ML v/ v v
 
 LIFE 
 
 or 
 
 SIR ISAAC NEWTON 
 
 BY 
 
 DAVID BREWSTER, LL.D. F.R.S. 
 
 Ergo vivida vis anim! pervicit, ct ejtra. 
 Processit longe fiammantia mccnia mundi ; 
 Atque omne immensuni peragravi' 
 
 The Birthplace of Rcwto* 
 
 NEW YORK: 
 
 HARPER & BROTHERS, PUBLISHERS 
 
 329 & 331 PEARL STREET, 
 
 FRANKLIN SQUARE.
 
 *HE RIGHT HONOURABLE 
 
 LORD BRAYBROOKE. 
 
 THE kindness with which your lordship intrusted 
 to me some very valuable materials for the, compo- 
 sition of this volume has induced me to embrace the 
 present opportunity of publicly acknowledging it. 
 But even if this personal obligation had been less 
 powerful, those literary attainments and that en- 
 lightened benevolence which reflect upon rank its 
 highest lustre would have justified me in seeking 
 for it the patronage of a name which they have so 
 justly honoured. 
 
 DAVID BREWSTER. 
 
 Allerly, June 1st, 1831.
 
 PREFACE. 
 
 A.S this is the only Life of Sir Isaac Newton on 
 any considerable scale that has yet appeared, I 
 have experienced great difficulty in preparing it for 
 the public. The materials collected by preceding 
 biographers were extremely scanty ; the particulars 
 of his early life, and even the historical details of 
 his discoveries, have been less perfectly preserved 
 than those of his illustrious predecessors ; and it is 
 not creditable to his disciples that they have allowed 
 a whole century to elapse without any suitable 
 record of the life and labours of a master who 
 united every claim to their affection and gratitude. 
 
 In drawing up this volume, I have obtained much 
 assistance from the account of Sir Isaac Newton in 
 the Biographia Britannica ; from the letters to Ol- 
 denburg, arid other papers in Bishop Horsley's 
 edition of his works ; from Tumor's Collections for 
 the History of the Town and Soke of Grantham ; 
 from M. Biot's excellent Life of Newton in the 
 Biographic Universelle ; and from Lord King's Life 
 and Correspondence of Locke. 
 
 Although these works contain much important 
 information respecting the Life of Newton, yet I 
 have been so fortunate as to obtain many new ma 
 terials of considerable value.
 
 10 PREFACE. 
 
 To the kindness of Lord Braybrooke I have been 
 indebted for the interesting correspondence of New- 
 ton, Mr. Pepys, and Mr. Millington, which is now 
 published for the first time, and which throws much 
 light upon an event in the life of our author that 
 has recently acquired an unexpected and a painful 
 importance. These letters, when combined with 
 those which passed between Newton and Locke, 
 and with a curious extract from the manuscript diary 
 of Mr. Abraham Pryme, kindly furnished to me by 
 his collateral descendant Professor Pryme of Cam- 
 bridge, fill up a blank in his history, and have ena- 
 bled me to delineate in its true character that tem- 
 porary indisposition which, from the view that has 
 been taken of it by foreign philosophers, has been 
 the occasion of such deep distress to the friends of 
 science and religion. 
 
 To Professor Whewell, of Cambridge, I owe very 
 great obligations for much valuable information. 
 Professor Rigaud, of Oxford, to whose kindness I 
 have on many other occasions been indebted, sup 
 plied me with several important facts, and with ex 
 tracts from the diary of Hearne hi the Bodleian 
 Library, and from the original correspondence be- 
 tween Newton and Flamstead, which the president 
 of Corpus Christi College had for this purpose com- 
 mitted to his care ; and Dr. J. C. Gregory, of Edin- 
 burgh, the descendant of the illustrious inventor of 
 the reflecting telescope, allowed me to use his un- 
 published account of an autograph manuscript of 
 Sir Isaac Newton, which was found among the pa- 
 pers of David Gregory, Savilian Professor of As- 
 tronomy at Oxford, and which throws some light on 
 the history of the Principia.
 
 PREFACE. 1 1 
 
 I have been indebted to many other friends for 
 the communication of books and facts, but espe- 
 cially to Sir William Hamilton, Bart., whose libe- 
 rality in promoting literary inquiry is not limited to 
 the circle of his friends. 
 
 D. B. 
 
 Alhrly, June 1st, 1831.
 
 CONTENTS. 
 
 CHAPTER I. Fbg. 
 
 The Pre-eminence of Sir Isaac Newton's Reputation The Interest 
 attached to the Study of his Life and Writings His Birth and 
 Parentage His early Education Is sent to Grantham School 
 His early Attachment to Mechanical Pursuits His Windmill 
 His Water-clock His Self-moving Cart His Sun-dials His 
 Preparation for the University 1* 
 
 CHAPTER II. 
 
 Newton enters Trinity College, Cambridge Origin of his Propen- 
 sity for Mathematics He studies the Geometry of Descartes unas- 
 sisted Purchases a Prism Revises Dr. Barrow's Optical Lec- 
 tures Dr. Barrow's Opinion respecting Colours Takes his De- 
 greesIs appointed a Fellow of Trinity College Succeeds Dr. 
 Barrow in the Lucasian Chair of Mathematics 26 
 
 CHAPTER III. 
 
 Newton occupied in grinding Hyperbolical Lenses His first Ex- 
 periments with the Prism made in 166fi He discovers the Com- 
 position of White Light, and the different Refrangibility of the 
 Rays which compose it Abandons his Attempts to improve Re- 
 fracting Telescopes, and resolves to attempt the Construction of 
 Reflecting ones He quits Cambridge on account of the Plague 
 Constructs two Reflecting Telescopes in 1668, the first ever exe- 
 cuted One of them examined by the Royal Society, and shown 
 to the King He constructs a Telescope with Glass Specula Re- 
 cent History of the Reflecting Telescope Mr. Airy's Glass Specula 
 Hadley's Reflecting Telescopes Short's Herschel's Ram- 
 age's Lord Oxmantown's 30 
 
 CHAPTER IV. 
 
 He delivers a Course of Optical Lectures at Cambridge Is elected 
 Fellow of the Royal Society He communicates to them his Dis- 
 coveries on the different Refrangibility and Nature of Light- 
 Popular Account of them They involve him in various Contro- 
 versiesHis Dispute with Pardies Linus Lucas Dr. Hooke 
 and Mr. Huygens The Influence of these Disputes on the mind 
 of Newton 47 
 
 CHAPTER V. 
 
 Mistake of Newton in supposing that the Improvement of Refract- 
 
 B
 
 1 4 CONTENTS. 
 
 ?? 
 
 ing Telescopes -was hopeless Mr. Hall invents the Achromatic 
 Telescope Principles of the Achromatic Telescope explained It 
 is reinvented by Dollond, and improved by future Artists Dr. 
 Blair's Aplanatic Telescope Mistakes in Newton's Analysis of 
 the Spectrum Modern Discoveries respecting the Structure of 
 theSpectrum 63 
 
 CHAPTER VI. 
 
 Colours of thin Plates first studied by Boyle and Hooke Newton 
 determines the Law of their Production His Theory of Fits of 
 easy Reflection and Transmission Colours of thick Plates 75 
 
 CHAPTER VII. 
 
 Newton's Theory of the Colours of Natural Bodies explained Ob- 
 jections to it stated New Classification of Colours Outline of a 
 new Theory proposed 89 
 
 CHAPTER VIII. 
 
 Newton's Discoveries respecting the Inflection or Diffraction of 
 Light Previous Discoveries of Grimaldi and Dr. Hooke I-abours 
 of succeeding Philosophers Law of Interference of Dr. Young 
 Fresnel's Discoveries New Theory of Inflection on the Hypothe- 
 sis of the Materiality of Light 9 
 
 CHAPTER IX. 
 
 Miscellaneous Optical Researches of Newton His Experiments on 
 Refraction His Conjecture respecting the Inflammability of the 
 Diamond His Law of Double Refraction His Observations on 
 the Polarization of Light Newton's Theory of Light His " Op- 
 tics" ioe 
 
 CHAPTER X. 
 
 Astronomical Discoveries of Newton Necessity of combined Exei 
 tion to the completion of great Discoveries Sketch of the History 
 of Astronomy previous to the time of Newton Copernicus, 1473 
 -1543 TychoBrahe, 1546-1601 Kepler, 1571-1631 Galileo, 1564 
 -1642 110 
 
 CHAPTER XI. 
 
 The first Idea of Gravity occurs lo Newton in 1666 His first Specu- 
 lations upon it Intermixed by his Optical Experiments He 
 resumes the Subject in consequence of a Discussin with Doctor 
 Hooke He discovers tlie true Law of Gravity and the Cause of 
 the Planetary Motions Dr. Halley urges him to publish his Prin- 
 cipia His Principles of Natural Philosophy Proceedings of the 
 Royal Society on this Subject The Principia appears in 1687 
 General Account of it, and of the Discoveries it contains They 
 meet with great Opposition, owing to the Prevalence of the Carte- 
 sian fiyslem Account of the Reception and Progress of the New- 
 tonian Philosophy in Foreign Countries Account of its Progress 
 and Establishment in England 140
 
 CONTENTS. 15 
 
 CHAPTER XIL Page . 
 
 iK>ctrine of Infinite Quantities Labours of Pappus Kepler Cava- 
 leri Roberval Fermat Wallis Newton discovers the Bino- 
 mial Theorem and the Doctrine of Fluxions in 1606 His Manu- 
 script Work containing this Doctrine communicated to his Friends 
 
 His Treatise on Fluxions His Mathematical Tracts His Uni- 
 versal Arithmetic His Methodus Differential is His Geometria 
 Analytica His Solution of the Problems proposed by Bernouilli 
 and Leibnitz Account of the celebrated Dispute respecting the 
 Invention of Fluxions Commercium Epistolicum Report of the 
 Royal Society General View of the Controversy ............... 168 
 
 CHAPTER XIH. 
 
 James II. attacks the Privileges of the University of Cambridge 
 Newton chosen one of the Delegates to resist this Encroachment 
 He is elected a Member of the Convention Parliament Burning 
 
 of his Manuscript His supposed Derangement of Mind View 
 taken of this by foreign Philosophers His Correspondence with 
 Mr. Pepys and Mr. Locke at the time of his Illness Mr. Milling- 
 
 . . . 
 
 ton's Letter to Mr. Pepys on the subject of Newton's Illness- 
 Refutation of the Statement that he laboured under Mental De- 
 rangement ..... .............................................. 200 
 
 CHAPTER XIV. 
 
 No Mark of National Gratitude conferred upon Newton Friendship 
 between him and Charles Montague, afterward Earl of Halifax 
 Mr. Montague appointed Chancellor of the Exchequer in 1694 
 He resolves upon a Recoinage Nominates Mr. Newton Warden 
 of the Mint in 1695 Mr. Newton appointed Master of the Mint in 
 1699Notice of the Earl of Halifax Mr. Newton elected Asso- 
 ciate of the Academy of Sciences in 1699 Member for Cambridge 
 in 1701 and President cf the Royal Society in 1703 Queen Anne 
 confers upon him the Honour of Knighthood in 1705 Second 
 Edition of the Principia, edited by Cotes His Conduct respecting 
 Mr. Ditton's Method of finding the Longitude ................... 223 
 
 CHAPTER XV. 
 
 Respect in which Newton was held at the Court of George I. The 
 Princess of Wales delighted with his Conversation Leibnitz en- 
 deavours to prejudice the Princess against Sir Isaac and Locke 
 Controversy occasioned by his Conduct The Princess obtains a 
 Manuscript Abstract of his System of Chronology The Abbe 
 Conti is, at her request, allowed to take a Copy of it on the prom- 
 ise of Secrecy He prints it surreptitiously in French, accompa- 
 nied with a Refutation by M. Freret Sir Isaac's Defence of his 
 System Father Souciet attacks it, and is answered by Dr. Halley 
 Sir Isaac's larger Work on Chronology published after hia 
 Death Opinions respecting it Sir Isaac's Paper on the Form of 
 the most ancient Year ....... i ............................... 234 
 
 CHAPTER XVI. 
 
 Theological Studies of Sir Isaac Their Importance to Cnristianjty 
 Motives to which they have been ascribed Opinions of Blot
 
 IH CONTENTS. 
 
 Pan 
 
 and La Place considered His Theological Researches begun be- 
 fore his supposed Mental Illness The Date of these Works fixed 
 Letters to Locke Account of his Observations on Prophecy- 
 His Lexicon Propheticum His Four Letters to Dr. Bentley Ori 
 gin of Newton's Theological Studies Analogy between the Book 
 ofNatoreand that of Revelation 242 
 
 CHAPTER XMI. 
 
 The Mir.or Discoveries and Inventions of Newton His Researches 
 on Heat On Fire and Flame On Elective Attraction On the 
 Structure of Bodies His supposed Attachment to Alchymy His 
 Hypothesis respecting Ether as the Cause of Light and Gravity 
 On the Excitation of Electricity in Glass His Reflecting Sex- 
 tant invented before 1700 His Reflecting Microscope His Pris- 
 matic Reflector as a Substitute for the small Speculum of Reflect- 
 ing Telescopes His Method of varying the Magnifying Power of 
 Newtonian Telescopes His Experiments on Impressions on the 
 Retina 265 
 
 CHAPTER XVHI. 
 
 His Acquaintance with Dr. Pemberton Who edits the Third Edi- 
 tion of the Principia His first Attack of ill Health His Recovery 
 He is taken ill in consequence of attending the Royal Society 
 His Death on the 20th March, 1727 His Body lies i"n state His 
 Funeral He is buried in Westminster Abbey His Monument de- 
 scribed His Epitaph A Medal struck in honour of him Roubil- 
 iac's full-length Statue of him erected in Cambridge Division 
 of Ms Property His Successors 284 
 
 CHAPTER XIX. 
 
 Permanence of Newton's Reputation Character of his Genius 
 His Method of Investigation similar to that used by Galileo- 
 Error in ascribing his Discoveries to the Use of the Methods 
 recommended by Lord Bacon The Pretensions of the Baconian 
 Philosophy examined Sir Isaac Newton's Social Character His 
 great Modesty The Simplicity of his Character His Religious 
 and Moral Character His Hospitality and Mode of Life His 
 Generosity and Charity His Absence His Personal Appear- 
 anceStatues and Pictures of him Memorials and Recollections 
 of him 292 
 
 APPKNDIX, No. I. Observations on the Family of Sir Isaac New- 
 ton 307 
 
 APPENDIX, No. II. Letter from Sir Isaac Newton to Francis Aston, 
 Esq., a young Friend who was on the eve of setting out on his 
 Travels 3]6 
 
 \PPKNDIX, No. HI. " A Remarkable and Curious Conversation be- 
 tween Sir Isaac Newton and Mr. Conduit " 32t
 
 ~t - OF 
 
 SIR ISAAC NEWTON 
 
 CHAPTER I. 
 
 Tfte Pie-eminence of Sir 7saac Newton's Reputation TTte Interest 
 attached, to the Study of his Life and Writings His Birth and 
 Parentage His early Education Is sent to Grantham School His 
 early Attachment to Mechanical Pursuits His Windmill His 
 Waterclock His Selfmoving Cart His Sundials His Preparation 
 for the University. 
 
 THE name of Sir Isaac Newton has by general 
 consent been placed at the head of those great men 
 who have been the ornaments of their species. 
 However imposing be the attributes with which 
 time has invested the sages and the heroes of anti- 
 quity, the brightness of their fame has been eclipsed 
 by the splendour of his reputation; and neither the 
 partiality of rival nations, nor the vanity of a presump- 
 tuous age, has ventured to dispute the ascendency 
 of his genius. The philosopher,* indeed, to whom 
 posterity will probably assign the place next to New- 
 ton, has characterized the Principia as pre-eminent 
 above all the productions of human intellect, and 
 has thus divested of extravagance the contemporary 
 encomium upon its author, 
 
 Nee fas est propius mortali attingere Divos. 
 
 HALLEY. 
 So near the gods man cannot nearer go. 
 
 * The Marquis La Place. See Systtmc du Monde, p. 336.
 
 18 SIR ISAAC NEWTON 
 
 The biography of an individual so highly renowned 
 cannot fail to excite a general interest. Though 
 his course may have lain in the vale of private life, 
 and may have ben unmarked with those dramatic 
 events which throw a lustre even round perishable 
 names, yet the inquiring spirit will explore the his- 
 tory of a mind so richly endowed, will study its 
 intellectual and moral phases, and will seek the 
 shelter of its authority on those great questions 
 which reason has abandoned to faith and hope. 
 
 If the conduct and opinions of men of ordinary 
 talent are recorded for our instruction, how inter- 
 esting must it be to follow the most exalted genius 
 through the incidents of common life ; to mark the 
 steps by which he attained his lofty pre-eminence ; 
 to see how he performs the functions of the social 
 and the domestic compact; how he exercises his 
 lofty powers of invention and discovery; how he 
 comports himself in the arena of intellectual strife ; 
 and in what sentiments, and with what aspirations 
 he quits the world which he has adorned. 
 
 In almost all these bearings, the life and writings 
 of Sir Isaac Newton abound with the richest counsel. 
 Here the philosopher will learn the art by which 
 alone he can acquire an immortal name. The mor- 
 alist will trace 'the lineaments of a character ad- 
 justed to all the symmetry of which our imperfect 
 nature is susceptible; and the Christian will con- 
 template with delight the high-priest of science 
 quitting the study of the material universe, the 
 scene of his intellectual triumphs, to investigate 
 with humility and patience the mysteries of his faith 
 
 Sir Isaac Newton was born at Woolsthorpe, a 
 hamlet in the parish of Colsterworth, in Lincoln- 
 shire, about six miles south of Grantham, on the 
 25th December, O. S., 1642, exactly one year after 
 Galileo died, and was baptized at Colsterworth on 
 the 1st January, 1642-3. His father, Mr. Isaac New
 
 1RTH. 19 
 
 ton, died at the early age of thirty-six, a little more 
 than a year after the death of his father Robert 
 Newton, and only a few months after his marriage 
 to Harriet Ayscough, daughter of James Ayscough 
 of Market Overton in Rutlandshire. This lady was 
 accordingly left in a state of pregnancy, and appears 
 to have given a premature birth to her only and 
 posthumous child. The helpless infant thus ushered 
 into the world WPS of such an extremely diminutive 
 size,* and seemed of so perishable a frame, that 
 two women who w -,re sent to Lady Pakenham's at 
 North Witham, to bring some medicine to strengthen 
 him, did not expect to find him alive on their return. 
 Providence, however, had otherwise decreed; and 
 that frail tenement which seemed scarcely able to 
 imprison its immortal mind was destined to enjoy 
 a vigorous maturity, and to survive even the average 
 term of human existence. The estate of Wools- 
 thorpe, in the manor-house of which this remarka- 
 ble birth took^place, had been more than a hundred 
 years in the possession of the family, who came 
 originally from Newton in Lancashire, but who had, 
 previous to the purchase of Woolsthorpe, settled at 
 Westby, in the county of Lincoln. The manor- 
 house, of which we have given an engraving, is 
 oituated in a beautiful little valley, remarkable for 
 its copious wells of pure spring water, on the west 
 side of the river Witham, which has its origin in the 
 neighbourhood, and commands an agreeable pros- 
 pect to the east towards Colsterworth. The manor 
 of Woolsthorpe was worth only 30/. per annum; 
 but Mrs. Newton possessed another small estate at 
 Sewstern,f which raised the annual value of their 
 property to about 8QL ; and it is probable that the 
 cultivation of the little farm on which she resided 
 
 * Sir Isaac Newton told Mr. Conduit, that he had often heard his 
 mother say that when he was born he was so little that they might 
 have put him into a quart mug. 
 
 t In Leicestershire, and about three miles south-east of Woolsthorp
 
 20 SIR ISAAC NEWTON. 
 
 somewhat enlarged the limited income upon which 
 she had to support herself, and educate her child. 
 
 For three years Mrs. Newton continued to watch 
 over her tender charge with parental anxiety ; but 
 in consequence of her marriage to the Reverend 
 Barnabas Smith, rector of North Witham, about a 
 mile south of Woolsthorpe, she left him under the 
 care of her own mother. At the usual age he was 
 sent to two day-schools at Skillington and Stoke, 
 where he acquired the education which such semi- 
 naries afforded; but when he reached his twelfth 
 year he went to the public school at Grantham, 
 taught by Mr. Stokes, and was boarded at the house 
 of Mr. Clark, an apothecary in that town. Accord- 
 ing to information which Sir Isaac himself gave to 
 Mr. Conduit, he seems to have been very inattentive 
 to his, studies, and very low in the school. The 
 boy, however, who was above him, having one day 
 given him a severe kick upon his stomach, from 
 which he suffered great pain, Isaac laboured inces- 
 santly till he got above him in the school, and from 
 that time he continued to rise till he was the head 
 boy. From the habits of application which this 
 incident had led him to form, the peculiar character 
 of his mind was speedily displayed. During the 
 hours of play, when the other boys were occupied 
 with their amusements, his mind was engrossed with 
 mechanical contrivances, either in imitation of some- 
 thing which he had seen, or in execution of some 
 o : 2rinal conception of his own. For this purpose 
 he provided himself with little saws, hatchets, ham- 
 mers, and all sorts of tools, which he acquired the 
 art of using with singular dexterity. The principal 
 pieces of mechanism which he thus constructed 
 were a windmill, a waterclock, and a carriage put in 
 motion by the person who sat in it. When a wind- 
 mill was erecting near Grantham on the road to 
 Gunnerby, Isaac frequently attended the operations 
 of the workmen, and acquired such a thorough
 
 MECHANICAL PURSUITS. 21 
 
 knowledge of the machinery that he completed a 
 working model of it, which excited universal admi- 
 ration. This model was frequently placed on the top 
 of the house in which he lodged at Grantham, and 
 was put in motion by the action of the wind upon 
 its sails. Not content with this exact 'imitation of 
 the original machine, he conceived the idea of driv- 
 ing it by animal power, and for this purpose he en- 
 closed in it a mouse which he called the miller, and 
 which, by acting upon a sort of treadwheel, gave 
 motion to the machine. According to some ac- 
 counts, the mouse was made to advance by pulling 
 a string attached to its tail, while others allege that 
 the power of the little agent was called forth by its 
 unavailing attempts to reach a portion of corn placed 
 above the wheel. 
 
 His waterclock was formed out of a box which 
 he had solicited from Mrs. Clark's brother. It was 
 about four feet high, and of a proportional breadth, 
 somewhat like a common houseclock. The index 
 of the dialplate was turned by a piece of wood, which 
 either fell or rose by the action of dropping water. 
 As it stood in his own bedroom he supplied it every 
 morning with the requisite quantity of water, and it 
 was used as a clock by Mr. Clark's family, and re- 
 mained in the house long after its inventor had 
 quitted Grantham.* His mechanical carriage was a 
 vehicle with four wheels, which was put in motion 
 with a handle wrought by the person who sat in it, 
 but, like Merlin's chair, it seems to have been used 
 only on the smooth surface of a floor, and not fitted 
 to overcome .the inequalities of a road. Although 
 
 * "I remember once," says Dr. Stukely, "when I was deputy to 
 Dr. Halley, secretary at the Royal Society, Sir Isaac talked of these 
 kind of instruments. That he observed the chief inconvenience in 
 them was, that the hole through which the water is transmitted being 
 necessarily very small, was subject to be furred up by impurities in the 
 water, as those made with sand will wear bigger, which at length causes 
 an inequality in time." -Stukely's Letter to Dr. Mead. Tumor's Col- 
 lections, p. 177.
 
 22 SIR ISAAC NEWTON. 
 
 Newton was at this time " a sober, silent, thinking 
 ]ad," who scarcely ever joined in the ordinary games 
 of his schoolfellows, yet he took great pleasure in 
 providing them with amusements of a scientific 
 character. He introduced into the school the flying 
 of paper kites ; and he is said to have been at great 
 pains in determining their best forms and propor- 
 tions, and in ascertaining the position and mimbei 
 of the points by which the string should be attached. 
 He made also "paper lanterns, by the light of which 
 he went to school in the winter mornings, and he 
 frequently attached these lanterns to the tails of 
 his kites in a dark night, so as to inspire the country 
 people with the belief that they were comets. 
 
 In the house where he lodged there were some 
 female inmates in whose company he appears to have 
 taken much pleasure. One of these, a Miss Storey, 
 sister to Dr. Storey, a physician at Buckminste'r, 
 near Colsterworth, was two or three years younger 
 than Newton, and to great personal attractions she 
 seems to have added more than the usual allotment 
 of female talent. The society of this young lady 
 and her companions was always preferred to that 
 of his own schoolfellows, and it was one of his most 
 agreeable occupations to construct for them little 
 tables and cupboards, and other utensils for holding 
 their dolls and their trinkets. He had lived nearly 
 six years in the same house with Miss Storey, and 
 there is reason to believe that their youthful friend- 
 ship gradually rose to a higher passion; but the 
 smallness of her portion and the inadequacy of his 
 own fortune appear to have prevented the consum- 
 mation of their happiness. Miss Storey was after- 
 ward twice married, and under the name of Mrs. 
 Vincent, Dr. Stukely visited her at Grantham in 1727, 
 at the age of eighty-two, and obtained from her 
 many particulars respecting the early history of our 
 author. Newton's esteem for her continued un- 
 abated during his life. He regularly visited her when
 
 SUNDIALS. 23 
 
 he went to Lincolnshire, and never failed to relieve 
 her from little pecuniary difficulties which seem to 
 have beset her family. 
 
 Among the early passions of Newton we must 
 recount his love of drawing ; and even of writing 
 verses. His own room was furnished with pictures 
 drawn, coloured, and framed by himself, sometimes 
 from copies, but often from life.* Among these 
 were portraits of Dr. Donne, Mr. Stokes, the mastei 
 of Grantham school, and King Charles I. undei 
 whose picture were the following verses. 
 
 A secret art my soul requires to try, 
 If prayers can give me what the wars deny. 
 Three crowns distinguished here, in order do 
 Present their objects to my knowing view. 
 Earth's crown, thus at my feet I can disdain, 
 Which heavy is, and at the best but vain. 
 But now a crown of thorns I gladly greet, 
 Sharp is this crown, but not so sharp as sweet, 
 The crown of glory that I yonder see 
 Is full of bliss and of eternity. 
 
 These verses were repeated to Dr. Stukely by Mrs. 
 Vincent, who believed them to be written by Sir 
 Isaac, a circumstance which is the more probable, 
 as he himself assured Mr. Conduit, with some ex- 
 pression of pleasure, that he " excelled in making 
 verses," although he had been heard to express a 
 contempt for poetical composition. 
 
 But while the mind of our young philosopher was 
 principally occupied with the pursuits which we have 
 now detailed, it was not inattentive to the move- 
 ments of the celestial bodies, on which he was des- 
 tined to throw such a brilliant light. The imperfec- 
 tions of his watei clock had probably directed his 
 thoughts to the more accurate measure of time which 
 the motion of the sun afforded. In the yard of the 
 
 * Mr. Clark informed Dr. Stukely that the walls of the room in which 
 Sir Isaac lodged were covered with charcoal drawings of birds, beasts, 
 men, ships, and mathematical figures, all of which were very well de- 
 signed.
 
 24 SIR ISAAC NEWTON. 
 
 house where he lived, he traced the varying move 
 merits of that luminary upon the walls and roofs of the 
 buildings, and by means of fixed pins he had marked 
 out the hourly and half-hourly subdivisions. One 
 of these dials, which went by the name of Isaac's 
 dial, and was often referred to by the country people 
 for the hour of the day, appears to have been drawn 
 solely from the observations of several years ; but 
 we are not informed whether all the dials -which he 
 drew on the wall of his house at Woolsthorpe, and 
 which existed after his death, were of the same 
 description, or were projected from his knowledge 
 of the doctrine of the sphere. 
 
 Upon the death of the Reverend Mr. Smith in the 
 year 1656, his widow left the rectory of North 
 Witham, and took up her residence at Woolsthorpe 
 along with her three children, Mary, Benjamin, and 
 Hannah Smith. Newton had now attained the 
 fifteenth year of his age, and had made great pro- 
 gress in his studies ; and as he was thought capable 
 of being useful in the management of the farm and 
 country business at Woolsthorpe, his mother, chiefly 
 from a motive of economy, recalled him from the 
 school at Grantham. In order to accustom him to 
 the art of selling and buying, two of the most im- 
 portant branches of rural labour, he was frequently 
 sent on Saturday to Grantham market to dispose 
 of grain and other articles of farm produce, and to 
 ptfrchase such necessaries as the family required. 
 As he had yet acquired no experience, an old trust- 
 worthy servant generally accompanied him on these 
 errands. The inn which they patronised was the 
 Saracen's Head at West Gate ; but no sooner had 
 they put up their horses than our young philosopher 
 deserted his commercial concerns, and betook him- 
 self to his former lodging in the apothecary's garret, 
 where a number of Mr. Clark's old books afforded 
 him abundance of entertainment till his aged guar- 
 dian had executed the family commissions, and a*
 
 PREPARATION FOR THE UNIVERSITY. 26 
 
 nounced to him the necessity of returning. At other 
 times he deserted his duties at an earlier stage, and 
 intrenched himself under a hedge by the way-side, 
 where he continued his studies till the servant re- 
 turned frbm Grantham. The more immediate affairs 
 of the farm were not more prosperous under his 
 management than would have been his marketings 
 at Grantham. The perusal of a book, the execu- 
 tion of a model, or the superintendence of a water- 
 wheel of his own construction, whirling the glitter- 
 ing spray from some neighbouring stream, absorbed 
 all his thoughts when the sheep were going astray, 
 and the cattle were devouring or treading down the 
 corn. 
 
 Mrs. Smith was soon convinced from experience 
 that her son was not destined to cultivate the soil, 
 and as his passion for study, and his dislike for every 
 other occupation increased with his years, she wisely 
 resolved to give him all the advantages which edu- 
 cation could confer. He was accordingly sent back 
 to Grantham school, where he continued for some 
 months in busy preparation for his academical stu- 
 dies. His uncle, the Reverend W. Ayscough, who 
 was rector of Burton Coggles, about three miles 
 east of Woolsthorpe, and who had himself studied 
 at Trinity College, recommended to his nephew to 
 enter that society, and it was accordingly determined 
 that he should proceed to Cambridge at the ap- 
 proaching term.* 
 
 * " One of his uncles," says M. Biot, " having one day found him 
 under a hedge with a book in his hand and entirely absorbed in medita- 
 tion, took it from him, and found that he was occupied in the solution of a 
 mathematical problem. Struck with finding so serious and so active 
 a disposition at so early an age, he urged his mother no longer to thwart 
 him, and to send him back to Grantham to continue his studies." I 
 hsve omitted this anecdote in the text, as I cannot find it in Tumor's 
 < Elections, from which M. Biot derived his details of Newton's infancy, 
 t^.r in any other work-
 
 26 SIR ISAAC NEWTON. 
 
 CHAPTER II. 
 
 Newton enters Trinity College, Cambridge Origin of his Piopensity 
 for Mathematics He studies the Geometry of Descartes unassisted 
 Purchases a Prism Revises Dr. Harrow's Optical Lectures Dr 
 Barrow's Opinion respecting Colours. Takes his Degrees 7s ap- 
 pointed a Fellow of Trinity College Succeeds Dr. Barrow in the 
 Lucasian Chair of Mathematics. 
 
 To a young mind thirsting for knowledge, and 
 ambitious of the distinction which it brings, the 
 transition from a village school to a university like 
 that of Cambridge, from the absolute solitude of 
 thought to the society of men imbued with all the 
 literature and science of the age, must be one of 
 eventful interest. To Newton it was a source of 
 peculiar excitement. The history of science affords 
 many examples where the young aspirant had been 
 early initiated into her mysteries, and had even ex- 
 ercised his powers of invention and discovery before 
 he was admitted within the walls of a college ; but he 
 who was to give philosophy her laws did not exhibit 
 such early talent ; no friendly counsel regulated his 
 youthful studies, and no work of scientific eminence 
 seems to have guided him in his course. In yield- 
 ing to the impulse of his mechanical genius, his 
 mind obeyed the laws of its own natural expansion, 
 and, following the line of least resistance, it was 
 thus drawn aside from the strongholds with which 
 it was destined to grapple. 
 
 When Newton, therefore, arrived at Trinity Col- 
 lege, he brought with him a more slender portion of 
 science than falls to the lot of ordinary scholars ; 
 but this state of his acquirements was perhaps not 
 unfavourable to the development of his powers. 
 Unexhausted by premature growth, and invigoratec 
 **y healthful repose, his mind was the better fitted to
 
 TRINITY COLLEGE. 27 
 
 make those vigorous and rapid shoots which soon 
 covered with foliage and with fruit the genial soil 
 to which it had been transferred. 
 
 Cambridge was consequently the real birthplace 
 of Newton's genius. Her teachers fostered his ear- 
 liest studies ; her institutions sustained his mightiest 
 efforts ; and within her precincts were all his dis- 
 coveries made and perfected. When he was called 
 to higher official functions, his disciples kept up the 
 pre-eminence of their master's philosophy, and their 
 successors have maintained this seat of learning in 
 the fulness of its glory, and rendered it the most 
 distinguished among the universities of Europe. 
 
 It was on the 5th of June, 1660, in the 18th year 
 of his age, that Newton was admitted into Trinity 
 College, Cambridge, during the same year that Dr. 
 Barrow was elected professor of Greek hi the uni- 
 versity. His attention was first turned to the study 
 of mathematics by a desire to inquire into the truth 
 of judicial astrology ; and he is said to have dis- 
 covered the folly of that study by erecting a figure 
 with the aid of one or two of the problems of 
 Euclid. The propositions contained in this ancient 
 system of geometry he regarded as self-evident 
 truths ; and without any preliminary study he made 
 himself master of Descartes's Geometry by his 
 genius and patient application. This neglect of the 
 elementary truths of geometry he afterward regarded 
 as a mistake in his mathematical studies, and he ex- 
 pressed to Dr. Pemberton his regret that " he had ap- 
 plied himself to the works of Descartes, and other alge- 
 braic writers, before he had considered the elements 
 of Euclid with that attention which so excellent a 
 writer deserved.* Dr. Wallis's Arithmetic of Infinites, 
 Saunderson's Logic, and the Optics of Kepler were 
 among the books which he had studied with care. On 
 these works he wrote comments during their perusal ; 
 
 * Pemberton'3 View qf Sir Isaac Newton's Philosophy. Pref.
 
 28 SIR ISAAC NEWTON. 
 
 and so great was his progress, that he is reported to 
 have found himself more deeply versed in some 
 branches of knowledge than the tutor who directed 
 his studies. 
 
 Neither history nor tradition has handed down to 
 us any particular account of his progress during the 
 first three years that he spent at Cambridge. It 
 appears from a statement of his expenses, that in 
 1664 he purchased a prism, for the purpose, as has 
 been said, of examining Ttescartes's theory of co- 
 lours ; and it is stated by Mr. Conduit, that he soon 
 established his own views on the subject, and de 
 tected the errors in those of the French philosopher 
 This, however, does not seem to have been the case 
 Had he discovered the composition of light in 106'i 
 or 1665, it is not likely that he would have withheld 
 it, not only from the Rojral Society, but from his 
 own friends at Cambridge till the year 1671. Hts 
 friend and tutor, Dr. Barrow, was made Lucasian 
 Professor of Mathematics in 1663, and the optical 
 lectures which he afterward delivered were published 
 in 1669. In the preface of this work he acknow- 
 ledges his obligations to his colleague, Mr. Isaac 
 Newton,* for having revised the MSS., and corrected 
 several oversights, and made some important sug- 
 gestions. In the twelfth lecture there are some ob- 
 servations on the nature and origin of colours^ 
 which Newton could not have permitted his friend 
 to publish had he been then in possession of their 
 tine theory. According to Dr. Barrow, White is 
 that which discharges a copious light equally clear 
 in every direction; Black is that which does not 
 emit light at all, or which does it very sparingly. 
 Red is that which emits a light more clear than 
 usual, but interrupted by shady interstices. Blue is 
 that which discharges a rarified light, as in bodies 
 which consist of white and black particles arranged 
 
 * Peregregiae vir indolls ac insignis psritiee. Epist ad, Lect
 
 APPOINTED PROFESSOR OF MATHEMATICS. 29 
 
 alternately. Green is nearly allied to blue. Yellow 
 is a mixture of much white and a little red; and 
 Purple consists of a great deal of blue mixed with 
 a small portion of red. The blue colour of the sea 
 arises from the whiteness of the salt which it con- 
 tains, mixed with the blackness of the pure watd 
 in which the salt is dissolved ; and the blueness of 
 the shadows of bodies, seen at the same time by 
 candle and daylight, arises from the whiteness of 
 the paper mixed with the faint light or blackness of 
 the twilight. These opinions savour so little of 
 genuine philosophy that they must have attracted 
 the observation of Newton, and had he discovered 
 at that time that white was a mixture of all the 
 colours, and black a privation of them all, he could 
 not have permitted the absurd speculations of his 
 master to pass uncorrected. 
 
 That Newton had not distinguished himself b} 
 any positive discovery so early as 1664 or 1665, maj 
 be inferred also from the circumstances which at 
 tended the competition for the law fellowship ol 
 Trinity College. The candidates for this appoint- 
 ment were himself and Mr. Robert Uvedale; and 
 Dr. Barrow, then Master of Trinity, having found 
 them perfectly equal in their attainments, con- 
 ferred the fellowship on Mr. Uvedale as the senior 
 candidate. 
 
 In the books of the university, Newton is recorded 
 is having been admitted sub-sizer in 16C1. He 
 became a scholar in 1664. In 1665 he took his de- 
 gree of Bachelor of Arts, and in 1666, in conse- 
 quence of the breaking out of the plague, he retired 
 to Woolsthorpe. In 1667 he was made Junior Fel* 
 low. In 1668 he took } ' ; s degree of Master of Arts 
 and in the same T-V^I- ne was appointed to a Senioi 
 Fellowship. In 1669, when Dr. Barrow had re 
 solved to devote his attention to theology, he re* 
 signed the Lucasian Professorship of Mathematics 
 in favour of Newton, who may now be considered 
 C
 
 30 SIR ISAAC NEWTON. 
 
 as having entered upon that brilliant career of dis- 
 covery the history of which will form the subject of 
 some of the following chapters. 
 
 CHAPTER III. 
 
 Newton occupied in grinding Hyperbolical Lenses His first Experi- 
 ments with the Prism made in 1666 He discovers the Composition of 
 White Light, and the different Refrangibility of the Rays which com- 
 pose it Abandons his Attempts to improve Refracting Telescopes and 
 ^esolves to attempt the Construction of Reflecting ones He quits Cam- 
 bridge on account of the Plague Constructs two Reflecting Telescopes 
 in 1668, the first ever executed One of them examined by the Royal So- 
 ciety, and shown to the King He constructs a Telescope with Glass 
 Specula Recent History of the Reflecting Telescope Mr. Airy's 
 Glass Specula Hadley's Reflecting Telescopes Short's Herschel'a 
 Ramage's Lord Oxmantoivri's. 
 
 THE appointment of Newton to the Lucasian 
 chair at Cambridge seems to have been coeval with 
 his grandest discoveries. The first of these of 
 which the date is well authenticated is that of the 
 different refrangibility of the rays of light, which he 
 established in 1666. 'The germ of the doctrine of 
 universal gravitation seems to have presented itself 
 to him in the same yea, or at least in 1667- and "in 
 the year 1666 or before"* he was hi possession of 
 his method of fluxions, and he had brought it to such 
 a state in the beginning of 1669, that he permitted 
 Dr. Barrow to communicate it to Mr. Collins on the 
 20th of June in that year. 
 
