Newton Defends His First Publication: The Newton-Lucas Correspondence

Newton Defends His First Publication: The Newton-Lucas CorrespondenceAuthor(s): Richard S. WestfallSource: Isis, Vol. 57, No. 3 (Autumn, 1966), pp. 299-314Published by: The University of Chicago Press on behalf of The History of Science SocietyStable URL: http://www.jstor.org/stable/228362 .

Accessed: 09/05/2014 00:30

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

The University of Chicago Press and The History of Science Society are collaborating with JSTOR to digitize,preserve and extend access to Isis.

http://www.jstor.org

This content downloaded from 169.229.32.137 on Fri, 9 May 2014 00:30:20 AMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=ucpress

http://www.jstor.org/action/showPublisher?publisherCode=hss

http://www.jstor.org/stable/228362?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


Newton Defends His First

Publication:

The Newton-Lucas Correspondence

By Richard S. Westfall *

Mr Aubrey I understand you have a letter from Mr Lucas for me.

Pray forbear to send me anything more of that nature.l

W ITH A STACCATO FLOURISH of his most trenchant style Isaac Newton brought to a close his correspondence of four

years with the English Jesuits of Liege. More than a correspondence was concluded. The period of discussion and exchange initiated in 1672 by the publication of Newton's first paper on colors now ended conclusively. For the second time within a space of six years plans for a fuller publication of his work in optics were dropped. After a fiery climax of wild fury the curtain fell on one act of Newton's life, marking the beginning of a long intermission of solitude and recuperation. The correspondence of Newton and Lucas holds interest then for a number of reasons. It contains a point of significance in the history of optics. It clarifies New- ton's abortive plans for publication. Above all, it illuminates Newton's personality - in a glaring and pitiless light.

As the culmination of the series of exchanges touched off by the paper of 1672, the correspondence with Lucas takes on its full significance when it is viewed in the light of them all. It has become a commonplace in Newtonian literature to suggest that the publication of the paper unleashed a torrent of criticism which left a permanent scar on Newton's psyche.2 A careful examination of the record hardly bears out the inter-

* Indiana University. Support from the Na- tional Science Foundation, which I gratefully acknowledge, has helped to make this article

possible. 1Newton to Aubrey, c. June, 1678, The

Correspondence of Isaac Newton, ed. H. W. Turnbull (3 vols. Cambridge: Published for the Royal Society at the Univ. Press, 1959-), Vol. 2, p. 269. While I cannot refrain from

quoting it, this magnificent letter was probably never sent. It exists only as a draft, and another draft (ibid., pp. 266-268), the same

message diluted to three pages, was undoubt-

edly the one sent.

2 See David Brewster, Memoirs of the Life, Writings, and Discoveries of Sir Isaac Newton (2 vols., 2nd ed. Edinburgh: Constable, 1860), Vol. 1, p. 69: " No sooner were these important discoveries given to the world, than they were criticised and assailed with a degree of viru- lence and ignorance which have not often been combined in scientific controversy." Cf. L. T. More, Isaac Newton, a Biography (reprint of

orig. ed. New York: Dover, 1962), pp. 82-92; E. N. da C. Andrade, Sir Isaac Newton (2nd ed. Garden City, N.Y.: Doubleday, 1958), pp. 64-65.

Isis, 1966, VOL. 57, 3, No. 189. 299



RICHARD S. WESTFALL

pretation. In the first four months after publication there were praises from Henry Oldenburg, a favorable comment from Christiaan Huygens, and another from James Gregory (which he may or may not have received from John Collins). Robert Moray's uncomprehending questions required a brief answer. Father Pardies' two letters probed more deeply, but they were courteous and respectful and indeed not lacking in praise for Newton. What is more, Father Pardies accepted Newton's replies and retired from the field. Only Robert Hooke's paper can truly be called critical. To be sure, it was more than critical. It was condescend- ing and offensive, and one can understand only too well the indignation that it might have aroused. Nevertheless it is difficult to describe such a driblet of responses, requiring a total of four replies, as a torrent, much less as a torrent of criticisms.3 And however offensive Hooke's critique may have been, it is difficult to see how a normal person could have allowed it to generate the savage bitterness revealed in Newton's reply, as though nothing less than Hooke's humiliation could atone for his crime. Of course, Newton was not a normal man. All too apparent in the correspondence of early 1672 are the terrible anxieties that publication excited; unable to be contained any longer, they poured forth in the reply to Hooke. It was not the last time that Newton's inner turmoil exploded into public view.

Newton had always feared publication. Only in the warm glow of the Royal Society's favorable reception of his telescope had he ventured to submit his paper. The telescope in its turn had not been proffered at Newton's initiative; the Royal Society had requested it when chance had told them of its existence. Newton did not step lightly into the public gaze, and the slightest hint of menace in its aspect made him long for shelter again. Already, as he was completing the reply to Hooke, he had written to Collins of his intention not to publish the optical lectures.4 Oldenburg was more difficult to silence. Not only did he refuse to understand two clear hints,5 but he clumsily blundered beyond that. On 6 July Newton proposed a series of eight questions, subject to experimental answer, to test his theory of colors. The eight questions form a logical progression leading from basic propositions to the final conclusion. The answers had already been supplied, of course, by the experiments recorded in the papers of February and June, and Newton clearly intended the questions as a polemic device that would force opponents to follow the logic of his argument. Thus they would settle the issue conclusively. Alas, Oldenburg missed the point. Although his praise of the theory of colors had been the most lavish, he now asked if Newton could not also devise experiments to answer the questions.6

3 See my article " Newton's Reply to Hooke and the Theory of Colors," Isis, 1963, 54:82-96, 1672 (ibid., pp. 194, 210). for a more detailed analysis of the early 6 Oldenburg to Newton, 9 July 1672. The response to the paper of 1672. letter is lost, but there is an indication of its

