245 Lower, Richard, Dr., 53, 62, lunar theory, 75, 79–80, 169, 230, 238 Magalotti, Count, 123 Manuel, Frank, 26, 130, 147 Mariotte, 110, 118–119, 174, 245 Mars, 53, 168, 203, 204, 208, 211, 213–214, 222–223, 244 Martin (Martyn), John printer, 52, 61, 91, 97, 115 Maunder minimum, 223 Mayow John, 128 mechanical philosophy, 38, 45, 145 microscopy, xv, 22, 24, 46, 87, 105–106, 247 Mills, Peter, 31, 89

Index

277

Montague House, see Hooke, architecture Montague Lord, 73, 121 Monument, 6–7, 70, 101–102, 109, 113, 132 – experiments, 11, 104, 109, 113, 129–131, see also Hooke Moore, Sir Jonas, 93, 223, 263 motion, laws of, see collisions motion quantity of, 55, 154 natural philosophy, see Hooke, Newton Nauenberg, Michael, xi, 186, 200–201 Neile, Sir Paul, 34, 37, 41, 55, 62, 205 Newton, Isaac, xiii–xviii, 7, 14–20, 22, 25–26, 45, 51, 56, 76, 84, 101, 114, 130– 131, 145, 157, 165, 167–168, 190, 193, 197, 200, 204–205, 208, 227, 231, 235, 237–238, 241–243, 246, 248 – aether theory of gravity, 168, 173 – alchemy, 170, 173, 181, 189, 243, 255 – Boyle’s Law, 118–119 – calculus, 76, 159 – Cambridge, 29, 51, 68 – centrifugal force, 191, 196, 245 – centripetal force, 167, 187, 191 – comets, 112, 215 – corpuscular nature of light, 145 – correspondence, 126, 193 – with Hooke, 178–182, 196, 214, 229 – De Motu, 68, 99, 132, 172–173 183, 186–187, 201 – and Flamsteed, 109 – gravity, 168, 171, 196, 198 – and Halley, 27, 29, 114, 170–173, 193, 199 – Halley’s Comet, 173 – and Hooke, 14, 29, 70, 98–99, 116, 118, 126–127, 135–137, 139–142, 147, 153– 154, 166, 169, 173, 177–182, 189, 196, 198, 229–230 – and Huygens, 173, 194 – inverse-square law, 122, 159, 167–168, 170, 172, 177, 182–183, 198, 201 – Kepler’s laws, 165, 186–187, 189, 201 – light and color, 57–58, 126, 135–137, 139–141, 148 – Lucasian Professor, 129 – lunar theory, 75, 79–80, 238 – mathematics, 79, 129, 149, 170, 221 – Micrographia, 117, 144, 173, 209, 244 – natural philosophy, 157–159, 161 – and Oldenburg, 95, 147 – Opticks, 142–145, 159, 163 – planetary motion, 85, 99

278

Index

– president RS, 74, 76–77 – Principia, xiv, 67–68, 100, 157–159, 165, 168, 173, 187–189, 214, 229–231, 234, 243, 245–246 – reflecting telescope, 57, 64, 107, 144 – and Royal Society, 122 – universal gravitation, 117 Oldenburg, Henry, xv, xvi, xviii, 13, 21, 37, 51, 53, 60–61, 63, 67 – balance spring watch affair, 93–98, 123 – and Boyle, 122 – correspondence, xv, xix, 62, 67, 90, 213, 242 – and Hooke, xv, 13, 21, 26, 30, 82, 86, 90–99, 115, 122–126, 132 – and Huygens, 92–95, 108, 174 – Newton-Hooke affair, 58, 95, 136, 138–142, 147, 161, 196 – Transactions, 50, 60, 66, 70, 90, 108, 210 Opticks, see Newton Oxford, 2, 3, 34, 36, 40, 60, 228 – Christ Church College, see Hooke – Wadham College, see Wilkins Oxford club (group, society), 2, 34, 36–37, 40, 116 Papin, Denys, 67, 71, 100, 127 parallax, see Hooke pendulum, pendulum clocks; see Hooke, Huygens Pepys, Samuel, 15, 127, 220 – on Brouncker, 14 – Diary, 25, 29, 42 – on Hooke, 14, 60, 112, 131, 133, 223 – relationship with, xvi, 7, 13, 18, 228 – on Micrographia, 133 – plague, 1665–1666, 120 – and Principia, 68 – and Royal Society, 1, 25, 68, 99, 121, 126 periodicty of comets, see Hooke, comets; Halley Petty, William, 2, 25, 34, 37, 40–41, 65, 69, 85, 89, 99, 126, 223 Philosophical Collections, see Hooke Philosophical Transactions, see Hooke, Oldenburg plague, xvi, 5, 25, 45, 50–2, 60, 89, 106, 165, 167, 211, 232 planetary motion, see Halley, Hooke, Newton, Wren Plus Ultra, see Glanvill Pope, Walter, 61 Posthumous Works, see Hooke Power, Henry, 4, 82, 89, 103, 118,-119, 133 Principia, see Halley, Hooke, Newton