 Although we have already mentioned, on the au- 
 thority of a written memorandum of Newton him 
 self, that he purchased a prism at Cambridge in 1664, 
 yet he does not appear to have made any use of it, 
 as he informs us that it was in 1666 tha't he "pro- 
 
 * See Newton's Letter to the Abbe Conti, dated February 26. 171S-16, 
 in the Additamenta Comm. Epistoitci.
 
 REFRACTING TELESCOPE. 31 
 
 cured a triangular glass prism to try therewith tne 
 celebrated phenomena of colours."* During- that 
 year he had applied himself to the grinding of "op- 
 tic -glasses, of other figures than spherical," and 
 having, no doubt, experienced the impracticability 
 of executing such lenses, the idea of examining the 
 phenomena of colour was one of those sagacious 
 and fortunate impulses which more than once led 
 him to discovery. Descartes in his Dioptrice^ pub- 
 lished in 1629, and more recently James Gregory in 
 his Optica Promota published in 1663, had shown 
 that parallel and diverging rays could be reflected or 
 refracted, with mathematical accuracy, to a point or 
 focus, by giving the surface a parabolic, an elliptical, 
 or a hyperbolic form, or some other form not spher- 
 ical. Descartes had even invented and described 
 machines by which lenses of these shapes could be 
 ground and polished, and the perfection of the re- 
 fracting telescope was supposed to depend on the 
 degree of accuracy with which they could be exe- 
 cuted. 
 
 In attempting to grind glasses that were not spher- 
 ical, Newton seems to have conjectured that the de- 
 fects of lenses, and consequently of refracting tele- 
 scopes, might arise from some other cause than the 
 imperfect convergency of rays to a single point, and 
 this conjecture was happily realized in those fine 
 discoveries of which we shall now endeavour to 
 give some account. 
 
 When Newton began this inquiry, philosophers of 
 the highest genius were directing all the energies of 
 their mind to the subject of light, and to the im- 
 provement of the refracting telescope. James 
 Gregory of Aberdeen had invented his reflecting 
 telescope. Descartes had explained the theory and 
 exerted himself in perfecting the construction of the 
 common refracting telescope, and Huygens had not 
 
 * Newtoni Opera, torn. iv. p. 205, Letter to Oldenburg.
 
 32 SIR ISAAC NEWTON. 
 
 only executed the magnificent instruments by which 
 he discovered the ring and the satellites of Saturn, 
 but had begun those splendid researches respecting 
 the nature of light, and the phenomena of double 
 refraction, which have led his successors to such 
 brilliant discoveries. Newton, therefore, arose when 
 the science of light was ready for some great ac- 
 cession, and at the precise time when he was re- 
 quired to propagate the impulse which it had received 
 from his illustrious predecessors. 
 
 The ignorance which then prevailed respecting 
 the nature and origin of colours is sufficiently ap- 
 parent from the account we have already given of 
 Dr. Barrow's speculations on this subject. It was 
 always supposed that light of every colour was 
 equally refracted or bent out of its direction when 
 it passed through any lens or prism, or other refract- 
 ing medium ; and though the exhibition of colours 
 by the prism had been often made previous to the 
 time of Newton, yet no philosopher seems to have 
 attempted to analyze the phenomena. 
 
 When he had procured his triangular glass prism, 
 <t section of which is shown at ABC, (Jig. 1,) he 
 
 Fig. 1. 
 
 made a hole H in one of his window-shutters, SHT 
 and having darkened his chamber, he let in a con 
 vement quantity of the sun's light RR, which, pass
 
 EXPERIMENTS ON COLOURS. 33 
 
 mg through the prism ABC, was so refracted us to 
 exhibit all the different colours on the wall at MN, 
 forming an image about five times as long as it was 
 broad. " It was at first," says our author, " a very 
 pleasing divertisement to view the vivid and intense 
 colours produced thereby," but this pleasure was 
 immediately succeeded by surprise at various circum- 
 stances which he had not expected. According to 
 the received laws of refraction, he expected the 
 image MN to be circular, like the white image at W, 
 which the sunbeam RR had formed on the wall 
 previous to the interposition of the prism; but when 
 he found it to be no less than five times larger than 
 its breadth, it. " excited in him a more than ordinary 
 curiosity to examine from whence it might proceed. 
 He could scarcely think that the various thickness of 
 the glass, or the termination with shadow or dark- 
 ness, could have any influence on light to produce such 
 an effect: yet he thought it not amiss first to examine 
 those circumstances, and so find what would happen 
 by transmitting light through parts of the glass of 
 divers thicknesses, or through holes in the window 
 of divers bignesses, or by setting the prism without 
 (on the other side of ST), so that the fight might 
 pass through it and be refracted before it was termi- 
 nated by the hole ; but he found none of these cir- 
 cumstances material. The fashion of the colours 
 was in all those cases the same." 
 
 Newton next suspected that some uneyenness in 
 the glass, or other accidental irregularity, might 
 cause the dilatation of the colours. In order to try 
 this, he took another prism BCD', and placed it in 
 such a manner that the light RRW passing through 
 them both might be refracted contrary ways, and 
 thus returned by BOB' into that course RRW, from 
 which the prism ABC had diverted it, for by this 
 means he thought the regular effects of the prism 
 ABC would be destroyed by the prism BCB, and the 
 irregular ones more augmented by the multiplicity
 
 34 SIR ISAAC NEWTON. 
 
 1 of refractions. The result was, that the light which 
 was diffused by the first prism ABC into an oblong 
 form, was reduced by the second prism BOB' into a 
 circular one W, with as much regularity as when it 
 did not pass through them at all; so that whatever 
 was the cause of the length of the image MN, it did 
 not arise from any irregularity in the prism. 
 
 Our author next proceeded to examine more critic- 
 ally what might be effected by the difference of the 
 incidence of the rays proceeding from different parts 
 of the sun's disk; but by ..taking accurate measures 
 of the lines and angles, he found that the angle of 
 the emergent rays should be 31 minutes equal to the 
 sun's diameter, whereas the real angle subtended by 
 MN at the hole H was 2 49'. But as this computa- 
 tion was founded on the hypothesis, that the sine of 
 the angle of incidence was proportional to the sine 
 of the angle of refraction, which from his own ex- 
 perience he could not imagine to be so erroneous as 
 to make that angle but 31', which was in reality 2 
 49', yet " his curiosity caused him again to take up 
 his prism" ABC, and having turned it round in both 
 directions, so as to make the rays RR fall both with 
 greater anfl with less obliquity upon the face AC, he 
 found that the colours on the wall did not sensibly 
 change their place; and hence he obtained a decided 
 proof that they could not be occasioned by a differ- 
 ence in the incidence of the light radiating from dif- 
 ferent parts of the sun's disk. 
 
 Newton then began to suspect that the rays, after 
 passing through the prism, might move in curve lines, 
 and, in proportion to the different degrees of curva- 
 ture, might tend to different parts of the wall; and 
 this suspicion^was strengthened by the recollection 
 that he had often seen a tennis-ball struck with an 
 oblique racket describe such a curve line. In this 
 case a circular and a progressive motion is commu- 
 nicated to the. ball by the stroke, and in consequence 
 of this, the direction of its motion was curvilineal,
 
 EXPERIMKNTS ON COLOURS. 35 
 
 so that if the rays of light were globular bodies, 
 they might acquire a circulating motion by their ob- 
 lique passage out of one medium into another, and 
 thus move like the tennis-ball in a curve line. Not- 
 withstanding, however, "this plausible ground of 
 suspicion," he could discover no such curvature in 
 their direction, and, what was enough for his pur- 
 pose, he observed that the difference between the 
 length MN of the image, and the diameter of the 
 hole H, was proportional to their distance HM, 
 which could not have happened had the rays moved 
 in curvilineal paths. 
 
 These different hypotheses, or suspicions, as New- 
 ton calls them, being thus gradually removed, he 
 was at length led to an experiment which deter- 
 mined beyond a doubt the true cause of the elonga- 
 tion of the coloured image. Having taken a board 
 with a small hole in it, he placed it behind the face 
 BC of the prism, and close to it, so that he could 
 transmit through the hole any one of the colours in 
 MN, and keep back all the rest. When the hole, 
 for example, was near C, no other light but the red 
 fell upon the wall at N. He then placed behind N 
 another board with a hole in it, and behind this 
 board he placed another prism, so as to receive the 
 red light at N, which passed through this hole in the 
 second board. He then turned round the first prism 
 ABC so as to make all the colours pass in succession 
 through these two holes, and he marked their places 
 on the wall. From the variation of these places, 
 he saw that the red rays at N were less refracted by 
 the second prism than the orange rays, the orange. 
 less than the yellow, and so on, the violet being more 
 refracted than all the rest. 
 
 Hence he drew the grand conclusion, that light 
 was not homogeneous, but consisted of rays, some of 
 which were more refrangible than others* 
 
 As soon as this important truth was established, 
 Sir Isaac saw that a lens which refracts light exactly
 
 36 blR ISAAC NKWTON. 
 
 like a prism must also refract the differently coloured 
 rays with different degrees of force, bringing the 
 violet rays to a focus nearer the glass than the red 
 rays. This is shown in Jig. 2, where LL is a con- 
 vex lens, and S, L, SL rays of the sun falling upon it 
 
 Fig. 2. 
 
 M 
 
 M 
 
 in parallel directions. The violet rays existing in 
 the white light SL being more refrangible than the 
 rest, will be more refracted or bent, and will meet at 
 V, foiming there a violet image of the sun. In like 
 manner the yellow rays will form an image of the 
 sun at Y, and so on, the red rays, which are the least 
 refrangible, being brought to a focus at R, and there 
 forming a red image of the sun. 
 
 Hence, if we suppose LL to be the object-glass of 
 a telescope directed to the sun, and MM an eye-glass 
 through which the eye at E sees magnified the image 
 or picture of the sun formed by LL, it cannot see 
 distinctly all the different images between R and V. 
 If it is adjusted so as to see distinctly the yellow 
 image at Y, as it is in the figure, it will not see dis- 
 tinctly either the red or violet images, nor indeed any 
 of them but the yellow one. There will conse- 
 quently be a distinct yellow image, with indistinct 
 images of all the other colours, producing great con- 
 fusion and indistinctness of vision. As soon as Sir 
 Isaac perceived this result of his discovery, he aban- 
 doned his attempts to improve the refracting tele-
 
 IMPERFECTIONS OF TELESCOPES. 37 
 
 scope, and took into consideration the principle of re- 
 flection; and as he found that rays of all colours 
 were reflected regularly, so that the angle of reflec- 
 tion was equal to the angle of incidence, he con- 
 cluded that, upon this principle, optical instruments 
 might be brought to any degree of perfection imaginable, 
 provided a reflecting substance could be found which 
 could polish as finely as glass, and reflect as much 
 light as glass transmits, and provided a method of 
 communicating to it a parabolic figure could be ob- 
 tained. These difficulties, however, appeared to him 
 very great, and he even thought them insuperable 
 when he considered that, as any irregularity in a re- 
 flecting surface makes the rays deviate five or six 
 times more from their true path than similar irregu- 
 larities in a refracting surface, a much greater de- 
 gree of nicety would be required in figuring reflect- 
 ing specula than refracting lenses. 
 
 Such was the progress of Newton's optical dis- 
 coveries, when he was forced to quit Cambridge in 
 1666 by the plague which then desolated England, 
 and more than two years elapsed before he pro- 
 ceeded any farther. In 1668 he resumed the inquiry, 
 and having thought of a delicate method of polish- 
 fng, proper for metals, by which, as he conceived, 
 " the figure would be corrected to the last," he began 
 to put this method to the test of experiment. At 
 this time he was acquainted with the proposal of 
 Mr. James Gregory, contained in his Optica Promota, 
 to construct a reflecting telescope with two concave 
 specula, the largest of which had a hole in the 
 middle of the larger speculum, to transmit the light 
 to an eye-glass;* but he conceived that it would be 
 
 * M. Biot, in his Life of Newton, has stated that Newton was pre- 
 ceded in the invention of the reflecting telescope by Gregory, but proba- 
 bly without knowing it. It is quite certain, however, that Newton was 
 acquainted with Gregory's invention, as appears from the following 
 avowal of it. " When I first applied myself to try the effects of reflec- 
 tion, Mr. Gregory's Optica Promota (printed in the year 1663) having 
 fallen into my hands, where there is an instrument described with a hole
 
 38 SIR ISAAC NEWTON. 
 
 an improvement on this instrument to place the eye* 
 glass at the side of the tube, and to reflect the rays 
 to it by an oval plane speculum. One of these 
 instruments he actually executed with his own 
 hands; and he gave an-account of it in a letter to a 
 friend, dated February 23d, 1668-9, a letter which is 
 also remarkable for containing the first allusion to 
 his discoveries respecting colours. Previous to this 
 he was in correspondence on the subject with Mr. 
 Ent, afterward Sir George Ent, one of the original 
 council of the Royal Society, an eminent medical 
 writer of his day, and President of the College of 
 Physicians. In a letter to Mr. Ent he had promised 
 an account of his telescope to their mutual friend, 
 and the letter to which we now allude contained the 
 fulfilment of that promise. The telescope was six 
 inches long. It bore an aperture in the large specu- 
 lum something more than an inch, and as the eye- 
 glass was a plano-convex lens, whose focal length 
 was one-sixth or one-seventh of an inch, it magni- 
 fied about forty times, which, as Newton remarks, 
 was more than any six-foot tube (meaning refracting 
 telescopes) could do with distinctness. On account 
 of the badness of the materials, however, and the 
 want of a good polish, it represented objects less 
 distinct than a six-feet tube, though he still thought 
 it would be equal to a three or four feet tube di- 
 rected to common objects. He had seen through it 
 Jupiter distinctly with his four satellites, and also 
 the horns or moon-like phases of Venus, though this 
 last phenomenon required some niceness in adjusting 
 the instrument. 
 Although Newton considered this little instru- 
 
 in the midst of fne object-glass, to transmit the light to an eye-glasa 
 placed behind it, I had thence an occasion of considering that sort of con- 
 Btruction, and found their disadvantages so great, that I saw it necessary 
 before I attempted any thing in the practice to alter the design of them 
 and place the eye-glass at the side of the tube rather than at the middle. 
 ^Letter to Oldenburg, May 4th, 1672
 
 p 
 b 
 
 REFLECTING TELESCOPE. 39 
 
 ment as in itself contemptible, yet he regarded it as 
 an " epitome of what might be done ;" and he ex- 
 ressed his conviction that a six-feet telescope might 
 e made after this method, which would perform as 
 well as a sixty or a hundred feet telescope made in 
 the common way; and that if a common refracting 
 telescope could be made of the "purest glass exqui- 
 sitely polished, with the best figure that any geo- 
 metrician (Descartes, &c.) hath or can design," it 
 would scarcely perform better than a common tele 
 scope. This, he adds, may seem a paradoxical as 
 sertion, yet he continues, " it is the necessary con- 
 sequence of some experiments which I have made 
 concerning the nature of light." 
 
 The telescope now described possesses a very pe- 
 culiar interest, as being the first reflecting one which 
 was ever executed and directed to the heavens. 
 James Gregory, indeed, had attempted, in 1664 or 
 1665, to construct his instrument. He employed 
 Messrs. Rives and Cox, who were celebrated glass- 
 grinders of that time, to execute a concave speculum 
 of six feet radius, and likewise a small one ; but as 
 they had failed in polishing the large one, and as Mr. 
 Gregory was on the eve of going abroad, he troubled 
 himself no farther about the experiment, and the 
 tube of the telescope was never made. Some time 
 afterward, indeed, he "made some trials both with a 
 little concave and convex speculum," but, "pos- 
 sessed with the fancy of the defective figure, he 
 would not be at the pains to fix every thing in its due 
 distance." 
 
 Such were the earliest attempts to construct the 
 reflecting telescope, that noble instrument which 
 has since effected such splendid discoveries in as- 
 tronomy. Looking back from the present advanced 
 state of practical science, how great is the contrast 
 between the loose specula of Gregory and the fine 
 Gregorian telescopes of Hadley, Short, and Veitch, 
 between the humble six-inch tube of Newton and 
 the gigantic instruments of Herschel and Ramage.
 
 40 SIR ISAAC NEWTON. 
 
 The success of this first experiment inspired New- 
 ton with fresh zeal, and though his mind was now 
 occupied with his optical discoveries, with the ele- 
 ments of his method of fluxions, and with the ex- 
 panding germ of his theory of universal gravitation, 
 yet with all the ardour of youth he applied himself 
 to the laborious operation of executing another re- 
 flecting telescope With his own hands. This instru- 
 ment, which was better than the first, though it lay 
 by him several years, excited some interest at Cam- 
 bridge ; and Sir Is"aac himself informs us, that one 
 of the fellows of Trinity College had completed a 
 telescope of the same kind, which he considered as 
 somewhat superior to his own. The existence of 
 these telescopes having become known to the Royal 
 Society, Newton was requested to send his instru- 
 ment for examination to that learned body. He ac- 
 cordingly transmitted it to Mr. Oldenburg in Decem- 
 ber, 1671, and from this epoch his name began to 
 acquire that celebrity by which it has been so pecu- 
 liarly distinguished. 
 
 On the llth of January, 1672, it was announced 
 to the Royal Society that his reflecting telescope 
 had been shown to the king, and had been examined 
 by the president, Sir Robert Moray, Sir Paul Neale, 
 Sir Christopher Wren, and Mr. Hook. These gen- 
 tlemen entertained so high an opinion of it, that, in 
 order to secure the honour of the contrivance to its 
 author, they advised the inventor to send a drawing 
 and description of it to Mr. Huygens at Paris. Mr. 
 Oldenburg accordingly drew up a description of it 
 in Latin, which, after being corrected by Mr. New- 
 ton, was transmitted to that eminent philosopher. 
 This telescope, of which the annexed is an accurate 
 drawing, is carefully preserved in the library of the 
 Royal Society of London, with the following in- 
 scription : 
 
 " Invented by Sir Isaac Newton and made with his 
 own hands 1671."
 
 REFLECTING TELESCOPES. 
 
 41
 
 4-4 SIR ISAAC NEWTON. 
 
 It does not appear that Newton executed any other 
 reflecting telescopes than the two we have mentioned. 
 He informs us that he repolished and greatly im- 
 proved a fourteen-feet object-glass, executed by a 
 London artist, and having proposed hi 1678 to sub- 
 stitute glass reflectors in place of metallic specula, 
 he tried to make a reflecting telescope on this 
 principle four feet long, and with a magnifying power 
 of 150. The glass was wrought by a London artist, 
 and though it seemed well finished, yet, when it was 
 quicksilvered on its convex side, it exhibited all over 
 the glass innumerable inequalities, which gave an 
 indistinctness to every object. He expresses, how- 
 ever, his conviction that nothing but good work- 
 manship is wanting to perfect these telescopes, and 
 he recommends then: consideration " to the curious 
 in figuring glasses." 
 
 For a period of fifty years this recommendation 
 excited no notice. At last Mr. James Short of 
 Edinburgh, an artist of consummate skill, executed 
 about the year 1730 no fewer than six reflecting 
 telescopes with glass specula, three of fifteen inches, 
 and three of nine inches in focal length. He found 
 it extremely troublesome to give them a true figure 
 with parallel surfaces; and several of them when 
 finished turned out useless, in consequence of the 
 veins which then appeared in the glass. Although 
 these instruments performed remarkably well, yet 
 the light was fainter than he expected, and from this 
 cause, combined with the difficulty of finishing them, 
 he afterward devoted his labours solely to those 
 with metallic specula. 
 
 At a later period, in 1822, Mr. G. B. Airy of 
 Trinity College, and one of the distinguished suc- 
 cessors of Newton hi the Lucasian chair, resumed 
 the consideration of glass specula, and demonstrated 
 that the aberration both of figure and of colour 
 might be corrected in these instruments. Upon this 
 ingenious principle Mr. Airy executed more than
 
 REFLECTING TELESCOPES. 43 
 
 one telescope, but though the result of the experi- 
 ment was such as to excite hopes of ultimate suc- 
 cess, yet the construction of such instruments is 
 still a desideratum in practical science. 
 
 Such were the attempts which Sir Isaac Newton 
 made to construct reflecting telescopes ; but notwith- 
 standing the success of his labours, neither the phi- 
 losopher nor the practical optician seems to have 
 had courage to pursue them. A London artist, in 
 deed, undertook to imitate these instruments ; but 
 Sir Isaac informs us, that " he fell much short of 
 what he had attained, as he afterward understood 
 by discoursing with the under workmen he had em 
 ployed." After a long period of fifty years, John 
 Hadley, Esq. of Essex, a Fellow of the Royal So- 
 ciety, began in 1719 or 1720 to execute a reflecting 
 telescope. His scientific knowledge and his manual 
 dexterity fitted him admirably for such a task, and, 
 probably after many failures, he constructed two 
 large telescopes about five feet three inches long, 
 one of which, with a speculum six inches in diameter, 
 was presented to the Royal Society in 1723. The 
 celebrated Dr. Bradley and the Rev. Mr. Pound 
 compared it with the great Huygenian refractor 123 
 feet long. It bore as high a magnifying power as 
 the Huygenian telescope : it showed objects equally 
 distinct, though not altogether so clear and bright, 
 and it exhibited every celestial object that had been 
 discovered by Huygens, the five satellites of Sat- 
 urn, the shadow of Jupiter's satellites on his disk, 
 the black list in Saturn's ring, and the edge of his 
 shadow cast on the ring. Encouraged and instructed 
 by Mr. Hadley, Dr. Bradley began the construction 
 of reflecting telescopes, and succeeded so well that 
 he would have completed one of them, had he not 
 been obliged to change his residence. Some time 
 afterward he and the Honourable Samuel Molyneux 
 undertook the task together at Kew, and attempted 
 to execute specula about twenty-six inches in focal
 
 44 SIR ISAAC NEWTON. 
 
 'ength ; but notwithstanding Dr. Bradley's former 
 xperience, and Mr. Hadley's frequent instructions, 
 
 was a long time before they succeeded. The first 
 good instrument which they finished was in May, 
 1724. It was twenty-six inches in focal length ; but 
 they afterward completed a very large one of eight 
 feet, the largest that had ever been made. The first 
 of these instruments was afterward elegantly fitted 
 up by Mr. Molyneux, and presented to his majesty 
 John V. King of Portugal. 
 
 The great object of these two able astronomers 
 was to reduce the method of making specula to 
 such a degree of certainty that they could be manu- 
 factured for public sale. Mr. Hauksbee had indeed 
 made a good one about three and a half feet long, 
 and had proceeded to the execution of two others, 
 one of six feet, and another of twelve feet in focal 
 length ; but Mr. Scarlet and Mr. Hearne, having re- 
 ceived all the information which Mr. Molyneux had 
 acquired, constructed them for public sale ; and the 
 reflecting telescope has ever since been an article of 
 trade with every regular optician. 
 
 As Sir Isaac Newton was at this time President 
 of the Royal Society, he had the high satisfaction 
 of seeing his own invention become an instrument 
 of public use, and of great advantage to science, 
 and he no doubt felt the full influence of this triumph 
 of his skill. Still, however, the reflecting telescope 
 had not achieved any new discovery in the heavens. 
 The latest accession to astronomy had been made 
 oy the ordinary refractors of Huygens, labouring 
 under all the imperfections of coloured light ; and 
 this long pause in astronomical discovery seemed 
 to indicate that man had carried to its farthest limits 
 his power of penetrating into the depths of the uni- 
 verse. This, however, was only one of those sta- 
 tionary positions from which human genius takes a 
 new and a loftier elevation. While the English op- 
 ticians were thus practising the recent art of grinding
 
 DR. HERSCHEL'S TELESCOPES. 4A 
 
 specula, Mr. James Short of Edinburgh was devot- 
 ing to the subject all the energies of his youthful 
 mind. In 1732, and in the 22d year of his age, he 
 began his labours, and he carried to such high per- 
 fection the art of grinding and polishing specula, and 
 of giving them the true parabolic figure, that, with 
 a telescope fifteen inches in focal length, he read in 
 the Philosophical Transactions at the distance of 
 500 feet, and frequently saw the five satellites of 
 Saturn together, a power which was beyond the 
 reach even of Hadley's six-feet instrument. The 
 celebrated Maclaurin compared the telescopes of 
 Short with those made by the best London artists, 
 and so great was their superiority, that his small 
 telescopes were invariably superior to larger ones 
 from London. In 1742, after he had settled as an 
 optician in the metropolis, he executed for Lord 
 Thomas Spencer a reflecting telescope, twelve feet 
 in focal length, for 630/. ; in 1752 he completed one for 
 the King of Spain, at the expense of 1200/. ; and a 
 short time before his death, "which took place in 
 1768, he finished the specula of the large telescope 
 which was mounted equatorially for the observatory 
 of Edinburgh by his brother Thomas Short, who was 
 offered twelve hundred guineas for it by the King of 
 Denmark. 
 
 Although the superiority of these instruments, 
 which were all of the Gregorian form, demonstrated 
 the value of the reflecting telescope, yet no skilful 
 hand had yet directed it to the heavens ; and it was 
 reserved for Dr. Herschel to employ it as an instru- 
 ment of discovery, to exhibit to the eye of man new 
 worlds and new systems, and to bring within the 
 grasp of his reason those remote regions of space 
 to which his imagination even had scarcely ventured 
 to extend its power. So early as 1774 he completed 
 a five-feet Newtonian reflector, and he afterward 
 executed no fewer than two hundred 7 feet, one hun- 
 dred and fifty 10 feet, and eighty 20 feet specula. In 
 D l
 
 46 SIR ISAAC NEWTON. 
 
 1781 he began a reflector thirty feet long, and having 
 a speculum thirty-six inches in diameter ; and under 
 the munificent patronage of George III. he com- 
 pleted, in 1789, his gigantic instrument forty feet 
 long, with a speculum forty-nine and a half inches 
 in diameter. The genius and perseverance which 
 created instruments of such transcendant magnitude 
 were not likely to terminate with their construction. 
 In the examination of the starry heavens, the ulti- 
 mate object of his labours. Dr. Herschel exhibited 
 the same exalted qualifications, and in a few years 
 he rose from the level of humble life to the enjoy- 
 ment of a name more glorious than that of the sages 
 and warriors of ancient times, and as immortal as 
 the objects with which it will be for ever associated. 
 Nor was it in the ardour of the spring of life that 
 these triumphs of reason were achieved. Dr. Her- 
 schel had reached the middle of his course before 
 his career of discovery began, and it was in the au- 
 tumn and winter of his days that he reaped the full 
 harvest of his glory. The discovery of a new planet 
 at the verge of the solar system was the first trophy 
 of his skill, and new double and multiple stars, and 
 new nebulae, and groups of celestial bodies were 
 added in thousands to the system of the universe. 
 The spring-tide of knowledge which was thus let in 
 upon the human mind continued for a while to spread 
 its waves over Europe ; but when it sank to its ebb in 
 England, there was no other bark left upon the strand 
 but that of the Deucalion of Science, whose home 
 had been so long upon its waters. 
 
 During the life of Dr. Herschel, and during the 
 reign, and within the dominions of his royal patron, 
 four new planets were added to the solar system, 
 but they were detected by telescopes of ordinary 
 power ; and we venture to state, that since the reign 
 of George III no attempt has been made to keep 
 up the continuity of Dr. HerschePs discoveries. 
 
 Mr. Herschel, his distinguished son, has indeed
 
 ELECTED INT'J THE ROYAL SOCIETY. 47 
 
 c< rpleted more than one telescope of considerable! 
 size ; Mr. Ramage, of Aberdeen, has executed re- 
 flectors rivalling almost those of Slough ; and Lori 
 Oxmantown, an Insh nobleman of high promise, is, 
 now engaged on an instrument of great size. But 
 what avail the enthusiasm and the efforts of indi- 
 vidual minds in the intellectual rivalry of nations ? 
 When the proud science of England pines in obscu- 
 rity, blighted by the absence of the royal favour, and 
 of the nation's sympathy; when its chivalry fall 
 unwept and unhonoured; how can it sustain the 
 conflict against the honoured and marshalled genius 
 of foreign lands ? 
 
 CHAPTER IV. 
 
 He delivers a Course of. Optical Lectures at Cambridge Is elected Felloio 
 
 Influence of these Disputes on the Mind of Newton. 
 
 ALTHOUGH Newton delivered a course of lectures 
 on optics in the University of Cambridge in the 
 years 1669, 1670, and 1671, containing his principal 
 discoveries relative to the different refrangibility of 
 light, yet it is a singular circumstance, that these 
 discoveries should not have become public through 
 the conversation or correspondence of his pupils. 
 The Royal Society had acquired no knowledge of 
 them till the beginning of 1672, and his reputation 
 in that body was founded chiefly on his reflecting 
 telescope. On the 23d December, 1671, the cele- 
 brated Dr. Seth Ward, Lord Bishop of Sarum, who 
 was the author of several able works on astronomy, 
 and had filled the astronomical chair at Oxford, 
 proposed Mr. Newton as a Fellow of the Royal
 
 48 SIR ISAAC NEWTON. 
 
 Society. The satisfaction which he derived from this 
 circumstance appears to have been considerable; 
 and in a letter to Mr. Oldenburg, of the 6th January, 
 he says, " I am very sensible of the honour done 
 me by the Bishop of Sarum in proposing me a can- 
 didate ; and which, I hope, will be further conferred 
 upon me by my election into the Society ; and if 
 so, I shall endeavour to testify my gratitude, by 
 communicating what my poor and solitary endeav- 
 ours can effect towards the promoting your philo- 
 sophical designs." His election accordingly took 
 place on the llth January, the same day on which 
 the Society agreed to transmit a description of his 
 telescope to Mr. Huygens at Paris. The notice of 
 his election, and the thanks of the Society for the 
 communication of his telescope, were conveyed hi 
 the same letter, with an assurance that the Society 
 " would take care that all right should be done him 
 in the matter of this invention." In his next letter 
 to Oldenburg, written on the 18th January, 1671-2, 
 he announces his optical discoveries in the following 
 remarkable manner: "I desire that in your next 
 letter you would inform me for what time the So- 
 ciety continue their weekly meetings ; because if 
 they continue them for any time, I am purposing 
 them, to be considered of and examined, an account 
 of a philosophical discovery which induced me to the 
 making of the said telescope ; and I doubt not but 
 will prove much more grateful than the communica- 
 tion of that instrument ; being in my judgment the 
 oddest, if not the most considerable detection which 
 hath hitherto been made in the operations of nature." 
 This " considerable detection" was the discovery 
 of the different refrangibility of the rays of light 
 which we have already explained, and w r hich led 
 to the construction of his reflecting telescope. It 
 was communicated to the Royal Society in a letter 
 to Mr. Oldenburg, dated February 6th, and excited 
 great interest among its members. The "solemn
 
 COMMUNICATES HIS DISCOVERIES. 49 
 
 thanks" of the meeting were ordered to be trans- 
 mitted to its author for his "very ingenious dis- 
 course." A desire was expressed to have it imme- 
 diately printed, both for the purpose of having it 
 well considered by philosophers, and for " securing 
 the considerable notices thereof to the author against 
 ihe arrogations of others;" and Dr. Seth Ward, 
 Bishop of Salisbury, Mr. Boyle, and Dr. Hooke 
 were desired to peruse and consider it, and to bring 
 tn a report upon it to the Society. 
 
 The kindness of this distinguished body, and the 
 anxiety which they had already evinced for his 
 reputation, excited on the part of Newton a corres- 
 ponding feeling, and he gladly accepted of their pro- 
 posal to publish his discourse in the monthly num- 
 bers in which the Transactions were then given to 
 the world. " It was an esteem," says he,* " of the 
 Royal Society for most candid and able judges in 
 philosophical matters, encouraged me to present 
 them with that discourse of light and colours, which 
 since they have so favourably accepted of, I do ear- 
 nestly desire you to return them my cordial thanks. 
 I before thought it a great favour to be made a 
 member of that honourable body; but I am now 
 more sensible of the advantages ; for believe me, 
 sir, I do not only esteem it a duty to concur with 
 you in the promotion of real knowledge ; but a great 
 privilege, that, instead of exposing discourses to a 
 prejudiced and common multitude, (by which means 
 many truths have been baffled and lost), I may with 
 freedom apply myself to so judicious and impartial 
 an assembly. A s to the printing of that letter, I am 
 satisfied in theii judgment, or else I should have 
 thought it too straight and narrow for public view. 
 I designed it only to those that know how to im- 
 prove upon hints of things ; and, therefore, to spare 
 tediousness, omitted many such remarks and e\ 
 
 * Letter to Oldenburg, February 10, 1671
 
 60 
 
 SIR ISAAC NEWTON. 
 
 periments as might be collected by considering the 
 assigned laws of refractions ; some of which I be- 
 lieve, with the generality of men, would yet be 
 almost as taking as any I described. But yet, since 
 the Royal Society have thought it fit to appear pub- 
 licly, I leave it to their pleasure : and perhaps to 
 supply the aforesaid defects, I may send you some 
 more of the experiments to second it (if it be so 
 thought fit), in the ensuing Transactions." 
 
 Following the order which Newton himself adopted, 
 we have, in the preceding chapter, given an account 
 of the leading doctrine of the different refrangibility 
 of light, and of the attempts to improve the reflect- 
 ing telescope which that discovery suggested. We 
 shall now, therefore, endeavour to make the reader 
 acquainted with the other discoveries respecting 
 colours which he at this time communicated to the 
 Royal Society. 
 
 Having determined, by experiments 
 already described, that a beam oi 
 white light, as emitted from the sun, 
 consisted of seven different colours, 
 which possess different degrees of 
 refrangibility, he measured the re- 
 lative extent of the coloured spaces, 
 and found them to have the propor- 
 tions shown in fig. 4, which rep- 
 resents the prismatic spectrum, and 
 \\hich is nothing more than an elon- 
 
 gated image of the sun produced by g 
 the rays being separated in different 
 degrees from their original direction, 
 the red being refracted least, and the 
 violet most powerfully. 
 
 If we consider light as consisting 
 of minute particles of matter, we may 
 form some notion of its decomposi- 
 tion by the prism from the following 
 popular illustration. If we take steel
 
 DECOMPOSITION OF LIGHT. 51 
 
 filings of seven different degrees of fineness and 
 mix them together, there are two ways in which we 
 may conceive the mass to be decomposed, or, what 
 is the same thing, all the seven different kinds of 
 filings separated from each other. By means of 
 seven sieves of different degrees of fineness, and so 
 made that the finest will just transmit the finest 
 powder and detain all the rest, while the next in 
 fineness transmits the two finest powders and detains 
 all the rest, and so on, it is obvious that all the pow- 
 ders may be completely separated from each other. 
 If we again mix all the steel filings, and laying them 
 upon a table, hold high above them a flat bar magnet, 
 so that none of the filings are attracted, then if we 
 bring the magnet nearer and nearer, we shall come 
 to a point where the finest filings are drawn up to it. 
 These being removed, and the magnet brought 
 nearer still, the next finest powders will be attracted, 
 and so on till we have thus drawn out of the mass 
 all the powders in a separate state. We may con- 
 ceive the bar magnet to be inclined to the surface 
 of the steel filings, and so moved over the mass, 
 that at the end nearest to them the heaviest or 
 coarsest will be attracted, and all the remotest and 
 the finest or lighter filings, while the rest are at- 
 tracted to intermediate points, so that the seven 
 different filings are not only separated, but are found 
 adhering in separate patches to the surface of the 
 flat magnet. The first of these methods, with the 
 sieves, may represent the process of decomposing 
 light, by which certain rays of white light are ab- 
 sorbed, or stifled, or stopped in passing through 
 bodies, while certain other rays are transmitted. 
 The second method may represent the process of 
 decomposing light by refraction, or by the attraction 
 of certain rays farther from their original direction 
 than other rays, and the different patches of filings 
 upon the flat magnet may represent the spaces on 
 the spectrum
 
 52 SIR ISAAC NEWTON. 
 
 When a beam of white light is decomposed into 
 the seven different colours of the spectrum, any 
 particular colour, when once separated from the 
 rest, is not susceptible of any change, or farther 
 decomposition, whether it is refracted through prisms 
 or reflected from mirrors. It may become fainter 
 or brighter, but Newton never could, by any process, 
 alter its colour or its refrangibility. 
 
 Among the various bodies which act upon light, 
 it is conceivable that there might have been some 
 which acted least upon the violet rays and mosl 
 upon the red rays. Newton, however, found that 
 this never took place ; but that the same degree of 
 refrangibility always belonged to the same colour, 
 and the same colour to the same degree of refran- 
 gibility. 
 
 Having thus determined that the seven different 
 colours of the spectrum were original or simple, he 
 was led to the conclusion that whiteness or white 
 light is a compound of all the seven colours of the 
 spectrum, in the proportions in which they are rep- 
 resented in fig. 4. In order to prove this, or what 
 is called the recomposition of white light out of the 
 seven colours, he employed three different methods. 
 
 When the beam RR was separated into its ele- 
 
 colours bv the prism ABC. he received the
 
 RECOMPOSITION OF LIGHT. " 53 
 
 colours on another prism BOB', held either close to 
 the first or a little behind it, and by the opposite re- 
 fraction of this prism they were all refracted back 
 into a beam of white light BW, which formed a 
 white circular image on the wall at W, similar to 
 what took place before any of the prisms were 
 placed in its way. 
 
 The other method of recomposing white light 
 consisted in making the spectrum fall upon a lens at 
 some distance from it. When a sheet of white 
 paper was held behind the lens, and removed to a 
 proper distance, the colours were all refracted into 
 a circular spot, and so blended as to reproduce light 
 so perfectly white as not to differ sensibly from the 
 direct light of the sun. 
 
 The last method of recomposing white light was 
 one more suited to vulgar apprehension. It con- 
 sisted in attempting to compound a white by mix- 
 ing the coloured powders used by painters. He 
 was aware that such colours, from their very nature, 
 could not compose a pure white ; but even this im- 
 perfection in the experiment he removed by an in- 
 genious device. He accordingly mixed one part of 
 red lead, four parts of blue bice, and a proper propor- 
 tion of orpiment and verdigris. This mixture was 
 dun, like wood newly cut, or like the human skin. 
 He now took one-third of the mixture and rubbed 
 it thickly on the floor of his room, where the sun 
 shone upon it through the opened casement, and be- 
 side it, in the shadow, he laid a piece of white paper 
 of the same size. " Then going from them to the 
 distance of twelve or eighteen feet, so that he could 
 not discern the unevenness of the surface of the 
 powder nor the little shadows let fall from the gritty 
 particles thereof; the powder appeared intensely 
 white, so as to transcend even the paper itself in 
 whiteness." By adjusting the relative illumination 
 of the powders and the paper, he was able to 
 make them both appear of the very same degree 01 
 E
 
 54 SIR ISAAC NEWTON. 
 
 whiteness. " For," says he, " when I was trying 
 this, a friend coming to visit me, I stopped him at 
 the door, and before I told him what the colours 
 were, or w 7 hat I was doing, I asked him which of the 
 two whites were the best, and wherein they differed] 
 And after he had at that distance vie wed them well, he 
 answered, that they were both good whites, and that 
 he could not say which was best, nor wherein their 
 colours differed." Hence Newton inferred that 
 perfect whiteness may be compounded of different 
 colours. 
 