4Newton to Collins, 25 May 1672 (Corre- contents in a note by Oldenburg (ibid., p. 211). spondence, Vol. 1, p. 161). Cf. Newton to Oldenburg, 21 Sept. 1672 (ibid.,

5 Newton to Oldenburg, 19 June and 6 July p. 237).

300



NEWTON DEFENDS HIS FIRST PUBLICATION

Nearly two months passed before Newton could bring himself to reply; and the reply, when it came, held more than a pinch of the sardonic.7

September, 1672, was less than nine months removed from Newton's first exchange of letters with Oldenburg. By any rational account the nine months were more a triumph than a debacle. By September, nevertheless, Newton was consciously trying to sever the connection. The letter of 21 September, after a silence of two months, was a deliberate brush-off. When Oldenburg wrote again, Newton apparently refused to reply. His correspondence with Collins was interrupted as well. Newton allowed a commentary by Gregory on the reflecting telescope, which Collins had forwarded, to remain without a reply for nearly three months and a gift of books not to be acknowledged for six weeks, before he wrote in December. A morbid fear of involvement seems to permeate what survived of the exchange with Collins. "You will pardon this long scribble in wch I have been the more particular," he concluded his remarks on the reflecting telescope, "because Mr Gregory's discours looks as if intended for the Press." 8 Although the discussion with Gregory, which Collins mediated, was always conducted with respect and restraint, Newton now allowed it to lapse.9 He pointedly refused to comment on a mathematical question raised by Rene Sluse.'0 In June, 1674, after a silence of nearly a year, the gift of a book on gunnery and trajectories elicited both a brief reply and an immediate apprehen- sion. " If you should have occasion to speak of this to ye Author, I desire you would not mention me becaus I have no mind to concern my self further about it." 11

A not dissimilar pattern marked the correspondence with Oldenburg. After silence had endured through the autumn, Oldenburg hit upon the happy expedient of writing about a totally different subject. Having won a response, he proceeded forthwith to send along Huygens' latest comments. Huygens questioned whether chromatic aberration could be as great as Newton claimed, and he expressed his belief in a two-color system. Above all, he asserted that the theory would be incomplete until the differences of the colors were explained by a mechanical hypothesis.12 That is to say, the comments were mildly critical, although they must be read in the light of earlier favorable, if brief, references to the theory of colors--references that Newton had received. It was March before a curt reference to the comments, though not yet an answer to them, arrived in London, and Newton concluded the brief letter with a request to be dropped from the Royal Society. Although he honored the society,

7 Newton to Oldenburg, 21 Sept. 1672 (ibid., a letter from Gregory through Collins which pp. 237-238). he had not answered, and he found an excuse

8 Newton to Collins, 10 Dec. 1672 (ibid., not to answer it at that time. p. 252). 10 Newton to Collins, 20 May 1673 (ibid.,

9 Newton did write to Gregory about the p. 282). telescope again in a letter through Collins of 11 Newton to Collins, 20 June 1674 (ibid., 9 April 1673 (ibid., pp. 269-271). A letter to p. 309). Collins on 17 Sept. 1673 (ibid., p. 307) acknowl- 12 Huygens to Oldenburg, 14 Jan. 1672/3, edged that he had received a long time earlier N.S. (ibid., pp. 255-256).

301



RICHARD S. WESTFALL

he said, "yet since I see I shall neither profit them, nor (by reason of this distance) can partake of the advantage of their Assemblies, I desire to withdraw." 13 Because a brief postscript mentioned the dues of the Royal Society, Oldenburg interpreted Newton's letter to mean that he could not afford the quarterly payments. He offered to have them remitted, and he passed on the letter to Collins, so that Newton was forced to explain himself a second time, referring this time to "rude- ness " he had met. "And therefore I hope you will not think it strange if to prevent accidents of that nature for ye future I decline that con- versation wch hath occasioned what is past." 14

Meanwhile Huygens required an answer. In April he received it. To the recognized leader of European science, who had commented respect- fully on a paper by a young man hitherto unknown to the scientific com- munity, Newton chose to reply in tones suitable to a recalcitrant schoolboy. Huygens, he said, examined the nature of colors in an improper way, compounding colors that were already compounded instead of analyzing the light first into its component rays. " This will prove a tedious 8c difficult task to do it as it ought to be done but I could not be satisfied till I had gone through it. However I onely propound it, and leave every man to his own method." Newton proceeded then to explain why all colors could not be compounded from yellow and blue. " This is so plain that I conceive there can be no further scruple especially to them who know how to examin whether a colour be simple or compounded & of what colours it is compounded: which having explained in another place I need not now repeat." 15 Huygens did not mistake Newton's tone.'6 His response icily pointed out two contradictions in what Newton had said; and, he added, " seeing that he maintains his doctrine with some warmth, I do not care to dispute." 17 That was the final straw.

As for M. Hugens expression that I maintain my doctrine wth some concern, I confess it was a little ungratefull to me to meet wth objections wch had been answered before, without having the least reason given me why those answers were insufficient .. .18

Repeating his intention "to be no further sollicitous about matters of Philosophy," he concluded by refusing all further correspondence on the subject.

s3 Newton to Oldenburg, 8 March 1672/3 (ibid., p. 262). I am especially struck by the "Je vous puis assurer, que Monsieur Newton

phrase "I see I shall neither profit them . . ." est une personne de grande candeur, comme in which Newton interprets a little criticism il est homme qui ne dit l1gerement des choses and discussion as total rejection. qu'il avance" (ibid., p. 268).