Index

279

Protectorate, 33, 36, 40 Pugliese, Patri, 128, 183, 186, 189 Puritanism, 2, 9, 39–40 Ragley Hall, see Hooke, architecture Ranelagh (Ranelaugh), Lady, 10, 21, 27, 29, 40, 51 Reeves, Richard, 205, 220–221 reflecting telescope, see Gregory, Hooke, Newton Restoration, 22, 33, 34, 36–38, 43, 82, 118, 203 Ricciolus (Riccioli, Giovanni Battista), 81, 207 Robinson, Tancred, 67–68 Rømer, Nicolas, 161 Rooke, Lawrence, 2, 10, 34, 36, 40–41 Royal College of Physicians, 34, 37, 41 – College of Physicians (Hooke structure), see Hooke, architecture, Royal Society of London, xiii–xvi, xviii, 10, 19–20, 25, 30, 38–39, 41, 45–80, 56, 58, 59, 61, 65, 77, 123, 132, 165, 171, 177, 195, 234–235, 237–238, 241, 247 – Arundel House, 41, 52–53, 61 – balance-spring watch, see also Hooke, Huygens – and Boyle, 34, 37, 41, 50, 65, 77, 91, 99, 119–120 – Chelsea College, 53 – Crane Court, 68, 76 – Charles II, 36, 42, 48 – “Classified Papers”, 69, 128, 163, 229, 238, 248 – Curators, 85, 90, 100, 150 – Cutler, Sir John, 87 – experimental program, 65, 73, 119 – Fire, 52, 89 – founding, xiv, xv, 3, 17, 33–43 – Gresham College, 18, 41, 76 – and Hevelius, see also Hooke – Hooke Folio, see Hooke, Folio – and Huygens, 49, 54–55, 58–59, 92–94, 233–234 – laws of motion, see collisions – and Leeuvenhoek, see Leeuvenhoek – and Leibniz, see Leibniz – membership, 37, 85 – microscopy, 105 – and Newton, see Newton – Papin, Denys, 100 – Philosophical Transactions, 50, 60, 67, 74, 78; see also Hooke, Oldenburg – precursors, see 1645 group, Oxford group, invisible college – presidents, xv, 14, 21, 26, 41, 65, 69, 73–74, 112, 121, 228, 234 – Principia, 68–69, 74, 76, 107, 182

280 – – – – –

Index

plague, 50–51, 89, 165, 211 Royal charter, 37, 48, 49 Sprat, History of the Royal Society, see Sprat transfusions, 53, 62–63 Wilkins Lecture, 1, 8, 31

scientific revolution, xiv, 6, 25, 45, 77, 227, 241–242 Sloane collection, British Museum, 19, 28, 29, 229, 230, 237 Sloane, Sir Hans, 73–74, 76–77, 234 South, Robert, 38 Southwell, Robert, 46, 73, 121, 126, 231–232, 234 Sprat, Thomas, 9, 34, 36–43, 52–53, 92, 94–95, 121, 124 Spinoza, xv, 62 St. Paul’s Cathedral, 22, 24, 30, 52, 59, 90, 101, 104, 120, 129, 231, 246 St. Helen Bishopsgate, 237, 248, 250 stellar aberration, 63, 217, 219, 224–225, 239 Steno, Nicholas, 232, 239 Stephens, Elizabeth, see Hooke Stubbe, Henry, 37, 42 sunspots, 143, 204, 213, 223, 244 telescopic sights, see Hooke, Hevelius thermometry, 49, 50, 233 Tillotson John, 13, 18, 231, 239 Torricelli, Evangelista, 59, 101, 105, 127 Towneley, Richard, 82, 118–119 transfusions, 53, 62–63 Trinity College, Cambridge, 183–184, 200, 228 Turnbull, H.W. (Corresp.), xiv, xvi, 126, 193 Vaughan, John, 69, 121 verge escapement, see escapement, Huygens Wadham College, Oxford, 2, 10, 34, 40 Waller, Richard, 2, 8–10, 13–18, 25–29, 67, 74–75, 78, 86, 118, 132, 143, 150–151, 154–156, 160–161, 195, 234–237, 239 Wallis, John. 2, 10, 15, 34, 36–42, 50–51, 53–55, 57–58, 60, 62, 64, 67, 76, 78, 85, 106, 159, 233 Ward, Seth, Bishop of Salisbury, 37, 38, 40–41, 43, 55, 57, 65, 81, 136, 207 wave theory of light, see Hooke, Huygens Westminster Abbey, 10, 132, 231, 248, 250 Westminster School, 2, 9, 10, 17, 78, 81, 231, 248 Whiteside, D.T., 157, 177, 187, 189, 198, 221

Index

281

Wilkins, John, xvi, 1–3, 9–10, 17, 22, 25, 34, 36–41, 43, 46, 51, 53, 58, 60, 65, 85–87, 89, 93, 106 Wilkins Lecture, xiv, 1, 8, 31 Willen church (St. Mary Magdelen), 70, 132, 248–249 William and Mary, 78 Willis,Thomas, 2, 3, 34, 40 Willughby, William, 63 Woodroffe, Edward, 31, 69 Wren, Sir Christopher, xv, xvi, xix, 9, 16–17, 22, 33, 37–38, 40, 65, 76–77, 85, 89 – aether, 109, 155 – architecture, 7, 17, 21, 24, 51–52, 58 – City churches, 6–7, 11, 90 – collision theory, 54–56, 62–63, 106 – comets, 50, 112 – founding the RS, see Royal Society – Greenwich Observatory, 7, 58 – Gresham Professor of Astronomy, 36, 40 – and Hooke, xv, 3–5, 13, 15, 17–24, 27–31, 58, 66, 90, 106, 116, 131, 132, 166, 169, 186, 198, 200, 202, 205, 221, 228, 246, 248 – inverse-square law, 177, 196 – laws of motion, see collisions – and Micrographia, 132–133 – and Monument, see the Monument – and Oldenburg, 13, 97, 122 – at Oxford, 10, 34 – planetary motion, 29, 108, 114, 165, 169–170, 172, 182, 186, 193, 195–196 – rebuilding London, post-Fire, 31, 52, 61, 69, 89 – and Royal Society, 65, 77, 213, 231 – presidency of, 99, 121, 126 – St. Paul’s, 90, 120, 228, 231 – Savilian Professor, Oxford, 40 – Sheldonian Theater, 38, 48, 59