 As all the various shades of colour which appear 
 in the material world can be imitated by intercept- 
 ing certain rays in the spectrum, and uniting all the 
 rest, and as bodies always appear of the same coloui 
 as the light in which they are placed, he concluded, 
 that the colours of natural bodies are not qualities 
 inherent in the bodies themselves, but arise from the 
 disposition of the particles of each body to stop or 
 absorb certain rays, and thus to 'reflect more copiously 
 the rays which are not thus absorbed. 
 
 No sooner were these discoveries given to the 
 world than they were opposed with a degree of viru- 
 lence and ignorance which have seldom been com- 
 bined in scientific controversy. Unfortunately for 
 Newton, the Royal Society contained few individuals 
 of pre-eminent talent capable of appreciating the 
 truth of his discoveries, and of protecting him against 
 the shafts of his envious and ignorant assailants. 
 This eminent body, while they held his labours in 
 the highest esteem, were still of opinion that his 
 discoveries were fair subjects of discussion, and 
 their secretary accordingly communicated to him all 
 the papers which were written in opposition to his 
 views. The first of these was by a Jesuit named 
 Ignatius Pardies, Professor of Mathematics at Cler- 
 raont, who pretended that the elongation of the sun's 
 image arose from the inequal incidence of the dif- 
 ferent rays on the first fa^e of the prism, although
 
 CONTROVERSY WITH LINUS, 55 
 
 Newton Iiad demonstrated in his own discourse that 
 this was not the case. In April, 1672, Newton trans- 
 mitted to Oldenburg a decisive reply to the animad- 
 versions ofPardies; but, unwilling to be vanquished, 
 this disciple of Descartes took up a fresh position, 
 and maintained that the elongation of the spectrum 
 might be explained by the diffusion of light on the 
 hypothesis of Grimaldi, or by the diffusion of undu- 
 lations on the hypothesis of Hook. Newton again 
 replied to these feeble reasonings ; but he contented 
 himself with reiterating his original experiments, 
 and confirming them by more popular arguments, 
 and the vanquished Jesuit wisely quitted the field. 
 
 Another combatant soon sprung up in the person 
 of one Francis Linus, a physician in Liege,* who, 
 on the 6th October, 1674, addressed a letter to a 
 friend in London, containing animadversions on 
 Newton's doctrine of colours. He boldly affirms, 
 that in a perfectly clear sky the image of the sun 
 made by a prism is never elongated, and that the 
 spectrum observed by Newton was not formed by 
 the true sunbeams, but by rays proceeding from 
 some bright cloud. In support of these assertions, 
 he appeals to frequently repeated experiments on 
 the refractions and reflections of light which he 
 had exhibited thirty years before to Sir Kenelm 
 Digby, " who took notes upon them ;" and he un- 
 blushingly states, that, if Newton had used the 
 same industry as he did, he would never have 
 " taken so impossible a task in hand, as to explain 
 the difference between the length and breadth of 
 the spectrum by the received laws of refraction." 
 VVhen this letter was shown to Newton, he refused 
 
 * This gentleman was the author of a paper in the Philosophical 
 Fransactions, entitled "Optical Assertions concerning the Rainbow." 
 How such a paper could be published by so learned a body seems in the 
 present day utterly incomprehensible. The dials which Linus erected 
 at Liege, and which were the originals of those formerly in the Priory 
 Gardens in London, are noticed in the Philosophical Transactions for 
 1703. In one of them the hours were distinguished by touch
 
 56 SIR ISAAC NEWTON. 
 
 to answer it ; but a letter was sent to Linus referring 
 him to the answer to Pardies, and assuring him that 
 the experiments on the spectrum were made when 
 there was no bright cloud hi the heavens. This 
 reply, however, did not satisfy the Dutch experi- 
 mentalist. On the 25th February, 1675, he addressed 
 another letter to his friend, in which he gravely 
 attempts to prove that the experiment of Newton 
 was not made in a clear day; that the prism was 
 not close to the hole, and that the length of the 
 spectrum was not perpendicular, or parallel to the 
 length of the prism. Such assertions could not but 
 irritate even the patient mind of Newton. He more 
 lhan once declined the earnest request of Oldenburg 
 to answer these observations; he stated, that, as 
 the dispute referred to matters of fact, it could only 
 be decided before competent witnesses, and he 
 referred to the testimony of those who had seen 
 his experiments. The entreaties of Oldenburg, how- 
 ever, prevailed over his own better judgment, and, 
 "lest Mr. Linus should make the more stir," this 
 great man was compelled to draw up a long and 
 explanatory reply to reasonings utterly contempti- 
 ble, and to assertions altogether unfounded. This 
 answer, dated November 13th, 1675, could scarcely 
 have been perused by Linus, who was dead on the 
 15th December, when his pupil Mr. Gascoigne, took 
 up the gauntlet, and declared that Linus had shown 
 to various persons in Liege the experiment which 
 proved the spectrum to be circular, and that Sii 
 Isaac could not be more confident on his side 
 than they were on the other. He admitted, how- 
 ever, that the different results might arise from dif- 
 ferent ways of placing the prism. Pleased with the 
 " handsome genius of Mr. Gascoigne's letter," New 
 ton replied even to it, and suggested that tbe spec- 
 trum seen by Linus may have been the circular one 
 formed by one reflexion, or, what he thought more 
 probable, the circular one formed by two refractions,
 
 CONTROVERSY WITH LUCAS. 57 
 
 and one intervening reflection from the base of the 
 prism, which would be coloured if the prism was 
 not an isosceles one. This suggestion seems to 
 have enlightened the Dutch philosophers. Mr. Gas- 
 coigne, having no conveniences for making the ex- 
 periments pointed out by Newton, requested Mr. 
 Lucas of Liege to perform them in his own house. 
 This ingenious individual, whose paper gave great 
 satisfaction to Newton, and deserves the highest 
 praise, confirmed the leading results of the English 
 philosopher ; but though the refracting angle of his 
 prism was 60 and the refractions equal, he never 
 eould obtain a spectrum whose length was more 
 than from three to three and a half times its breadth, 
 while Newton found the length to be jive times its 
 breadth. In our author's reply, he directs his atten- 
 tion principally to this point of difference. He 
 repeated his measures with each of the three angles 
 of three different prisms, and he affirmed that Mr. 
 Lucas might make sure to find the image as long or 
 longer than he had yet done, by taking a prism with 
 plain surfaces, and with an angle of 66 or 67. 
 He admitted that the smallness of the angle in Mr. 
 Lucas's prism, viz. 60, did not account for the 
 shortness of the spectrum which he obtained with 
 it ; and he observed in one of his own prisms that 
 the length of the image was greater in proportion 
 to the refracting angle than it should have been ; an 
 effect which he ascribes to its having a greater 
 refractive power. There is every reason to believe 
 that the prism of Lucas had actually a less disper- 
 sive power than that of 'Newton ; and had the Dutch 
 philosopher measured its refractive power instead 
 of guessing it, or had Newton been less confident 
 than he was* that all other prisms must give a 
 
 * Newton speaks with singular positiveness on this subject. " For 7 
 know," says he, "that Mr. Lucas's observations cannot hold where Che 
 refracting angle of the prism is full 60, and the day is clear, and the 
 ftill length of the colours is measured, and the breadth of the image 
 answers to the sun's diameter : and seeing I am well assured of ths
 
 58 SIR ISAAC NEWTON. 
 
 spectrum of the same length as his in relation to its 
 refracting angle and its index of refraction, the in- 
 vention of the achromatic telescope would have 
 been the necessary result. The objections of Lucas 
 drove our author to experiments which he had never 
 before made, to measure accurately the lengths of 
 the spectra with different prisms of different angles 
 and different refractive powers ; and had the Dutch 
 philosopher maintained his position with more ob- 
 stinacy, he would have conferred a distinguished 
 favour upon science, and would have rewarded 
 Newton for all the vexation which had sprung from 
 the minute discussion of his optical experiments. 
 
 Such was the termination of his disputes with the 
 Dutch philosophers, and it can scarcely be doubted 
 that it cost him more trouble to detect the origin of 
 his adversaries' blunders, than to establish the great 
 truths which they had attempted to overturn. 
 
 Harassing as such a controversy must have been 
 to a philosopher like Newton, yet ft did not touch 
 those deep-seated feelings which characterize the 
 noble and generous mind. No rival jealousy yet 
 pointed the arguments of his opponents ; no charges 
 of plagiarism were yet directed against his personal 
 character. These aggravations of scientific contro- 
 versy, however, he was destined to endure ; and in 
 the dispute which he was called to maintain both 
 against Hooke and Huygens, the agreeable con- 
 sciousness of grappling with men of kindred powers 
 was painfully imbittered by the personality and 
 jealousy with which it was conducted. 
 
 Dr. Robert Hooke was about seven years older 
 than Newton, and was one of the ninety-eight 
 original or unelected members of the Royal Society. 
 
 trnth and exactness of my own observations, I shall be unwilling to be 
 diverted by any other experiments from having a fair end made of this 
 in the first place." On the supposition that his prism was one of rery 
 low dispersive power, Mr. Lucas might, with perfect truth, have used 
 the very same language towards Newton.
 
 CHARACTER OF DR. HOOKE. 59 
 
 He possessed great versatility of talent, yet, though 
 his genius was of the most original cast, and his 
 acquirements extensive, he had not devoted himself 
 with fixed purpose to any particular branch of 
 knowledge. His numerous and ingenious inven- 
 tions, of which it is impossible to speak too highly, 
 gave to his studies a practical turn which unfitted 
 him for that continuous labour which physical re- 
 searches so imperiously demand. The subjects 
 of light, however, and of gravitation seem to have 
 deeply occupied his thoughts before Newton ap- 
 peared in the same field, and there can be no doubt 
 that he had made considerable progress in both of 
 these inquiries. With a mind less divergent in its 
 pursuits, and more endowed with patience of thought, 
 he might have unveiled the mysteries in which both 
 these subjects were enveloped, and preoccupied the 
 intellectual throne which was destined for his rival ; 
 but the infirm state of his health, the peevishness 
 of temper which this occasioned, the number of 
 unfinished inventions from which he looked both 
 for fortune and fame, and, above ah 1 , his inordinate 
 love of reputation, distracted and broke down the 
 energies of his powerful intellect. In the more 
 matured inquiries of his rivals he recognised, and 
 often truly, his own incompleted speculations ; and 
 when he saw others reaping the harvest for which 
 he had prepared the ground, and of which he had 
 sown the seeds, it was not easy to suppress the 
 mortification which their success inspired. In the 
 history of science, it has always been a difficult task 
 to adjust the rival claims of competitors, when the 
 one was allowed to have completed what the other 
 was acknowledged to have begun. He who com- 
 mences an inquiry, and publishes his results, often 
 goes much farther than he has announced to the 
 world, and, pushing his speculations into the very 
 heart of the subject, frequently submits them to th& 
 ear of friendship. From the pedestal of his pub-
 
 60 SIR ISAAC NEWTON. 
 
 lished labours his rival begins his researches, and 
 brings them to a successful issue ; while he has in 
 reality done nothing more than complete and de- 
 monstrate the imperfect speculations of liis prede- 
 cessor. To the world, and to himself, he is no 
 doubt in the position of the principal discoverer: 
 but there is still some apology for his rival when 
 he brings forward his unpublished labours ; and some 
 excuse for the exercise of personal feeling, when he 
 measures the speed of his rival by his own proximity 
 to the goal. 
 
 The conduct of Dr. Hooke would have been 
 viewed with some such feeling, had not his arro- 
 gance on otjier occasions checked the natural cur- 
 rent of our sympathy. When Newton presented 
 his reflecting telescope to the Royal Society, Dr. 
 Hooke not only criticised the instrument with undue 
 severity, but announced that he possessed an infal- 
 lible method of perfecting all kinds of optical instru- 
 ments, so that " whatever almost hath been in 
 notion and imagination, or desired in optics, may 
 be performed with great facility and truth." 
 
 Hooke had been strongly impressed with the 
 belief, that light consisted in the undulations of a 
 liighly elastic medium pervading all bodies ; and, 
 guided by his experimental investigation of the phe- 
 nomena of diffraction, he had even announced the 
 great principle of interference, which has performed 
 such an important part in modern science. Regard- 
 ing himself, therefore, as in possession of the true 
 theory of light, he examined the discoveries of 
 Newton in their relation to his own speculative 
 views, and, finding that their author was disposed to 
 consider that element as consisting of material par- 
 ticles, he did not scruple to reject doctrines which 
 he believed to be incompatible with truth. Dr. 
 Hooke was too accurate an observer not to admit 
 the general correctness of Newton's observations. 
 He allowed the existence of different refractions.
 
 CONTROVERSY WITH HUYGENS. 61 
 
 the unchangeableness of the simple colours, and the 
 production of white light by the union of all the 
 colours of the spectrum ; but he maintained that the 
 different refractions arose from the splitting and 
 rarefying of ethereal pulses, and that there are only 
 two colours in nature, viz. red and violet, which pro- 
 duce by their mixture all the rest, and which are 
 themselves formed by the two sides of a split pulse 
 or undulation. 
 
 In reply to these observations, Newton wrote an 
 able letter to Oldenburg, dated June 11, 1672, in 
 which he examined with great boldness and force 
 of argument the various objections of his opponent, 
 and maintained the truth of his doctrine of colours, 
 as independent of the two hypotheses respecting 
 the origin and production of light. He acknow- 
 ledged his own partiality to the doctrine of the 
 materiality of light ; he pointed out the defects of 
 the undulatory theory ; he brought forward new ex- 
 periments in confirmation of his former results; 
 and he refuted the opini >ns of Hooke respecting the 
 existence of only two simple colours. No reply 
 was made to the powe ill arguments of Newton ; 
 and Hooke contented h nself with laying before the 
 Society his curious ob? nations on the colours of 
 soap-bubbles, and of plates of air, and in pursuing 
 his experiments on the diffraction of light, which, 
 after an interval of two years, he laid before the 
 same body. 
 
 After he had thus silenced the most powerful of 
 his adversaries, Newton was again called upon to 
 defend himself against a new enemy. Christian 
 Huygens, an eminent mathematician and natural 
 philosopher, who, like Hooke, had maintained the 
 undulatory theory of light, transmitted to Olden- 
 burg various animadversions on the Newtonian doc- 
 trine ; but though his knowledge of optics was of 
 the most extensive kind, yet his objections were 
 nearly as groundless as those of his less enlightened
 
 62 SIR ISAAC NEWTON. 
 
 countryman. Attached to his own hypothesis re- 
 specting the nature of light, namely, to the system 
 of undulation, he seems, like Dr. Hooke, to have 
 regarded the discoveries of Newton as calculated to 
 overturn it ; but his principal objections related to 
 the composition of colours, and particularly of white 
 light, which he alleged could be obtained from the 
 union of two colours, yellow and blue. To this and 
 similar objections, Newton replied that the colours 
 in question were not simple yellows and blues, but 
 were compound colours, in which, together, all the 
 colours of the spectrum were themselves blended ; 
 and though he evinced some strong traces of feeling 
 at being ugain put upon his defence, yet his high 
 respect for Huygens induced him to enter with 
 patience on a fresh development of his doctrine. 
 Huygens felt the reproof which the tone of this 
 answer so gently conveyed, and in writing to Olden- 
 burg, he used the expression, that Mr. Newton 
 " maintained his doctrine with some concern." To 
 this our author replied, " As for Mr. Huygens's ex- 
 pression, I confess it was a little ungrateful to me, 
 to meet with objections which had been answered 
 before, without having the least reason given me 
 why those answers were insufficient." But though 
 Huygens appears in this controversy as a rash 
 objector to the Newtonian doctrine, it was after- 
 ward the fate of Newton to play a similar part 
 against the Dutch philosopher. When Huygens 
 published his beautiful law of double refraction in 
 Iceland spar, founded on the finest experimental 
 analysis of the phenomena, though presented as a 
 result of the undulatory system, Newton not only 
 rejected it, but substituted for it another law entirely 
 inconsistent with the experiments of Huygens, which 
 Newton himself had praised, and with those of aH 
 succeeding philosophers. 
 
 The influence of these controversies on the mind 
 of Newton seems to have been highly exciting
 
 REFRACTING TELESCOPES. 63 
 
 Even the satisfaction of humbling all his antago- 
 nists he did not feel as a sufficient compensation 
 for the disturbance of his tranquillity. " I intend." 
 says he,* " to be no farther solicitous about matters 
 of philosophy. And therefore I hope you will not 
 take it ill if you find me never doing any thing more 
 in that kind ; or rather that you will favour me in 
 my determination, by preventing, so far as you can 
 conveniently, any objections or other philosophical 
 letters that may concern me." In a subsequent let- 
 ter in 1675, he says, " I had some thoughts of writing 
 a further discourse about colours, to be read at on< 
 of your assemblies ; but find it yet against the grail 
 to put pen to paper any more on that subject ;" ant 
 in a letter to Leibnitz, dated December the 9th, 1675^ 
 he observes, " I was so persecuted with discussion* 
 arising from the publication of my theory of light, 
 that I blamed my own imprudence for parting with 
 so substantial a blessing as my quiet to run after a 
 shadow." 
 
 CHAPTER V. 
 
 Mistake of Newton in supposing that the Improvement of Refracting 
 Telescopes was hopeless Mr. Hall invents the Achromatic Telescope 
 Principles of the Achromatic Telescope explained It is re-invented 
 by Dollond, and improved by future Artists Dr. Blair's Aplanatic 
 Telescope Mistakes in Newton's Analysis of the Spectrum Modern 
 Discoveries respecting the Structure of the Spectrum. 
 
 THE new doctrines of the composition of light, 
 and of the different refrangibility of the rays which 
 compose it, having been thus established upon an 
 impregnable basis, it will be interesting to take a 
 general view of the changes which they have under- 
 
 T etter to Oldenburg in 1672, containing his first reply to Huygens
 
 64 SIR ISAAC NEWTON. 
 
 gone since the time of Newton, and of their influ- 
 ence on the progress of optical discovery. 
 
 There is no fact hi the history of science more 
 singular than that Newton should have believed 
 that all bodies produced spectra of equal length, or 
 separated the red and violet rays to equal distances 
 when the refraction of the mean rays was the 
 same. This opinion, unsupported by experiments, 
 and not even sanctioned by any theoretical views, 
 seems to have been impressed upon his mind with 
 all the force of an axiom.* Even the shortness of 
 the spectrum observed by Lucas did not rouse him 
 to further inquiry ; and when, under the influence 
 of this blind conviction he pronounced the improve- 
 ment of the refracting telescope to be desperate, he 
 checked for a long time the progress of this branch 
 of science, and furnished to future philosophers a 
 lesson which cannot be too deeply studied. 
 
 In 1729, about two years after' the death of Sir 
 Isaac, an individual unknown to science broke the 
 spell in which the subject of the spectrum had been 
 so singularly bound. Mr. Chester More Hall, of 
 More Hall in Essex, while studying the mechanism 
 of the human eye, was led to suppose that tele- 
 scopes might be improved by a combination of 
 lenses of different refractive powers, and he actually 
 completed several object-glasses upon this principle. 
 The steps by which he arrived at such a construc- 
 tion have not been recorded ; but it is obvious that 
 he must have discovered what escaped the sagaci ty 
 of Newton, that prisms made of different kinds of 
 
 * In an experiment made by Newton, he had occasion to counteract 
 the refraction of a prism of glass by another prism of water ; and had 
 
 he completed the experiment, and studied the result of it, he could not 
 have failed to observe a quantity of uncorrected colour, which would 
 nave led him to the discovery of the different dispersive powers of bodies. 
 
 . 
 
 But in order to increase the refractive power of the water, he mixed 
 with it a little sugar of lead, the high dispersive power of which seems 
 to have rendered the dispersive power of the water equal to that of the 
 glass, and thus to have corrected the uncom pen sated colour of the glass 
 prism.
 
 ACHROMATIC TELESCOPE. 65 
 
 glass produced different degrees of separation of the 
 red and violet rays, or gave spectra of different 
 lengths when the refraction of the middle ray of the 
 spectrum was the same. 
 
 In order to explain how such a property led him 
 to the construction of a telescope without colour, or 
 an achromatic telescope, let us take a lens LL of 
 crown or plate glass, whose focal length LY is 
 about twelve inches. When the sun's rays SL, 
 
 Fig. 6. 
 
 SL fall upon it, the red will be refracted to R, the 
 yellow to Y, and the violet to V. If we now place 
 behind it a concave lens II of the same glass, and 
 of the same focus or curvature, it will be found, 
 both by experiment and by drawing the refracted 
 rays, according to the rules given in elementary 
 works, that the concave glass // will refract the 
 rays LR, LR into LS', LS', and the rays LV, LV 
 into LS', LS' free of all colour ; but as these rays 
 will be parallel, the two lenses will not have a 
 focus, and consequently cannot form an image so 
 as to be used as the object-glass of a telescope. 
 This is obvious from another consideration; ''for 
 since the curvatures of the convex and concave 
 lenses are the same, the two put together will be 
 exactly the same as if they were formed out of a 
 single piece of glass, having parallel surfaces like a 
 watch-glass, so that the parallel rays of light SL,
 
 66 SIR ISAAC NfcWTON. 
 
 SL will pass on in the same direction LS', LS' 
 affected by equal and opposite refractions as in a 
 piece of plane glass. 
 
 Now, since the convex lens LL separated the 
 white light SL, SL into its component coloured 
 rays, LV, LV being the extreme violet, and LR 
 LR the extreme red ; it follows that a similar con- 
 cave lens of the same glass is capable of uniting 
 into white light LS', LS' rays, as much separated 
 as LV, LR are. Consequently, if we take a con- 
 cave lens II of the same, or of a greater refractive 
 power than the convex one, and having the power 
 of uniting rays farther separated than LV, LR are, 
 a less concavity in the lens II will be sufficient to 
 unite the rays LV, LR into a white ray LS' ; but 
 as the lens // is now less concave than the lens LL 
 is convex, the concavity will predominate, and the 
 uncoloured rays LS', LS' will no longer be parallel, 
 but will converge to some point O, where they will 
 form a colourless or achromatic image of the sun. 
 
 The effect now described may be obtained by 
 making the convex lens LL of crown or of plate 
 glass, and the concave one of flint glass, or that of 
 which wineglasses are made. If the concave lens 
 II has a greater refractive power than LL, wirich is 
 always the case, the only effect of it will be to 
 make the rays converge to a focus more remote 
 than O, or to render a less curvature necessary in 
 //, if O is fixed for the focus of the combined lenses. 
 
 Such is the principle of the achromatic telescope 
 as constructed by Mr. Hall. This ingenious indi- 
 vidual employed working opticians to grind his 
 lenses, and he furnished them with the radii of the 
 surfaces, which were adjusted to correct the aber- 
 ration of figure as well as of colour. His invention, 
 therefore, was not an accidental combination of a 
 convex and a concave lens of different kinds of 
 glass, which might have oeen made merely for ex- 
 periment; but it was a complete achromatic tele-
 
 ACHROMATIC TELESCOPES. 67 
 
 scope, founded on a thorough knowledge of the 
 different dispersive powers of crown and flint glass. 
 It is a curious circumstance, however, in the his- 
 tory of the telescope, that this invention was ac- 
 tually lost. Mr. Hall never published any account 
 of his labours, and it is probable that he kept them 
 secret till he should be able to present his instru- 
 ment to the public in a more perfect form ; and it 
 was not till John Dollond had discovered the pro- 
 perty of light upon which the instrument depends, 
 and had actually constructed many fine telescopes, 
 that the previous labours of Mr. Hall were laid be- 
 fore the public.* From this period the achromatic 
 telescope underwent gradual improvement, and by 
 the successive labours of Dollond, Ramsden, Blair, 
 Tulley, Guinand, Lerebours, and Fraunhofer, it has 
 become one of the most valuable instruments in 
 physical science. 
 
 Although the achromatic telescope, as constructed 
 by Dollond, was founded on the principle that the 
 spectra formed by crown and flint glass differed 
 only in their relative lengths, when the refraction 
 of the mean ray was the same, yet by a more mi- 
 nute examination of the best instruments, it was 
 found that they exhibited white or luminous objects 
 tinged on one side with a green fringe, and on the 
 other with one of a claret colour. These colours, 
 which did not arise from any defect of skill in the 
 artist, were found to arise from a difference in the 
 extent of the coloured spaces in two equal spectra 
 formed by crown and by flint glass. This property 
 was called the irrationality of the coloured spaces, 
 and the uncorrected colours which remained when 
 the primary spectrum of the crown glass was cor- 
 rected by the primary spectrum of the flint glass 
 were called the secondary or residual spectrum. By 
 
 * See the article OPTICS in the Edinburgh Encyclopaedia, vd xv 
 p 479, note.
 
 G8 SIR ISAAC NEWTON. 
 
 a happy contrivance, which it would be out of place 
 here to describe, Dr. Blair succeeded in correcting 
 this secondary spectrum, or in removing the green 
 and claret-coloured fringes which appeared in the 
 best telescopes, and to this contrivance he gave the 
 name of the Aplanatic Telescope. 
 
 But while Newton thus overlooked these remark- 
 able properties of the prismatic spectrum, as formed 
 by different bodies, he committed some considera- 
 ble mistakes in Ms examination of the spectrum 
 which was under his own immediate examination. 
 It does not seem to have occurred to him that the 
 relations of the coloured spaces must be greatly 
 modified by the angular magnitude of the sun or the 
 luminous body, or aperture from which the spec- 
 trum is obtained ; and misled by an apparent ana- 
 logy between the length of the coloured spaces and 
 the divisions of a musical chord,* he adopted the 
 latter, as representing the proportion of the col- 
 oured spaces in every beam of white light. Had 
 two other observers, one situated in Mercury, and 
 the other in Jupiter, studied the prismatic spectrum 
 of the sun by the same, instruments, and with the 
 same sagacity as Newton, it is demonstrable that 
 they would have obtained very different results. On 
 account of the apparent magnitude of the sun in Mer- 
 cury, the observer there would obtain a spectrum 
 entirely without green, having red, orange, and yel- 
 low at one end, the white in the middle, and termi- 
 nated at the other end with Uue and violet. The 
 observer in Jupiter would, on the contrary, have 
 obtained a spectrum in which the colours were 
 much more condensed. On the planet Saturn a 
 spectrum exactly similar would have been obtained, 
 
 * " This result was obtained," as Newton says, " by an assistant 
 whose eyes were more critical than mine, and who, by right lines drawn 
 across the spectrum, noted the confines of the colours. And this opera- 
 lion being divers times repeated both on the same and on several papers, 
 I found that the observations agreed well enough with one -another." 
 OPTICS, Part II. Book III.
 
 PRISMATIC SPECTRUM. 69 
 
 notwithstanding the greater diminution of the sun's 
 apparent diameter. It may now be asked, which of 
 all these spectra are we to consider as exhibiting 
 the number, and arrangement, and extent of the 
 coloured spaces proper to be adopted as the true 
 analysis of a solar ray. 
 
 The spectrum observed by Newton has surely no 
 claim to our notice, merely because it was observed 
 upon th^ surface of the earth. The spectrum ob- 
 tained in Mercury affords no analysis at all of the 
 incident beam, the colours being almost all com- 
 pound, and not homogeneous, and that of Newton 
 is liable to the same objection. Had Newton ex- 
 amined his spectrum under the very same circum- 
 stances in winter and in summer, he would have 
 found the analysis of the beam more complete in 
 summer, on account of the diminution of the sun's 
 diameter ; and, therefore, we are entitled to say that 
 neither the number nor the extent of the coloured 
 spaces, as given by Newton, are those which belong 
 to homogeneous and uncompounded light. 
 
 The spectrum obtained in Jupiter and Saturn is 
 the only one where the analysis is complete, as it is 
 incapable of having its character altered by any far- 
 ther diminution of the sun's diameter. Hence, we 
 are forced to conclude, not only that the number 
 and extent of the primitive homogeneous colours, 
 as given by Newton, are incorrect ; but that if he had 
 attempted to analyze some of the primitive tints in 
 the spectrum, he would have found them decidedly 
 composed of heterogeneous rays. There is one 
 consequence of these observations which is some- 
 what interesting. A rainbow formed in summer, 
 when the sun's diameter is least, must have its col- 
 ours more condensed and homogeneous than in win- 
 ter, when the size of its disk is a maximum, and 
 when the upper or the under limb of the sun is 
 eclipsed, a rainbow formed at that time will lose 
 entirely the yellow rays, and have the green and the
 
 70 SIR ISAAC NEWTON. 
 
 red in perfect contact. For the same reason, a rain- 
 bow formed in Venus and Mercury will be destitute 
 of green rays, and have a brilliant bow of white 
 light separating two coloured arches ; while in Mars, 
 Jupiter, Saturn, and the Georgian planet, the bow 
 will exhibit only four homogeneous colours. 
 
 From his analysis of the solar spectrum, Newton 
 concluded, " that to the same degree of refrangibility 
 ever belonged the same colour, and to the same 
 colour ever belonged the same degree of refrangi- 
 bility ;" and hence he inferred, that red, orange, yel- 
 low, green, blue, indigo, and violet were primary and 
 simple colours. He admitted, indeed, that "the 
 same colours in specie with these primary ones may 
 be also produced by composition. For a mixture of 
 yellow and blue makes green, and of red and yellow 
 makes orange ;" but such compound colours were 
 easily distinguished from the simple colours of the 
 spectrum by the circumstance, that they are always 
 capable of being resolved by the action of the prism 
 into the two colours which compose them. 
 
 This view of the composition of the spectrum 
 might have long remained unchallenged, had we not 
 been able to apply to it a new mode of analysis. 
 Though we cannot separate the green rays of the 
 spectrum into yellow and blue by the refraction of 
 prisms, yet if we possessed any substance which 
 nad a specific attraction for blue rays, and which 
 stopped them in their course, and allowed the yel- 
 low rays to pass, we should thus analyze the green 
 as effectually as if they were separated by refraction. 
 The substance which possesses this property is a 
 purplish blue glass, similar to that of which finger- 
 glasses are made. When we view through a piece 
 of this glass, about the twentieth of an inch thick, 
 a brilliant prismatic spectrum, we find that it has 
 exercised a most extraordinary absorptive action on 
 the different colours which compose it. The red 
 part of the spectrum is divided into two red spaces/
 
 SPECTRUM OF THREE COLOURS. 71 
 
 separated by an interval entirely devoid of light. 
 Next to the inner red space comes a space of bright 
 yellow, separated from the red by a visible interval. 
 After the yellow come* the green, with an obscure 
 space between them, then follows the Hue and the 
 violet, the last of which has suffered little or no 
 diminution. Now it is very obvious, that in this 
 experiment, the blue glass has actually absorbed 
 the red rays, which, when mixed with the yellow 
 on one side, constituted orange, and the blue rays, 
 which, when mixed with the yellow on the other 
 side, constituted green, so that the insulation of 
 the yellow rays thus effected, and the disappearance 
 of the orange, and of the greater part of the green 
 light, proves beyond a doubt that the orange and 
 green colours in the spectrum are compound col- 
 ours, the former consisting of red and yelloio rays, 
 and the latter of yellow and blue rays of the very 
 same ref Tangibility. If we compare the two red 
 spaces of the spectrum seen through the blue glass 
 with the red space seen without the blue glass, it 
 will be obvious that the red has experienced such 
 an alteration in its tint by the action of the blue 
 glass, as would be effected by the absorption of a 
 small portion of yellow rays ; and hence we con- 
 clude, that the red of the spectrum contains a slight 
 tinge of yellow, and that the yellow space extends 
 over more than one-half of the spectrum, including 
 the red, orange, yellow, green, and Hue spaces. 
 
 I have found also that red light exists in the yel- 
 low space, and it is certain that in the violet space 
 red light exists in a state of combination with the 
 blue rays. From these and other facts which it 
 would be out of place here to explain, I conclude 
 that the prismatic spectrum consists of three differ- 
 ent spectra, viz. red, yellow, and blue, all having 
 the same length, and all overlapping each other. 
 Hence red, yellow, and blue rays of the very same 
 refrangibility coexist at every point of the spec-
 
 72 SIR ISAAC NEWTON. 
 
 trum ; but the colour at any one point will be that 
 of the predominant ray, and will depend upon the 
 relative distance of the point from the maximum 
 ordinate of the curve which represents the intensity 
 of the light of each of the three spectra. 
 
 This structure of the spectrum, which harmo- 
 nizes with the old hypothesis of three simple colours, 
 will be understood from the annexed diagram, 
 where MN is the spectrum of seven colours, all 
 compounded of the three simple ones, red, yellow, 
 
 Fig. 7. 
 
 and blue. The ordinates of the curves R, Y, and 
 B will express the intensities of each colour at dif- 
 ferent points of the spectrum. At the red extrem- 
 ity M of the spectrum, the pure red is scarcely 
 altered by the very slight intermixture of yellow 
 and blue. Farther on in the red space, the yellow 
 begins to make the red incline to scarlet. It then 
 exists in sufficient quantity to form orange, and, as 
 the red declines, the yellow predominates over the 
 feeble portion of red and blue which are mixed with 
 it. As the yellow decreases in intensity, the in- 
 creasing blue forms with it a good green, and the 
 blue rising to its maximum speedily overpowers the 
 small portion of yellow and red. When the blue 
 becomes very faint, the red exhibits its influence 
 in converting it into violet, and the yellow ceases
 
 LINES IN THE SPECTRITM. 73 
 
 lo exercise a marked influence on the tint. The 
 influence of the red over the blue space is scarcely 
 perceptible, on account of the great intensity of the 
 blue light ; but we may easily conceive it to reap- 
 pear and form the violet light, not only from the 
 rapid decline of the blue light, but from the greater 
 influence of the red rays upon the retina. 
 
 These views may, perhaps, be more clearly under- 
 stood by supposing that a certain portion of white 
 light is actually formed at every point of the spec- 
 trum by the union of the requisite number of the 
 three coloured rays that exist at any point. The 
 white light thus formed will add to the brilliancy 
 without affecting the tint of the predominant colour. 
 
 In the violet space we may conceive the small 
 portion of yellow which exists there to form white 
 light with a part of the blue and a part of the red, 
 so that the resulting tint will be violet, composed 
 of the blue and the small remaining portion of red, 
 mixed with the white light. This white light will 
 possess the remarkable property of not being sus- 
 ceptible of decomposition by the analysis of the 
 prism, as it is composed of red, yellow, and blue 
 rays of the very same reffangibility. The insula- 
 tion of this white light by the absorption of the 
 predominant colours I have effected in the green, 
 yellow, and red spaces, and by the use of new ab- 
 sorbing media we may yet hope to exhibit it in some 
 of the other colours, particularly in the brightest 
 part of the blue space, where an obvious approxi- 
 mation to it take? place. 
 
 Among the most important modern discoveries 
 respecting the spectrum we must enumerate that 
 of fixed dark and coloured lines, which we owe to 
 the sagacity of Dr. Wollaston and M. Fraunhofer. 
 Two or three of these lines were discovered by Dr. 
 Wollaston, but nearly 600 have been detected by 
 means of the fine prisms and the magnificent appa- 
 ratus of the Bavarian optician. These lines are
 
 74 SIR ISAAC NEWTOW. 
 
 parallel to one another, and perpendicular to the 
 length of the spectrum. The largest occupy a 
 space from 5" to 10" in breadth. Sometimes they 
 occur in well-defined lines, and at other times in 
 groups ; and in all spectra formed from solar light, 
 they preserve the same order and intensity, and the 
 same relative position to the coloured spaces, what- 
 ever be the nature of the prism by which they are 
 produced. Hence these lines are fixed points, by 
 which the relative dispersive powers of different 
 media may be ascertained with a degree of accu- 
 racy hitherto unknown in this branch of science. In 
 the light of the fixed stars, and in that of artificial 
 flames, a different system of lines is produced, and 
 this system remains unaltered, whatever be the na- 
 ture of the prism by which the spectrum is formed. 
 The most important fixed lines in the spectrum 
 formed by light emitted from the sun, whether it is 
 reflected from the sky, the clouds, or the moon, may 
 be easily seen by looking at a narrow slit in the 
 window-shutter of a dark room, through a hollow 
 prism formed of plates of parallel glass, and filled 
 with any fluid of a considerable dispersive power. 
 The slit should not greatly exceed the twentieth of 
 an inch, and the eye should look through the thinnest 
 edge of the prism where there is the least thickness 
 of fluid. These lines I have found to be the boun- 
 daries of spaces within which the rays have par 
 ticular affinities for particular bodies.
 
 COLOURS OF THIN PLATES, 75 
 
 CHAPTER VI. 
 
 Colours of thin Plates first studied by Boy and Hooke Newton de- 
 termines the Law of their Production His Theory of Fits of Easy 
 Reflection and Transmission Colours of thick Plates. 
 
 IN examining the nature and origin of colours as 
 the component parts of white light, the attention of 
 Newton was directed to the curious subject of the 
 colours of thin plates, and to its application to ex- 
 plain the colours of natural bodies. His earliest 
 researches on this subject were communicated, in 
 his Discourse on Light and Colours, to the Royal 
 Society, on the 9th December, 1675, and were read 
 at subsequent meetings of that body. This discourse 
 contained fuller details respecting the composition 
 and decomposition of light than he had given in his 
 letter to Oldenburg, and was concluded with nine 
 propositions, showing how the colours of thin trans- 
 parent plates stand related to those of all natural 
 bodies. 
 
 The colours of thin plates seem to have been 
 first observed by Mr. Boyle. Dr. Hooke afterward 
 studied them with some care, and gave a correct 
 account of the leading phenomena, as exhibited in 
 the coloured rings upon soap-bubbles, and between 
 plates of glass pressed together. He recognised 
 that the colour depended upon some certain thick- 
 ness of the transparent plate, but he acknowledges 
 that he had attempted in vain to discover the rela- 
 tion between the thickness of the plate and the 
 colour which it produced. 
 
 Dr. Hooke succeeded in splitting a mineral sub- 
 stance, called mica, into films of such extreme thin- 
 ness as to give brilliant colours. One p^te, for ex-
 
 76 SIR ISAAC NEWTON. 
 
 ample, gave a yellow colour, another a blue coloui s 
 and the two together a deep purple ; but, as plates 
 which produced those colours were always less than 
 the 12,000th part of an inch thick, it was quite im- 
 practicable, by any contrivance yet discovered, to 
 measure their thickness, and determine the law ac- 
 cording to which the colour varied with the thick- 
 ness of the film. Newton surmounted this difficulty 
 by laying a double convex lens, the radius of curva- 
 ture of each *side of which was fifty feet, upon the 
 flat surface of a plano-convex object-glass, and in 
 this way he obtained a plate of air or of space vary- 
 ing from the thinnest possible edge at the centre of 
 the object-glass where it touched the plane surface, 
 to a considerable thickness at the circumference of 
 the lens. When light was allowed to fall upon the 
 object-glass, every different thickness of the plate 
 of air between the object-glass gave different colours, 
 so that the point where the two object-glasses 
 touched one another was the centre of a number of 
 concentric coloured rings. Now, as the curvature 
 of the object-glass was known, it was easy to cal- 
 culate the thickness of the plate of air at which any 
 particular colour appeared, and thus to determine 
 the law of the phenomena. 
 