14 Newton to Collins, 20 May 1673 (ibid., 17 Huygens to Oldenburg, 10 June 1673, N.S.

p. 282). (ibid., p. 285). When he wrote again on 14 15 Newton to Oldenburg, 3 April 1673 (ibid., June, Huygens had evidently regretted the

pp. 264-265). tone of his response, and he asked Oldenburg 16 Neither did Oldenburg, and when he for- not to send it to Newton.

warded the comment to Huygens on 7 April 18 Newton to Oldenburg, 23 June 1673 (ibid., he felt obliged to include an explanation: pp. 292-295).

302




And then silence. The effort - which had begun the summer before - to cut his ties with the world succeeded at last. In the autumn of 1673 he responded to Collins' request for a letter of testimony for a young mathematician, Michael Dary. In 1674 two letters of Collins drew cold and laconic replies. A letter of 19 October 1675 from Collins to Gregory mentioned that " I have nott writt to or seene [Newton] this 11 or 12 Months," and went on to say that he had apparently abandoned mathematical studies.19 From June, 1673, until the autumn of 1675 Newton exchanged one set of letters with Oldenburg. Since Collins and Oldenburg were his sole contacts with the scientific world outside Cambridge, Newton had deliberately iso- lated himself. Correspondence with Dary and with another young mathematician, John Smith, was characterized by such an obvious master-scholar relationship that it does not alter the judgment. Although his brief contact in 1672 with the world outside the cloister may appear unexciting enough to us, to Newton it appeared sufficiently menacing that he could not too quickly regain the solitude which was incapable of touching and wounding his morbid sensitivity.

Into this solitude there plunged, in the autumn of 1674, the first letter from Franciscus Linus, S.J., Professor of Hebrew and Mathematics in the English college at Liege. Letters from Linus were difficult to reconcile with solitude. Born Francis Hall in 1595, Linus had filled the chair in Liege long and honorably,20 but apparently he had too long been raised on his podium too high above contradiction. In 1674 he was approaching eighty; if we may judge by the letter, he was well into his dotage. To be blunt, it was the letter of an old fool. He denied outright that the basic experiment with the prism, in which a spectrum was projected on the wall, could have worked the way Newton reported it. There must have been clouds near the sun which were illuminated and acted as larger suns, increasing the angle of the incident pencil of rays and producing the result. The whole prism must have been illuminated, and the length of the spectrum was obviously proportional to that of the prism. " What I have heere sayd, needes noe other confirmation then meere experience, wch any one may quickly try." He had done the experiment himself some thirty years earlier for Sir Kenelm Digby, who had taken many notes on it. " Wch Industry if they also had used, who endeavour to explicate the aforesayd difference betwene the length and breadth of this coloured spectrum, by the receaved laws of Refraction, would never have taken soe impossible a task in hand." He closed with a cheery word of encouragement for the " learned person " who had written the paper; he himself might have made the same mistake had the sun been behind a cloud when he first tried it.21

The situation was ripe with comic possibilities as Linus' total lack of understanding covered its nakedness with senile self-confidence. Instead of

19 Collins to Gregory, 19 Oct. 1675 (ibid., patetic (1595-1675)," Osiris, 1962, 14:222-253. p. 356). 21 Linus to Oldenburg, 26 Sept. 1674 (Corre-

20 See Conor Reilly, S.J., " Francis Line, Peri- spondence, Vol. 1, pp. 317-319).

303



RICHARD S. WESTFALL

a Falstaff to play the scene, however, it had in Newton a melancholy Dane. The snort of laughter Linus deserved was impossible for him. When we consider the reply to Huygens, we might expect to find that Linus' letter provoked a greater rage. This too did not happen. Quite the contrary, instead of driving Newton further into his shell, Linus became the occasion of his re-emergence.

The effect was not produced immediately. Newton's first reaction, contained in his one letter of 1674 to Oldenburg, was a blunt refusal to discuss.22 During the following spring Newton paid a visit to London, and he attended a meeting of the Royal Society. He met Hooke. He learned -what was surely the crucial factor--that Hooke had been converted to Newton's theory of colors.23 Hooke, after all, was the author of the one serious criticism he had received. The following November Newton received an indirect communication from Oldenburg. It was Linus' third letter, demanding that his second letter be printed in order to preserve his reputa- tion. The second letter, which, like the first, had simply denied that the experiment with the prism could have worked as it was reported, had been written in February.24 Newton had seen it during his visit to London and had told Oldenburg it was not worth a reply. When the third letter arrived, Oldenburg did not venture to send it directly, but rather, through an inter- mediary. To Oldenburg's surprise a different Isaac Newton received it. Not only did he reply to Linus, but at the end of the letter he offered to send the Royal Society another discourse on colors.25

Something of the events of early 1672 were now re-enacted. Faced with some form of publication, Newton could not easily part with his papers. Two weeks later they were still with him. He had intended to send them that week, he wrote, " but upon reviewing them it came into my mind to write another little scrible to accompany them." 26 Early in December they finally went, and the " Hypothesis of Light" and the " Discourse of Obser-

22 Newton to Oldenburg, 5 Dec. 1674 (ibid., pp. 328-329).

23 See the "Hypothesis of Light" (ibid., pp. 362-363):

I was glad to understand, as I apprehended, from Mr Hooks discourse at my last being at one of your Assemblies, that he had changed his former notion of all colours being compounded of only two Originall ones, made by the two sides of an oblique pulse, & accomodated his Hypothesis to this my suggestion of colours, like sounds, being various according to the various bignesse of the Pulses.

In the context of Newton's papers on colors the statement that Hooke had abandoned the notion of compounding colors from two basic ones and had accepted the idea that each color is distinguished by a certain size of pulse was equivalent to stating that Hooke had abandoned a modification theory for one of analysis; cf. Newton to Oldenburg, 13 Nov. 1675, in which he relates that when Linus' letter

was read before the Royal Society (apparently when Newton was present) it was Hooke who spoke of his experiment " as a thing not to be questiond" (ibid., p. 358).

24 Linus to Oldenburg, 25 Feb. 1675, N.S. (ibid., pp. 334-336).

25 Newton to Oldenburg, 13 Nov. 1675 (ibid., p. 358).

26 Newton to Oldenburg, 30 Nov. 1675 (ibid., p. 359). The deprecatory phrase, "little scrible," is a typical Newtonian device to ward off possible criticism by pretending not to be committed. Cf. the "Hypothesis" (ibid., p. 361):

I have not scrupled to describe one [an hypothesis] so far as I could on a sudden recollect my thoughts about it, not con- cerning my self whether it shall be thought probable or improbable so it do but render ye papers I send you, and others sent formerly, more intelligible.

A draft of the " Hypothesis " had in fact been written as early as 1672.

304




vations," composed and nearly published almost four years before, were, if not published, at least displayed before the membership of the Royal Society and registered in their books. Linus, then, produced one effect: without his letters the great papers of 1675 would probably not have been sent to the Royal Society.

Except insofar as Linus' letters occasioned their being submitted, the papers of 1675 did not figure in the correspondence with the Liegeois, and there is no need to discuss their content here. One event connected with the papers is relevant. No sooner had the " Hypothesis of Light" been read before the Royal Society than Hooke asserted - or at least was reported to Newton to have asserted - that most of it was contained in his Micro-

graphia. When he had sent in the " Hypothesis," Newton had written that he " had formerly purposed never to write any Hypothesis of light 8c colours, fearing it might be a means to ingage 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 other by occasion) may defend me from yt fear." 27 Within two weeks he found himself heatedly writing a letter of self-defense. And because he was never able to purge his mind of an imagined wrong, he wrote a second letter three weeks later after he had had time to brood more fully.28 Although a handsome letter from Hooke dispelled the issue at that point, it had already revealed to Newton the same alarming menace from which he had recoiled in 1672. Nor was the ephemeral controversy with Hooke the only thing. The "Hypothesis " had mentioned in passing an experiment with static electricity, which excited the interest of the Royal Society. When they were unable to make it work, they wrote for further instructions, and Newton had to describe the experiment anew, and more than once, before they were satisfied - another source of fretful involvement.

In the midst of this agitation a new letter arrived from Liege. Linus was dead, but one John Gascoines, his scholar, announced the intention to vindicate his master's name. He began by demanding that Linus' second letter be published at once; and, asserting the accuracy of their experiments in Liege, he challenged Newton's report of his own and requested that the Royal Society settle the issue by having the experiment tried before themselves.29

With some exaggeration, perhaps, but not wholly without reason, Newton read Gascoines' letter as another challenge to his honesty. In the very letter in which, for the second time, he rejected Hooke's claim he replied to Gascoines as well. After describing the basic experiment with the prismatic spectrum once more, he recited the history of the correspondence with Linus:

This is ye history of Mr Linus buisines so far as I know't: wch I have set down yt his friends may see he has not been dealt wth obliquely as they seem

27 Newton to Oldenburg, 7 Dec. 1675 (ibid., pp. 405-406) and 10 Jan. 1675/6 (ibid., p. 408). p. 361). 29 Gascoines to Oldenburg, 15 Dec. 1675

28 Newton to Oldenburg, 21 Dec. 1675 (ibid., (ibid., pp. 393-395).

305



RICHARD S. WESTFALL

to apprehend. All I think that they can object to you is that you were at a stand becaus you could not ingage me in ye controversy, & to me yt I had no mind to be ingag'd: a liberty every body has a right to &8 may gladly make use of, sometimes at least, &8 especially if he want leisure or meet wth prejudice or groundles insinuations.30

Gascoines quickly passed from the scene. A dilettante who did not enjoy the respect even of his fellow Liegeois, he was incapable of carrying on the discussion.31 The letter already cited measured the extent of his partici-

pation. Linus was succeeded by Anthony Lucas, however, and Lucas took up the cause with a letter in May. Lucas is usually considered as one of the abler men who disputed the theory of colors with Newton. Certainly there is some element of truth in the judgment. His first letter began with the confirmation of Newton's basic experiment, which the Liegeois had been unable to perform successfully heretofore. He devised further experiments as well, and if he disputed Newton's theory, at least he disputed it on experimental grounds. Nevertheless, a close scrutiny of Lucas' letters simply cannot sustain a high regard for his scientific ability, and it cannot be main- tained that the central interest of his correspondence with Newton lies in its intellectual content.

Some years ago Rosenfeld pointed out the imprecision of Lucas' experiments compared to Newton's.32 What is more, his letters manifest a failure to comprehend the very nature of experimental investigation. In Newton's reply to Lucas' first letter, after thanking him for examining the theory with experiments, he had made an important methodological assertion:

But yet it will conduce to his more speedy & full satisfaction if he a little change ye method wch he has propounded, & instead of a multitude of things try only the Experimentum Crucis. For it is not number of Expts, but weight to be regarded; & where one will do, what need of many? [Let Lucas examine the experiments given.] For if any of those be demonstrative, they will need no assistants nor leave room for further disputing about what they demonstrate. The main thing he goes about to examin is ye different refrangibility of light. And this I demonstrated by ye Experimentum Crucis. Now if this demonstration be good, there needs no further examination of ye thing; if not good ye fault of it is to be shewn, for ye only way to examin a demonstrated proposition is to examin ye demonstration.33

Lucas' response shows how little he understood what Newton was saying. He objected to Newton's proposal to examine those experiments by Lucas

which Lucas himself considered most important,

... unlesse the defect of these two experiments, considered by him, be shown to run through the rest allso, for otherwise the remainder of the experiments

30 Newton to Oldenburg, 10 Jan. 1675/6 31 See Lucas to Newton, 4/14 March 1677/8 (ibid., p. 411). When Linus' second letter was (ibid., Vol. 2, p. 251). published and Newton read it again, he wrote 32 L. Rosenfeld, " La thdorie des couleurs de

once more in vindication of his honor (Newton Newton et ses adversaires," Isis, 1927, 9:44-65. to Oldenburg, 29 Feb. 1675/6, ibid., pp. 423- 33 Newton to Oldenburg, 18 Aug. 1676

425). (Correspondence, Vol. 2, pp. 79-80).