 In order to understand how he proceeded, let 
 CED be the convex surface of the one object-glass, and 
 AEB the flat surface of the other. Let them touch 
 at the point E, and let homogeneous red rays fall 
 upon them, as shown in the figure. At the point 
 of contact E, where the plate of air is inconceiva- 
 bly thm, not a single ray of the pencil RE is re- 
 flected. The light is wholly transmitted, and, con- 
 sequently, to an eye above E, there will appear at 
 E a black spot. At a, where the plate of air is 
 thicker, the red light ra is reflected in the direction 
 aa f , and as the air has the same thickness in a circle 
 round tho. point E, the eye above E, at a, will see 
 next the black spot E a ring of red light. At m.
 
 COLOURS OF THIN PLATES. 
 
 Fig. 8. 
 
 where the thickness of the air is a little greater than 
 at a, the light r m is all transmitted as at E, and not 
 a single ray suffers reflection, so that to an eye 
 above E at m' there will be seen without the red ring 
 a a dark ring m. In like, manner, at greater thick- 
 nesses of the plate of air, there is a succession of 
 red and dark rings, diminishing in breadth as shown 
 in the diagram. 
 
 When the same experiment was repeated in orai^e, 
 yellow, green, Hue, indigo, and violet light, the very 
 same phenomenon was observed; with this differ- 
 ence only, that the rings were largest in red light, 
 and smallest in violet light, and had intermediate 
 magnitudes in the intermediate colours. 
 
 If the observer now places his eye below E, so 
 as to see the transmitted rays, he will observe a set 
 of rings as before, but they will have a bright spot 
 in their centre at E, and the luminous rings will now 
 correspond with those which were dark when seen 
 by reflection, as will be readily understood from in- 
 specting the preceding diagram. 
 
 When the object-glasses are illuminated by white
 
 78 SIR ISAAC NEWTON. 
 
 light, the seven systems of rings, formed by all the 
 seven colours which compose white light, will now 
 be seen at once. Had the rings in each colour been 
 all of the same diameter they would all have formed 
 brilliant white rings, separated by dark intervals; 
 but, as they have all different diameters, they will 
 overlap one another, producing rings of various 
 colours by their mixture. These colours, reckoning 
 from the centre E, are as follows : 
 
 1st Order. Black, blue, white, yellow, orange, red. 
 
 2d Order. Violet, blue, green, yellow, orange, red. 
 
 3d Order. Purple, blue, green, yellow, red, bluish- 
 red. 
 
 4th Order. Bluish-green, green, yellowish-green, 
 red. 
 
 5th Order. Greenish-blue, red. 
 
 6th Order. Greenish-blue, red. 
 
 By accurate measurements, Sir Isaac found that 
 the thicknesses of air at which the most luminous 
 parts of the first rings were produced, were in parts 
 of an inch Tr^V^* TT*Tmr TT& 5 ff?nr Trwiro* I^BOO.OJ 
 p^l. if the medium or the substance of the thin 
 plate is water, as hi the case of the soap-bubble, 
 which produces beautiful colours according to its 
 different degrees of thinness, the thicknesses at 
 which the most luminous parts of the rings appear 
 are produr.ed at T-sV* of the thickness at which they 
 are produced in air, and in the case of glass or mica 
 at T . y l 2? of that thickness; the numbers 1.336, 1.525 
 expressing the ratio of the sines of the angles of 
 incidence and refraction in the substances which 
 produce the colours. 
 
 From the phenomena thus briefly described, Sir 
 Isaac Newton deduces that ingenious, though hy- 
 pothetical, property of light, called its fits of easy 
 reflection and transmission. This property consists in 
 supposing that every particle of light from its first 
 discharge from a luminous body possesses, at equally 
 distant intervals, dispositions to be reflected from,
 
 FITS OF REFLECTION, ETC 79 
 
 and transmitted through, the surfaces of bodies upon 
 which it is incident. Hence, if a particle of light 
 reaches a reflecting surface of glass when it is in 
 its fit of reflection, or in its disposition to be reflected, 
 it will yield more readily to the reflecting force of 
 the surface ; and, on the contrary, if it reaches the 
 same surface while in a fit of easy transmission, or 
 in a disposition to be transmitted, it will yield with 
 more difficulty to the reflecting force. Sir Isaac 
 has not ventured to inquire into the cause of this 
 property ; but we may form a very intelligible idea 
 of it by supposing, that the particles of light have 
 two attractive and two repulsive poles at the ex- 
 tremities of two axes at right angles to each other, 
 and that the particles revolve round their axes, and 
 at equidistant intervals bring one or other of these 
 axes into the line of the direction in which the par- 
 ticle is moving. If the attractive axis is in the line 
 of the direction in which the particle moves when it 
 reaches the refracting surface, the particle will yield 
 to the attractive force of the medium, and be re- 
 fracted and transmitted ; but if the repulsive axis is 
 in the direction of the particle's motion when it 
 reaches the surface, it will yield to the repulsive 
 force of the medium, and be reflected from it. 
 
 The application of the theory of alternate fits of 
 reflection and transmission to explain the colours of 
 thin plates is very simple. When the light falls upon 
 the first surface AB, Fig. 8 of the plate of air be- 
 tween AB and CED, the rays that are in a fit of re- 
 flection are reflected, and those that are in a fit of 
 transmission are transmitted. Let us call F the 
 length of a fit, or the distance through which the 
 particle of light moves while it passes from the state 
 of being in a fit of reflection to the state of being in 
 a fit of transmission. Now, as all the particles of 
 light transmitted through AB were in a state of easy 
 transmission when they entered AB, it is obvious, 
 that, if the plate of air at E is so thin as to be less
 
 80 SIR ISAAC NEWTON. 
 
 than one-half of F, the particles of light will still 
 be in their disposition to be transmitted, and conse- 
 quently the light will be all transmitted, and none 
 reflected at the curve surface at E. When the plate 
 becomes thicker towards a, so that its thickness ex- 
 ceeds half of F, the light will not reach the surface 
 CE till it has come under its fit of reflection, and 
 consequently at a the light will be all reflected, and 
 none transmitted. As the thickness increases to- 
 wards ra, the light will have come under its fit of 
 transmission, and so on, the light being reflected at 
 a, /, and transmitted at E, m. This will perhaps be 
 still more easily understood from fig. 9, where we 
 
 may suppose AEC to be a thin wedge of glass or 
 any other transparent body. When light is incident 
 on the first surface AE, all the particles of it that 
 are in a fit of easy reflection will be reflected, and 
 all those in a fit of easy transmission will be trans- 
 mitted. As the fits of transmission all commence 
 at AE, let the first fit of transmission end when the 
 particles of light have reached ab, and the second 
 when they have reached ef; and let the fits of re- 
 flection commence at cd and gh. Then, as the fit 
 of transmission continues from AE to ab, all the 
 light that falls upon the portion w?E of the second 
 surface will be transmitted and none reflected, so 
 that to an eye above E the space mE will appear 
 black. As the fit of reflection commences at ab % and
 
 COLOURS OF TH* :K PLATES. 81 
 
 continues to cd, all the light which falls upon the 
 portion nm will be reflected, and none transmitted ; 
 and so on, the light being transmitted at raE and 
 pra, and reflected at nm and qp. Hence to an eye 
 above E the wedge-shaped film of which AEC is 
 a section will be covered with parallel bands or 
 fringes of light separated by dark fringes of the 
 same breadth, and they will be all parallel to the 
 thin edge of the plate, a dark fringe corresponding 
 to the thinnest edge. To an eye placed below CE 
 similar fringes will be seen, but the one correspond- 
 ing to the thinnest edge mE will be luminous. 
 
 If the thickness of the plate does not vary accord- 
 ing to a regular law as in fig. 9, but if, like a film of 
 blown glass, it has numerous inequalities, then the 
 alternate fringes of light and darkness will vary with 
 the thickness of the film, and throughout the whole 
 length of each fringe the thickness of the film will 
 be the same. 
 
 We have supposed in the preceding illustration 
 that the light employed is homogeneous. If it is 
 white, then the differently coloured fringes will form 
 by their superposition a system of fringes analogous 
 to those seen between two object-glasses, as already 
 explained. 
 
 The same periodical colours which we have now 
 described as exhibited by thin plates were discov- 
 ered by Newton in thick plates, and he has ex- 
 plained them by means of the theory of fits ; but it 
 would lead us beyond the limits of a popular work 
 like this to enter into any details of his observations, 
 or to give an account of the numerous and important 
 additions which this branch of optics has received 
 from the discoveries of /ucc feeding authors.
 
 SIR ISAAC NEWTON. 
 
 CHAPTER VII. 
 
 Newton's Theory of the Colours of Natural Bodies explained Objec- 
 tions to it stated New Classification of Colours Outline of a New 
 Theory proposed, 
 
 IF the objects of the material world had been 
 illuminated with white light, all the particles of 
 which possessed the same degree of refrangibility, 
 and were equally acted upon by the bodies on which 
 they fall, all nature would have shone with a leaden 
 hue*, and all the combinations of external objects, 
 and all the features of the human countenance, would 
 have exhibited no other variety but that which they 
 possess in a pencil sketch or a China-ink drawing. 
 The rainbow itself would have dwindled into a nar- 
 row arch of white light, the stars would have shone 
 through a gray sky, and the mantle of a wintry 
 twilight would have replaced the golden vesture of 
 the rising and the setting sun. But He who has ex- 
 hibited such matchless skill in the organization of 
 material bodies, and such exquisite taste in the forms 
 upon which they are modelled, has superadded that 
 ethereal beauty which enhances their more per- 
 manent qualities, and presents them to us in the 
 ever-varying colours of the spectrum. Without this 
 the foliage of vegetable life might have filled the eye 
 and fostered the fruit which it veils, but the youth- 
 ful green of its spring would have been blended with 
 the dying yellow of its autumn. Without this the 
 diamond might have displayed to science the beauty 
 of its forms, and yielded to the arts its adamantine 
 virtues ; but it would have ceased to shine in the 
 chaplet of beauty, and to sparkle in the diadem of 
 princes. Without this the human countenance might
 
 COLOURS OF NATURAL BODIES. . 83 
 
 have expressed all the sympathies of the heart, but 
 the " purple light of love" would not have risen on 
 the cheek, nor the hectic flush been. the herald of 
 its decay. 
 
 The gay colouring with which the Almighty has 
 decked the pale marble of nature is not the result 
 of any quality inherent in the coloured body, or in 
 the particles by which it may be tinged, but is merely 
 a property of the light in which they happen to be 
 placed. Newton was the first person who placed 
 this great truth in the clearest evidence. He found 
 that all bodies, whatever were their peculiar colours, 
 exhibited these colours only in white light. ' When 
 they were illuminated by homogeneous red light 
 they appeared red, by homogeneous yellow light, 
 yellow, arid so on, " their colours being most brisk 
 and vivid under the influence of their own daylight 
 colours." The leaf of a plant, for example, ap- 
 peared green in the white light of day, because it 
 had the property of reflecting that light in greater 
 abundance than any other. When it was placed in 
 homogeneous red light, it could no longer appear 
 
 freen, because there was no greeri"light to reflect ; 
 lit it reflected a portion of red light, because there 
 was some red in the compound green which it had 
 the property of reflecting. Had the leaf originally 
 reflected a pure homogeneous green, unmixed with 
 red, and reflected no white light from its outer sur- 
 face, it would have appeared quite black in pure ho- 
 mogeneous red light, as this light does not contain 
 a single ray which the leaf was capable of reflect- 
 ing. Hence the colours of material bodies are owing 
 to the property which they possess of stopping cer- 
 tain rays of white light, while they reflect or trans- 
 mit to the eye the rest of the rays of which white 
 light is composed. 
 
 So far the Newtonian doctrine of colours is ca- 
 pable of rigid demonstration; but its author was 
 not content with carrying it thus far : he sought to
 
 84 SIR ISAAC NEWTON. 
 
 determine the manner in which particular rays are 
 stopped, while others are reflected or transmitted ; 
 and the result of this profound inquiry was his theory 
 of the colours of natural bodies, which was commu- 
 nicated to the Royal Society on the 10th February, 
 1675. This theory is perhaps the loftiest of all his 
 speculations ; and though, as a physical generaliza- 
 tion, it stands on a perishable basis, and must soon 
 be swept away in the progress of science, it yet 
 bears the deepest impress of the grasp of his pow- 
 erful intellect. 
 
 The principles upon which this theory is founded 
 are the following : 
 
 1. Bodies that have the greatest refractive powers 
 reflect the greatest quantity of light; and at the 
 confines of equally refracting media there is no re- 
 flection. 
 
 2. The least particles of almost all natural bodies 
 are in some measure transparent. 
 
 3. Between the particles of bodies are many pores 
 or spaces, either empty or filled with media of less 
 density than the particles. 
 
 4. The particles of bodies and their pores, or the 
 spaces between the particles, have some definite 
 size. 
 
 Upon these principles Newton explains the origin 
 of transparency, opacity, and colour. 
 
 Transparency^ considers as arising from the par- 
 ticles and their intervals or pores being too small to 
 cause reflection at their common surfaces,* so that 
 all the light which enters transparent bodies passes 
 through them without any portion of it being turned 
 from its path by reflection. If we could Qbtain, for 
 example, a film of mica whose tni^-fcss does not 
 exceed two-thirds of the millionth part of an inch, 
 all the light which fell upon it would pass through it, 
 and none would be .reflected. If this film was then 
 
 * Optics, Book ii. Prop. iv.
 
 
 COLOURS OF NATURAL BODIES. 8S 
 
 cut into fragments, a number of such fragments 
 would constitute a bundle, which would also trans- 
 mit all the light which fell upon it, and be perfectly 
 transparent. 
 
 Opacity in bodies arises, he thinks, from an oppo- 
 site cause, viz. when the parts of bodies are of such 
 a size as to be capable of reflecting the light which 
 falls upon them, in which case the light is " stopped 
 or stifled" by the multitude of reflections. 
 
 The colours of natural bodies have, in the New- 
 tonian hypothesis, the same origin as the colours of 
 thin plates, their transparent particles, according to 
 their several sizes, reflecting rays of one colour, and 
 transmitting those of another. "For if a thinned 
 or plated body which, being of an uneven thickness, 
 appears all over of one uniform colour, should be slit 
 into threads, or broken into fragments of the same 
 thickness with the plate or film, every thread or frag- 
 ment should keep its colour, and consequently, a 
 heap of such threads or fragments should constitute 
 a mass or powder of the same colour which the 
 plate exhibited before it was broken: and the parts 
 of all natural bodies being like so many fragments 
 of a plate, must, on the same grounds, exhibit the 
 same colour." 
 
 Such is the theory of the colours of natural 
 bodies, stated as clearly and briefly as we can. It 
 has been very generally admitted by philosophers, 
 both of our own and of other countries, and has been 
 recently illustrated and defended by a French philoso- 
 pher of distinguished eminence. That this theory 
 affords the true explanation of certain colours, or, 
 to speak more correctly, that certain colo ins in natu- 
 ral bodies are the colours of thin plates, cannot be 
 doubted; but it will not be difficult to ^ow that it is 
 quite inapplicable to that great class of phenomena 
 which may be considered as representing the colours 
 of natural bodies. 
 
 The first objection to the Newtonian theory is the
 
 86 SIR ISAAC NEWTON. 
 
 total absence of all reflected light from the particles 
 of transparent coloured media, such as coloured 
 gems, coloured glasses, and coloured fluids. This 
 objection was urged long ago by Mr. Delaval, who 
 placed coloured fluids on black grounds, and never 
 could perceive the least trace of the reflected tints. 
 I have repeated the experiment with every precau- 
 tion, and with every variation that I could think of, 
 and I consider it as" an established fact, that in such 
 coloured bodies the complementary reflected colour 
 cannot be rendered visible. If the fluid, for example, 
 be red, the green light from which the red has been 
 separated ought to appear either directly by looking 
 into the coloured mass, or ought to be recognised 
 by its influence in modifying the light really re- 
 flected; but as it cannot be seen, we must conclude 
 that it has not been reflected, but has been de- 
 stroyed by some other property of the coloured 
 body. 
 
 A similar objection may be drawn from the disap- 
 pearance of the transmitted complementary colour 
 in the leaves of plants and petals of flowers. I have 
 ascertained from numerous experiments, tUtt the 
 transmitted colour is almost invariably the same 
 with the reflected colour, and that the same holds 
 true with the coloured juices expressed from them. 
 The complementary tints are never seen, and wher- 
 ever there has been any thing like an approximation 
 to two tints, I have invariably found that it arose 
 from there being two different coloured juices exist- 
 ing hi different sides of the leaf. 
 
 In the phenomena of the light transmitted by 
 coloured glasses, there are some peculiarities which, 
 we think, demonstrate that their colours are not 
 those of thin plates. The light, for example, trans- 
 mitted through a particular land of blue glass, has a 
 blue colour of such a peculiar composition that there 
 is no blue in any of the orders of colours hi thin 
 plates which has any resemblance to it. It is entirely
 
 
 COLOURS OF NATURAL BODIES. 87 
 
 destitute of the red rays which form the middle of 
 the red space in the spectrum; so that the particles 
 on which the colour depends must reflect the middle 
 red rays, and transmit those on each side of it, a 
 property which cannot be deduced from the New- 
 tonian doctrine. 
 
 The explanation of opacity, as arising from a 
 multitude of reflections, is liable to the same ob- 
 jection which we have urged against the explana- 
 tion of colour. In order to appreciate its weight, 
 we must distinguish opacity into two kinds, namely, 
 the opacity of whiteness and the opacity of blackness. 
 Those bodies which possess the powerj of reflection 
 in the highest degree, such as white metals, chalk, 
 and plaster of Paris, never reflect more than one- 
 half of the light which falls upon them. The other 
 half of the incident light is, according to Newton, 
 lost by a multitude of reflections. But how is it 
 lost ? Reflection merely changes the direction of the 
 particles of light, so that they must again emerge 
 from the body, unless they are reflected into fixed 
 retmmng orbits, which detain them for ever in a 
 state 01 motion within the body. In the case of 
 black opacity, such as that of coal, which reflects 
 from its first surface only ^ T th of the white light, 
 the difficulty is still greater, and we cannot conceive 
 how any system of interior reflections could so 
 completely stifle ||ths of the whole incident light, 
 without some of it returning to the eye in a visible 
 form. 
 
 In determining the constitution of bodies that pro- 
 duce transparency and blackness, the Newtonian 
 theory encounters a difficulty which its author has 
 by no means surmounted. Transparency, as we 
 have already seen, arises from the "particles and 
 their interstices being too small to cause reflections 
 in their common surfaces," that is, they must be 
 "less than any of those which exhibit colours," or 
 "less than is requisite to reflect the white and very
 
 88 IR ISAAC NEWTON. 
 
 faint blue of the first order. But this is the very same 
 constitution which produces blackness by reflection, 
 and in order to explain the cause of blackness by 
 transmission, or black opacity, Newton is obliged to 
 introduce a new principle. 
 
 ".For the production of black" says he, "the cor- 
 puscles must be less than any of those which ex- 
 hibit colours. For at all greater sizes there is too 
 much light reflected to constitute this colour. But 
 if they be supposed a little less than is requisite to 
 reflect the white and very faint blue of the first or- 
 der, they will reflect so very little light as to appear 
 intensely black, and yet may perhaps variously refract* 
 it to and fro within themselves so long, until it hap- 
 pens to be stifled and lost, by which means they will 
 appear black hi all positions of the eye, without any 
 transparency." 
 
 This very remarkable passage exhibits, in a striking 
 manner, the perplexity in which our author was in- 
 volved by the difficulties of his subject. As the par- 
 ticles which produce blackness by reflection are 
 necessarily so small as to exclude the existen^ of 
 any reflective forces, he cannot ascribe the loss of 
 the intromitted light, as he does in the case of white 
 opacity, to " a multitude of reflections ;" and there- 
 fore he is compelled to have recourse to refracting 
 forces to perform the same office. The reluctance 
 with which he avails himself of this expedient is 
 well marked in the mode of expression which he 
 adopts ; and I am persuaded that when he wrote the 
 above passage, he felt the full force of the objec- 
 tions to this hypothesis, which cannot fail to pre- 
 sent themselves. As the size of the particles which 
 produce blackness are intermediate between those 
 
 * In the same paragraph, when speaking of black bodies becoming 
 hot, and burning sooner than others, he says that their " effect may pro- 
 ceed partly from the multitude of refractions in a little room, and partly 
 from the easy commotion of so very small corpuscles." Optics, Part iii, 
 Prop. vii. p. 335.
 
 COLOURS OF NATURAL BODIES. 89 
 
 which produce transparency and those which pro- 
 duce colour, approaching closely to the latter, it is 
 difficult to conceive why they should refract the in- 
 tromitted light, while the greater and smaller par- 
 ticles, and even those almost of the same size, should 
 be destitute of that property. It is, besides, not easy 
 to understand how a refraction can take place within 
 bodies which shall stifle all the light, and prevent it 
 from emerging. Nay, we may admit the existence 
 of such refractions, and. yet understand how, by a 
 compensation in their direction, the refracted rays 
 may all emerge from the opaque body. 
 
 The force of these objections is tacitly recognised 
 in Pemberton's View of Sir Isaac Newton's Philoso- 
 phy ;* and as Newton not only read and approved of 
 that work, but even perused a great part of it along 
 with its author, we may fairly consider the opinion 
 there stated to be his own. 
 
 "For producing black, the particles ought to be 
 smaller than for exhibiting any of the colours, viz. 
 of a size answering to the thickness of the bubble, 
 whenby reflecting little or no light, it appears colour- 
 less; but yet they must not be too small, for that will 
 make them transparent through deficiency of reflec- 
 tions in the inward parts of the body, sufficient to 
 stop the light from going through it; but they must 
 be of a size bordering upon that disposed to reflect 
 the faint blue of the first order, which affords an 
 evident reason why blacks usually partake a little 
 of that colour." In this passage all idea of refrac- 
 tion is abandoned, and that precise degree of size is 
 assumed for the particles which leaves a small power 
 of reflection, which is deemed sufficient to prevent 
 the body from becoming transparent; that is, suffi- 
 cient to render it opaque or black. 
 
 The last objection which we shall state to this 
 theory is one to which we attach great weight, and, 
 
 * See uage 354.
 
 90 SIR ISAAC NEWTON. 
 
 as it is founded on discoveries and views which have 
 been published since the time of Newton, we ven- 
 ture to believe, that, had he been aware of them, he 
 would never have proposed the theory which we 
 are considering. 
 
 When light falls upon a thin film such as AEC, 
 fig. 9, p. 80, so as to produce the colours of thin 
 plates, it follows, from Sir Isaac Newton's theory 
 of fits, that a portion of the light is, as usual, re- 
 flected at the first surface AE,* while the light which 
 forms the coloured image is that which is reflected 
 from the second surface EC, so that all the colours 
 of thin plates are diluted with the white light re- 
 flected from the first surface. Now, in the modern 
 theory, which ascribes the colours of thin plates to 
 the interference of the light reflected from the 
 second surface EC, with the light reflected from the 
 first surface AE, the resulting tint arises from the 
 combination of these two pencils, and consequently 
 there is no white light reflected from the surface 
 AE. In like manner, when the thickness of the 
 film is such that the two interfering pencils com- 
 pletely destroy one another, and produce black, 
 there is not a ray of light reflected from the first 
 surface. Here, then, we have a criterion for de- 
 ciding between the theory of fits and the theory of 
 interference ; for if there is no white light reflected 
 from the first surface AE, the theory of fits must be 
 rejected. In a remarkable phenomenon of black- 
 ness arising from minute fibres, which I have had 
 occasion to describe, there was no perceptible re- 
 flection from the surface of the fibres ;f and M. 
 Fresnel describes an experiment made to deter- 
 mine the same noint, and states the result of it to 
 
 * When Newton speaks of bodies losing their reflecting power from 
 their thinness, he means the reflecting power of their second surface^, 
 as is evident from the reason he assigns. See Optics, Part iii. Prop. *iiy 
 p.257. 
 
 \ Edinburgh Journal of Science, No L p. 108.
 
 COLOURS OF NATURAL BODIES. 91 
 
 have been unequivocally in favour of the doctrine 
 of interference. 
 
 In order to apply this important fact, let us take 
 a piece of coal, one of the blackest and most opaque 
 of all substances, and which does not reflect to the 
 eye a single ray out of those which enter its sub- 
 stance. The size of its particles is so small, that 
 they are incapable of reflecting light. When a num- 
 ber of these particles are placed together, so as to 
 form a surface, and other particles behind them, so 
 as to form a solid, they will not acquire by this 
 process the power of reflection ; and consequently, a 
 piece of coal so composed should be destitute of the 
 property of reflecting light from its first surface. 
 But this is not the case, light is abundantly re- 
 flected from the first surface of the coal, and conse- 
 quently, its elementary particles must possess the 
 same power. Hence the blackness of coal must be 
 ascribed to some other cause than to the minute- 
 ness of its transparent atoms. 
 
 To transparent bodies this_ argument has a similar 
 application. As their atoms are still less than those 
 of black bodies, their inability to reflect light is still 
 greater, and hence arises their transparency. But 
 the particles forming the surface of such bodies do 
 reflect light, and, therefore, their transparency must 
 have another origin. 
 
 In the case of coloured bodies, too, the particles 
 forming their surfaces reflect white light like those 
 of all other bodies, so that these particles cannot 
 produce colour on the same principles as those of 
 thin plates. In many of those cases of colour which 
 seem to depend upon the minuteness of the particles 
 of the body, the reflection of white light may never- 
 theless be observed, but this will be found to arise 
 from a thin transparent film, behind which the colo- 
 rific particles are placed. 
 
 Whatever answer may be given to these objec- 
 tions, we think it will be admitted by those who
 
 92 SIR ISAAC NEWTON. 
 
 have studied the subject most profoundly, that a 
 satisfactory theory of the colours of natural bodies 
 is still a desideratum in science. How far we may 
 be able to approach to it in the present state of 
 optics the reader will judge from the following 
 views. 
 
 Colours may be arranged into seven classes, each 
 of which depends upon different principles. 
 
 1. Transparent coloured fluids transparent col 
 cured gems transparent coloured glasses coloured 
 powders and the colours of the leaves and flowers 
 of plants. 
 
 2. Oxidations on metals colours of Labradoi 
 feldspar colours of precious and hydrophanous 
 opal, and other opalescences the colours of the 
 feathers of birds, of the wings of insects, and of the 
 scales of fishes. 
 
 3. Superficial colours, as those of mother-of-pearl 
 and striated surfaces. 
 
 4. Opalescences and colours in composite crystals 
 having double refraction. 
 
 5. Colours from the absorption of common and 
 polarized light by doubly refracting crystals. 
 
 6. Colours at the surfaces of media of different 
 dispersive powers. 
 
 7. Colours at the surface of media in which the 
 reflecting forces extend to different distances, or fol- 
 low different laws. 
 
 The first two of these classes are the most im- 
 portant. The Newtonian theory appears to be 
 strictly applicable to the phenomena of the second 
 class ; but those of the first class cannot, we con- 
 ceive, be referred to the same cause. 
 
 The rays of solar light possess several remarkable 
 physical properties : They heat they illuminate 
 they promote chymical combination they effect 
 chymical decompositions they impart magnetism 
 to steel the}. alter the colours of bodies thev
 
 NEW THEORY OF COLOURS. 93 
 
 communicate to plants and flowers their peculiar 
 colours, and are in many cases necessary to the 
 development of their characteristic qualities. It is 
 impossible to admit for a moment that these varied 
 effects are produced by a mere mechanical action, 
 or that they arise from the agitation of the particles 
 of bodies by the vibration of the ether which is con- 
 sidered to be the cause of light. Whatever be the 
 difficulties which attach to the theory which sup- 
 poses light to consist of material particles, we are 
 compelled, by its properties, to admit that light acts 
 as if it were material, and that it enters into combi- 
 nations with bodies, in order to produce the effects 
 which we have enumerated. 
 
 When a beam of light falls upon a body, and the 
 whole or a part of that which enters its substance 
 totally disappears, we are entitled to say, that it is 
 detained by some power exercised by the particles 
 of the body over the particles of light. When this 
 light is said to be lost by a multitude of reflections 
 or refractions, the statement is not only hypotheti- 
 cal, but it is an hypothesis incompatible with optical 
 principles. That the light detained within bodies 
 has been stopped by the attractive force of the par- 
 ticles seems to be highly probable, and the mind 
 will not feel any repugnance to admit that the par- 
 ticles of all bodies, whether solid, fluid, or aeriform, 
 have a specific affinity for the particles of light. 
 Considering light, therefore, as material, it is not 
 difficult to comprehend how it should, like other 
 elementary substances, enter into combination with 
 bodies, and produce many chymical and physical 
 effects, but particularly the phenomena of transpa- 
 rency, opacity, and colour. 
 
 In transparent colourless bodies, such as water 
 and glass,, the intromitted light experiences a con- 
 siderable loss, because a certain number of its par- 
 ticles are attracted and detained by the atoms of the 
 water or glass, and the light which emerges is 
 H
 
 94 SIR ISAAC NEWTON. 
 
 colourless, because the particles exercise a propor- 
 tional action over all the simple colours which 
 compose white light. 
 
 When the transparent body has any decided 
 colour, such as those enumerated in Class I., then 
 the particles of the body have exercised a specific 
 attraction over those rays of white light which are 
 complementary to those which compose the colour 
 of the transmitted light. If the transparent body, 
 for example, is red, then its particles have detained 
 the green rays which entered into the incident light, 
 or certain other rays, which with 'the red are neces- 
 sary to compose white light. In compound bodies, 
 like some of the artificial glasses, the particles will 
 attract and detain rays of light of different colours, 
 as may be seen by analyzing the transmitted light 
 with a prism, which will exhibit a spectrum deprived 
 of all the rays which have been detained. In black 
 bodies the particles exercise a powerful attraction 
 over light, and detain all the intromitted rays. 
 
 When coloured bodies are opaque, so as to ex- 
 hibit their colours principally by reflection, the light 
 which is reflected back to the observer has received 
 its colour from transmission through part of the 
 thickness of the body, or, what is the same thing, 
 the colour reflected to the eye is complementary to 
 that which has been detained by the particles of the 
 body while the light is passing and repassing 
 through a thickness terminated by the reflecting 
 surfaces ; and as only a part of this light is reflected, 
 as in the case of leaves and flowers, the transmitted 
 light must have the same colour as the reflected 
 light. 
 
 When coloured bodies exhibit two different colours 
 complementary to each other, the one seen by re- 
 flection and the other by transmission, it is then 
 highly probable that the colours are those of thin 
 plates, though there are still other optical principles 
 to which they may be referred. As the particles of
 
 NEW THEORY OF COLOURS. 95 
 
 bodies, and the medium which unites them, or, as 
 the different atoms of a compound body may have 
 different dispersive powers, while they exercise the 
 same refractive force over a particular part of the 
 spectrum, the rays for which this compensation 
 takes place will be transmitted, while part of the 
 complementary light is reflected.* Or in cases 
 where the refractive and dispersive powers are the 
 same, the reflective forces of the particles may vary 
 according to a different law, so that at the separat- 
 ing surfaces either white or coloured light may be 
 reflected.! 
 
 In those cases of colour where the reflected and 
 the transmitted tints are not complementary, as in 
 leaf-gold, where the former is yellow and the latter 
 green ; in leaf-silver, where they are white and blue, 
 and in certain'pieces of fir-wood, where the reflected 
 light is whitish yellow, and the transmitted light a 
 brilliant homogeneous red, we may explain the sepa- 
 ration of the colours either by the principles we 
 have already laid down or by the doctrine of 'thin 
 plates. On the first principle, the colour of the re- 
 flected light, which is supposed to be the same as 
 that of the transmitted light, will be modified by the 
 law according to which the particles of the body 
 attract different rays out of the beam of white light. 
 In pitch, for example, the blue rays are first ab- 
 sorbed, so that at small thicknesses the transmitted 
 light is a fine yellow, while, by the action of a 
 greater thickness, the yellow itself is absorbed, and 
 the transmitted light is a bright homogeneous red. 
 Now in leaf-gold the transmitted colour of thinner 
 films than we can obtain may be yellow, and, con- 
 sequently, the light reflected from the first strata of 
 interrupting faces will be yellow, and will determine 
 the predominant tint of the reflected light. On the 
 Newtonian doctrine, Mr. Herschel has explained it 
 
 * See the Phil. Trans. 1829, Part I. p. 189 t Idem.
 
 96 SIR ISAAC NEWTON. 
 
 Dy saying. " that the transmitted rays have traversed 
 the whole thickness of the medium, and therefore 
 undergo many more times the action of its atoms 
 than those reflected, especially those near the first 
 surface to which the brighter part of the reflected 
 colour is due." 
 
 The phenomena of the absorption of common 
 and polarized light, which I have described in an- 
 other place,* throw much light on the subject of 
 coloured bodies. The relation of the absorbent ac- 
 tion to the axes of double refraction, and, conse- 
 quently, to the poles of the molecules of the crystal, 
 shows how the particles of light attracted by the 
 molecules of the body will vary, both in their nature 
 and number, according to the direction in which 
 they approach the molecules ; and explains how the 
 colour of a body may be changed, either tempora- 
 rily or permanently, by heat, according as it pro- 
 duces a temporary or a permanent change in the 
 relative position of the molecules. This is not the 
 place to enlarge on this subject ; but we may be 
 permitted to apply the idea to the curious experi- 
 ment of Thenard on phosphorus. When this sub- 
 stance is rendered pure by repeated distillation, it 
 is transparent, and transmits jfcllow light ; but when 
 it is thrown in a melted state into cold water, it 
 becomes jet black. When again melted, it resumes 
 its original colour and transparency. According to 
 the Newtonian theory, we must suppose that the 
 atoms of the phosphorus have been diminished in 
 size by sudden cooling, an effect which it is not 
 easy to comprehend; but, according to the pre- 
 ceding views, we may suppose that the atoms of 
 the phosphorus have been forced by sudden cooling 
 into relative positions quite different from those 
 which they take when they slowly assume the solio 
 ?tate, and their poles of maximum attraction, in 
 
 * Phil. Trans. 1819, p. 11
 
 NEW THEORY OF COLOURS. 97 
 
 place of being turned to one another, are turned in 
 different directions, and then allowed to exercise 
 their full action in attracting the intromitted light, 
 and detaining it wholly within the body.* 
 
 Before concluding this chapter, there is one topic 
 peculiarly deserving our notice, namely, the change 
 of colour produced in bodies by continued exposure 
 to light. The general effect of light is to diminish 
 or dilute the colours of bodies, and in many cases 
 to deprive them entirely of their colour. Now, it 
 is not easy to understand how repeated undulations 
 propagated through a body could diminish the size 
 of its particles, or how the same effect could be 
 produced by a multitude of reflections from particle 
 to particle. But if light is attracted by the particles 
 of bodies, and combines with. them, it is easy to 
 conceive that, when the molecules of a body have 
 combined with a great number of particles of a 
 green colour, for example, their power of combina- 
 tion with others will be diminished, and, conse- 
 quently, the number of particles of any colour 
 absorbed or detained must diminish with the time 
 that the body has been exposed to light ; that is, 
 these particles must enter into the transmitted and 
 reflected pencils, and diminish the intensity of their 
 colour. If the body, for example, absorbs red light, 
 and transmits and reflects green, then if the quan- 
 tity of absorbed red light is diminished, it will enter 
 into the reflected and transmitted pencils, and, form- 
 ing white light by its mixture with a portion of the 
 green rays, will actually dilute them in the same 
 manner as if a portion of white light had been 
 added.f 
 
 * If this view of the matter be just, we should expect that the specifl* 
 gravity of the black would exceed that of the yellow phosphorus. 
 
 t Since the two preceding chapters were written, I have had occasion 
 to confirm and extend the views which they contain by many new ex- 
 periments.
 
 98 SIR ISAAC NEWTON. 
 
 CHAPTER VIII. 
 
 Newton's Discoveries respecting the Inflection or DiffrMtion of Light 
 Previous Discoveries of Grimaldi and Dr. Hooke Labours of sue* 
 ceeding Philosophers Law of Interference of Dr. Young FresneFt 
 DiscoveriesNew Theory of Inflection on the Hypothesis of the Ma- 
 teriality of Light. 
 
 ALTHOUGH the discoveries of Newton respecting 
 the Inflection of Light were first published in his 
 Optics in 1704, yet there is reason to think that 
 they were made at a much earlier period. Sir Isaac, 
 indeed, informs us, in his preface to that great work, 
 that the third book, which contains these discove- 
 ries, " was put together out of scattered papers ;" 
 and he adds at the end of his observations, that " he 
 designed to repeat most of them with more care and 
 exactness, and to make some new ones for determin- 
 ing the manner how the rays of light are bent in their 
 passage by bodies, for making the fringes of colours 
 with the dark lines between them. But I was then 
 interrupted, and cannot now think of taking these 
 things into consideration." On the 18th March, 1674, 
 Dr. Hooke had read a valuable memoir on the phe- 
 nomena of diffraction; and, as Sir Isaac makes no 
 allusion whatever to this work, it is the more proba- 
 ble that his " scattered papers" had been written 
 previous to the communication of Dr. Hooke's ex- 
 periments. 
 
 The phenomena of the inflection of liffht were first 
 discovered by Francis Maria Grimaldi, a learned 
 Jesuit, who has described them in a posthumous 
 work published in 1665, two years after his death.* 
 
 Having admitted a be am of the sun's light through 
 
 * Physico-Mathesis de Lumine caloribus et iride aliisque anntxis 
 Eonon 1665.
 
 INFLECTION OF LIGHT. 509 
 
 a small pin-hole in a piece of lead or card into a 
 dark chamber, he found that the light diverged from 
 this aperture in the form of a cone, and that the 
 shadows of all bodies placed in this light were not 
 only larger than might have been expected, but were 
 surrounded with three coloured fringes, the nearest 
 being the widest, and the most remote the narrowest. 
 In strong light he discovered analogous fringes 
 within the shadows of bodies, which increased in 
 number with the breadth of the body, and became 
 more distinct when the shadow was received obliquely 
 and at a greater distance. When two small aper- 
 tures or pin-holes were placed so near each other 
 that the cones of light formed by each of them 
 intersected one another, Grimaldi observed, that a 
 spot common to the circumference of each, or, which 
 is the same thing, illuminated by rays from each 
 cone, was darker than the same spot when illumi- 
 nated by either of the cones separately ; and he an- 
 nounces this remarkable fact in the following para- 
 doxical proposition, " that a body actually illuminated 
 may become more dark by adding a light to that which 
 it already receives" 
 
 Without knowing what had been done by the 
 Italian philosopher, our countryman, Dr. Robert 
 Hooke, had been diligently occupied with the same 
 subject. In 1672, he communicated his first obser- 
 vations to the Royal Society, and he then spoke of 
 his paper as " containing the discovery of a new 
 property of light not mentioned by any optical wri- 
 ters before him." In his paper of 1674, already 
 mentioned, and which is no doubt the one to which 
 he alludes, he has not only described the leading 
 phenomena of the inflection, or the deflection of 
 light, as he calls it, but he has distinctly announced 
 the doctrine of interference, which has performed so 
 great a part in the subsequent history of optics.* 
 
 This doctnne is thus announced. 1. That the same rays of light 
 tailing upon the same point of an object will turn into all sorts of colours
 
 100 
 
 SIR ISAAC NEWTON. 
 
 Such was the state of the subject when Newton 
 directed to it his powers of acute and accurate ob- 
 servation. His attention was turned only to the 
 enlargement of the shadow, and to the three fringes 
 which surrounded it ; and he begins his observations 
 by ascribing the discovery of these facts to Gri- 
 maldi. After taking exact measures of the diameter 
 of the shadow of a human hair, and of the breadth 
 of the fringes at different distances behind it, he 
 discovered the remarkable fact that these diame- 
 ters and breadths were not proportional to the dis- 
 tances from the hair at which they were measured. 
 In order to explain these phenomena, Newton sup- 
 posed that the rays which passed by the edge of the 
 hair are deflected or turned aside from it, as if by a 
 repulsive force, the nearest rays suffering the great- 
 est, and those more remote a less degree of deflec- 
 tion. 
 
 Fig. 10. 
 
 by the various inclination of the object. 2. That colours begin to appear 
 when two pulses of light are blended so well and so near together that 
 the sense takes them for one.
 
 INFLECTION OF LIGHT. 101 
 
 Thus, if X, fig. 10, represents a section of the 
 hair, and AB, CD, EF, GH, &c. rays passing at dif- 
 ferent distances from X, the ray AB will be more 
 deflected than CD, and will cross it at m, the ray 
 CD will for the same reason cross EF at n, and 
 EF will cross GH at o. Hence the curve or caustic 
 formed by the intersections m, n, o, &c. will be con- 
 vex outward, its curvature diminishing as it recedes 
 from the vertex. As none of the passing light can 
 possibly enter within this curve, it will form the 
 boundary of the shadow of X. 
 
 The explanation given by Sir Isaac of the coloured 
 fringes is less precise, and can be inferred only from 
 the two following queries. 
 
 1. "Do not the rays which differ in refrangibility 
 differ also in flexibility, and are they not, by these 
 different inflections separated from one another, so 
 as after separation to make the colours in the three 
 fringes above described ? And after what manner 
 are they inflected to make those fringes ? 
 
 2. " Are not the rays of light in passing by the 
 edges and sides of bodies bent several times back- 
 wards and forwards with a motion like that of an 
 eel? And do not the three fringes of light above 
 mentioned arise from three such bendings ?" 
 
 The idea thus indistinctly thrown out in the pre- 
 ceding queries has been ingeniously interpreted by 
 Mr. Herschel in the manner represented in fig. 11, 
 where SS are two rays passing by the edge of the 
 body MN. These rays are supposed to undergo 
 several bendings, as at a, , c, and the particles of 
 light are thrown off at one or other of the points 
 of contrary flexure, according to the state of their 
 fits or other circumstances. Those that are thrown 
 outwards in the direction aA, B, cC, rfD, will 
 produce as many caustics by their intersections as 
 there are deflected rays; and each caustic, when re- 
 ceived on a screen at a distance, will depict on it 
 the brightest part or maximum of a fringe.
 
 102 SIR ISAAC NEWTON* 
 
 Fig. 11. S S 
 
 In this unsatisfactory state was the subject of the 
 inflection of light left by Sir Isaac. His inquiries 
 were interrupted, and never again renewed; and 
 though he himself found that the phenomena were 
 the same, " whether the hair was encompassed with 
 air or with any other pellucid substance," yet this 
 important result does not seem to have shaken his 
 conviction, that the phenomena had their origin in 
 the action of bodies upon light. 
 
 During two sets of experiments which I made on 
 the inflection of light, the first in 1798, and the 
 second in 1812 and 1813, 1 was desirous of examin- 
 ing the influence of density and refractive power 
 over the fringes produced by inflection, T com-
 
 PR. YOUNG'S LAW OF INTERFERENCE. 103 
 
 pared the fringes formed by gold-leaf with those 
 formed by masses of gold, and those produced by 
 films which gave the colours of thin plates with 
 those formed by masses of the same substance. I 
 examined the influence of platinum, diamond, and 
 cork in inflecting light, the effect of non-reflecting 
 grooves and spaces in polished metals, and of cylin- 
 ders of glass immersed in a mixture of oil of cassia 
 and oil of olives of the same refractive power ; and, 
 as the fringes had the same magnitude and charac- 
 ter under all these circumstances, I concluded that 
 they were not produced by any force inherent in 
 the bodies themselves, but arose from a property 
 of the light itself, which always showed itself when 
 light was stopped in its progress. 
 
 Dr. Thomas Young, who had supported with great 
 ingenuity and force of argument the undulatory 
 theory of light, as maintained by Hooke and Huy- 
 gens, was the first who gave a plausible explana- 
 tion of the inflection of light. By interposing a 
 small screen at B, fig. 10, and intercepting the 
 rays that passed near the hair X, he was surprised 
 to find that all the fringes within the shadow disap- 
 peared. The same effect took place when the screen 
 intercepted the rays on the other side ; and hence 
 he concluded, that the rays on each side of the hair 
 were necessary to the production of the inner fringes, 
 and that the fringes were produced by the inter- 
 ference of the rays that passed on one side of the 
 hair with those that passed on the other side. In 
 order to account for the coloured fringes without the 
 shadow, Dr. Young conceived that the rays which 
 pass near the edge of the hair interfere with others, 
 which he supposes may be reflected after falling 
 very obliquely upon its edge, a supposition which, 
 if correct, would certainly produce fringes very 
 similar to those actually observed. 
 
 In pursuing these researches so successfully begu> 
 by Dr. Young, M. Fresnel had the good fortune t
 
 104 SIR ISAAC XEWTOX. 
 
 explain all the phenomena of inflection by means of 
 the tmdulatoiy doctrine combined with the principle 
 of interference. In place of transmitting the light 
 through a small aperture, he caused it to diverge 
 from the focus of a deep convex lens, and instead 
 of receiving the shadow and its fringes upon a 
 smooth white surface, as was done by Newton, he 
 viewed them directly with his eye through a lens 
 placed behind the shadow ; and by means of a mi- 
 croscope he was able to measure the dimensions of 
 the fringes with the greatest exactness. By this 
 mode of observation he made the remarkable dis- 
 covery, that the inflection of the light depended on 
 the distance of the inflecting body from the aperture or 
 from the focus of divergence ;* the fringes being ob- 
 served to dilate as the body approached that focus, 
 and to contract as it receded from it, their relative 
 distances from each other, and from the margin of 
 the shadow contrnuing invariable. In attempting to 
 account for the formation of the exterior fringes, M. 
 Presnel found it necessary to reject the supposition 
 of Dr. Young, that they were owing to fight re 
 fleeted from the edge of the body. He not only 
 ascertained that the real place of the fringe was the 
 i^th of a millimetre different from what it should 
 be on that supposition, but he found that the fringes 
 preserved the same intensity of light, whether the 
 inflecting body had a round or a sharp edge, and 
 even when the edge was such as not to afford suffi- 
 cient light for their production. From this difficulty 
 the undulatory theory speedily released him, and he 
 was led by its indications to consider the exterior 
 fringes, as produced by an infinite number of ele- 
 mentary waves of light emanating from a primitive 
 wave when partly interrupted by an opaque body. 
 The various phenomena of inflection, which had 
 
 * This eflfeet is so grot, that at the distance of/our inches from the 
 x*mofdirergeiM^Ueanfii!armnaucmofthredrayoflhefimfrinfe 
 mV ", whaeattiie fiiabee of about twenty feet, it is onlv * 56"
 
 NEW THEORY OF INFLECTION. 105 
 
 so long resisted every effort to generalize them, 
 having thus received so beautiful and satisfactory an 
 explanation from the tindulatory doctrine, they must 
 of course be regarded as affording to that doctrine 
 the most powerful support, while the Newtonian 
 hypothesis of the materiality of light is proportion- 
 ally thrown into the shade. It is impossible, indeed, 
 even for national partiality to consider the views of 
 Newton as furnishing any explanation of the facts 
 discovered by Fresnel ; and, as no attempt has been 
 made by the'small though able phalanx of his dis- 
 ciples to stay the decision with which, on this count 
 at least, the doctrine of emission has been threat- 
 ened, we shall venture to suggest some principles 
 by which the refractory phenomena may perhaps 
 be yet brought within the pale of the Newtonian 
 theory. 
 
 That the particles of light, like those of heat, 
 are endowed with a repulsive force which prevents 
 them from accumulating when in a state of conden- 
 sation, or when they are detained by the absorptive 
 action of opaque bodies, will be readily admitted. 
 By this power a beam of light radiating from a 
 luminous point has, in every azimuth, the same de- 
 gree of intensity at the same distance from its centre 
 of divergence ; but if we intercept a portion of such 
 a beam by an opaque body, the repulsive force of the 
 light which formerly occupied its shadow is with- 
 drawn, and consequently the rays which pass near 
 the body will be repelled into the shadow, and will 
 form, by their interference with those similarly re- 
 pelled on the other side, the interior fringes, which 
 are parallel to the edges of the body. The rays 
 which pass at a greater distance will in like manner 
 be bent towards the body, but with less force, and, 
 interfering with those rays which retain their primi- 
 tive direction, from the state of their fits or the 
 position of their poles, they will form the exterior 
 fringes. When the inflecting body is placed near
 
 10(5 SIR ISAAC NEWTON. 
 
 the point of divergence, the greater proximity of 
 the rays will produce a greater repulsive force, and 
 consequently a greater inflection of the passing 
 light ; while the removal of the body from the point 
 of divergence will be accompanied with an increased 
 distance of the particles, an inferior repulsive force, 
 and a feebler inflection. As the phenomena of in- 
 flection, considered under this aspect, arise from a 
 property of the light itself, it follows that they will 
 remain invariable, whatever be the nature or den- 
 sity of the body, or the form of the edge which 
 acts upon the passing rays. 
 
 CHAPTER IX. 
 
 Miscellaneous Optical Researches of Newton His Experiments on 
 Refraction His Conjecture respecting the Inflammability of the 
 Diamond His Law of Double Refraction His Observations on the 
 Polarization of LiglU Newton's Theory of Light His "Optics." 
 
 BEFORE concluding our account of Newton's op- 
 tical discoveries, it is necessary to notice some of 
 his minor researches, which, though of inferior im- 
 portance in the science of light, have either exer- 
 cised an influence over the progress of discovery, 
 or been associated with the history of other branches 
 of knowledge. 
 
 One of the most curious of these inquiries related 
 to the connexion between the refractive powers and 
 the chymical composition of bodies. Having meas- 
 ured the refractive powers and the densities of twenty- 
 two substances, he found that the forces which 
 reflect and refract light are very nearly proportional 
 to the densities of the same bodies. In^ this law, 
 however, he noticed a remarkable exception in the 
 case of unctuous and sulphureous bodies, such as 
 camphire, olive oil, linseed oil, spirit of tuipentine.
 
 DOUBLE REFRACTION OF LIGHT. 107 
 
 *nd diamond, which have their refractive powers 
 two or three times greater in respect of their densi- 
 ties than the other substances in the table, while 
 among 1 themselves their refractive powers are pro- 
 portional to their densities, without any considerable 
 variation. Hence he concluded that diamond "is 
 an unctuous substance coagulated," a sagacious 
 prediction, which has been verified in the discoveries 
 of modern chymistry. The connexion between a 
 high degree of inflammability and a great refracting 
 force has been still more strongly established by the 
 high refractive power which I detected in phospho- 
 rus, and which was discovered in hydrogen by MM. 
 Biot and Arago. 
 
 There is no part of the optical labours of Newton 
 which is less satisfactory than that which relates to 
 the double refraction of light. In 1690, Huygens, 
 published his admirable treatise on light, in which 
 he has given the law of double refraction in calca- 
 reous spar, as deduced from his theory of light, and 
 as confirmed by direct experiment. Viewing it 
 probably as a theoretical deduction, Newton seems 
 to have regarded it as incorrect, and though he has 
 given Huygens the credit of describing the phe- 
 nomena more exactly than Bartholinus, yet, without 
 assigning any reason, he rejected the law of the 
 Dutch philosopher, and substituted another in its 
 place. These observations of our author form the 
 subject of the twenty-fifth and twenty-sixth queries at 
 the end of his Optics, which was published fourteen 
 years after the appearance of Huygens's work. The 
 law adopted by Newton is not accompanied with any 
 of the experiments from which it was deduced ; and 
 though he has given it without expressing any doubt 
 of its accuracy, it is, nevertheless, entirely incom- 
 patible with observation, and has been rejected by 
 aU succeeding philosophers. 
 
 In his speculations respecting the successive dis- 
 appearance and reappearance of two of the four
 
 108 SIR ISAAC NEWTON. 
 
 images which are formed when a luminous object 
 is viewed through two rhombs of calcareous spar, 
 one of which is made to revolve upon the other, 
 Newton has been more successful He concluded 
 from these phenomena that every ray of light has 
 two opposite sides originally endued with the prop- 
 erty on which the unusual refraction depends, and 
 other two opposite sides not endued with that prop- 
 erty; and he suggested it as a subject for future 
 inquiry, whether there are not more properties of 
 light by which the sides of the rays differ, and are 
 distinguished from one another. This is the first 
 occasion on which the idea of a polarity in the rays 
 of light has been suggested.* 
 
 From the various optical inquiries in which New- 
 ton was engaged, he was strongly impressed with 
 the belief that light consists of small material par- 
 ticles emitted from shining substances, and that 
 these particles could be again recombined into solid 
 matter, so that " gross bodies and light were con- 
 vertible into one another." He conceived also that 
 the particles of solid bodies and of light exerted a 
 mulaal action upon each other, the former being 
 agitated and heated by the latter, and the latter 
 being attracted and repelled by the former, with 
 forces depending on the inertia of the luminous par- 
 ticles. These forces he regarded as insensible at 
 all measurable distances, and he conceived that the 
 distances between the particles of bodies were very 
 small when compared with the extent of their sphere 
 of attraction and repulsion. 
 
 With the exception of Hooke, Huygens, and 
 Euler, almost all the contemporaries and successors 
 of Newton maintained the doctrine of the mate- 
 riality of light. It was first successfully assailed by 
 Dr. Thomas Young, and since that time it has been 
 shaken to its foundation by those great discoveries 
 
 * See the twenty-ninth query at the end of his Optics, where the sides 
 of a ray "are compared with the poles of a magnet.
 
 OPTICS. 109 
 
 which have illustrated the commencement of the 
 present century. The undulatory theory, which has 
 thus triumphed in its turn, is still subject to grave 
 difficulties, and we fear another century must elapse 
 before a final decision can be pronounced on this 
 long-agitated question. 
 
 The most important of the optical discoveries of 
 Newton, of which we have given a general history, 
 were communicated to the Royal Society in de- 
 tached papers ; but the disputes in which they had 
 involved their author made him hesitate about the 
 publication of his other discoveries. Although he 
 had drawn up a connected view of his labours under 
 the title of " Opticks, or a Treatise on the Reflex- 
 ions, Refractions, Inflexions, and Colours of Light," 
 yet he resolved not to publish this work during the 
 life of Hooke, by whose rival jealousy his tranquillity 
 had been so frequently interrupted. Hooke, how- 
 ever, died in 1702, and the Optics of Newton ap- 
 peared in English in 1704. Dr. Samuel Clark pro- 
 posed a Latin edition of it, which appeared in 1706, 
 and he was generously presented by Sir Isaac with 
 500Z. (or 100/. for each of his five children), as a 
 token of the approbation and gratitude of the author. 
 Both the English and the Latin editions have been 
 frequently reprinted both in England and on the 
 Continent,* and there perhaps never was a. work of 
 profound science so widely circulated 
 
 * Tfce English edition was reprinted at London in 1714, 1721, and 
 1730, and the Latin one at London in 1700, 1719, 1721, 1728, at Lausanne 
 in 1740, and at Padua in 1773 
 
 1
 
 110 SIR ISAAC NEWTON. 
 
 CHAPTER X. 
 
 Astronomical Discoveries of Newton Necessity of combined Exertion 
 to the Completion of great Discoveries Sketch of the History of As- 
 tronomy previous to the Time of Newton Copernicus, 1473-1543 
 Tycho Brake, 1546-1601 Kepler, 1571-1631 Galileo, 1564-1642. 
 
 FROM the optical labours of Newton we now pro- 
 ceed to the history of his astronomical discoveries 
 those transcendent deductions of human reason 
 by which he has secured to himself an immortal 
 name, and vindicated the intellectual dignity of his 
 species. Pre-eminent as his triumphs have been, it 
 would be unjust to affirm that they were achieved 
 by his single aim. The torch of many a preceding 
 age had thrown its light into the strongholds of 
 the material universe, and the grasp of many a pow- 
 erful hand had pulled down the most impregnable of 
 its defences. An alliance, indeed, of many kindred 
 spirits had been long struggling in this great cause, 
 and Newton was but the leader of their mighty 
 phalanx, the director of their combined genius, 
 the general who won the victory, and therefore 
 wears its laurels. 
 
 The history of science presents us with no ex- 
 ample of an individual mind throwing itself far in 
 advance of its contemporaries. It is only in the 
 career of crime and ambition that reckless man 
 takes the start of his species, and uncurbed by 
 moral and religious restraint, erects an unholy dy- 
 nasty upon the ruins of ancient and venerable insti- 
 tutions. The achievements of intellectual power, 
 though often begun by one mind and completed by 
 another, have ever been the results of combined ex- 
 ertions. Slow in their growth, they gradually ap- 
 proximate to a more perfect condition : the vaViety
 
 ASTRONOMICAL DISCOVERIES. Ill 
 
 IK the phenomena of nature call forth a variety of 
 intellectual gifts ; the powers of analysis and com- 
 bination are applied to the humbler labours of obser 
 vation and experiment, and in the ordeal of riva 
 inquiry truth is finally purified from error. How 
 different is it with those systems which the imagi- 
 nation rears, those theories of wild import which 
 are directed against the consciences and hopes of 
 man. The fatal upas-tree distils its poison in the 
 spring as well as the autumn of its growth, but the 
 fruit which sustains life must have its bud prepared 
 before the approach of winter, its blossom expanded 
 in the spring, and its juices elaborated by the light 
 and heat of the summer and the autumnal sun. 
 
 In the century which preceded the birth of New- 
 ton the science of astronomy advanced with the 
 most rapid steps. Emerging from the darkness of 
 the middle ages, the human mind seemed to rejoice 
 in its new-born strength, and to apply itself with 
 elastic vigour to unfold the mechanism of the heavens. 
 The labours of Hipparchus and Ptolemy had indeed 
 furnished many important epochs and supplied many 
 valuable data; but the cumbrous appendages of 
 cycles and epicycles with which they explained the 
 stations and retrogradations of the planets, and the 
 vulgar prejudices which a false interpretation of 
 Scripture had excited against a belief in the motion 
 of the earth, rendered it difficult even for great 
 minds to escape from the trammels of authority, 
 and appeal to the simplicity of nature. 
 
 The sovereign of Castile, the generous and noble- 
 minded Alphonso, had long before proscribed the 
 rude expedients of his predecessors ; and when he 
 declared that if the heavens were thus constituted, 
 he could have given the Deity good advice, he must 
 not only have felt the absurdity of the prevailing 
 system, but must have obtained some foresight of a 
 more simple arrangement. But neither he nor the 
 astronomers whom he so liberally protected seem to
 
 112 SIR ISAAC NEWTON. 
 
 have established a better system, and it was left 
 to Copernicus to enjoy the dignity of being the 
 restorer of astronomy. * 
 
 This great man, a native of Thorn in Prussia, fol- 
 lowing his father's profession, began his career as a 
 doctor of medicine, but an accidental attendance on 
 the mathematical lectures of Brudzevius excited a 
 love for astronomy, which became the leading pas- 
 sion of his life. Quitting a profession uncongenial 
 to such pursuits, he went to Bologna to study 
 astronomy under Dominic Maria ; and after having 
 enjoyed the friendship and instruction of that able 
 philosopher, he established himself at Rome in the 
 humble situation of a teacher of mathematics. Here 
 he made numerous astronomical observations which 
 served him as the basis of future researches ; but 
 an event soon occurred which, though it interrupted 
 for a while his important studies, placed him in a 
 situation for pursuing them with new zeal. The 
 death of one of the canons enabled his uncle, who 
 was Bishop of Ermeland, to appoint him to a can- 
 onry in the chapter of Frauenburg, where, in a 
 house situated on the brow of a mountain, he con- 
 tinued, in peaceful seclusion, to carry on his astro- 
 nomical observations. During his residence at Rome 
 his talents had been so well appreciated, that the 
 Bishop of Fossombrona, w T ho presided over the 
 council for reforming the calendar, solicited the aid 
 of Copernicus in this desirable undertaking. At first 
 he entered warmly into the views of the council 
 and charged himself with the determination of the 
 length of the year and of the month, and of the 
 other motions of the sun and moon that seemed to 
 be, required ; but he found the task too irksome, and 
 probably felt that it would interfere with those 
 interesting discoveries which had already begun to 
 dawn upon his mind. 
 
 Copernicus is said to have commenced his inqui- 
 ries by an historical examination of the opinions of
 
 COPERNICUS. 1 ] 3 
 
 ancient authors on the system of the universe ; buf 
 it is more likely that he sought for the authority of 
 their great names to countenance his peculiar views, 
 and that he was more desirous to present his own 
 theory as one that he had received, rather than as 
 one which he had invented. His mind had b*en 
 long imbued with the idea that simplicity and har- 
 mony should characterize the arrangements of the 
 planetary system, and, in the complication and dis- 
 order which reigned in the hypothesis of Ptolemy, 
 he saw insuperable objections to its being regarded 
 as a representation of nature. In the opinions of 
 the Egyptian sages, in those of Pythagoras, Philo- 
 laus, Aristarchus, and Nicetas, he recognised his 
 own earliest conviction that the earth was not the 
 centre of the universe ; but he appears to have con- 
 sidered it as still possible that our globe might per- 
 form some function in the system more important 
 than that of the other planets; and his attention 
 was much occupied with the speculation of Martia- 
 nus CapeUa, who placed the sun between Mars and 
 the moon, and made Mercury and Venus revolve 
 round him as a centre; and with the system of 
 Apollonius Pergaeus, who made all the planets re- 
 volve round the sun, while the sun and moon were 
 carried round the earth in the centre of the universe. 
 The examination, however, of these hypotheses 
 gradually dispelled the difficulties with which the 
 subject was beset; and after the labours of more 
 than thirty years, Ke was permitted to see the true 
 system of the heavens. The sun he considered as 
 immoveable in the centre of the system, while the 
 ^arth revolved between the orbits of Venus and 
 Mars, and produced by its rotation about its axis aU 
 the diurnal phenomena of the celestial sphere. The 
 precession of the equinoxes was thus referred to 3 
 Blight motion of the earth's axis, and the stations 
 and retrogradations of the planets were the neces- 
 sary consequence of their own motions combined
 
 114 SIR ISAAC NEWTON. 
 
 with that of the earth about the sun. These re- 
 markable views were supported by numerous as- 
 tronomical observations; and in 1530 Copernicus 
 brought to a close his immortal work on the Revolu- 
 tions of the Heavenly Bodies. 
 
 But while we admire the genius which triumphed 
 over so many difficulties, we cannot fail to commend 
 the extraordinary prudence with which he ushered 
 his new system into the world. Aware of the preju- 
 dices, and even of the hostility with which such a 
 system would be received, he resolved neither to 
 startle the one nor provoke the other. He allowed 
 his opinions to circulate in the slow current of per- 
 sonal communication. The points of opposition 
 which they presented to established doctrines were 
 gradually worn down, and they insinuated them- 
 selves into reception among the ecclesiastical circles 
 by the very reluctance of their author to bring them 
 into notice. In the year 1534, Cardinal Schonberg, 
 Bishop of Capua, and Gyse, Bishop of Culm, exerted 
 all their influence to induce Copernicus to lay his 
 system before the world ; but he resisted their so- 
 licitations ; and it was not till 1539 that an accidental 
 circumstance contributed to alter his resolution. 
 George Rheticus, professor of mathematics at Wir- 
 temberg, having heard of the labours of Copernicus, 
 resigned his chair, and repaired to Frauenberg to 
 make himself master of his discoveries. This zeal 
 ous disciple prevailed upon his master to permit the 
 publication of his system ; and they seem to have 
 arranged a plan for giving it to the world without 
 alarming the vigilance of the church, or startling 
 the prejudices of individuals. Under the disguise 
 of a student of mathematics, Rheticus published in 
 1540 an account of the manuscript volume of Coper- 
 nicus. This pamphlet was received without any 
 disapprobation, and its author was encouraged to 
 reprint it at Basle, in 1541, with his own name. 
 The success of these publications, and the flattering
 
 TYCHO BRAHE. 115 
 
 manner in which the new astronomy was received 
 by several able writers, induced Copernicus to place 
 his MSS. in the hands of Rheticus. It was accord- 
 ingly printed at the expense of Cardinal Schon- 
 berg, and appeared at Nuremberg in 1543. Its illus- 
 trious author, however, did not live to peruse it. 
 A complete copy was handed to him in his last 
 moments, and he saw and touched it a few hours 
 before his death. This great work was dedicated 
 to the Holy Pontiff, in order, as Copernicus himself 
 says, that the authority of the head of the church 
 might silence the calumnies of individuals who had 
 attacked his views by arguments drawn from reli- 
 gion. Thus introduced, the Copernican system met 
 with no ecclesiastical opposition, and gradually made 
 its way in spite of the ignorance and prejudices 
 of the age. 
 
 Among the astronomers who provided the mate- 
 rials of the Newtonian philosophy the name of 
 Tycho Brahe merits a conspicuous place. De- 
 scended from an ancient Swedish family, he was 
 born at Knudstorp, in Norway, in 1546, three years 
 after the death of Copernicus. The great eclipse 
 of the sun which happened on the 26th August, 
 1560, while he was at the University of Copenhagen, 
 attracted his notice : and when he found that all 
 its phenomena had been accurately predicted, he 
 was seized with the most irresistible passion tp,ac- 
 quire the knowledge of a science so infallible in its 
 results. Destined for the profession of the law, his 
 friends discouraged the pursuit which now engrossed 
 his thoughts; and such were the reproaches and 
 even persecutions to which he was exposed, that he 
 quitted his country with the design of travelling 
 through Germany. At the very commencement of 
 his journey, however, an event occurred in which 
 the impetuosity of Ms temper had nearly cost Mm 
 Ms life. At a wedding-feast in Rostock, a question- 
 able point hi geometry involved him in a dispute .
 
 116 SIR ISAAC NEWTON. 
 
 with a Danish nobleman of the same temperament 
 with himself; and the two mathematicians resolved 
 to settle the difference by the sword. Tycho, 
 however, seems to have bee'n second in the conflict, 
 for he lost the greater part of his nose, and was 
 obliged to supply its place by a substitute of gold 
 and silver, which a cement of glue attached to his 
 face. During his stay at Augsburg he inspired the 
 burgomaster of the city, Peter Hainzell, with a love 
 of astronomy. This public-spirited citizen erected 
 an excellent observatory at his own expense, and 
 here Tycho began that distinguished career which 
 has placed him in the first rank of practical as- 
 tronomers. 
 
 Upon his return to Copenhagen in 1570, he was 
 received with every mark of ; respect. The king in 
 vited him to court, and persons of all ranks harassed 
 him with their attentions. At Herritzvold, near his 
 native place, the house of his maternal uncle afforded 
 him a retreat from the gayeties of the capital, and 
 he was there offered eveiy accommodation for the 
 prosecution of his astronomical studies. Here, 
 however, the passion of love and the pursuits of 
 alchymy distracted his thoughts; but though the 
 peasant girl of whom he was enamoured was of 
 easier attainment than the philosopher's stone, the 
 marriage produced an open quarrel with his relations, 
 which it required the interference of the king to allay. 
 In the tranquillity of domestic happiness, Tycho re- 
 sumed his study of the heavens, and in 1572 he 
 enjoyed the singular good fortune of observing, 
 through all its variations, the new star in Cassiopeia, 
 which appeared with such extraordinary splendour 
 as to be visible in the daytime, and which gradually 
 disappeared in the following year. 
 
 Dissatisfied with his residence in Denmark, Tycho 
 resolved to settle in some distant country ; and hav- 
 ing gone as far as Venice in search of a suitable 
 residence, he at last fixed upon Basle, in Switzer*
 
 TYCHO BRAKE. 117 
 
 land. The King of Denmark, however, had learned 
 his intention from the Prince of Hesse ; and when 
 Tycho returned to Copenhagen to remove his family 
 and his instruments, his sovereign announced to him 
 his resolution to detain him in his kingdom. He 
 presented him with ; the canonry of Roschild, with 
 an income of 2000 crowns per annum. To this he 
 added a pension of 1000 crowns ; and he promised 
 to give him the island of Huen, with a complete 
 observatory erected under his own eye. This gene- 
 rous offer was instantly accepted. The celebrated 
 observatory of Uraniburg was established at the 
 expense of about 20,000/. ; and in this magnificent 
 retreat Tycho continued for twenty-one years to en- 
 rich astronomy with the most valuable observations. 
 Admiring disciples crowded to this sanctuary of the 
 sciences to acquire the knowledge of the heavens ; 
 and kings* and princes felt themselves honoured 
 by becoming the guests of the great astronomer of 
 the age. 
 
 One of the principal discoveries of Tvcho was 
 that of the inequality of the moon's motion, called 
 the variation. He detected, also, the annual equa- 
 tion which affects the place of her apogee and nodes, 
 and he determined the greatest and the least inclina- 
 tion of the lunar orbit. His observations on the 
 planets were numerous and precise, and have formed 
 the data of the present generalizations in astronomy. 
 
 * When James I. went to Copenhagen in 1590, to "conclude his mar- 
 riage with the Princess Anne of Denmark, he spent eight days under 
 the roof of Tycho at Uraniburg. As a token of his gratitude,' he com- 
 posed a set of Latin verses in honour of the astronomer, and left him a 
 magnificent present at his departure. He gave him also his royal license 
 for the publication of his works in England, and accompanied it with 
 the following complimentary letter: 
 
 " Nor am 1 acquainted with these things on the relation of others, or 
 from a mere perusal of your works, but I have seen them with my own 
 eyes, and heard them with my own ears, in your residence at Urani 
 burg, during the various learned and agreeable conversations which 1 
 there held with you, which even now affect my mind to such a degree, 
 that it is difficult to decide whether I recollect them with greater pleasure 
 or admiration."
 
 118 SIR ISAAC NEWTON. 
 
 Though thus skilful in the observation of phenomena, 
 his mind was but little suited to investigate their 
 cause, and it was probably owing to this defect that 
 he rejected the system of Copernicus. The vanity 
 of giving his own name to another system was not 
 likely to actuate a mind such as his, a'nd it was more 
 probable that he was led to adopt the immobility of 
 the earth, and to make the sun, with all his attendant 
 planets, circulate round it, from the great difficulty 
 which still presented itself by comparing the apparent 
 diameter of the stars with the annual parallax of the 
 earth's orbit. 
 
 The death of Frederick in 1588 proved a severe 
 calamity to Tycho, and to the science which he cul- 
 tivated. During the first years of the minority of 
 Christian IV. the regency continued the royal patron- 
 age to the observatory of Uraniburg; and in 1592 
 the young king paid a visit of some days to Tycho, 
 and left him a gold chain in token of his favour. 
 The astronomer, however, had made himself enemies 
 at court, and the envy of his high reputation had 
 probably added fresh malignity to the irritation of 
 personal feelings. Under the ministry of Wolchen- 
 dorf, a name for ever odious to science, Tycho's 
 pension was stopped ; he was in 1597 deprived of 
 the canonry of Roschild, and was thus forced, with 
 his wife and children, to seek an asylum in a foreign 
 land. His friend, Henry Rantzau, of Wansbeck, 
 under whose roof he found a hospitable shelter, was 
 fortunately acquainted with the emperor Rodolph II., 
 who, to his love of science, added a passion for 
 alchymy and astrology. The reputation of Tycho 
 having already reached the imperial ear, the recom- 
 mendation of Rantzau was scarcely necessaiy to en- 
 sure him his warmest friendship. Invited by the em- 
 peror, he repaired in 1599 to Prague, where lie met 
 with the kindest reception. A pension of three 
 thousand crowns was immediately settled upon him, 
 and a commodious observatory erected for his use
 
 TYCHO BRAKE. 119 
 
 In the vicinity of that city. Here the exiled astrono- 
 mer renewed with delight his interrupted labours, 
 and the gratitude which he cherished for the royal 
 favour increased the satisfaction which he felt in 
 having so unexpectedly found i resting-place for 
 approaching age. These prospects of better days 
 were enhanced by the good fortune of receiving two 
 such men as Kepler and Longomontanus for his 
 pupils ; but the fallacy of human anticipation was 
 here, as in so many other cases, strikingly displayed. 
 Tycho was not aware of the inroads which both his 
 labours and his disappointments had made upon his 
 constitution. Though surrounded with affectionate 
 friends and admiring disciples, he was still an exile 
 in a foreign land. Though his country had been 
 base in its ingratitude, it was yet the land which he 
 loved, the scene of his earliest affection, the 
 theatre of his scientific glory. These feelings con- 
 tinually preyed upon his mind, and his unsettled 
 spirit was ever hovering among his native mountains. 
 In this condition he was attacked with a disease of 
 the most painful kind, and though the paroxysms of 
 its agonies had lengthened intermissions, yet he saw 
 that death was approaching. He implored his pupils 
 to persevere in their scientific labours. He conversed 
 with Kepler on some of the profoundest points of 
 astronomy, and with these secular occupations he 
 mingled frequent acts of piety and devotion. In 
 this happy condition he expired without pain at the 
 age of fifty-five, the unquestionable victim of the 
 councils of Christian IV. 
 
 Notwithstanding the accessions which astronomy 
 had received from the labours of Copernicus and 
 Tycho, no progress was 'yet made in developing 
 the general laws of the system, and scarcely an idea 
 had been formed of the power by which the planets 
 were retained in their orbits. The labours of as- 
 siduous observers had supplied the materials for this
 
 120 SIR ISAAC NEWTON. 
 
 purpose, and Kepler arose to lay the foundations of 
 physical astronomy. 
 
 John Kepler was born at Wiel, in Wirtemberg, in 
 1571. He was educated for the church, and dis- 
 charged even some of the clerical functions ; but his 
 devotion to science withdrew him from the study of 
 theology. Having received mathematical instruc- 
 tion from the celebrated Maestlinus, he had made 
 such progress in the science, that he was invited in 
 1594 to fill the mathematical chair of Gratz in Sty- 
 ria. Endowed with a fertile imagination, his mine 1 
 was ever intent upon subtle and ingenious specula- 
 tions. In the year 1596 he published his peculiar 
 views in a work on the Harmonies and Analogies of 
 Nature. In this singular production, he attempts to 
 solve what he calls the great cosmographical mys- 
 tery of the admirable proportion of the planetary 
 orbits ; and by means of the six regular geometrical 
 solids,* he endeavours to assign a reason why there 
 are six planets, and why the dimensions of their 
 orbits and the time of their periodical revolutions 
 were such as Copernicus had found them.. If a 
 cube, for example, were inserted in a sphere, of which 
 Saturn's orbit was one of the great circles, it would, 
 he supposed, touch by its six planes the lesser 
 sphere of Jupiter ; and, in like manner, he proposes 
 to determine, by the aid of the other geometrical 
 solids, the magnitude of the spheres of the other 
 planets. A copy of this work was presented by its 
 author to Tycho Brahe, who had been too long 
 versed in the severe realities of observation to at- 
 tach any value to such wild theories. He advised 
 his young friend " first to lay a solid foundation for 
 his views by actual observation, and then, by ascend- 
 ing from these, to strive to reach the causes of 
 things ;" and there is reason to think that, by the aid 
 of the whole Baconian philosophy, thus compressed 
 
 * The cube, the sphere, the tetrahedron, the octohedron, the dodeca 
 hcdron, and the icosahedron.
 
 KEPLER. 12 1 
 
 by anticipation into a single sentence, he abandoned 
 for a while his visionary inquiries. 
 
 In the year 1598 Kepler suffered persecution for 
 his religious principles, and was compelled to quit 
 Gratz ; but though he was recalled by the States of 
 Styria, he felt his situation insecure, and accepted of 
 a pressing invitation from Tycho to settle at Prague, 
 and assist him in his calculations. Having arrived 
 in Bohemia in 1600, he was introduced by his friends 
 to the Emperor Rodolph, from whom he ever after- 
 ward received the kindest attention. On the death 
 of Tycho in 1601, he was appointed mathematician 
 to the emperor, a situation in which he was con- 
 tinued during the successive reigns of Matthias and 
 Ferdinand; but what was of more importance to 
 science, he was put in possession of the valuable 
 collection of Tycho's observations. These obser- 
 vations were remarkably numerous ; and as the orbit 
 of Mars was more oval than that of any of the other 
 planets, they were peculiarly suitable for determin- 
 ing its real form. The notions of harmony and 
 symmetry in the construction of the solar system, 
 which had filled the mind of Kepler, necessarily led 
 him to believe that the planets revolved with a uni- 
 form motion in circular orbits. So firm, indeed, was 
 this conviction, that he made numerous attempts to 
 represent the observations of Tycho by this hy- 
 pothesis. The deviations were too great to be as- 
 cribed to errors of observation ; and in trying various 
 other curves, he was led to the discovery that Mars 
 revolved round the sun in an elliptical orbit, in one 
 of the foci of which the sun itself was placed. The 
 same observations enabled him to determine the 
 dimensions of the planet's orbit, and by comparing 
 together the times in which Mars passed over 
 different portions of its orbit, he found that they 
 were to one another as the areas described by the 
 lines drawn from the centre of the planet to the 
 centre of the sun, or, in more technical terms, that
 
 122 SIR ISAAC NEWTON. 
 
 the radius vector describes equal areas in equal 
 times. These two remarkable discoveries, the first 
 that were ever made in physical astronomy, were 
 extended to all the other planets of the system, and 
 were communicated to the world in 1609, in his 
 " Commentaries on the Motions of the Planet Mars, 
 as deduced from the observations of Tycho Brahe." 
 Although our author was conducted to these great 
 laws by the parent examination of well-established 
 facts, his imagination was ever hurrying him among 
 the wilds of conjecture. Convinced that the mean 
 distances of the planets from the sun bore to one 
 another some mysterious relation, he not only com- 
 pared them with the regular geometrical solids, but 
 also with the intervals of musical tones ; an idea 
 which the ancient Pythagoreans had suggested, and 
 which had been adopted by Archimedes himself. 
 All these comparisons were fruitless ; and Kepler 
 was about to abandon an inquiry of about seventeen 
 years' duration, when, on the 8th March, 1618, he 
 conceived the idea of comparing the powers of the 
 different members which express the planetary dis- 
 tances, in place of the numbers themselves. He 
 compared the squares and the cubes of the distances 
 with the same powers of the periodic times ; nay, he 
 tried even the squares of the times with the cubes 
 of the distances ; but his hurry and impatience led 
 him into an error of calculation, and he rejected this 
 law as having no existence in nature ! On the 15th 
 May, his mind again reverted to the same notion, 
 and upon making the calculations anew, and free from 
 error, he discovered the great law, that the squares 
 of the periodic times of any two planets are to one 
 another as the cubes of their distances from the sun. 
 Enchanted with this unexpected result, he could 
 scarcely trust his calculations ; and, to use his own 
 language, he at first believed that he was dreaming, 
 and had taken for granted the very truth of which 
 he was in search. This brilliant discovery was pub-
 
 KEPLER. 123 
 
 lished in 1619, in his "Harmony of the World;" a 
 work dedicated to James VI. of Scotland. Thus 
 were established what have been called the three 
 laws of Kepler, the motion of the planets in ellip- 
 tical orbits, the proportionality between the areas 
 described and their times of description, and the 
 relations between the squares of the periodic times 
 and the cubes of the distances. 
 