306




will stand still in their full force in opposition to his Experimentum crucis, and, for ought I know, of as full weight too.34

Newton himself would object to the procedure had he published all the experiments he claimed to have made.

For, suppose then, that one or two were shewn unconcludeing; questionlesse Mr Newton would not therfore have thought his Theory defeated, while the Experimentum crucis remaind still unshaken, seing it might still have had the same weight he now fancies it to have.35

That is to say, Lucas espoused the grab-bag method of experimentation. That an experiment might be a precise question put to nature under conditions controlled to insure a clear answer was beyond his ken. " Experi- ment " to him was equivalent to " observation." Any experiment stood on a plane of equality with any other; and since apparently no system of order was expected to reveal itself in their outcome, theory could be determined by the number of experiments in the majority - a strangely democratic theory from the Society of Jesus.

Lucas' conception of light was no more impressive than his conception of method. He suggested "that not onely the direct sun beams but alsoe other extraneous light might possibly influence the colour'd spectrum...." If there were a more luminous body behind the sun, we should probably see the colors of the spectrum reversed in order.36 When he placed a circle of black paper against the dark shutters of his window, the circle appeared oblong but not colored. Hence, he concluded, " were there the same pro- portion of light betweene the Sun and the Solar sphere as is between the black circle and window shutts, wee might still have an oblong spectrum in a closed room, th6 without any variety of colours at all." 37 Lucas appeared to believe that Newton's theory held the rays themselves to be colored and to be refrangible at a certain angle because of their color. When he tried to perform the experimentum crucis and found red rays among the purple, he decided that the whole theory was erroneous. According to the theory, one might compare an unrefracted ray of light to " a twist consisting of 5 differently coloured threads, namely red, yellow, green, blew and violet." Suppose there were a porous body reputed to " bend each thread after a different manner, according to their respective colours. . . ." If red threads were still found " interlaced" with the violet, no one could rationally maintain " the red threads, confined of their owne nature, to a certaine determinate degree of bending .. ." 38 The colored spectrum, then, was not caused by the different refrangibility of distinct rays, but rather " the red rayes are of their owne nature wholly indifferent to the refractions of the red and violet. i.e. to the most opposit degrees of

34 Lucas to Oldenburg, 23 Jan./2 Feb. 1676/7 pp. 10-11). (ibid., p. 191). 37 Lucas to Oldenburg, 13 Oct. 1676 (ibid.,

35 Ibid. Cf. Lucas to Oldenburg, 23 Oct. p. 108). 1676, N.S. (ibid., pp. 104-105). 38 Lucas to Oldenburg, 13 Oct. 1676 (ibid.,

36 Lucas to Oldenburg, 17 May 1676 (ibid., p. 106).

307



RICHARD S. WESTFALL

refractions in Mr Newtons Theory." 39 In their strict interpretation Lucas' words appear to assert the reign of chance over law in nature. Beyond that surprising distinction, his conception (almost unconception) of light can claim no place in the history of optics.

Although his experiments were not good and his theory bad, Lucas did have one thing. He had a measurement. If his first letter confirmed New- ton's basic experiment, Lucas' spectrum did not measure five times its width as Newton's did; it was only three and a half times as long. Newton refused even to consider that Lucas' measurement could be correct, and historians have been almost unanimous in asserting that his obstinacy prevented his discovery of the achromatic lens. Lucas must have been using a prism made of a different glass; the shorter spectrum was the result of its lower dispersive power. Had Newton been able freely to consider the implications of Lucas' measurement, he would have seen at once the possibility of correcting chromatic aberration.40 Unfortunately, a close examination of the correspondence strips poor Lucas even of this last distinction. Our concept of dispersive power is, in effect, the ratio of the angle of dispersion to the mean refraction of the beam. Only the angle of dispersion was implicit in the length of the spectrum. What was the angle of mean refraction? That would depend, among other things, on the refracting angle of the prism, and Newton was suspicious of Liegeois precision. He saw immediately that the length of the spectrum would be related to the total refraction. Newton measured the angles of his prisms to the minute of a degree; they said only that their angle was about 60 degrees. Perhaps this implied that they had not measured at all but had merely assumed that the three angles of the prism were equal. If Lucas were using a smaller angle, the difference in length would be accounted for. If the sides of his prism were concave, the image would tend to be shortened and the difference would be accounted for. It would be accounted for if he had not measured the whole length of the spectrum but only its straight sides. Through one exchange of letters Lucas ignored Newton's demand for exact measurements, but Newton's insistence ended by winning a full concession from him:

I thought it indeed impropper (and think so still) to spend time on the precise length of the coloured images before the maine Theory be agreed on ... yet ... I resolved on the first convenience of weather, prismes and leisure to make the experiments a new, and acquaint him with the result.41

Meanwhile three considerations should confirm "Mr Newtons repute in point of accuratness...."