 The relation of the movements of the planets to 
 the sun, as the general centre of all their orbits, 
 3ould not fail to suggest to Kepler that some power 
 resided in that luminary by which these various mo- 
 tions were produced ; and he went so far as to con- 
 jecture that this power diminishes as the square of 
 the distance of the body on which it was exerted ; 
 but he immediately rejects this law, and prefers that 
 of the simple distances. In his work on Mars, he 
 speaks of gravity as a mutual and corporeal affec- 
 tion between similar bodies. He maintained that 
 the tides were occasioned by the moon's attraction, 
 and that the irregularities of the lunar motions, as 
 detected by Tycho, were owing to the joint actions 
 of the sun and the earth ; but the relation between 
 gravity, as exhibited on the earth's surface, and as 
 conducting the planets in their orbits, required 
 more patience of thought than he could command, 
 and was accordingly left for the exercise of higher 
 powers. 
 
 The misery in which Kepler lived forms a painful 
 contrast with the services which he performed to 
 science. The pension on which he subsisted was 
 always in arrears, and though the three emperors 
 whose reigns he adorned directed their ministers 
 to be more punctual in its payment, the disobe- 
 dience of their commands was a source of continued 
 vexation to Kepler. When he retired to Sagan, in 
 Silesia, to spend in retirement the remainder of his 
 days, his pecuniary difficulties became still more 
 harassing. Necessity at last compelled him to apply
 
 124 SIR ISAAC NEWTON. 
 
 personally for the arrears which were due ; and he 
 accordingly set out in 1630 for Ratisbon; but in 
 consequence of the great fatigue which so long a 
 journey on horseback produced, he was seized with 
 a fever, which carried him off on the 30th Novem- 
 ber, 1630, in the 59th year of his age. 
 
 While Kepler was thus laying the foundation of 
 physical astronomy, Galileo was busily employed in 
 extending the boundaries of the solar system. This 
 distinguished philosopher was born at Pisa in 1564. 
 He was the son of a Florentine nobleman, and was 
 educated for the medical profession ; but a passion 
 for geometry took possession of his mind, and called 
 forth all his powers. Without the aid of a master, 
 he studied the writings of Euclid and of Archimedes_; 
 and such were his acquirements, that he was ap- 
 pointed by the Grand-duke of Tuscany to the mathe- 
 matical chair of Pisa in the twenty-fifth year of his 
 age. His opposition to the Aristotelian philosophy 
 gained him many enemies, and at the end of three 
 years he quitted Pisa, and accepted of an invitation 
 to the professorship of mathematics at Padua. Here 
 he continued for eighteen years adorning the uni- 
 versity by his name, and diffusing around him a 
 taste for the physical sciences. With the excep- 
 tion of some contrivances of inferior importance, 
 Galileo had distinguished himself by no discovery 
 till he had reached the forty-fifth year of his age. 
 In the year 1609, the same year in which Kepler 
 published his celebrated commentary on Mars, Gali- 
 leo paid a visit to Venice, where he heard, in the 
 course of conversation, that a Dutchman of the 
 name of Jansens had constructed and presented to 
 Prince Maurice an instrument through which he saw 
 distant objects magnified and rendered more distinct, 
 as if they had been brought nearer to the observer. 
 This report was credited by some and disbelieved 
 by others ; but, in the course of a few days, Galileo 
 received a letter from James Badovere at Paris,
 
 GALILEO. 125 
 
 which placed beyond a doubt the existence of such 
 an instrument. The idea instantly filled his mind 
 as one of the utmost importance to science ; and so 
 thoroughly was he acquainted with the properties 
 of lenses, that he not only discovered the principle 
 of its construction, but was able to complete a tele- 
 scope for his own use. Into one end of a leaden 
 tube he fitted a spectacle-glass plane on one side 
 and convex on the other, and in the other end be 
 placed another spectacle-glass concave on one side 
 and plane on the other. He then applied his eye 
 to the concave glass, and saw objects "pretty large 
 and pretty near him." They appeared three times 
 nearer, and nine times larger in surface, than to the 
 naked eye. He soon after made another, which 
 represented objects above sixty times larger ; and, 
 sparing neither labour nor expense, he finally con- 
 structed an instrument so excellent, as "to show 
 things almost a thousand times larger, and above 
 thirty times nearer to the naked eye." 
 
 There is, perhaps, no invention that science has 
 presented to man so extraordinary in its nature, and 
 so boundless in its influence, as that of the tele- 
 scope. To the uninstructed mind, the power of 
 seeing an object a thousand miles distant, as large 
 and nearly as distinct as if it were brought within 
 a mile of the observer, must seem almost miracu- 
 lous ; and to the philosopher, even, who thoroughly 
 comprehends the principles upon which it acts, it 
 must ever appear one of the most elegant applioa* 
 tions of science. To have been the first astronomer 
 in whose hands such a gift was placed was a prefer- 
 ence to which Galileo owed much of his future 
 reputation. 
 
 No sooner had he completed his telescope than 
 he applied it to the heavens, and on the 7th Janu- 
 ary, 1618, the first day of its use, he saw round 
 Jupiter three bright little stars lying in a line par- 
 allel to the ecliptic two to the east, and one to tho 
 K
 
 126 SIR ISAAC NEWTON. 
 
 west of the planet. Regarding them as ordinary 
 stars, he never thought of estimating their dtocances. 
 On the following day, when he accidentally Directed 
 his telescope to Jupiter, he was surprised to see 
 the three stars to the west of the planet. To pro- 
 duce this effect it was requisite that the motion of 
 Jupiter should be direct, though, according to calcu- 
 lation, it was actually retrograde. In this dilemma 
 he waited with impatience for the evening of the 
 9th, but unfortunately the sky was covered with 
 clouds. On the 10th he saw only two stars to the 
 east a circumstance which he was no longer able 
 to explain by the motion of Jupiter. He was there- 
 fore compelled to ascribe the change to the stars 
 themselves; and upon repeating his observations 
 on the llth, he no longer doubted that he had dis- 
 covered three planets revolving round Jupiter. On 
 the 13th January he for the first time saw the 
 fourth satellite.* 
 
 This discovery, though of the utmost importance 
 in itself, derived an additional value from the light 
 which it threw on the true system of the universe. 
 While the earth was the only planet enlightened 
 by a moon, it might naturally be supposed that it 
 alone was habitable, and was therefore entitled to 
 the pre-eminence of occupying the centre of the 
 system ; but the discovery of four moons round a 
 much larger planet deprived this argument of its 
 force, and created a new analogy between the earth 
 and the other planets. When Kepler received the 
 " Sidereal Messenger," the work in which Galileo 
 announced his discovery in 1610, he perused it with 
 the deepest interest ; and while it confirmed and 
 extended his substantial discoveries, it dispelled at 
 the same time some of those harmonic dreams which 
 still hovered among his thoughts. In the "Dis- 
 
 * Simon Marias, mathematician to the Marquis of Brandenburg, 
 assures us that he discovered the satellites of Jupiter in Novemoe^ 
 1609.
 
 GALILEO. 127 
 
 sertation" which he published on the discovery of 
 Galileo, he expresses his hope that satellites will 
 be discovered round Saturn and Mars, he conjec- 
 tures that Jupiter has a motion of rotation about 
 his axis, and states his surprise, that, after what 
 had been written on the subject of telescopes by 
 Baptista Porta, they had not been earlier introduced 
 into observatories. 
 
 In continuing his observations, Galileo applied 
 his telescope to Venus, and in 1610 he discovered 
 the phases of that planet, which exhibited to him 
 the various forms of the waxing and the waning 
 moon. This fact established beyond a doubt that 
 the planet revolved round the sun, and thus gave 
 an additional blow to the Ptolemaic system. In his 
 observations on the sun, Galileo discovered his spots, 
 and deduced from them the rotation of the central 
 luminary. He observed that the body of Saturn 
 bad handles attached to it ; but he was unable to 
 detect the form of its ring, or render visible its 
 minute satellites. On the surface of the moon he 
 discovered her mountains and valleys, and deter- 
 mined the curious fact of her libration, in virtue of 
 which parts of the margin of her disk occasionally 
 appear and disappear. In the Milky Way he de- 
 scried numerous minute stars which the unassisted 
 eye was unable to perceive ; and as the largest fixed 
 stars, in place of being magnified by the telescope, 
 became actually minute brilliant points, he inferred 
 their immense distance as rendered necessary by the 
 Copernican hypothesis. All his discoveries, indeed, 
 furnished fresh arguments in favour of the new 
 system ; and the order of the planets and their re- 
 lation to a central sun may now be considered as 
 established by incontrovertible evidence. 
 
 While Galileo was occupied with these noble pur- 
 suits at Pisa, to which he had been recalled in 1611, 
 his generous patron, Cosmo II. Grand-duke of Tus- 
 cany, invited him to Florence, that he might punme
 
 128 SIR ISAAC NEWTON. 
 
 with uninterrupted leisure his astronomical obser- 
 vations, and carry on his correspondence with the 
 German astronomers. His fame had now resounded 
 through all Europe ; the strongholds of prejudice 
 and ignorance were unbarred ; and the most obsti- 
 nate adherents of ancient systems acknowledged 
 the meridian power of the day-star of science. 
 Galileo was ambitious of propagating the great 
 truths which he contributed so powerfully to estab- 
 lish. He never doubted that they would be re- 
 ceived with gratitude by all, by the philosopher as 
 the -consummation of the greatest efforts of human 
 genius, and by the Christian as the most transcend- 
 ent displays of Almighty power. But he had mis- 
 taken the disposition of his species, and the charac- 
 ter of the age. That same system of the heavens 
 which had been discovered by the humble eccle- 
 siastic of Frauenberg, which had been patronised by 
 the kindness of a bishop, and .published at the ex- 
 pense of a cardinal, and which the pope himself 
 had sanctioned by the warmest reception, was, aftei 
 the lapse of a hundred years, doomed to the most 
 violent opposition, as subversive of the doctrines 
 of the Christian faith. On no former occasion has 
 the human mind exhibited such a fatal relapse into 
 intolerance. The age itself had improved in libe- 
 rality; the persecuted doctrines themselves had 
 become more deserving of reception ; the light of 
 the Reformed faith had driven the Catholics from 
 some of their most obnoxious positions ; and yet 
 under all these circumstances, the church of Rome 
 unfurled her banner of persecution against the pride 
 of Italy, against the ornament of his species, and 
 against truths immutable and eternal. 
 
 In consequence of complaints laid before the Holy 
 [nquisition, Galileo was summoned to appear at 
 Rome in 1615, to answer for the heretical opinions 
 which he had promulgated. He was charged with 
 M maintaining as true the false doctrine held by
 
 GALILEO. 129 
 
 many, that the sun was immoveable in the centie 
 of the world, and that the earth revolved with a 
 diurnal motion; with having certain disciples to 
 whom he taught the same doctrine ; with keeping 
 up a correspondence on the subject with several 
 German mathematicians; with having published 
 letters on the solar spots, in which he explained the 
 same doctrine as true ; and with having glossed 
 over with a false interpretation the passages of 
 Scripture which were urged against it." The con- 
 sideration of these charges came before a meeting 
 of the Inquisition, which assembled on the 25th 
 February, 1616 ; and the court, declaring their dis- 
 position to deal gently with the prisoner, pro- 
 nounced the following decree : " That Cardinal 
 Bellarmine should enjoin Galileo to renounce en- 
 tirely the above-recited false opinions ; that, on his 
 refusal to do so, he should be commanded by the 
 commissary of the Inquisition to abandon the said 
 doctrine, and to cease to teach and defend it ; and 
 that, if he did not obey this command, he should 
 be thrown into prison." On the 26th of February- 
 Galileo appeared before Cardinal Bellarmine, and, 
 after receiving from him a gentle admonition, he 
 was commanded by the commissary, in the presence 
 of a notary and witnesses, to desist altogether from 
 his erroneous opinions ; and it was declared to be 
 unlawful for him in future to teach them in any 
 way whatever, either orally or in his writings. To 
 these commands Galileo promised obedience, and 
 was dismissed from the Inquisition. 
 
 The mildness of this sentence was no doubt partly 
 owing to the influence of the Grand-duke of Tus- 
 cany, and other persons of rank and influence at the 
 papal court, who took a deep interest in the issue 
 of the trial. Dreading, however, that so slight a 
 punishment might not have the effect of putting 
 down the obnoxious doctrines, the Inquisition issued 
 a decree denouncing the new opinions as false and
 
 130 SIR ISAAC NEWTON. 
 
 contrary to the sacred writing's, and .prohibiting the 
 sale of eveiy book in which they should be main- 
 tained. 
 
 Thus liberated from his persecutors, Galileo re- 
 turned to Florence, where he pursued his studies 
 with his wonted diligence and ardour. The recanta- 
 tion of his astronomical opinions was so formal 
 and unreserved, that ordinary prudence, if not a 
 sense of personal honour, should have restrained him 
 from unnecessarily bringing them before the world. 
 No anathema was pronounced against his scientific 
 discoveries ; no interdict was laid upon the free 
 exercise of his genius. He was prohibited merely 
 from teaching a doctrine which the church of Rome 
 considered to be injurious to its faith. We might 
 have expected, therefore, that a philosopher so con- 
 spicuous in the eyes of the world would have re- 
 spected the prejudices, however base, of an institu- 
 tion whose decrees formed part of the law of the 
 land, and which possessed the power of life and 
 death within the limits of its jurisdiction. Galileo, 
 however, thought otherwise. A sense of degrada- 
 tion* seems to have urged him to retaliate, and before 
 six years had elapsed, he began to compose his 
 " Cosmical System, or Dialogues on the two greatest 
 Systems of the World, the Ptolemean and the Co- 
 pernican," the concealed object of which is to 
 establish the opinions which he had promised to 
 abandon. In this work the subject is discussed by 
 three speakers, Sagredo, Salviatus, and Simplicius, 
 a peripatetic philosopher, who defends the system of 
 
 * It is distinctly stated in the sentence of the Inquisition, that Galileo's 
 enemies had charged him with ha%'ing abjured his opinions in 1616, and 
 affirmed that he had been punished by the Inquisition. In order to re- 
 fute these calumnies, Galileo applied to Cardinal Bellarmine for a certifi- 
 cate to prove that he neither abjured his opinions nor suffered any pun- 
 ishment for them ; but that the doctrine of the motion of the earth .and 
 the stability of the sun was only denounced to him as contrary to Scrip- 
 ture, and as one which could not be defended or maintained. Cardinal 
 Bellarmine drew up such a certificate in bis own handwriting.
 
 GALILEO. 131 
 
 Ptolemy with much skill against the o\ erwhelming 
 arguments of the rival disputants. Galileo hoped to 
 escape notice by this indirect mode of propagating 
 the new system, and he obtained permission to pub- 
 lish his work, which appeared at Florence in 1632. 
 
 The Inquisition did not, as might have been ex- 
 pected, immediately summon Galileo to their pres- 
 ence. Nearly a year elapsed before they gave any 
 indication of their design; and, according to their 
 own statement, they did not even take the subject 
 under consideration till they saw that the obnoxious 
 tenets were every day gaining ground, in conse- 
 quence of the publication of the Dialogues. They 
 then submitted the work to a careful examination, 
 and having found it to be a direct violation of the 
 injunction which had been formerly intimated to its 
 author, they again cited him before their tribunal in 
 1633. The venerable sage, now in his seventieth 
 year, was thus compelled to repair to Rome, and 
 when he arrived he was committed to the apart- 
 ments of the Fiscal of the Inquisition. The un- 
 changeable friendship, however, of the Grand-duke 
 of Tuscany obtained a remission of this severity, 
 and Galileo was allowed to reside at the house of 
 the Tuscan ambassador during the two months 
 which the trial occupied. When brought before 
 the Inquisition, and examined upon oath, he ac- 
 knowledged that the Dialogues were written by him- 
 self, and th,at he obtained permission to publish them 
 without notifying to the person who gave it that he 
 had been prohibited from holding, defending, or 
 teaching the heretical opinions. He confessed also 
 that the Dialogues were composed in such a manner, 
 that the arguments in favour of the Copernican sys- 
 tem, though given as partly false, were yet managed 
 in such a manner that they were more likely to con- 
 firm than overturn its doctrines ; but that this error, 
 which was not intentional, arose from the natural 
 desire of making an ingenious defence of false propo-
 
 132 SIR ISAAC NEWTON. 
 
 sitions, and of opinions that had the semblance of 
 probability. 
 
 After receiving 1 these confessions and excuses, the 
 Inquisition allowed Galileo a proper time for giving 
 in his defence; but this seems to have consisted 
 solely in bringing forward the certificate of Cardinal 
 Bellarmine already mentioned^ which made no allu- 
 sion to the promise under which Galileo had come 
 never to defend, nor teach in any way whatever, the 
 Copernican doctrines. The court held this defence 
 to be an aggravation of the crime rather than an 
 excuse for it, and proceeded to pronounce a sentence' 
 which will be ever memorable in the history of the 
 human mind. 
 
 Invoking the name of our Saviour, they declare, 
 that Galileo had made himself liable to the suspicion 
 of heresy, by believing the doctrine, contrary to 
 Scripture, that the sun was the centre of the earth's 
 orbit, and did not move from east to west ; and by 
 defending as probable the opinion that the earth 
 moved, and was not the centre of the world ; and 
 that he had thus incurred all the censures and penal- 
 ties which were enacted by the church against such 
 offences ; but that he should be absolved from these 
 penalties, provided he sincerely abjured and cursed 
 all the errors and heresies contained in the formula 
 of the church, which should be submitted to him. 
 That so grave and pernicious a crime should not 
 pass altogether unpunished, that he might become 
 more cautious in future, and might be an example 
 to others to abstain from such offences, they decreed 
 that his Dialogues should be prohibited by a formal 
 edict, that he should be condemned to the prison 
 of the Inquisition during pleasure, and that, during 
 the three following years, he should recite once a 
 week the seven penitential psalms. 
 
 This sentence was subscribed by seven cardinals ; 
 and on the 22d June, 1633, Galileo signed an abjura- 
 tion humiliating to himself and degrading to philoso-
 
 GALILEO. 133 
 
 phy. At the age of seventy, on his bended knees, 
 and with his right hand resting on the Holy Evan- 
 gelists, did this patriarch of science avow his present 
 and his past belief in all the dogmas of the Romish 
 Church, abandon as false and heretical the doctrine 
 of the earth's motion and of the sun's immobility, 
 and pledge himself to denounce to the Inquisition 
 any other person who was even suspected of heresy. 
 He abjured, cursed, and detested those eternal and 
 immutable truths which the Almighty had permitted 
 him to be the first to establish. What a mortifying 
 picture of moral depravity and intellectual weakness ! 
 If the unholy zeal of the assembly of cardinals has 
 been branded with infamy, what must we think of 
 the venerable sage whose gray hairs were entwined 
 with the chaplet of immortality, quailing under the 
 fear of man, and sacrificing the convictions of his 
 conscience and the deductions of his reason at the 
 altar of a base superstition ? Had Galileo but added 
 the courage of the martyr to the wisdom of the 
 sage, had he carried the glance of his indignant 
 eye round the circle of his judges, had he lifted 
 his hands to heaven, and called the living God to 
 witness the truth and immutability of his opinions, 
 the bigotry of his enemies would have been dis- 
 armed, and science would have enjoyed a memorable 
 triumph. 
 
 The great truths of the Copernican system, instead 
 of being considered as heretical, had been actually 
 adopted by many pious members of the Catholic 
 church, and even some of its dignitaries did not 
 scruple to defend it openly. Previous to the first 
 persecution of Galileo in 1615, a Neapolitan noble- 
 man, Vincenzio Caraffa, a person equally distin- 
 guished by his piety and birth, had solicited Paul 
 Anthony Foscarinus, a learned Carmelite monk, to 
 illustrate and defend the new system of the universe. 
 With this request the ecclesiastic speedily complied ; 
 and in the pamphlet which he completed on the 6th
 
 134 SIR ISAAC NEWTON. 
 
 Tanuary, 1615, he defends the Copernican system 
 with much boldness and ingenuity; Tie reconciles 
 the various passages of Scripture with the new doc- 
 trine, and he expresses the hope that such an attempt, 
 now made for the first time, will prove agreeable to 
 philosophers, but particularly to those very learned 
 men, Galileo Galilei, John Kepler, and all the mem- 
 bers of the Lyncean Academy, who, he believes, 
 entertain the same opinion. This remarkable pro- 
 duction, written from the convent of the Carmelites 
 at Naples, is dedicated to the very Reverend Sebas- 
 tian Fantoni, general of the order of Carmelites, and 
 was published at Florence, with the sanction of the 
 ecclesiastical authorities, in 1630 ; three years before 
 the second persecution of Galileo. 
 
 It would be interesting to know the state of public 
 feeling in Italy when Galileo was doomed to the 
 prisons of the Inquisition. No appeal seems to have 
 been made against so cruel a sentence ; and neither 
 in remonstrance nor in derision does an individual 
 voice seem to have been raised. The master spirits 
 of the age looked with sullen indifference on the 
 persecution of exalted genius; and Galileo lay in 
 chains, deserted and unpitied. This unrebuked tri- 
 umph of his enemies was perhaps favourable to the 
 object of their vengeance. Resistance might have 
 heightened the rigour of a sentence, which submis- 
 sion seems to have alleviated. The interference 
 of some eminent individuals of Rome, among whom 
 we have no doubt that the Grand-duke of Tuscany 
 was the most influential, induced Pope Urban VIII., 
 not only to shorten the period, but to soften the 
 rigour of Galileo's imprisonment. From the dun- 
 geon of the Inquisition, where he had remained only 
 four days, he was transported to the ambassador's 
 palace in the Garden de Medici at Rome ; and when 
 his health had begun to suffer, he was permitted to 
 leave the metropolis ; and would have been allowed 
 to return to Florence, but as the plague raged in
 
 GALILEO. 135 
 
 that city, he was sent, in July, 1633, to the archi- 
 episeopal palace of Sienna, the residence of the Arch- 
 bishop Piecolimini, where he carried on and com- 
 pleted his valuable investigations respecting the 
 resistance of solids. Here he continued five months, 
 when, in consequence of the disappearance of the 
 plague at Florence, he was allowed to retire to his 
 villa at Bellosguardo, and afterward to that of Ar- 
 cetri in the vicinity of Florence. 
 
 Though Galileo was now, to a certain degree, 
 liberated from the power of man, yet the afflicting 
 dispensations of Providence began to fall thickly 
 around him. No sooner had he returned to Arcetri, 
 than his favourite daughter, Maria, was seized with 
 a dangerous illness, which soon terminated in her 
 death. He was himself attacked with hernia, pal- 
 pitation of the heart, loss of appetite, and the most 
 oppressive melancholy; and though he solicited 
 permission to repair to Florence for medical assist- 
 ance, yet this deed of mercy was denied him. In 
 1638, however, the pope permitted him to pay a visit 
 to Florence, and his friend, Father Castelli, was 
 allowed to visit him in the company of an officer of 
 the Inquisition. But this indulgence was soon with- 
 drawn, and at the end of a few months he was re- 
 manded to Arcetri. The sight of his right eye had 
 begun to fail in 1636, from an opacity of the cornea. 
 In 1637 his left eye was attacked with the same 
 complaint ; so that in a few months he was affected 
 with total and incurable blindness. Before this ca- 
 lamity had supervened, he had noticed the curious 
 phenomenon of the moon's libration, in consequence 
 of which, parts of her visible disk that are exposed 
 to view at one time are withdrawn at another. He 
 succeeded in explaining two of the causes of this 
 curious phenomenon, viz. the different distances of 
 the observer from the line joining the centre of the 
 earth and the moon, which produces the diurnal 
 libration, and the unequal motion of the moon in her
 
 136 SIR ISAAC NEWTON. 
 
 orbit, which produces the libration in longitude. It 
 was left, however, to Hevelius to discover the libra- 
 tion in latitude, which arises from the inclination of 
 her axis being a little less than a right angle to the 
 ecliptic ; and to Lagrange to discover the spheroidal 
 libration, or that which arises from the action of the 
 earth upon the lunar spheroid. 
 
 The sorrows with which Galileo was now beset, 
 seemed to have disarmed the severity of the Inqui- " 
 sition. He was freely permitted to enjoy the society 
 of his friends, who now thronged around him to 
 express their respect and their sympathy. The 
 Grand-duke of Tuscany was his frequent visiter, 
 and Gassendi, Deodati, and our countryman Milton 
 went to Italy for the purpose of visiting him. He 
 entertained his friends with the warmest hospitality, 
 and though simple and abstemious in his diet, yet he 
 was fond of good wine, and seems even in his last 
 days to have paid particular attention to the excel- 
 lence of his cellar. 
 
 Although Galileo had nearly lost his hearing as 
 well as his sight, yet his intellectual faculties were 
 unimpaired; and while his mind was occupied in 
 considering the force of percussion, he was seized 
 with fever and palpitation of the heart, which, aftei 
 two months' illness, terminated his life on the 8th 
 of January, 1642. 
 
 Among the predecessors of Newton in astro- 
 nomical research we must not omit the names of 
 Bouillaud (Bullialdus), Borelli, and Dr. Hooke. 
 Ismael Bouillaud, a native of Laon in France, and 
 the author of several valuable astronomical works, 
 has derived more reputation from a single sentence 
 in his Aslronomica Philolaica, published in 1645, than 
 from all the rest of his labours. He was not a be- 
 liever in the doctrine of attraction, which, as we 
 have already seen, had been broached by Copernicus, 
 and discovered by Kepler ; but in speaking of that 
 power as the cause of the planetary motions, he
 
 BORELLI HOOKE. 137 
 
 remarks, " that if attraction existed, it would de 
 crease as the square of the distance." The influ- 
 ence of gravity was still more distinctly developed 
 by Borelli, a Neapolitan philosopher, who published 
 in 1666 a work on Jupiter's satellites.* In this work 
 he maintains, that all the planets perform their mo- 
 tions round the sun according to a general law ; that 
 the satellites of Jupiter and of Saturn move round 
 their primary planets in the same manner as the 
 moon does round the earth, and that they all re- 
 volve round the sun, which is the only source of 
 any virtue, and that this virtue attaches them, and 
 unites them so that they cannot recede from their 
 centre of action.f 
 
 Our countryman Dr. Robert Hooke seems to 
 have devoted much of his attention to the cause of 
 the planetary motions. On the 21st March, 1666, 
 he read to the Royal Society an account of a series 
 of experiments for determining if bodies experience 
 any variation in their weight at different distances 
 from the centre of the earth. His experiments, as 
 Hooke himself saw, were by no means satisfactory, 
 and hence he was led to the ingenious idea of 
 measuring the force of gravity by observing, at dif- 
 ferent altitudes, the rate of a pendulum clock. 
 About two months afterward, he exhibited to the 
 Society an approximate representation of the forces 
 which retain the planets in their orbits, in the paths 
 described by a circular pendulum impelled with dif- 
 
 * TheoricaR Medicearum planetarum ex causis physicis deductas. 
 
 /M Delambre maintains that these views of Borelli are only those of 
 Kepler slightly modified. Newton and Huygens have attached to them 
 a greater value. The last of these philosophers remarks, " Refert I'lu- 
 tarchns, fuisse jam olim qui putaret ideo manere lunam in orbe suo, quod 
 vis recedendi a terra, ob motum circularem, inhiberetur pan vi gravi- 
 tatis, qua ad terram accedere conaretur. Idemque sevo nostro, non a 
 luna tantum sed et planetis ceteris statuit Alphonsus Borellus, ut neinpe 
 pnmariis eorum gravitas esset solem versus; lunis vero ad terram 
 Jovem ac Saturnum quos comitantnr." Huygen, Cosmotheor, lib ; 
 Opera, t. ii. p. 720.
 
 138 SIR ISAAC NEWTON. 
 
 ferent degrees of force ; but though this experiment 
 illustrated the production of a curvilineal motion, by 
 combining a tangential force with a central power 
 of attraction, yet it was only an illustration, and 
 could not lead to the true cause of the planetary mo- 
 tions. At a later period, however, viz. in 1674, 
 Hooke resumed the subject in a dissertation entitled 
 " An Attempt to prove the Motion of the Earth from 
 Observation," which contains the following remark- 
 able observations upon gravity: 
 
 " I shall hereafter explain a system of the world 
 differing in many particulars from any yet known, 
 answering in all things to the common rules of me- 
 chanical motions. This depends upon three suppo- 
 sitions : first, that all celestial bodies whatsoever 
 have an attraction or gravitating power towards 
 their own centres, 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 also do attract all the other celestial bodies 
 that are within the sphere of their activity, and con- 
 sequently, 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 Mercury, Venus, 
 Mars, Jupiter, and Saturn, also, by their attractive 
 powers, have a considerable influence upon its mo- 
 tion, as in the same manner the corresponding at- 
 tractive power of the earth hath a considerable in- 
 fluence upon every one of their motions also. The 
 second supposition is this, that all bodies what- 
 soever that are put into a direct and simple motion 
 will so continue to move forward in a straight line, 
 till they are, by some other effectual powers, de- 
 flected, and sent into a motion describing a circle, 
 ellipsis, or some other more compounded curve line. 
 The third supposition is, that those attractive pow- 
 eis are so much the more powerful in operating by 
 how much the nearer the body wrought upon is to their 
 own centres. Now,ichat these several degrees are>l
 
 LAW OF GRAVITY. 139 
 
 have not yet experimentally verified ; but it is a notion 
 which, if fully prosecuted, as it ought to be, will 
 mightily assist the astronomers to reduce all the 
 celestial motions to a certain rule, which I doubt 
 will never be done without it. He that understands 
 the nature of the circular pendulum and circular 
 motion will easily understand the whole of this 
 principle, and will know where to find directions in 
 nature for the true stating thereof. This I only 
 hint at present to such as have ability and opportu- 
 nity of prosecuting this inquiry, and are not wanting 
 of industiy for observing and calculating, wishing 
 heartily such may be found, having myself many 
 other things in hand, which I would first complete, 
 and therefore cannot so well attend it. But this I 
 do not promise the undertaker, that he will find all 
 the great motions of the world to be influenced by 
 this principle, and that the true understanding 
 thereof will be the true perfection of astronomy." . 
 
 This passage, which has been considered as a re- 
 markable one by the philosophers of every country, 
 has, we think, been misapprehended by M. Delam- 
 bre, when he asserts that every thing which it con- 
 tains "is to be found expressly in Kepler."* 
 
 * Hist, de I'Astronomie aux fiix-Jmitieme Sidcte, p. 9;
 
 140 SIR ISAAC NEWTON. 
 
 CHAPTER XI. 
 
 Titejirtt Idea of Gravity occurs to Newton in 1666 His first Spec* 
 lotions upon it Interrupted by his Optical Experiments He re- 
 sumes the Subject in consequence of a Discussion with Dr. Hooke 
 He.discovers the true Law of Gravity and the Cause of the Planetary 
 Motions Dr. HaUey urges him to publish his PrincipiaHis Prin- 
 ciples of Natural Philosophy Proceedings of the Royal Society on 
 this SubjectThe Principia appears in 16S7 General Account of it, 
 and of the Discoveries it contains They meet with great Opposition, 
 owing to the Prevalence of the Cartesian System Account of the Re- 
 ception and Progress of the Newtonian Philosophy in foreign Coun- 
 tries Account of its Progress and Establishment in England. 
 
 SUCH is a brief sketch of the labours and lives of 
 those illustrious men who prepared the science of 
 astronomy for the application of Newton's genius. 
 Copernicus had determined the arrangement and 
 general movements of the planetary bodies : Kepler 
 had proved that they moved in elliptical orbits ; 
 that their radii vectares described arcs proportional 
 to the times ; and that their periodic times wer 
 related to their distances. Galileo had added to the 
 universe a whole system of secondary planets ; and 
 several astronomers had distinctly referred the mo- 
 tion of the heavenly bodies to the power of attraction. 
 
 In the year 1666, when the plague had driven 
 Newton from Cambridge, he was sitting alone in 
 the garden at Woolsthorpe, and reflecting on the 
 nature of gravity, that remarkable power which 
 causes all bodies to descend towards the centre of 
 the earth. As this power is not found to suffer any 
 sensible diminution at the greatest distance from 
 the earth's centre to which we can reach, being aa 
 powerful at the tops of the highest mountains as at 
 the bottom of the deepest mines, he conceived it 
 highly probable, that it must extend much farther 
 than was usually supposed. No sooner had this
 
 NEWTON'S IDEA OF GRAVITY. 141 
 
 happy conjecture occurred to his mind, than he con- 
 sidered what would be the effect of its extending as 
 far as the moon. That her motion must be influ- 
 enced by such a power he did not for a moment 
 doubt ; and a little reflection convinced him that it 
 might be sufficient for retaining that luminary in her 
 orbit round the earth. Though the force of gravity 
 suffers no sensible diminution at those small dis- 
 tances from the earth's centre at which we can 
 place ourselves, yet he thought it very possible, 
 that, at the distance of the moon, it might differ 
 much in strength from what it is on the earth. In 
 order to form some estimate of the degree of its 
 diminution, he considered that, if the moon be re- 
 tained in her orbit by the force of gravity, the pri- 
 mary planets must also be carried round the sun by 
 the same power ; and by comparing the periods of 
 the different planets with their distances from the 
 sun, he found, that if they were retained in their 
 orbits by any power like gravity, its force must de- 
 crease in the duplicate proportion,* or as the squares 
 of their distances from the sun. In drawing this 
 conclusion, he supposed the planets to move in or- 
 bits perfectly circular, and having the sun in their 
 centre. Having thus obtained the law of the force 
 by which the planets were drawn to the sun, his 
 next object was to ascertain if such a force, ema- 
 nating from the earth and directed to the moon, was 
 sufficient, when diminished in the duplicate ratio of 
 the distance, to retain her in her orbit. In perform- 
 ing this calculation, it was necessary to compare 
 the space through which heavy bodies fall in a second 
 at a given distance from the centre of the earth, viz. 
 at its surface, with the space through which the 
 moon, as it were, falls to the earth in a second of 
 time while revolving in a circular orbit. Being at 
 
 * " But for the duplicate proportion, I gathered it from Kepler's theo 
 rem about twenty years ago." Newton's Letter to Halley, July 14, 1686
 
 142 SIR ISAAC NEWTON. 
 
 a distance from books when he made this compu- 
 tation, he adopted the common estimate of the earth's 
 diameter then in use among geographers and navi- 
 gators, and supposed that, each degree of latitude 
 contained sixty English miles. In this way he 
 found that the force which retains the moon in her 
 orbit, as deduced from the force which occasions the 
 fall of heavy bodies to the earth's surface, was one- 
 sixth greater than that which is actually observed in 
 her circular orbit. This difference threw a doubt 
 upon all his speculations ; but, unwilling to abandon 
 what seemed to be otherwise so plausible, he endeav- 
 oured to account for the difference of the two forces, 
 by supposing that some other cause* must have been 
 united with the force of gravity in producing so 
 great a velocity of the moon in her circular orbit. 
 As this new cause, however, was beyond the reach 
 of observation, he discontinued all further inquiries 
 into the subject, and concealed from his friends the 
 speculations in which he had been employed. 
 
 After his return to Cambridge in 1666, his atten- 
 tion was occupied with those optical discoveries of 
 which we have given an account in a preceding 
 chapter ; but he had no sooner brought them to a 
 close than his mind reverted to the great subject of 
 the planetary motions. Upon the death of Olden- 
 burg in August, 1678, Dr. Hooke was appointed 
 secretary to the Royal Society ; and as this learned 
 body had requested the opinion of Newton about a 
 system of physical astronomy, he addressed a letter 
 to Dr. Hooke on the 28th NoVember, 1679. In this 
 letter he proposed a direct experiment for verifying 
 the motion of the earth, viz. by observing whether 
 or not bodies that fall from a considerable height 
 descend in a vertical direction, for if the earth were 
 at rest the body would describe exactly a vertical 
 
 * Whiston asserts that this cause was supposed by Newton to ba 
 something analogous to the vortices of Descartes. See YVhiston's Me- 
 moirs of himself, p. 231.
 
 LAW OF GRAVITY. 143 
 
 line, whereas if it revolved round its axis, the falling 
 body must deviate from the vertical line towards the 
 east. The Royal Society attached great value to 
 the idea thus casually suggested, and Dr. Hooke was 
 appointed to put it to the test of experiment. Being 
 thus led to consider the subject more attentively, he 
 wrote to Newton, that wherever the direction of 
 gravity was oblique to the axis on which the earth 
 revolved, that is, in every part of the earth ex- 
 cept the equator, falling bodies should approach 
 to the equator, and the deviation from the ver- 
 tical, in place of being exactly to the east, as 
 Newton maintained, should be to the south-east of 
 the point from which the body began to move. 
 Newton acknowledged that this conclusion was cor- 
 rect in theory, and Dr. Hooke is said to have given 
 an experimental demonstration of it before the Royal 
 Society in December, 1679.* Newton had errone- 
 ously concluded that the path of the falling body 
 would be a spiral; but Dr. Hooke, on the same 
 occasion on which he made the preceding experi- 
 ment, read a paper to the Society, in which he proved 
 that the path of the body would be an eccentric 
 ellipse in vacuo, and an ellipti-spiral, if the body 
 moved in a resisting medium. f 
 . This correction of Newton's error, and the dis- 
 covery that a projectile would move in an elliptical 
 orbit when under the influence of a force varying in 
 the inverse ratio of the square of the distance, led 
 Newton, as he himself informs us in his letter to 
 Halley,J to discover " the theorem by which he af- 
 terward examined the ellipsis," and to demonstrate 
 the celebrated proposition, that a planet acted upon 
 by an attractive force varying inversely as the 
 squares of the distances will describe an elliptical 
 orbit, in one of whose foci the attractive force re- 
 sides. 
 
 * Waller's Life of Hooke, p. 22. t Ibid. 
 
 t July 27, 1686, Biog. Brit. p. 2662.
 
 144 SIR ISAAC NEWTON. 
 
 But though Newton had thus discovered the true 
 cause of all the celestial motions, he did not yet 
 possess any evidence that such a force actually re- 
 sided in the sun and planets. The failure of his 
 former attempt to identify the law of falling bodies 
 at the earth's surface with that which guided the 
 moon in her orbit threw a doubt over all his specu- 
 lations, and prevented him from giving any account 
 of them to the public. 
 
 An accident, however, of a very interesting nature 
 induced him to resume his former inquiries, and 
 enabled him to bring them to a close. In June, 
 1682, when he was attending a meeting of the Royal 
 Society of London, the measurement of a degree of 
 the meridian, executed by M. Picardin 1679, became 
 the subject of conversation. Newton took a memo- 
 randum of the result obtained by the French astron- 
 omer, and having deduced from it the diameter of the 
 earth, he immediately resumed his calculation of 
 1665, and began to repeat it with these new data. 
 In the progress of the calculation he saw that the 
 result which he had formerly expected was likely to 
 be produced, and he was thrown into such a state of 
 nervous irritability that he was unable to carry on 
 the calculation. In this state of mind he intrusted 
 it to one of his friends, and he had the high satisr 
 faction of finding his former views amply realized. 
 The force of gravity which regulated the fall of 
 bodies at the earth's surface, when diminished as 
 the square of the moon's distance from the earth, 
 was found to be almost exactly equal to the centri' 
 fugal force of the moon as deduced from her observed 
 distance and velocity. 
 
 The influence of such a result upon such a mind 
 may be more easily conceived than described. The 
 whole material universe was spread out before him , 
 the sun with all his attending planets ; the planets 
 with all their satellites; the comets wheeling in 
 *very direction in their eccentric orbits ; and the
 
 PLANETARY MOTIONS. 145 
 
 systems of the fixed stars stretching to the remotest 
 limits of space. All the varied and complicated 
 movements of the heavens, in short, must have been 
 at once presented to his mind, as the necessary result 
 of that law which he had established in reference to 
 the earth and the moon. 
 
 After extending this law to the other bodies of 
 the system, he composed a series of propositions 
 on the motion of the primary planets about the sun, 
 which were sent to London about the end of 1683, 
 and were soon afterward communicated to the 
 Royal Society.* 
 
 About this period other philosophers had been 
 occupied with the same subject. Sir Christopher 
 Wren had many years before endeavoured to ex- 
 plain the planetary motions " by the composition 
 of a descent towards the sun, and an impressed 
 motion ; but he at length gave it over, not finding 
 the means of doing- it." In January, 1683-4, Dr. 
 Halley had concluded, from Kepler's Law of the 
 Periods and Distances, that the centripetal force de- 
 creased in the reciprocal proportion of the squares 
 of the distances, and having one day met Sir Chris- 
 topher Wren and Dr. Hooke, the latter affirmed 
 that he had demonstrated upon that principle all 
 the laws of the celestial motions. Dr. Halley con- 
 fessed that his attempts were unsuccessful, and 
 Sir Christopher, in order to encourage the inquiry, 
 offered to present a book of forty shillings' value to 
 either of the two philosophers who should, in the 
 space of two months, bring him a convincing de- 
 monstration of it. Hooke persisted in the decla- 
 ration that he possessed the method, out avowed it 
 to be his intention to conceal it for some time. He 
 promised, however, to show it to Sir Christopher ; 
 but there is every reason to believe that this prom- 
 ise was never fulfilled. 
 
 In August, 1684, Dr. Halley went to Cambridge 
 
 * Commercium Epistolicum, No. 7
 
 146 SIR ISAAC NEWTON. 
 
 for the express purpose of consulting Newton on 
 this interesting subject. Newton assured him that 
 he had brought this demonstration to perfection, 
 and promised him a copy of it. This copy was re- 
 ceived in November by the doctor, who made a 
 second visit to Cambridge, in order to induce its 
 author to have it inserted in the register book of 
 the society. On the 10th of December, Dr. Halley 
 announced to the society, that he had seen at Cam- 
 bridge Mr. Newton's treatise De Motu Corporum, 
 which he had promised to send to the society to be 
 entered upon their register ; and Dr. Halley was de- 
 sired to unite with Mr. Paget, master of the mathe- 
 matical school in Christ's Hospital, in reminding 
 Mr. Newton of his promise "for securing the inven- 
 tion to himself till such time as he can be at leisure 
 to publish it." On the 25th February Mr. Aston. 
 the secretary, communicated a letter from Mr. 
 Newton, in which he expressed his willingness " to 
 enter in the register his notions about motion, and 
 his intentions to fit them suddenly for the press." 
 The progress of his work was, however, interrupted 
 by a visit of five or six weeks which he made in 
 Lincolnshire ; but he proceeded with such diligence 
 on his return, that he was able to transmit the manu- 
 script to London before the end of April. This 
 manuscript, entitled Philosophic, Naturalis Principia 
 Mathematica, and dedicated to the society, was pre- 
 sented by Dr. Vincent on the 28th April, 1686, when 
 Sir John Hoskins, the vice-president, and the par- 
 ticular friend of Dr. Hooke, was in the chair. Dr. 
 Vincent passed a just encomium on the novelty and 
 dignity of the subject ; and another member added, 
 that " Mr. Newton had carried the thing so far, that 
 there was no more to be added." To these remarks 
 the vice-president replied, that the method " was so 
 much the more to be prized as it was both invented 
 and perfected at the same time." Dr. Hooke took 
 offence at these remarks, and blamed Sir John for
 
 PRINCIPIA. 14? 
 
 not having mentioned " what he had discovered to 
 him ;" but the vice-president did not seem to recol- 
 lect any such communication, and the consequence 
 of this discussion was, that " these two, who til. 
 then were the most inseparable cronies, have since 
 scarcely seen one another, and are utterly fallen 
 out." After the breaking up of the meeting, the 
 society adjourned to the coffee-house, where Dr. 
 Hooke stated that he not only had made the same, 
 discovery, but had given the first hint of it to Newton. 
 
 An account of these proceedings was communi- 
 cated to Newton through two different, channels. 
 In a letter dated May 22d, Dr. Halley wrote to him 
 "that Mr. Hooke has some pretensions upon the 
 invention of the rule of the decrease of gravity be- 
 ing reciprocally as the squares of the distances from 
 the centre. He says you had the notion from him, 
 though he owns the demonstration of the curves 
 generated thereby to be wholly your own. How 
 much of this is so you know best, as likewise what 
 you have to do in this matter. Only Mr. Hooke 
 seems to expect you would make some mention of 
 him in the preface, which it is possible you may 
 see reason to prefix." 
 
 'This communication from Dr. Halley induced 
 our author, on the 20th June, to address a long 
 letter to him, in which he gives a minute and able 
 refutation of Hooke's claims ; but before this letter 
 was despatched, another correspondent, who had 
 received his information from one of the members 
 that were present, informed Newton " that Hooke 
 made a great stir, pretending that he had all from 
 him, and desiring they would see that he had justice 
 done him." This fresh charge seems to have ruf- 
 fled the tranquillity of Newton ; and he accordingly 
 added an angry and satirical postscript, in which he 
 treats Hooke with little ceremony, and goes so far 
 as to conjecture that Hooke might have acquired 
 his knowledge of the law from a letter of his own
 
 148 SIR ISAAC NEWTON. 
 
 to Huygens, directed to Oldenburg, and dated Janu- 
 ary 14th, 1672-3. "My letter to Hugenius was 
 directed to Mr. Oldenburg, who used to keep the 
 originals. His papers came into Mr. Hooke's pos- 
 session. Mr. Hooke, knowing my hand, might have 
 the curiosity to look into that letter, and there take 
 the notion of comparing the forces of the planets 
 arising from their circular motion ; and so what he 
 wrote to me afterward about the rate of gravity 
 might be nothing but the fruit of my own garden."' 
 
 In replying to this letter, Dr. Halley assured him 
 that Hooke's "manner of claiming the discovery 
 had been represented to him in worse colours than 
 it ought, and that he neither made public application 
 to the society for justice, nor pretended that you 
 had all from him." The effect of this assurance 
 was to make Newton regret that he had written the 
 angry postscript to his letter; and in replying to 
 Halley on the 14th July, 1686, he not only expresses 
 his regret, but recounts the different new ideas 
 which he had acquired from Hooke's correspon- 
 dence, and suggests it as the best method " of com- 
 promising the present dispute," to add a scholium, 
 in which Wren, Hooke, and Halley are acknowledged 
 to have independently deduced the law of gravity 
 from the second law of Kepler.* 
 
 At the meeting of the 28th April, at which the 
 manuscript of the Principia was presented to the 
 Royal Society, it was agreed that the printing of it 
 should be referred to the council ; that a letter of 
 thanks should be written to its author; and at a 
 meeting of the council on the 19th May, it was 
 resolved that the MSS. should be printed at the 
 society's expense, and that Dr. Halley should super- 
 intend it while going through the press. These 
 resolutions were communicated by Dr. Halley in a 
 letter dated the 22d May ; and in Newton's reply OP 
 the 20th June already mentioned, he makes the fol 
 
 * This Scholium ia added to Prop. iv. lib. i. coroll 6
 
 PRINCIPIA. 149 
 
 lowing observations : " The proof you sent me I 
 like very well. I designed the whole to consist of 
 three books ; the second was finished last summer, 
 being short, and only wants transcribing, and draw- 
 ing the cuts fairly. Some new propositions I have 
 since thought on, which I can as well let alone. 
 The third wants the theory of comets. In autumn 
 last I spent two months in calculation to no purpose 
 for want of a good method, which made me after- 
 ward return to the first book, and enlarge it with 
 diverse propositions, some relating to comets, others 
 to other things found out last winter. The third I 
 now design to suppress. Philosophy is such an im- 
 pertinently litigious lady, that a man had as good be 
 engaged in lawsuits as have to do with her. I 
 found it so formerly, and now I can no sooner come 
 near her again but she gives me warning. The first 
 two books without the third will not so well bear 
 the title of Philosophies Naturalis Principia Mathe- 
 matica ; and therefore I had altered it to this, De 
 Motu Corporum Libri duo. But after second thoughts 
 I retain the former title. It will help the sale of the 
 book, which I ought not to diminish now 'tis yours." 
 
 In replying to this letter on the 29th June, Dr. 
 Halley regrets that our author's tranquillity should 
 have been thus disturbed by envious rivals; and 
 implores him in the name of the society not to 
 suppress the third book. " I must again beg you," 
 says he, " not to let your resentments run so high 
 as to deprive us of your third book, wherein your 
 applications of your mathematical doctrine to the 
 theory of comets, and several curious experiments, 
 which, as I guess by what you write ought to com- 
 pose it, will undoubtedly render it acceptable to 
 those who will call themselves philosophers without 
 mathematics, which are much the greater number." 
 
 To these solicitations Newton seems to have 
 readily yielded. His second book was sent to the 
 society," and presented on the 3d March, 1686-7 
 M
 
 150 SIR ISAAC NEWTON. 
 
 The third book was also transmitted, and presented 
 on the 6th April, and the whole work was completed 
 and published in the month of May, 1687. 
 
 Such is a brief account of the publication of a 
 work which is memorable, not only in the annals of 
 one science or of one country, but which will form 
 an epoch in the history of the world, and will ever 
 be regarded as the brightest page in the records of 
 human reason. We shall endeavour to convey to 
 the reader some idea of its contents, and of the bril- 
 liant discoveries which it disseminated over Europe. 
 
 The Principia consists of three books. The first 
 and second, which occupy three-fourths of the work, 
 are entitled, On the Motion of Bodies ; and the third 
 bears the title, On the System of the World. The 
 first two books contain the mathematical principles 
 of philosophy, namely, the laws and conditions of 
 motions and forces ; and they are illustrated with 
 several philosophical scholia, which treat of some of 
 the most general ancf best established points in phi- 
 losophy, such as the density and resistance of bodies, 
 spaces void of matter, and the motion of sound and 
 light. The object of the third book is to deduce 
 from these principles the constitution of the system 
 of the world ; and this book has been drawn up in 
 as popular a style as possible, in order that it may 
 be generally read. 
 
 The great discovery which characterizes the 
 Principia is that of the principle of universal gravi- 
 tation, as deduced from the motion of the moon, 
 and from the three great facts or laws discovered by 
 Kepler. This principle is, that every particle */ 
 matter is attracted by, or gravitates to, every other 
 particle of matter, with a farce inversely proportional 
 to the squares of their distances. From the first law 
 of Kepler, namely, the proportionality of the areas 
 to the times of their description, Newton inferred 
 that the force which kept the planet in its orbit was 
 always directed to the sun; and from the second
 
 UNIVERSAL GRAVITATION. 15 
 
 law of Kepler, that every planet moves in an ellipse 
 with the sun in one of its foci, he drew the still mor? 
 general inference, that the force by which the planei 
 moves round that focus varies inversely as the 
 square of its distance from the focus. As this la\* 
 was true in the motion of satellites round their pri- 
 mary planets, Newton deduced the equality of gravity 
 in all the heavenly bodies towards the sun, upon the 
 supposition that they are equally distant from its* 
 centre ; and in the case of terrestrial bodies, he sue 
 ceeded in verifying this truth by numerous and accu 
 rate experiments. 
 
 By taking- a more general view of the sublet 
 Newton demonstrated that a conic section was the 
 only curve in which a body could move when acted 
 upon by a force varying inversely as the square of 
 the distance ; and he established the conditions de- 
 pending on the velocity and the primitive position 
 of the body, which were requisite to make it de- 
 scribe a circular, an elliptical, a parabolic, or a 
 hyperbolic orbit. 
 
 Notwithstanding the generality and importance 
 of these results, it still remained to be determined 
 whether the force resided in the centres of the 
 planets, or belonged to each individual particle of 
 which they were composed. Newton removed this 
 uncertainty by demonstrating, that if a spherical 
 body acts upon a distant body with a force varying 
 as the distance of this body from the centre of the 
 sphere, the same effect will be produced as if each 
 of its particles acted upon the distant body accord- 
 ing- to the same law. And hence it follows that the 
 spheres, whether they are of uniform density, or 
 consist of concentric layers, with densities varying 
 according to any law whatever, will act upon each 
 other in the same manner as if their force resided 
 in their centres alone. But as the bodies of the 
 solar system are very nearly spherical, they will all 
 act upon one another, and upon bodies placed on
 
 152 SIR ISAAC NEWTON. 
 
 their surface, as if they were so many centres of 
 attraction ; and therefore we obtain the law of gravity 
 which subsists between spherical bodies, namely, 
 that one sphere will act upon another with a force 
 directly proportional to the quantity of matter, and 
 inversely as 'the square of the distance between the 
 centres of the spheres. From the equality of action 
 and reaction, to which no exception can be found, 
 Newton concluded that the sun gravitated to the 
 planets, and the planets to their satellites ; and the 
 earth itself to the stone which falls upon its surface ; 
 and, consequently, that the two mutually gravitating 
 bodies approached to one another with velocities 
 inversely proportional to their quantities of matter. 
 
 Having established this universal law, Newton 
 was enabled, not only to determine the weight which 
 the same body would have at the surface of the sun 
 and the planets, but even to calculate the quantity 
 of matter in the sun, and in all the planets that had 
 satellites, and even to determine the density or 
 specific gravity of the matter of which they were 
 composed. In this way he found that the weight of 
 the same body would be twenty-three times greater 
 at the surface of the sun than at the surface of the 
 earth, and that the density of the earth was four times 
 greater than that of the sun, the planets increasing 
 in density as they receded from the centre of the 
 system. 
 
 If the peculiar genius of Newton has been dis- 
 played in his investigation of the law of universal 
 gravitation, it shines with no less lustre in the pa- 
 tience and sagacity with which he traced the conse- 
 quences of this fertile principle. 
 
 The discovery of the spheroidal form of Jupiler 
 by Cassini had probably directed the attention of 
 Newton to the determination of its cause, and con 
 sequently to the investigation of the true figure of 
 the earth. The spherical form of the planets have 
 bee-n ascribed by Copernicus to the gravity or natural
 
 FIGURE OF THE EARTH. 153 
 
 appetency of their parts ; but upon considering the 
 earth as a body revolving upon its axis, Newton 
 quickly saw that the figure arising from the mutual 
 attraction of its parts must be modified by another 
 force arising from its rotation. When a body re- 
 volves upon an axis, the velocity of rotation in- 
 creases from the poles, where it is nothing, to the 
 equator, where it is a maximum. In consequence 
 of this velocity the bodies on the earth's surface 
 have a tendency to fly off from it, and this tendency 
 increases with the velocity. Hence arises a centrifu- 
 gal force which acts in combination with a force 
 of gravity, and which Newton found to be the 289th 
 part of the force of gravity at the equator, and de- 
 creasing, as the cosine of the latitude, from the 
 equator to the poles. The great predominance of 
 gravity over the centrifugal force prevents the latter 
 from carrying off any bodies from the earth's sur- 
 face, but the weight of all bodies is diminished by 
 the centrifugal force, so that the weight of anybody 
 is greater at the poles than it is at the equator. If 
 we now suppose the waters at the pole to commu- 
 nicate with those at the equator by means of a ca- 
 nal, one branch of which goes from the pole to the 
 centre of the earth, and the other from the centre 
 of the earth to the equator, then the polar branch 
 of the canal will be heavier than the equatorial 
 branch, in consequence of its weight not being di- 
 minished by the centrifugal force, and, therefore, in 
 order that the two columns may be in equilibrio, the 
 equatorial one must be lengthened. Newton found 
 that the length of the polar must be to that of the 
 equatorial canal as 229 to 230, or that the earth's polar 
 radius must be seventeen miles less than its equa- 
 torial radius ; that is, that the figure of the earth is 
 an oblate spheroid, formed by the revolution of an 
 ellipse round its lesser axis. Hence it follows, that 
 the intensity of gravity at any point of the earth's 
 surface is in the inverse ratio of the distance of that
 
 154 6IR ISAAC NEWTON. 
 
 point from the centre, and, consequently, that it di- 
 minishes from the equator to the poles, a result 
 which he confirmed by the fact, that clocks required 
 to have their pendulums shortened in order to beat 
 true time when carried from Europe towards the 
 equator. 
 
 The next subject to which Newton applied the 
 principle of gravity was the tides of the ocean. 
 The philosophers of all ages have recognised the 
 connexion between the phenomena of the tides and 
 the position of the moon. The College of Jesuits 
 at Coimbra, and subsequently Antonio de Dominia 
 and Kepler, distinctly referred the tides to the attrac- 
 tion of the waters of the earth by the moon, but so 
 imperfect was the explanation which was thus given 
 of the phenomena, that Galileo ridiculed the idea of 
 lunar attraction, and substituted for it a fallacious 
 explanation of his own. That the moon is the 
 principal cause of the tides is obvious from the well- 
 known fact, that it is high water at any given place 
 about the time when she is in the meridian of that 
 place ; and that the sun performs a secondary part 
 in their production may be proved from the circum- 
 stance, that the highest tides take place when the 
 sun, the moon, and the earth are in the same straight 
 line, that is, when the force of the sun conspires 
 with that of the moon, and that the lowest tides 
 take place when the lines drawn from the sun and 
 moon to the earth are at right angles to each other, 
 that is, when the force of the sun acts in opposition 
 to that of the moon. The most perplexing phe- 
 nomenon in the tides of the ocean, and one which is 
 still a stumbling-block to persons slightly acquainted 
 with the theory of attraction, is the existence of 
 high water on the side of the earth opposite to the 
 moon, as well as on the side next the moon. To 
 maintain that the attraction of the moon at the same 
 instant draws the waters of the ocean towards her- 
 self, and also draws them from the earth in an oppo-
 
 TIDES. 155 
 
 site direction, seems at first sight paradoxical ; but 
 the difficulty vanishes when we consider the earth, 
 or rather the centre of the earth, and the water on . 
 each side of it as three distinct bodies placed at dif- 
 ferent distances from the moon, and consequently 
 attracted with forces inversely proportional to the 
 squaies of their distances. The water nearest the 
 moon will be much more powerfully attracted than 
 the centre of the earth, and the centre of the earth 
 more powerfully than the water farthest from the 
 moon. The consequence of this must be, that the 
 waters nearest the moon will be drawn away from 
 the centre of the earth, and will consequently rise 
 from their level, while the centre of the earth will 
 be drawn away from the waters opposite the moon, 
 which will, as it were, be left behind, and conse- 
 quently be in the same situation as if they were 
 raised from the earth in a direction opposite to 
 that in which they are attracted by the moon. 
 Hence the effect of the moon's action upon the 
 earth is to draw its fluid parts into the form of an 
 oblong spheroid, the axis of which passes through 
 the moon. As the action of the sun will produce 
 the very same effect, though in a smaller degree, 
 the tide at any place will depend on the relative po- 
 sition of these two spheroids, and will be always 
 equal either to the sum or to the difference of the 
 effects of the two luminaries. At the time of new 
 and full moon the two spheroids will have their axes 
 coincident, and the height of the tide, which will 
 then be a spring one, will be equal to the sum of the 
 elevations produced in each spheroid considered 
 separately, while at the first and third quarters the 
 axes of the spheroids will be at right angles to each 
 other, and the height of the tide, which will tlien be 
 a neap one, will be equal to the difference of the 
 elevations produced in each separate spheroid. By 
 comparing the spring and neap tides, Newton found 
 that the force with which the sun acted upon th
 
 156 SIR ISAAC NEWTON. 
 
 waters of the earth was to that with which the sun 
 acted upon them as 4.48 to 1 ; that the force of the 
 moon produced a tide of 8.63 feet; that of the sun 
 one of 1.93 feet; and both of 'them combined, one 
 f 10 French feet, a result which in the open sea 
 does not deviate much from observation. Having 
 thus ascertained the force of the moon on the waters 
 of our globe, he found that the quantity of matter 
 In the moon was to that in the earth as 1 to 40, and 
 the density of the moon to that of the earth as 11 
 to 9. 
 
 The motions of the moon, so much within the 
 reach of our own observation, presented a fine field 
 for the application of the theory of universal gravi- 
 tation. The irregularities exhibited in the lunar 
 motions had been known hi the time of Hipparchus 
 and Ptolemy. Tycho had discovered the great in- 
 equality called the variation, amounting to' 37', and 
 depending on the alternate acceleration and retard- 
 ation of the moon in every quarter of a revolution, 
 and he had also ascertained the existence of the 
 annual equation. Of these two inequalities Newton 
 gave a most satisfactory explanation. The action 
 of the sun upon the moon may be always resolved 
 into two, one acting in the direction of the line join- 
 ing the moon and earth, and consequently tending 
 to increase or diminish the moon's gravity to the 
 earth, and the other in a direction at right angles to 
 this, and consequently tending to accelerate or re- 
 tard the motion in her orbit. Now, it was found by 
 Newton that this last force was reduced to nothing, 
 or vanished at the syzigies or quadratures, so that 
 at these four points the moon described areas pro- 
 portional to the times. The instant, however, that 
 the moon quits these positions, the force under con- 
 sideration, which we may call the tangential force, 
 begins, and it reaches its maximum in^the four oc- 
 tants. The force, therefore, compounded of these 
 two elements of the solar force, or the diagonal of
 
 LUNAR THEORY. 157 
 
 the parallelogram which they form, is no longer 
 directed to the earth's centre, but deviates from it at 
 a maximum about 30 minutes, and therefore affects 
 the angular motion of the moon, the motion being 
 accelerated in passing from the quadratures to the 
 syzigies, and retarded in passing from the syzigies 
 to the quadratures. Hence the velocity is in its 
 mean state in the octants, a maximum in the syzi- 
 gies, and a minimum in the quadratures. 
 
 Upon considering the influence of the solar force 
 in diminishing or increasing the moon's gravity to 
 the earth, Newton saw that her distance and her 
 periodic time must from this cause be subject to 
 change, and in this way he accounted for the annual 
 equation observed by Tycho. By the application 
 of similar principles, he explained the cause of the 
 motion of the apsides, or of the greater axis of the 
 moon's orbit, which has an angular progressive mo- 
 tion of 3 4' nearly in the course of one lunation ; 
 and he showed that the retrogradation of the nodes, 
 amounting to 3' 10" daily, arose from one of the ele- 
 ments of the solar force being exerted in the plane 
 of the ecliptic, and not in the plane of the moon's 
 orbit, the effect of which was to draw the moon 
 down to the plane of the ecliptic, and thus cause the 
 line of the nodes, or the intersection of these two 
 planes, to move in a direction opposite to that of the 
 moon. The lunar theory thus blocked out by New- 
 ton, required for its completion the labours of another 
 century. The imperfections of the fluxionary cal- 
 culus prevented him from explaining the other ine- 
 qualities of the moon's motions, and it was reserved 
 to Euler, D'Alembert, Clairaut, Mayer, and Laplace 
 to bring the lunar tables to a high degree of perfec- 
 tion, and to enable the navigator to determine his 
 longitude at sea with a degree of precision which 
 the most sanguine astronomer could scarcely have 
 anticipated. 
 
 By the consideration of the retrograde motion of
 
 158 SIR ISAAC NEWTON. 
 
 the moon's nodes, Newton was led to discover the 
 cause of the remarkable phenomenon of the preces- 
 sion of the equinoctial points, which moved 50" an- 
 nually, and completed the circuit of the heavens in 
 25,920 years. Kepler had declared himself incapa- 
 ble of assigning any cause for this motion, and we 
 do not believe that any other astronomer ever made 
 the attempt. From the spheroidal form of the earth, 
 it may be regarded as a sphere with a spheroidal 
 ring surrounding its equator, one-half of the ring 
 beit^ above the plane of the ecliptic and the othei 
 half below it. Considering this excess of matter 
 as a system of satellites adhering to the earth's sur- 
 face, Newton saw that the combined actions of the 
 sun and moon upon these satellites tended to pro- 
 duce a retrogradation in the nodes of the circles 
 which they described in their diurnal rotation, and 
 that the sum of all the tendencies being communi- 
 cated to the whole mass of the planet, ought to pro- 
 duce a slow retrogradation of the equinoctial points. 
 The effect produced by the motion of the sun he 
 found to be 40", and that produced by the action of 
 the moon 10". 
 
 Although there could be little doubt that the 
 comets were retained in their orbits by the same 
 laws which regulated the motions of the planets, 
 yet it was difficult to put this opinion to the test of 
 observation. The visibility of comets only in a 
 small part of their orbits rendered it difficult to as- 
 certain their distance and periodic times, and as their 
 periods were probably of great length, it was impos- 
 sible to correct approximate results by repeated ob- 
 servation. Newton, however, removed this diffi- 
 culty, by showing how to determine the orbit of a 
 comet, namely, the form and position of the orbit 
 and the periodic time, by three observations. By 
 . applying this method to the comet of 1680, he cal- 
 culated the elements of its orbit, and from the agree- 
 ment of the comouted places with those which
 
 COMETS. 159 
 
 were observed, he justly inferred that the motions 
 of comets were regulated by the same laws as those 
 of the planetary bodies. This result was one of 
 great importance ; for as the comets enter our sys- 
 tem in every possible direction, and at all angles 
 with the ecliptic, and as a great part of their orbits 
 extend far beyond the limits of the solar system, it 
 demonstrated the existence of gravity in spaces far 
 removed beyond the planet, and proved that the law 
 of the inverse ratio of the squares of the distance 
 was true in every possible direction, and at very re- 
 mote distances from the centre of our system.* 
 
 Such is a brief view of the leading discoveries 
 which the Principia first announced to the world. 
 The grandeur of the subjects of which it treats, the 
 beautiful simplicity of the system which it unfolds, 
 the clear and concise reasoning by which that sys- 
 tem is explained, and the irresistible evidence by 
 which it is supported might have ensured it the 
 warmest admiration of contemporary mathemati- 
 cians, and the most welcome reception in ail the 
 schools of philosophy throughout Europe. This, 
 however, is not the way in which great truths are 
 generally received. Though the astronomical dis- 
 coveries of Newton were not assailed by the class 
 of ignorant pretenders who attacked his optical 
 writings, yet they were every where resisted by the 
 errors and prejudices which had taken a deep hold 
 even of the strongest minds. The philosophy of 
 Descartes was predominant throughout Europe. 
 Appealing to the imagination, and not to the reason 
 of mankind, it was quickly received into popular 
 favour, and the same causes which facilitated its in- 
 troduction extended its influence, and completed its 
 dominion over the human mind. In explaining alJ 
 the movements of the heavenly bodies by a system 
 
 * In writing to Flamstead, Newton requests from him the long diame- 
 ters of the orbits of Jupiter and Saturn, that he " may see how the ses- 
 quialteral proportion Jills the heavens."
 
 160 SIR ISAAC NEWTON. 
 
 of vortices in a fluid medium diffused through the 
 uni\:erse, Descartes had seized upon an analogy of 
 the most alluring and deceitful kind. Those who 
 had seen heavy bodies revolving in the eddies of a 
 whirlpool, or in the gyrations of a vessel of water 
 thrown into a circular motion, had no difficulty in 
 conceiving how the planets might revolve round the 
 sun by analogous movements. The mind instantly 
 grasped at an explanation of so palpable a character, 
 and which required for its development neither the 
 exercise of patient thought nor the aid of mathe- 
 matical skill. The talent and perspicuity with which 
 the Cartesian system was expounded, and the show 
 of experiments with which it was sustained, con- 
 tributed powerfully to its adoption, while it derived a 
 still higher sanction from the excellent character 
 and the unaffected piety of its author. 
 
 Thus intrenched, as the Cartesian system was, in 
 the strongholds of the human mind, and fortified by 
 its most obstinate prejudices, it was not to be won- 
 dered at that the pure and sublime doctrines of the 
 Principia were distrustfully received and persever- 
 ingly resisted. The uninstructed mind could not 
 readily admit the idea, that the great masses of the 
 planets were suspended in empty space, and retained 
 in theii orbits by an invisible influence residing in 
 the sun ; and even those philosophers who had been 
 accustomed to the rigour of true scientific research, 
 and who possessed sufficient mathematical skill for 
 the examination of the Newtonian doctrines, viewed 
 them at first as reviving the occult qualities of the 
 ancient physics, and resisted their introduction with 
 a pertinacity which it is not easy to explain. Preju- 
 diced, no doubt, in favour of his own metaphysical 
 views, Leibnitz himself misapprehended the princi- 
 ples of the Newtonian philosophy, and endeavoured 
 to demonstrate the truths in the Principia by the appli- 
 cation of different principles. Huygens, who above all 
 other men was qualified to appreciate the new philo-
 
 NEWTONIAN PHILOSOPHY. 161 
 
 sophy, rejected the doctrine of gravitation as existing 
 between the individual particles of matter, and re- 
 ceived it only as an attribute of the planetary masses. 
 John Bernouilli, one of the first mathematicians of 
 Ms age, opposed the philosophy of Newton. Mai- 
 ran, in the early part of his life, was a strenuous de- 
 fender of the system of vortices. Cassini and Ma- 
 raldi were quite ignorant of the Principia, and occu- 
 pied themselves with the most absurd methods of 
 calculating the orbits of comets long after the New 
 tonian method had been established on the most 
 impregnable foundation ; and even Fontenelle, a man 
 of liberal views and extensive information, continued, 
 throughout the whole of his life, to maintain the 
 doctrines of Descartes. 
 
 The Chevalier Louville of Paris had adopted the 
 Newtonian philosophy before 1720. S'Gravesande 
 had introduced it into the Dutch universities at 8 
 somewhat earlier period, and Maupertuis, in conse- 
 quence of a visit which he paid to England in 1728, 
 became a zealous defender of it ; but notwithstand- 
 ing these and some other examples that might be 
 quoted, we must admit the truth of the remark of 
 Voltaire, that though Newton survived the publica- 
 tion of the Principia more than forty years, yet at 
 the time of his death he had not above twenty fol- 
 lowers out of England. 
 
 With regard to the progress of the Newtonian 
 philosophy in England, some difference of opinion 
 has been entertained. Professor Playfair gives the 
 following account of it. " In the universities of 
 England, though the Aristotelian physics had made 
 an obstinate resistance, they had been supplanted 
 by the Cartesian, which became firmly established 
 about the time when their foundation began to be 
 sapped by the general progress of science, and par- 
 ticularly by the discoveries of Newton. For more 
 than thirty years after the publication of these dis- 
 coveries- thp system of vortices kept its ground; and
 
 162 SIR ISAAC NEWTON. 
 
 a translation from the French into Latin of the Phy- 
 sics of Rohault, a work entirely Cartesian, con- 
 tinued at Cambridge to be the text for philosophical 
 instruction. About the year 1718, a new and more 
 elegant translation of the same book was published 
 by Dr. Samuel Clarke, with the addition of notes, in 
 which that profound and ingenious writer explained 
 the views of Newton on the principal objects of 
 discussion, so that the notes contained virtually a 
 refutation of the text ; they did so, however, only 
 virtually, all appearance of argument and contro- 
 versy being carefully avoided. Whether this escaped 
 the notice of the learned doctor or not is uncertain, 
 but the new translation, from its better Latinity, and 
 the name of the editor, was readily admitted to all 
 the academical honours which the old one had en- 
 joyed. Thus the stratagem of Dr. Clarke com- 
 pletely succeeded ; the tutor might prelect from the 
 text, but the pupil would sometimes look into the 
 notes ; and error is never so sure of being exposed 
 as when the truth is placed close to it, side by side, 
 without any thing to alarm prejudice, or awaken 
 from its lethargy the dread of innovation. Thus, 
 therefore, the Newtonian philosophy first entered 
 the university of Cambridge under the protection of 
 the Cartesian." To this passage Professor Playfaii 
 adds the following as a note : 
 
 " The universities of St. Andrew's and Edinburgh 
 were, I believe, the first in Britain where the New- 
 tonian philosophy was made the subject of the aca- 
 demical prelections. For this distinction they are 
 indebted to James and David Gregory, the first in 
 some respects the rival, but both the friends of 
 Newton. Whiston bewails, hi the anguish of his 
 heart, the difference, in this respect, between those 
 universities and his own. David Gregory taught in 
 Edinburgh for several years prior to 1690, when he 
 removed to Oxford; and Whiston says, 'He had 
 already caused several of his scholars to keep acts.
 
 NEWTONIAN PHILOSOPHY. 163 
 
 as we call them, upon several branches of the New- 
 tonian philosophy, while we at Cambridge, poor 
 wretches, were ignominiously studying the fictitious 
 hypotheses of the Cartesians.'* I do not, however, 
 mean to say, that from this date the Cartesian phi- 
 losophy was expelled from those universities ; the 
 Physics of Renault were still in use as a text-book, 
 at least occasionally, to a much later period than this, 
 and a great deal, no Jj'iibt, depended on the character 
 of the individual. Professor Keill introduced the 
 Newtonian philosophy in his lectures at Oxford in 
 1697 ; but the instructions of the tutors, which con- 
 stitute the real and efficient system of the univer- 
 sity, were not cast in that mould till long afterward." 
 Adopting the same view of the subject, Mr. Dugald 
 Stewart has stated, " that the philosophy of Newton 
 was publicly taught by David Gregory at Edinburgh, 
 and by his brother, James Gregory, at St. Andrew's,! 
 before it was able to supplant the vortices of Des- 
 cartes in that very university of which Newton 
 was a member. It was in the Scottish universities 
 that the philosophy of Locke, as well as that of 
 Newton, was first adopted as a branch of academi- 
 cal education." 
 
 Anxious as we should have been to have awarded 
 to Scotland the honour of having first adopted the 
 Newtonian philosophy, yet a regard for historical 
 truth compels us to take a different view of the sub- 
 ject. It is well known that Sir Isaac Newton de- 
 livered lectures on his own philosophy from the 
 Lucasian chair before the publication of the Prin- 
 cipia ; and in the very page of Whiston's life quoted 
 by Professor Playfair, he informs us that he had 
 heard him read such lectures hi the public schools, 
 
 * Whiston's Memoirs of his own Life. 
 
 t " Dr. Reid states, that James Gregory, Professor of Philosophy at 
 St. Andrew's, printed a thesis at Edinburgh in 1690, containing twenty- 
 five positions, of which twenty-two were a compend of Newton's Prin- 
 
 cipm."
 
 164 SIR ISAAC NEWTON. 
 
 though at that time he did not at all understand 
 them. Newton continued to lecture till 1699, and 
 occasionally, we presume, till 1703, when Whiston 
 became his successor, having been appointed his 
 deputy in 1699. In both ftf these capacities Whis- 
 ton delivered in the public schools a course of lec- 
 tures on astronomy, and a course of physico-mathe- 
 matieal lectures, in which the mathematical philoso- 
 phy of Newton was explained and demonstrated, 
 and both these courses were published, the one in 
 1707, and the other in 1710, " for the use of the 
 young men hi the university." In 1707, the cele- 
 brated blind mathematician Nicholas Saunderson 
 took up his residence in Christ's College without 
 being admitted a member of that body. The society 
 not only allotted to him apartments, but gave him 
 the free use of their library. With the concurrence 
 of Whiston he delivered a course of lectures " on 
 the Principia, Optics, and Universal Arithmetic of 
 Newton," and the popularity of these lectures was 
 so great, that Sir Isaac corresponded on the subject 
 of -them with their author ; and on the ejection of 
 Whiston from the Lucasian chair in 1711, Saunderson 
 was appointed his successor. In this important office 
 he continued to teach the Newtonian philosophy till 
 the time of his death, which took place in 1739. 
 
 But while the Newtonian philosophy was thus 
 regularly taught in Cambridge, after the publication 
 of the Principia, there were not wanting other exer- 
 tions for accelerating its progress. About 1694, the 
 celebrated Dr. Samuel Clarke, while an under-grad- 
 uate, defended, in the public schools, a question taken 
 from the Newtonian philosophy ; and his translation 
 of Rohault's Physics, which contains references in 
 the notes to the Principia, and which was published 
 in 1697 (and not in 1718, as stated by Professor 
 Playfair), shows how early the Cartesian system 
 was attacked by the disciples of Newton. The 
 author of the Life of Saunderson informs us, that
 
 PROGRESS IN ENGLAND. 165 
 
 public exercises or acts founded on every part of the 
 Newtonian system were veiy common about 1707, 
 and so general \vere such studies in, the university, 
 that the Principia rose to four times its original 
 price.* One of the most ardent votaries of the 
 Newtonian, philosophy was Dr. Laughton, who had 
 been tutor in Clare Hall from 1694, and it is probable 
 that during the whole, or at least a greater part, of 
 his tutorship he had inculcated the same doctrines. 
 In 1709-10, when he was proctor of that college, in- 
 stead of appointing a moderator, he discharged the 
 office himself, and devoted his most active exertions 
 to the promotion of mathematical knowledge. Pre- 
 vious to this, he had even published a paper of ques- 
 tions on the Newtonian philosophy, which appear to 
 have been used as theses for disputations ; and such 
 was his ardour and learning that they powerfully 
 contributed to the popularity of his college. Be- 
 tween 1706 and 1716, the year of his death, the cele- 
 brated Roger Cotes, the friend and disciple of New- 
 ton, filled the Plumian chair of astronomy and ex- 
 perimental philosophy at Cambridge. During this 
 period he edited the second edition of the Principia, 
 which he enriched with an admirable preface, and 
 thus contributed, by his writings as well as 2 by his 
 lectures, to advance the philosophy of his master. 
 About the same time, the learned Dr. Bentley, \vho 
 first made known the philosophy of his friend to the 
 readers of general literature, filled the high office oi 
 master of Trinity College, and could not fail to have 
 exerted his utmost influence in propagating doctrines 
 which he so greatly admired. Had any opposition 
 been offered to the introduction of the true system 
 of the universe, the talents and influence of these 
 individuals would have immediately suppressed it ; 
 but no such opposition seems to have been made ; 
 
 * Nichols's Literary Anecdotes, vol. iii. p. 322. Cotes states in his 
 preface to the second edition of the Principia, that copies of the first 
 edition could only be obtained at an immense price. 
 