... lo that the sides of his prism were somwhat convex, wheras mine are considerably concave. 2? that his observations seeme to suppose the ayre free

39 Lucas to Oldenburg, 13 Oct. 1676 (ibid.). In the copy of this letter that Lucas sent to as pretended by Mr Newton" (Lucas to Hooke, Hooke early in 1678 he added a further elab- ? Feb. 1677/8, ibid., p. 248). oration of his meaning-" that different rays 40 E.g., n. 3, ibid., p. 81. (the red ones for instance) have not any set 41 Lucas to Oldenburg, 23 Jan./2 Feb. 1676/7 degree of refrangibility propper to themselves, (ibid., pp. 190-191).

308




from gross vapours; wheras mine imply no such supposition, as haveing bin cheefly made in ye morning between 6 and 7 a clocke at which time not onely the vapours are thicker than at midday, but allsoe the Section of the Atmosphere made by the Sun beames, considerably greater. 30 that somewhat allso may be allowed for the difference of glasse the prismes are made of; for the different diameters of the Sun at severall times of ye years 8&c.42

Which appears to say that there had not been any exact measurements whatever. It is, of course, possible that the men in Liege used a glass with a lower dispersive power. There is absolutely no solid evidence to demonstrate that they did, however. Newton had every reason to suspect their precision. They had required a year and a half even to project a spectrum successfully. Nothing in the letters of Lucas, much less of Linus, suggested even an approach to the standards of accuracy that Newton demanded of himself. Optics, then, does not appear to have teetered on the brink of discovering achromaticity in 1676. It remains true, of course, that Newton would have rejected it because the concept was inconceivable to his mechanical philosophy - as it continued to be inconceivable to the very men who perfected the achromatic lens in the eighteenth century.

The central interest of the Lucas correspondence lies, not in its optical content, but in the revelation it affords of Newton. In 1672 and 1673 something of his inner tensions had revealed itself in the passion of his replies to Hooke and to Huygens. As though frightened by what he had seen of himself, Newton had withdrawn again into seclusion. Now Lucas was to be the unwitting agent of an undamped explosion. Already he was feeling aggrieved when he composed his reply to Lucas' first. His answer,

42 Ibid. The irrelevant considerations under Lucas' second point are a further illustration of his knowledge of optics. The variation of apparent diameter of the sun, mentioned under the third point, was suggested to him by Newton. At the end of his letter of 13 Oct. 1676 Lucas had said he would check Newton's measurements when he had a chance but considered it preposterous to worry about the " precise" length of the spectrum before the theory was confirmed (ibid., p. 108). In his letter of 4/14 March 1677/8 he said, " As to ye angle of my prisme, I have measured it anew with a Sector, for your satisfaction; and finde it still between 59 and 60 deg." Furthermore, he had obtained another prism, but the glass was so impure and the sides so irregular that he could do nothing with it (ibid., p. 252). " Between 59 and 60 deg." is not an impressive measurement beside Newton's, and what he says of the other prism does not increase our confidence. Newton thought that he had proof from Lucas' letters that the angle could not have been over 40 degrees. In one experiment Lucas had set one face of the prism per- pendicular to the incident beam so that it was refracted only at the second face; as Newton argued, if the refracting angle had been much

greater than 40 degrees, there would have been total internal reflection at the second face. The question might hinge on the number of prisms Lucas had. In the letter cited above he reported that he got "another" prism, implying a second. It is difficult, however, to imagine that he could have mistaken 40 for 60 degrees, and in his first letter he cited an experiment which would have required three prisms if it was in fact performed. It appears to me that the crucial piece of evidence is his admission that the faces of his prism were very concave. Moreover, he never did say what part of the spectrum he measured, the total length or just the straight edges.

If there was any evidence of the variability of dispersive power, it was in Newton's own measurements of the spectra projected by two different prisms; when the difference in angles had been accounted for, the spectra projected by one prism were slightly longer than those of the other. Again, however, it is pertinent to point out that dispersive power is a ratio, and the different refractive powers of the prisms would probably account for most of the (very small) difference in length, as Newton claimed (ibid., p. 77).

309



RICHARD S. WESTFALL

he wrote to Oldenburg, was not as full as he had intended but perhaps more to the purpose, " considering who I have to deale wth, whose buisiness it is to cavill." 43 Over the second letter he brooded a good month.

Sr I promised to send you an answer to Mr Lucas this next Tuesday but I

find I shall scarce finish what I have designed, so as to get a copy taken of it by that time, & therefore I beg your patience a week longer. I see I have made my self a slave to Philosophy, but if I get free of Mr Linus's buisiness I will resolutely bid adew to it eternally, excepting what I do for my privat satisfaction or leave to come out after me. For I see a man must either resolve to put out nothing new or to become a slave to defend it.44

We can sympathize with Newton's annoyance, but we should remember also the objective facts of his " slavery." In the period of two years since Linus' first letter had arrived, there had been exactly six letters from Liege, including three from Linus, to only two of which Newton replied. None of the letters had required new thought or new experimentation. He did measure the angles of some prisms and the lengths of corresponding spectra for Lucas, it is true. During the same period there had been the brief flurry of self-justification in the face of Hooke's claim. By any objective standard of judgment such a correspondence falls well short of slavery.

And the annoyance hardly seems adequate to the answer it provoked. For the answer, when it came late in November, 1676, was an untempered shriek of rage. In his first reply Newton had refused to discuss Lucas' experiments until Lucas considered the experimentum crucis. " The main thing he goes about to examin is ye different refrangibility of light." 45

Very well, Lucas discussed differential refraction in his second letter. He did not measure the length of the spectrum. Linus had challenged Newton's experiment, Gascoines his honesty, Hooke his honor, now Lucas his accuracy. What was differential refraction beside the need for vindication?

The examining my Theory is but a new attempted digression. Tis ye truth of my experiments which is ye business in hand. On this my Theory depends, & which is of more consequence, ye credit of my being wary, accurate and faithfull in ye reports I have made or shall make of experiments in any subject, seeing yt a trip in any one will bring all ye rest into suspicion.46

It was as though Lucas had touched accidentally on something so deep that Newton could not bear to discuss it or even to contemplate it enough to recognize the insignificance of what had passed. He could only hurl back the charge in rage. He was unable to tear it from his mind; in the final paragraph it obtruded on the letter again:

The Question in hand is this. Whether ye Image in ye Experiment set down in my first letter about colours printed in ye Transactions Num 80 could be

43 Newton to Oldenburg, 22 Aug. 1676 (ibid., 45 Newton to Oldenburg, 18 Aug. 1676 (ibid., p. 83). p. 79).

44 Newton to Oldenburg, 18 Nov. 1676 (ibid., 46 Newton to Oldenburg, 28 Nov. 1676 (ibid., pp. 182-183). pp. 183-184).

310




five times longer than broad as I have there exprest it, or but three or at most three and a half as Mr Lucas has represented it. To this I desire a direct answer: which I hope will be so free as (wthout putting me to any further wayes of justifying myself) may take off all suspicion of my misrepresenting matter of fact. If Mr Lucas hath not yet procured a Prism with an angle about ye bigness of mine there used, 8c with sides not at all concave, but plain or onely a very little convex, let him onely upon ye receipt of this signify without any insinuation of suspicion yt he sees no reason to oppose or question me further upon ye experiments they have hitherto made and proceeded on, 8c I shall acquiesce and begin wth his Objections....47

It must have been around the time of the incredible letter of November, 1676, that Newton began seriously to plan anew the publication of his optical work. That he did plan such a publication is well established; there is no reason for me to repeat the evidence here.48 I must indicate, however, that the correspondence with Liege figured in his plans. Early in 1678 he wrote to Lucas for copies, not only of Lucas' letters, but of Gascoines' as well. Somewhat later a letter to John Aubrey explained how variations in the copies had led him to abandon plans to publish.49 A letter to Hooke in 1677 asking for exact measurements of the length of spectra in relation to the size of the refracting angle explicitly coupled the request to his intention of publishing the correspondence. The recently discovered sheets of an aborted edition of Newton's optical papers, which must have been identical with the plans evident in 1677, suggest more about the intended role of the correspondence with Liege. The sheets recovered include the final passages of Newton's original paper, of February, 1672, the first questions put to him, those of Robert Moray, and the beginning of Newton's reply. Notes added to his own paper explain his meaning in response to other criticisms.50 When we consider his evident plans to include the correspondence from Liege, it appears to me that he intended to print his paper together with all the criticism and his answers to them. The publication would be reminiscent of Descartes' Meditations, and designed of course to vindicate Newton's theory. Would mere vindication suffice? What we know of Newton's mood throughout the correspondence with Lucas suggests not. The letter of November, 1676, did not confine itself to the vindication of his theory. His letter to Lucas in 1678 suggests that nothing less than the humiliation of the Liegeois could satisfy him. Lucas' first letter, in confirming Newton's basic experiments, had tried to salvage Linus' reputa- tion as well. His explanation of Linus' blunder was transparently contrived, but it might have been accepted as a gesture toward a man now dead. By 1678 Newton would not allow it to stand:

47 Newton to Oldenburg, 28 Nov. 1676 (ibid., is in Collins to Newton, 5 March 1676/7 p. 185). (Correspondence, Vol. 2, pp. 200-201).

48 The evidence was all collected by A. R. 49 Newton to Aubrey, ? June 1678 (ibid., Hall, "Newton's First Book (I)," Archives p. 267). Internationales d&Histoire des Sciences, 1960, 50 See I. Bernard Cohen, "Versions of Isaac 13:39-54. One of the most important pieces of Newton's First Published Paper," Arch. int. evidence, which I will cite to establish a date, Hist. Sci., 1958, 11:357-375.

311



RICHARD S. WESTFALL

If now all yt I have written can prevail wth you to acknowledge any of your mistakes, I must intimate yt you are to begin wth ye original mistake committed by Mr Line & let your reader at length know what way he took to find an Image in a clear day, not longer than broad for your mistake here you have not yet acknowledged though convicted of it both by ye tryal of ye Royal Society & by ye testimony of your own eyes. [When Linus' friends finally determined that Newton's experiment was valid,] they deferred to let me have any account of it till you had find out a set of new objections, ye whole stay amounting to about half a year: and then instead of acknowledging his mistake ye business was represented as if none had been committed by him.... But if you will not freely let us know your mistakes but hope to mend ye matter by new disputes, you are at your liberty.51

It appears to me that the planned edition was to be quasi-apocalyptic -

the " conspiracy " against Newton would reap as its reward total discomfi- ture. Then fire struck in Newton's chamber and the manuscripts were destroyed. In haste he wrote to Hooke and to Lucas for copies. The letter to Lucas is not pleasant to contemplate. The letter itself has disappeared, but if we judge by Lucas' open reply, Newton concealed his real intent in order to get the copies. They came, but the edition stopped. The well- known passage that Edleston discovered in the diary of a student, Abraham de la Pryme, usually cited in connection with Newton's breakdown in the summer of 1693 although it is dated a year and a half earlier, makes inter- esting reading with the events of February, 1678. Under the date of Febru- ary, 1692, he entered a story he had just heard about Mr. Newton, a fellow of Trinity College, famous as a mathematician and as the author of a book on the Mathematical Principles of Philosophy. Among Newton's writings there was " one of colours & light," on which he had worked for twenty years. Just as the author was completing it, a candle set fire to the manu-

script while he was at chapel, and it was utterly consumed: " But when Mr. Newton came from chappel and had seen what was done, every one thought he would have run mad, he was so troubled thereat that he was not himself for a month after." 52 Undoubtedly rumor had added its liberal share to the story de la Pryme heard, but the story must have had some original basis in fact. We do know that papers were accidentally lost early in 1678. The letter that Newton finally sent to Lucas on 5 March 1678 testifies to a frame of mind not wholly unlike that which de la Pryme described. Fifteen months, which had passed since the letter of November, 1676, had done nothing to abate his fury:

Sr, The stirr you make about your Objections, draws this from me to let you

see how easy it was to answer your Letters had not other considerations (particularly your contemning my profer to answer one or two wch you should recommend for ye best) made me averse from meddling further wth

51 Newton to Lucas, 5 March 1677/8 (Corre- spondence, Vol. 2, pp. 259-260). Yorkshire Antiquary, ed. Charles Jackson (Dur-

52 The Diary of Abraham de la Pryme, the ham, 1870), p. 23.

312




your matters. To goe over your Letters your first objection, that of ye Micro- scope, depends on these three mistakes. .. .53

The greeting is a reasonable sample of the whole. Remorselessly and relent- lessly Newton laid out the mistakes in Lucas' experiments, exposed the errors in his conceptions, and explained how his experiments really sup- ported Newton's theory. The icy hostility of the letter tends to convey the impression that Newton composed it with his anger channeled if not subdued. The impression dissolves in the final paragraphs as the tone rises again to the scream of rage heard before:

Were I minded I could say much of your reconciliation of Mr Line wth Me 8c truth, of your staying to find new objections before you would venter to send yt reconcilation.... I could I say write much in explaining these things, but as I desire not to be put upon disputes of this Nature, so I had rather Mr Gascoin &c ye rest of Mr Line's Friends in your Colledge would consider how to compose things to your common credit. But if you will go on you may use your discretion; Only let me tell you yt what I find don in your Name I must esteem done by them who upon Mr Lines death engaged themselves (as Mr Gascoigne exprest) to pursue this business on 8c afterwards employed your pen in it, wch I say not to reflect on ym but to make them cautious in what they doe.54

And then silence again. The early explosion had been followed by with- drawal, as though stability could be regained only in solitude. So now Newton consciously severed his ties with the scientific world. Oldenburg was dead; Newton refused to open serious correspondence with his suc- cessors. His curt rejection of Hooke's offer in 1679 is well known. Although Collins lived until 1683, Newton apparently never wrote to him again. With John Flamsteed, and at Flamsteed's initiative, he exchanged a few letters on comets in 1681, but when the correspondence began to get inter- esting, he deleted (from the letter that he sent) a suggestive passage composed in a draft and allowed the exchange to lapse.55 There is some evidence that a correspondence with Boyle, initiated only in 1676, did continue; the long

53 Newton to Lucas, 5 March 1677/8 (Corre- spondence, Vol. 2, p. 254).

54 Newton to Lucas, 5 March 1677/8 (ibid., p. 260). Newton sent two letters to Lucas on that date; the second, which answers Lucas' third letter, was as furious as the first:

Do men use to press one another into Dis- putes? Or am I bound to satisfy you? It seems you thought it not enough to propound Objections unless you might insult over me for my inability to answer them all, or durst not trust your own judgement in choosing ye best. But how know you yt I did not think them too weak to require an answer . . ." (ibid., p. 263).

The draft of a letter in June to Aubrey was equally pervaded by the sense of a conspiracy against him:

Thus formerly when they found by their own trialls Mr Lines mistake in opposin the round image in a clear day they made a stop for half a year to look about for new observations though in candor & aequity they ought to have sent an immediate acknowl- edgment to take of those suspicions of error & dishonesty in me wch Mr Line had (as far as in him lay) raised, yet they made objections, & then instead of acknowledging Mr Lines mistake, sent a reconciliation of him wth me & truth, & at ye end of it added these new objections to divert ye readers eye as I presently apprehended & run of ye business into a new dispute (ibid., p. 267). 55 Newton to Flamsteed, 16 April 1681 (ibid.,

pp. 363-366). Cf. the draft of the same letter (ibid., pp. 358-362, especially p. 361).

313



RICHARD S. WESTFALL

letter written early in 1679, describing his theory of the ether, was part of it. The evidence of Newton's handwriting found in his alchemical manuscripts, testifies that this was the period of his most intense study of alchemical literature, as though its arcane tradition spoke to his isolation. There is more than one hint that the correspondence with Boyle concerned itself with alchemical questions.56 For the most part, however, the six and a half

years in Newton's life following the outburst of 1678 remain a blank in our knowledge of him. A number of things indicate that by 1684 he was beginning to turn outward again. Halley's visit in August could not have been more happily timed.

Inevitably the letters to Lucas invite comparison with the famous letters to Locke and to Pepys in 1693 at the time of his so-called breakdown. If we ignore the patent fact that the letters of 1693 had nothing to do with optics, we cannot, I believe, fail to be impressed by the similarities. A paranoid suspicion of conspiracy against him pervades all the letters. It is no less evident in the letter of 1678 to Lucas than it is in the letter charging that Locke sought to embroil him with women. Indeed the climactic letters to Lucas express as complete a loss of control as do those of 1693. A similar pattern was to reveal itself in the controversy with Leibniz. To speak of Newton's " breakdown " is obviously a mistake; we must speak rather of his " breakdowns." With sorrow and sympathy and without any suggestion of triumph, we must recognize, I believe, that his whole life was lived on the verge of breakdown, in acute tension that threatened to snap at every moment should external circumstances strain it too far. And all his magnificent achievement must have been torn from his inner turmoil in suffering and pain.

56 See Newton to Locke, 7 July and 2 Aug. 1692 (ibid., Vol. 3, pp. 215, 217-219).

314



Documents

Newton Defends His First Publication: The Newton-Lucas Correspondence