 N
 
 166 SIR ISAAC NEWTON. 
 
 and though there may have been individuals at Cam- 
 bridge ignorant of mathematical science, who ad- 
 hered to the system of Descartes, and patronised 
 the study of the Physics of Rohault, yet it is pro- 
 bable that similar persons existed in the universities 
 of Edinburgh and St. Andrew's ; and we cannot re- 
 gard their adherence to error as disproving the gen- 
 eral fact, that the philosophy of Newton was quickly 
 introduced into all the universities of Great Britain. 
 But while the mathematical principles of the New- 
 tonian system were ably expounded in our seats of 
 learning, its physical truths were generally studied, 
 and were explained and communicated to the public 
 by various lecturers on experimental philosophy. 
 The celebrated Locke, who was incapable of under- 
 standing the Principia from his want of mathemati- 
 cal knowledge, inquired of Huygens if all the mathe- 
 matical propositions in that work were true. When 
 he was assured that he might depend upon their cer- 
 tainty, he took them for granted, and carefully ex- 
 amined the reasonings and corollaries deduced from 
 them. In this manner he acquired a knowledge of 
 the physical truths in the Principia, and became a 
 firm believer in the discoveries which it contained. 
 In the same manner he studied the treatise on Op- 
 tics, and made himself master of every pait of it 
 which was not mathematical.* From a manuscript 
 of Sir Isaac Newton's, entitled "A demonstration 
 that the planets, by their gravity towards the sun, 
 may move in ellipses,! found among the papers of 
 Mr. Locke, and published by Lord King," it would 
 appear that he himself had been at considerable 
 trouble in explaining to his friend that interesting 
 doctrine. This manuscript is endorsed, " Mr. New- 
 ton, March, 1689." It begins with three hypotheses 
 
 * Preface to'Desaguliers's' Experimental Philosophy. Dr. Desaguliers 
 states that he was told this anecdote several times by Sii Isaac Newton 
 himself. 
 
 t The Life of John Locke, p. 209-215, Lond. 1829.
 
 PROGRESS IN ENGLAND. 167 
 
 (the first two being the two laws of motion, and the 
 third the parallelogram of motion), which introduce 
 the proposition of the proportionality of the areas 
 to the times in motions round an immoveable centre 
 of attraction.* Three lemmas, containing properties 
 of the ellipse, then prepare the reader for the cele- 
 brated proposition, that when a body moves in 5 an 
 ellipse,! the attraction is reciprocally as the square 
 of the distance of the body from the focus to which 
 it is attracted. These propositions are demonstrated 
 in a more popular manner than in the Principia, but 
 there can be no doubt that, even in their present 
 modified form, they were beyond the capacity of 
 Mr. Locke. 
 
 Dr. John Keill was the first person who publicly 
 taught natural philosophy by experiments. Desa- 
 guliers informs us that this author " laid down very 
 simple propositions,which he proved by experiments, 
 and from these he deduced others more compound, 
 which he still confirmed by experiments, till he had 
 instructed his auditors in the laws of motion, the 
 principles of hydrostatics and optics, and some of 
 the chief propositions of Sir Isaac Newton concern- 
 ing light and colours. He began these courses in 
 Oxford about the year 1704 or 1705, and in that way 
 introduced the love of the Newtonian philosophy." 
 When Dr. Keill left the university, Desaguliers be- 
 gan to teach the Newtonian philosophy by experi- 
 ments. He commenced his lectures at Harthall in 
 Oxford, in 1710, and delivered more than a hundred 
 and twenty courses ; and when he went to settle in 
 London in 1713, he informs us that he found " the 
 Newtonian philosophy generally received among 
 persons of all ranks" and professions, and even 
 among the ladies by the help of experiments." 
 Such were the steps by which the Newtonian phi- 
 losophy was established in Great Britain. From 
 
 * ^"cmia. lib. i. ->p. i. f Ib. lib i. prop, xi
 
 168 SIR ISAAC NEWTON. 
 
 the time of the publication of the Principia, its 
 mathematical doctrines formed a regular part of aca- 
 demical education; and before twenty years had 
 elapsed, its physical truths were communicated to 
 the public in popular lectures illustrated by experi- 
 ments, and accommodated to the capacities of those 
 who were not versed in mathematical knowledge. 
 The Cartesian system, though it may have lingered 
 for a while in the recesses of our universities, was 
 soon overturned ; and long before his death, Newton 
 enjoyed the high satisfaction of seeing his philoso- 
 phy triumphant in his native land. 
 
 CHAPTER XII. 
 
 Doctrine of Infinite Quantities Labours of Pappus Kepler Cavalen 
 Roberval Fermat Wallis Newton discovers the Hinomial Theo- 
 rem and, the Doctrine of Fluxions in 1666 His Manuscript Work 
 containing this Doctrine communicated to his Friend* His Treatise 
 on Fluxions His Mathematical Tracts His Universal Arithmetic 
 His Methodus DifferentiolisHis Geometria AnalyticaHis Solu- 
 tion of the Problems proposed by BernouiUi aud Leibnitz Account 
 of the celebrated Dispute respecting the Invention of Fluxions Com- 
 mercium Epistolicum Report of the Royal Society^General View 
 of the Controversy. 
 
 PREVIOUS to the time of Newton, the doctrine of 
 infinite quantities had been the subject of profound 
 study. The ancients made the first step in this 
 curious inquiry by a rude though ingenious attempt 
 to determine the area of curves. The method of 
 exhaustions which was used for this purpose con- 
 sisted in finding a given rectilineal area to which the 
 inscribed and circumscribed polygonal figures con- 
 tinually approached by increasing the number of 
 their sides. This area was obviously the area 
 of the curve, and in the case of the parabola it was 
 found by Archimedes to be two-thirds of the area
 
 INFINITE QUANTITIES. 169 
 
 formed by multiplying the ordinate by the abscissa. 
 Although the synthetical demonstration of the re- 
 sults was perfectly conclusive, yet the method itself 
 was limited and imperfect. 
 
 The celebrated Pappus of Alexandria followed 
 Archimedes in the same inquiries ; and in his demon- 
 stration of the property of the centre of gravity 
 of a plane figure, by which we may determine the 
 solid formed by its revolution, he has shadowed 
 forth the discoveries of later times. 
 
 In his curious tract on Stereometry, published in 
 1615, Kepler made some advances in the doctrine 
 of infinitesimals. Prompted to the task by a dis- 
 pute with the seller of some casks of wine, he 
 studied the measurement of solids formed by the 
 revolution of a curve round any line whatever. 
 In solving some of the simplest of these problems, 
 he conceived a circle to be formed of an infinite 
 number of triangles having all their vertices in the 
 centre, and their infinitely small bases in the circum- 
 ference of the circle, and by thus rendering familiar 
 the idea of quantities infinitely great and infinitely 
 small, he gave an impulse to this branch of mathe- 
 matics. The failure of Kepler, too, in solving some 
 of the more difficult of the problems which he him- 
 self proposed roused the attention of geometers, 
 and seems particularly to have attracted the notice 
 of Cavaleri. 
 
 This ingenious mathematician was born at Milan 
 in 1598, and was Professor of Geometry at Bologna. 
 In his method of Indivisibles, which was published 
 in 1635, he considered a line as composed of an in- 
 finite number of points, a surface of an infinite 
 number of lines, and a solid of an infinite number 
 of surfaces ; and he lays it down as an axiom that 
 the infinite sums of such lines and surfaces have the 
 same ratio when compared with the linear or super- 
 ficial unit, as the surfaces and solids which are to 
 be determined. As it is not true that an infinite
 
 170 SIR -ISAAC NEWTON. 
 
 numbei of infinitely small points can make a line, 
 or an infinite number of infinitely small linos a sur- 
 face, Pascal removed this verbal difficulty by con- 
 sidering a line as composed of an infinite number 
 of infinitely short lines, a surface as composed of 
 an infinite number of infinitely narrow parallelo- 
 grams, and a solid of an infinite number of infinitely 
 thin solids. But, independent of this correction, 
 the conclusions deduced by Cavaleri are rigorously 
 true, and his method of ascertaining the ratios of 
 areas and solids to one another, and the theorems 
 which he deduced from it may be considered as 
 forming an era in mathematics. 
 
 By the application of this method, Roberval and 
 Toricelli showed that the area of the cycloid is three 
 times that of its generating circle, and the former 
 extended the method of Cavaleri to the case where 
 the powers of the terms of the arithmetical pro- 
 gression to be summed were fractional. 
 
 In applying the doctrine of infinitely small quanti- 
 ties to determine the tangents of curves, and the 
 maxima and minima of their ordinates, both Ro- 
 berval and Fermat made a near approach to the 
 invention of fluxions so near indeed that both 
 Lagrange and Laplace* have pronounced the latter 
 to be the true inventer of the differential calculus. 
 Roberval supposed the poii t which describes a 
 curve to be actuated by two motions, by the compo- 
 sition of which it moves in the direction of a tan- 
 gent ; and had he possessed the method of fluxions, 
 he could, in every case, have determined the rela- 
 tive velocities of these motions, which depend on 
 the nature of the curve, and consequently the 
 direction of the tangent which he assumed to be in 
 the diagonal of a parallelogram whose sides had the 
 
 * " On peut regarder Format," says Lagrange, "*omme le premier 
 inventeur des nouveaux calculs ;" and Laplace observes, "II paraitque 
 Fermat, le veritable inventeur du calcul differentiel, Fait envisage comme 
 un cas particulier d? celui des differences," &c.
 
 INFINITE QUANTITIES. 171 
 
 saine ratio as the velocities. But as he was able 
 to determine these velocities only in the conic sec- 
 tions, &c. his ingenious method had but few appli- 
 cations. 
 
 The labours of Peter Fermat, a counsellor of the 
 parliament of Toulouse, approached still nearer to 
 the fluxionary calculus. In his method of deter- 
 mining the maxima and minima of the ordinates of 
 curves, he substitutes x-\-e for the independent 
 variable x in the function which is to become a 
 maximum, Snd as these two expressions should be 
 equal when e becomes infinitely small or 0, he frees 
 this equation from surds and radicals, and after di- 
 viding the whole by e, e is made = 0, and the equation 
 for the maximum is thus obtained. Upon a similar 
 principle he founded his method of drawing tangents 
 to curves. But though the methods thus used by 
 Fermat are in principle the same with those which 
 connect the theory of tangents and of maxima 
 and minima with the analytical method of exhibit- 
 ing the differential calculus, yet it is a singular ex- 
 ample of national partiality to consider the inventer 
 of these methods as the inventer of the method of 
 fluxions. 
 
 " One might be led," says Mr. Herschel, " to sup- 
 pose by Laplace's expression that the calculus of 
 finite differences had then already assumed a sys- 
 tematic form, and that Fermat had actually observed 
 the relation between the two calculi, and derived 
 the one from the other. The latter conclusion 
 would scarcely be less correct than the former. No 
 method can justly be regarded as bearing any anal- 
 ogy to the differential calculus which does not lay 
 down a system of rules (no matter on what consid- 
 erations founded, by what names called, or by what 
 extraneous matter enveloped) by means of which 
 the second term of the development of any function 
 of x-\-e in powers of e, can be correctly calculated, 
 'quae extendet se,' to use Newton's expression.
 
 172 SIR ISAAC NEWTON. 
 
 1 citra ulluni molestum calculum in terminis surdis 
 seque ac in integris procedens.' It would be strange 
 to suppose Fermat or any other in possession of 
 such a method before any single surd quantity had 
 ever been developed in a series. But, in point of 
 fact, his writings present no trace of the kind ; and 
 this, though fatal to his claim, is allowed by both the 
 geometers cited. Hear Lagrange's candid avowal. 
 ' II fait disparaitre dans cette equation,' that of the 
 maximum between x and e, * les radicaux et les frac- 
 tions s'il y en a.' Laplace, too, declares that ' il sa- 
 voit etendre son calcul aux fonctions irrationelles 
 en se debarrassant des irrationalites par 1'elevation 
 des radicaux aux puissances." This is at once giv- 
 ing up the point in question. It is allowing une- 
 quivocally that Fermat in these processes only took 
 a circuitous route to avoid a difficulty which it is 
 one of the most express objects of the differential 
 calculus to face and surmount. The whole claim 
 of the French geometer arises from a confusion (too 
 often made) of the calculus and its applications, the 
 means and the end, under the sweeping head of 
 ' nouveaux calculs' on the one hand, and an asser- 
 tion somewhat too unqualified, advanced in the 
 warmth and generality of a preface, on the other."* 
 The discoveries of Fermat were improved and 
 simplified by Hudde, Huygens, and Barrow ; and by 
 the publication of the Arithmetic of Infinites by Dr. 
 Wallis, Savilian professor of geometry at Oxford, 
 mathematicians were conducted to the very entrance 
 of a new and untrodden field of discovery. This 
 distinguished author had effected the quadrature of 
 all curves whose ordinates can be expressed by any 
 direct integral powers ; and though he had extended 
 his conclusions to the cases where the ordinates are 
 xpressed by the inverse or fractional powers, yet 
 
 * Art. Mathematics, in the Edinburgh Encyclopedia, volume xiil 
 p. 365.
 
 ARITHMETIC OF INFINITES. 173 
 
 he failed in its application. Nicolas Mercator (Kauff- 
 man) surmounted the difficulty by which Wallis 
 had been baffled, by the continued division of the 
 numerator by the denominator to infinity, and then 
 applying Wallis's method to the resulting positive 
 powers. In this way he obtained, in 1667, the first 
 general quadrature of the hyperbola, and, at the 
 same time, gave the regular development of a func- 
 tion in series. 
 
 In order to obtain the quadrature of the circle, Dr. 
 Wallis considered that if the equations of the curves 
 of which he had given the quadrature were arranged 
 in a series, beginning with the most simple, these 
 areas would form another series. He saw also that 
 the equation of the circle was intermediate between 
 the first and second terms of the first series, 01 
 between the equation of a straight line and that of 
 a parabola, and hence he concluded, that by interpo- 
 lating a term between the first and second term of 
 the second series, he would obtain the area of the 
 circle. In pursuing this singularly beautiful thought, 
 Dr. Wallis did not succeed in obtaining the indefinite 
 quadrature of the circle, because he did not employ 
 general exponents ; but he was led to express the 
 entire area of the circle by a fraction, the numerator 
 and denominator of which are each obtained by 
 the continued multiplication of a certain series of 
 numbers. 
 
 Such was the state of this branch of mathematical 
 science, when Newton, at an early age, directed to 
 it the vigour of his mind. At the very beginning 
 of his mathematical studies, when the works of Dr. 
 Wallis fell into his hands, he was led to consider 
 how he could interpolate the general values of the 
 areas in the second series of that mathematician. 
 With this view he investigated the arithmetical law 
 of the coefficients of the series, and obtained a 
 gejieral method of interpolating, not only the series 
 above rffc^red to, but also other series. These 
 O
 
 174 SIR ISAAC NEWTON. 
 
 were the first steps taken by Newton, and, as he 
 himself informs us, they would have entirely escaped 
 from his memory if he had not, a few weeks 
 befoie,* found the notes which he made upon the 
 subject. When he had obtained this method, it oc- 
 curred to him that the very same process was appli- 
 cable to the ordinates, and, by following out this 
 idea, he discovered the general method of reducing 
 radical quantities composed of several terms into 
 infinite series, and was thus led to the discovery of 
 the celebrated Binomial Theorem. He now neglected 
 entirely liis methods of interpolation, and employed 
 that theorem alone as the easiest and most direct 
 method for the quadratures of curves, and in the solu- 
 tion of many questions which had not even been 
 attempted by the most skilful mathematicians. 
 
 After having applied the Binomial theorem to the 
 rectification of curves, and to the determination of 
 the surfaces and contents of solids, and the position 
 of their centres of gravity, he discovered the general 
 principle of -deducing the areas of curves from the 
 ordinate, by considering the area as a nascent quan- 
 tity, increasing by continual fluxion in the propor- 
 tion of the length of the ordinate, and supposing 
 the abscissa to increase uniformly in proportion to 
 the time. In imitation of Cavalerius, he called the 
 momentary increment of a line a point, though it is 
 not a geometrical point, but an infinitely short line ; 
 and the momentary increment of an area or surface 
 he called a line, though it is not a geometrical line, 
 but an infinitely narrow surface. By thus regarding 
 lines as generated by the motion of points, surfaces 
 by the motions of lines, and solids by the motion of 
 surfaces, and by considering that the ordinates, ab- 
 scissae, &c. of curves thus formed, vary according 
 to a regular law depending on the equation of the 
 
 * These facts are mentioned in Newton's letter to Oldenburgh, Octo- 
 ber 94, 1676.
 
 DOCTRINE OF FLUXIONS. 175 
 
 curve, he deduces from this equation the velocities 
 with which these quantities are generated ; and by 
 the rules of infinite series he obtains the ultimate 
 value of the quantity required. To the velocities 
 with which every line or quantity is generated. 
 Newton gave the name of Fluxions, and to the lines 
 or quantities themselves that of Fluents. Thii- 
 method constitutes the doctrine of fluxions which 
 Newton had invented previous to 1666, when the 
 breaking out of the plague at Cambridge drove him 
 from that city, and turned his attention to other 
 subjects. 
 
 But though Newton had not communicated this 
 great invention to any of his friends, he composed 
 his treatise, entitled Analysis per equationes numero 
 terminorum infinitas, in which the principle of fluxions 
 and its numerous applications are clearly pointed 
 out. In the month of June, 1669, he communicated 
 this work to Dr. Barrow, who mentions it in a letter 
 to Mr. Collins, dated the 20th June, 1669, as the pro- 
 duction of a friend of his residing at Cambiidge, who 
 possesses a fine genius for such inquiries. On the 
 31st July, he transmitted the work to Collins; and 
 having received his approbation of it, he informs him 
 that the name of the author of it was Newton, a 
 fellow of his own college, and a young man who 
 had only two years before taken his degree of M.A. 
 Collins took a copy of this treatise, and returned the 
 original to Dr. Barrow ; and this copy having been 
 found among Collins's papers by his friend Mr. Wil- 
 liam Jones, and compared with the original manu- 
 script borrowed from Newton, it was published with 
 the consent of Newton in 1711, nearly fifty years 
 after it was written. 
 
 Though the discoveries contained in this treatise 
 were not at first given to the world, yet they were 
 made generally known to mathematicians by the 
 correspondence of Collins, who communicated them 
 to James Gregory; to MM. Bertet and Vernon in
 
 176 SIR ISAAC NEWTON. 
 
 France; to Slusius in Holland; to Borelli in Italy, 
 and to Strode, Townsend, and Oldenburg, in letters 
 dated between 1669 and 1672. 
 
 Hitherto the method of fluxions was known only 
 to the friends of Newton and their correspondents : 
 but, in the first edition of the Principia, which ap- 
 peared in 1687, he published, for the first time, the 
 fundamental principle of the fluxionary calculus, in 
 the second lemma of the second book. No infor- 
 mation, however, is here given respecting the algo- 
 rithm or notation of the calculus ; and it was not till 
 1693-5[?] that it was communicated to the mathemat- 
 ical world in the second volume of Dr. Wallis's works, 
 which were published in that year. This informa- 
 tion was extracted from two letters of Newton 
 written in 1692. 
 
 About the year 1672, Newton had undertaken to 
 publish an edition of Kinckhuysen's Algebra, with 
 notes and additions. He therefore drew up a trea- 
 tise, entitled, A Method of Fluxions, which he pro- 
 posed as an introduction to that work; but the fear 
 of being invoiced in disputes about this new dis- 
 covery, or perhaps the wish to render it more com- 
 plete, or to have the sole advantage of employing 
 it in his physical researches, induced him to abandon 
 this design. At a later period of his life he again 
 resolved to give it to the world ; but it did not ap- 
 pear till after his death, when it was translated into 
 English, and published in 1736, with a commentary 
 by Mr. John Colson, Professor of Mathematics in 
 Cambridge.* 
 
 To thq first edition of Newton's Optics, which 
 appeared in 1704, there were added two mathematical 
 
 * Dr. Pemberton informs u a that he had prevailed upon Sir Isaac to 
 publish this treatise during his lifetime, and that he had for this purpose 
 examined all the calculations and prepared part of the fieures. But as 
 the latter part of the treatise had never been finished, Sir f-::;ic \vas 
 about to let him have other papers to supply what was wanting, when 
 hia death put a stop to the plan. Preface to Pembcrton's View of Sir 
 Isaac Newton's Philosophy
 
 DOCTRINF OF FLUXIONS. 177 
 
 treatises, entitled, Tractatus duo de speciebus et mag- 
 nitudine figurarum curvilinearum, the one bearing the 
 title of Tractatus de Quadratura Curvarum, and the 
 other Enumeratio linearum tertii ordinis. The first 
 contains an explanation of the doctrine of fluxions, 
 and of its application to the quadrature of curves ; 
 and the second a classification of seventy-two curves 
 of the third order, with an account of their proper- 
 ties. The reason for publishing these two tracts in 
 his Optics (in the subsequent editions of which they 
 are omitted) is thus stated in the advertisement : 
 " In a letter written to M. Leibnitz in the year 1679, 
 and published by Dr. Wallis, I mentioned a method 
 by which I had found some general theorems about 
 squaring curvilinear figures on comparing them with 
 the conic sections, or other the simplest figures with 
 which they might be compared. And some years 
 ago I lent out a manuscript containing such theo- 
 rems ; and having since met with some things copied 
 out of it, I have on this occasion made it public, pre- 
 fixing to it an introduction, and joining a scholium 
 concerning that method. And I have joined with it 
 another small tract concerning the curvilineal figures 
 of the second kind, which was also written many 
 years ago, and made known to some friends, who 
 have solicited the making it public." 
 
 In the year 1707, Mr. Whiston published the alge- 
 braical lectures which Newton had, during nine years, 
 delivered at Cambridge, under the title of Arithmetica 
 Universalis, sive de Compositions et Resolutione Arith- 
 metica Liber. We are not accurately informed how 
 Mr. Whiston obtained pcssession of this work; but 
 it is stated by one of the editors of the English 
 edition, that " Mr. Whiston thinking it a pity that so 
 noble and useful a work should be doomed to a col- 
 lege confinement, obtained leave to make it public." 
 It was soon afterward translated into English by 
 Mr. Ralphson ; and a second edition of it, with im 
 provements by the author, was published at London
 
 178 SIR ISAAC NEWTON. 
 
 hi 1712, by Dr. Machm, secretary to the Royal So- 
 ciety. With the view of stimulating mathematicians 
 to write annotations on this admirable work, the 
 celebrated S'Gravesande published a tract, entitled, 
 Specimen Commentarii in Arithmeticam Universalem ; 
 and Maclaurin's Algebra seems to have been drawn 
 up in consequence of this appeal. 
 
 Among the mathematical works of Newton we 
 must not omit to enumerate a small tract entitled, 
 Methodus Differential**, which was published with 
 his consent in 1711. It consists of six propositions, 
 which contain a method of drawing a parabolic curve 
 through any given number of points, and which are 
 useful for constructing tables by the interpolation of 
 series, and for solving problems depending on the 
 quadrature of curves. 
 
 Another mathematical treatise of Newton's was 
 published for the first time in 1779, in Dr. Horsley 's 
 edition of his works.* It is entitled, Artis Analytics 
 Specimina, vel Geometria Analytica. In editing this 
 work, which occupies about 130 quarto pages, Dr. 
 Horsley used three manuscripts, one of which was 
 in the handwriting of the author ; another, written 
 in an unknowoa hand, was given by Mr. William 
 Jones to the Honourable Charles Cavendish ; and a 
 third, copied from this by Mr. James Wilson, the 
 editor of Robins's works, was given to Dr. Horsley 
 by Mr. John Nourse, bookseller to the king. Dr. 
 Horsley has divided it into twelve chapters, which 
 treat of infinite series ; of the reduction of affected 
 equations ; of the specious resolution of equations ; 
 of the doctrine of fluxions; of maxima and minima; 
 of drawing tangents to curves ; of the radius of cur- 
 vature ; of the quadrature of curves ; of the area of 
 curves which are comparable with the conic sec* 
 tions ; of the construction of mechanical problems, 
 and on finding the lengths of curves. 
 
 * Isari Newtoni Opera quae extant ornnia, vol. i p. 338-619,
 
 SOLUTION OF PROBLEMS. 179 
 
 In enumerating- the mathematical works of our 
 author, we must not overlook his solutions of the 
 celebrated problems proposed by Bernouilli and 
 Leibnitz. On the Kalends of January, 1697, John 
 Bernouilli addressed a letter to the most distin- 
 guished mathematicians in Europe,f challenging 
 them to solve the two following problems : 
 
 1. To determine the curve line connecting two 
 given points which are at different distances from 
 the horizon, and not in the same vertical line, along 
 which a body passing by its own gravity, and begin- 
 ning to move at the upper point, shall descend to the 
 lower point in the shortest time possible. 
 
 2. To find a curve line of this property that the 
 two segments of a right line drawn from a given 
 point through the curve, being raised to any given 
 power, and taken together, may make every where 
 the same sum. 
 
 On the day after he received these problems. 
 Newton addressed to Mr. Charles Montague, the 
 President of the Royal Society, a solution of them 
 both. He announced that the curve required in the 
 first problem must be a cycloid, and he gave a 
 method of determining it. He solved also the 
 second problem, and he showed that by the same 
 method other curves might be found which shall cut 
 off three or more segments having the like proper- 
 ties. Leibnitz, who was struck with the beauty of 
 the problem, requested Bernouilli, who had allowed 
 six months for its solution, to extend the period to 
 twelve months. This delay was readily granted, 
 solutions were obtained from Newton, Leibnitz, and 
 the Marquis de L'Hopital ; and although that of 
 Newton was anonymous, yet Bernouilli recognised 
 in it his powerful mind, " tanquam" says he, "ex 
 ungue leonem" as the lion is known by his claw. 
 
 The last mathematical effort of our author was 
 
 * " Acutissimis oui toto orbe norent Mathematicis."
 
 180 SIR ISAAC NEWTON. 
 
 made with his usual success, in solving a problem 
 which Leibnitz proposed in 1716, in a letter to the 
 Abbe Conti, " for the purpose, as he expressed it, 
 of feeling the pulse of the English analysts." The 
 object of this problem was to determine the curve 
 which should cut at right angles an infinity of curves 
 of a given nature, but expressible by the same equa- 
 tion. Newton received this problem about five 
 o'clock in the afternoon, as he was returning from 
 the Mint ; and though the problem was extremely 
 difficult, and he himself much fatigued with business, 
 yet he finished the solution of it before he went 
 to bed. 
 
 Such is a brief account of the mathematical writ- 
 ings of Sir Isaac Newton, not one of which were 
 voluntarily communicated to the world by himself. 
 The publication of his Universal Arithmetic is said 
 to have been a breach of confidence on the part of 
 Whiston ; and, however this may be, it was an un- 
 finished work, never designed for the public. The 
 publication of his Quadrature of Curves, and of his 
 Enumeration of Curve Lines, was rendered neces- 
 sary, in consequence of plagiarisms from the manu- 
 scripts of them which he had lent to his friends, and 
 the rest of his analytical writings did not appear till 
 after his death. It is not easy to penetrate into the 
 motives by which this great man was on these 
 occasions actuated. If his object was to keep pos- 
 session of his discoveries till he had brought them 
 to a higher degree of perfection, we may approve of 
 the propriety, though we cannot admire the prudence 
 of such a step. If he wished to retain to himself 
 his own methods, in order that he alone might have 
 the advantage of them in prosecuting his physical 
 inquiries, we cannot reconcile so selfish a measure 
 with that openness and generosity of character 
 which marked the whole of his life. If he withheld 
 his labours from the world in order to avoid the dis- 
 putes and contentions to which they might give rise,
 
 HISTORY OF FLUXIONS'. 18 J 
 
 he adopted the very worst method of securing his 
 tranquillity. That this was the leading motive under 
 which he acted, there is little reason to doubt. The 
 carry delay in the publication of his method of. flux- 
 ions, after" the breaking out of the plague at Cam- 
 bridge, was probably owing to his not having com- 
 pleted the algorithm of that calculus ; but no apology 
 can be made for the imprudence of withholding it 
 any longer from the public. Had he published this 
 noble discovery even previous to 1673, when his 
 great rival had not even entered upon those studies 
 which led him to the same method, he would have 
 secured to himself the undivided honour of the 
 invention, and Leibnitz could have aspired to no other 
 fame but that of an improver of the doctrine of flux- 
 ions. But he unfortunately acted otherwise. He 
 announced to his friends that he possessed a method 
 of great generality and power ; he communicated to 
 them a general account of its principles and applica- 
 tions ; and the information which was thus conveyed 
 directed the attention of mathematicians to subjects 
 to which they might not have otherwise applied their 
 powers. In this way the discoveries which he had 
 previously made were made subsequently by others ; 
 and Leibnitz, in place of appearing in the theatre of 
 science as the disciple and the follower of Newton, 
 stood forth with all the dignity of a rival ; and, by 
 the early publication of his discoveries had nearly 
 placed himself on the throne which Newton was 
 destined to ascend. 
 
 It would be inconsistent with the popular nature 
 of a work like this, to enter into a detailed history 
 of the dispute between Newton and Leibnitz re- 
 specting the invention of fluxions. A brief and 
 general account of it, however, is indispensable. 
 
 In the beginning of 1673, Leibnitz came to London 
 in the suite of the Duke of Hanover, and he became 
 acquainted with the great men who then adorned 
 the capital of England. Among these was Olden-
 
 182 SHI ISAAC NEWTON. 
 
 burg, a countryman of his own, who was then &et> 
 retary to the Royal Society. About the beginning 
 of March, in the same year, Leibnitz went to Paris, 
 where, with the assistance of Huygens, he devoted 
 himself to the study of the higher geometry. In 
 the month of July he renewed his correspondence 
 with Oldenburg, and he communicated to him some of 
 the discoveries which he had made relative to series, 
 particularly the series for a circular arc in terms of 
 the tangent. Oldenburg informed him in return of 
 the discoveries on series which had been made by 
 Newton and Gregory; and in 1676 Newton commu- 
 nicated to him, through Oldenburg, a letter of fifteen 
 closely printed quarto pages, containing many of his 
 analytical discoveries, and stating that he possessed 
 a general method of drawing tangents, which he 
 thought it necessary to conceal in two sentences of 
 transposed characters. In this letter neither the 
 method of fluxions nor any of its principles are 
 communicated ; but the superiority of the method 
 over all others is so fully described, that Leibnitz 
 could scarcely fail to discover that Newton pos- 
 sessed that secret of which geometers had so long 
 been in quest. 
 
 Had Leibnitz at the time of receiving this letter 
 been entirely ignorant of his own differential method, 
 the information thus conveyed to him by Newton 
 could not fail to stimulate his curiosity, and excite 
 his mightiest efforts to obtain possession of so great 
 a secret. That this new method was intimately 
 connected with the subject of series was clearly in- 
 dicated by Newton; and as Leibnitz was deeply 
 versed in this branch of analysis, it is far from im- 
 probable that a mind of such strength and acuteness 
 might attain his object by direct investigation. That 
 this was the case may be inferred from his letter to 
 Oldenburg (to be communicated to Newton) of the 
 21st June, 1677, where he mentions that he had for 
 some time been in possession of a method of draw-
 
 pl 
 d 
 
 HISTORY OF FLUXIONS. 183 
 
 ing tangents more general than that of Slusius, 
 namely, by the differences of ordinals. He then 
 proceeds with the utmost frankness to explain this 
 method, which was no other than the differential 
 calculus. He describes the algorithm which he had 
 adopted, the formation of differential equations, and 
 the application of the calculus to various geometrical 
 and analytical questions. No answer seems to have 
 been returned to this letter either by Newton or 
 Oldenburg, and, with the exception of a short letter 
 from Leibnitz to Oldenburg, dated 12th July, 1677, 
 no further correspondence seems to have taken 
 lace. This, no doubt, arose from the death of Ol- 
 enburg in the month of August, 1677,* when the 
 two rival geometers pursued their researches with 
 all the ardour which the greatness of the subject 
 was so well calculated to inspire. 
 
 In the hands of Leibnitz the differential calculus 
 made rapid progress. In the Acta JEruditorum, which 
 was published at Leipsic in November, 1684, he gave 
 the first account of it, describing its algorithm in the 
 same manner as he had done in his letter to Olden- 
 burg, and pointing out its application to the drawing 
 of tangents, and the determination of maxima and 
 minima. He makes a rerno* reference to the simi- 
 lar calculus of Newton, but ,dys no claim to the sole 
 invention of the differential method. In the same 
 work for June, 1686, he resumes the subject ; and 
 when Newton had not published a single word upon 
 
 * Henry Oldenburg, whose name is so intimately associated with the 
 history of Newton's discoveries, was born at Bremen, and was consul 
 from Hiat town to London during the usurpation of Cromwell. Having 
 lost his office, and being compelled to seek the means of subsistence, he 
 became tutor to an English nobleman, whom he accompanied to Oxford 
 in 1656. During his residence in that city he became acquainted with 
 the philosophers who established the Royal Society, and upon the death 
 of William Crown, the first secretary, he was appointed in 1663, joint 
 secretary along with Mr. Wilkins. He kept up an extensive correspond- 
 ence with the philosophers of all nations, and he was the author of sev- 
 eral papers in the Philosophical Transactions, and of some works which 
 have not acquired much celebrity. He died at Charlton, near Green 
 ich, in August, 1677.
 
 184 SIR ISAAC NEWTON. 
 
 fluxions, and had not even made known his notation, 
 the differential calculus was making rapid advances 
 on the Continent, and in the hands of James and 
 John Bernouilli had proved the means of solving 
 some of the most important and difficult problems. 
 
 The silence of Newton was at last broken, and in 
 the second lemma of the second book of the Prin- 
 cipia, he explained the fundamental principle of the 
 fluxionary calculus. His explanation, which occu- 
 pied only three pages, was terminated with the fol- 
 lowing scholium: "In a correspondence \vhich 
 took place about ten years ago between that very 
 skilful geometer, G. G. Leibnitz, and myself, I an- 
 nounced to him that I possessed a method of deter- 
 mining maxima and minima, of drawing tangents, 
 and of performing similar operations which was 
 equally applicable to rational and irrational quanti- 
 ties, and concealed the same in transposed letters 
 involving this sentence, (data equations quotcunque 
 fiuentes quantitates involvente^ fluxiones invenire et vice 
 versa). This illustrious man replied that he also 
 had fallen on a method of the same kind, and he 
 communicated to me his method which scarcely 
 differed from mine except in the notation [and in the 
 idea of the generation of quantities."]* This cele- 
 brated scholium, which is so often referred to in the 
 present controversy, has, in our opinion, been much 
 misapprehended. While M. Biot considers it as 
 " eternalizing the rights of Leibnitz by recognising 
 them in the Principia," Professor Playiair regards it 
 as containing " a highly favourable opinion ~on the 
 subject of the discoveries of Leibnitz." To -us it 
 appears to be nothing more than the simple state- 
 ment of the fact, that the method communicated by 
 Leibnitz was nearly the same as his own; and this 
 much he might have said, whether he believed that 
 Leibnitz had seen the fluxionary calculus among th 
 
 ' These words in brackets are in the second edition, but not in the first.
 
 HISTORY OF FLUXIONS. 185 
 
 papers of Collins, or was the independent inventor 
 of his own. It is more than probable, indeed, that 
 when Newton wrote this scholium he regarded 
 Leibnitz as a second inventor ; but when he found 
 that Leibnitz and his friends had showed a willing- 
 ness to believe, and had even ventured to throw out 
 the suspicion, that he himself had borrowed the doc- 
 trine of fluxions from the differential calculus, he 
 seems to have altered the opinion which he had 
 foimed of his rival, and to have been willing in his 
 turn to retort the charge. 
 
 This change of opinion was brought about by a 
 series of circumstances over which he had no con- 
 trol. M. Nicolas Fatio de Duillier, a Swiss mathe- 
 matician, resident in London, communicated to the 
 Royal Society, in 1699, a paper on the line of quick- 
 est descent, which contains the following observa- 
 tions : " Compelled by the evidence of facts, I hold 
 Newton to have been the first inventor of this cal- 
 culus, and the earliest by several years ; and whether 
 Leibnitz, the second inventor, has borrowed any thing 
 from the other, I would prefer to my own judgment 
 that of those who have seen the letters arid other 
 copies of the same manuscripts of Newton." This 
 imprudent remark, which by no means amounts to a 
 charge of plagiarism, for Leibnitz is actually desig- 
 nated the second inventor, may be considered as 
 showing that the English mathematicians had been 
 cherishing suspicions unfavourable to Leibnitz, and 
 there can be no doubt that a feeling had long pre- 
 vailed that this mathematician either had, or might 
 have seen, among the papers of Collins, the " Analy- 
 sis per Equationes, <5fc.? which contained the prin- 
 ciples of the fluxionary method. Leibnitz replied to 
 tlie remark of Duillier with much good feeling. 
 He appealed to the facts as exhibited in his corres- 
 pondence with Oldenburg ; he referred to Newton's 
 scholium as a testimony in his favour ; and, without 
 disoutinff or acknowledging the priority of Newton's
 
 186 SIR ISAAC NEWTON. 
 
 claim, he asserted his own right to the invention of 
 the differential calculus. Fatio transmitted a reply to 
 the Leipsic Acts ; but the editor refused to insert it. 
 The dispute, therefore, terminated, and the feelings 
 of the contending parties continued for some time 
 in a state of repose, though ready to break out on 
 the slightest provocation. 
 
 When Newton's Optics appeared in 1704, accom- 
 panied by his Treatise on the Quadrature of Curves, 
 and his enumeration of lines of the third order, the 
 editor of the Leipsic Acts (whom Newton supposed 
 to be Leibnitz himself) took occasion to review the 
 first of these tracts. After giving an imperfect 
 analysis of its contents, he compared the method 
 of fluxions with the differential calculus, and, in a 
 sentence of some ambiguity, he states that Newton 
 employed fluxions in place of the differences of Leib- 
 nitz, and made use of them in his Principia in the 
 same manner as Honoratus Fabri, in his Synopsis 
 of Geometry, had substituted progressive motion in 
 place of the indivisibles of Cavaleri.* As Fabri, 
 therefore, was not the inventor of the method 
 which is here referred to, but borrowed it from Ca- 
 valeri, and only changed the mode of its expression, 
 there can be no doubt that the artful insinuation 
 contained in the above passage was intended to con- 
 vey the impression that Newton had stolen his me- 
 thod of fluxions from Leibnitz. The indirect char- 
 acter of this attack, in place of mitigating its severity, 
 renders it doubly odious ; and we are persuaded that 
 no candid reader can peruse the passage without a 
 strong conviction that it justifies, in the fullest man- 
 
 * As this passage is of essential importance in this controversy, we * 
 shall give it in the original. "Pro differentiis igitur Leibnitianis D. 
 Newton-us adhibet, semperque adhilruit,Jliuriones, quse sum quam prox- 
 ime at fluentium augments, sequalibus temporis particulis quam mini 
 mis genita; iisque tarn in suis Principiis Naturae Mathematicis, turn in 
 sliis postea editis, eleganter est usus ; quern admodum et HonoratUM 
 Fabrius in sua Synopsi Geometrica, motuumque progressus Cavalle 
 rianae methodo substituit."
 
 HISTORY OF FLUXIONS, 187 
 
 ner, the indignant feelings which it excited among 
 the English philosophers. If Leibnitz was the authpi 
 of the review, or if he was in any way a party to it, 
 he merited the full measure of rebuke which was 
 dealt out to him by the friends of Newton, and de- 
 served those severe reprisals which doubtless im- 
 bittered the rest of his days. He who dared to ac- 
 cuse a man like Newton, or indeed any man holding 
 a fair character in society, with the odious crime of 
 plagiarism, placed himself without the pale of the 
 ordinary courtesies of life, and deserved to have 
 the same charge thrown back upon himself. The 
 man who conceives his fellow to be capable of such 
 intellectual felony, avows the possibility of himself 
 committing it, and almost substantiates the weakest 
 evidence of the worst accusers. 
 
 Dr. Keill, as the representative of Newton's 
 friends, could not brook this base attack upon his 
 countryman. In a letter printed in the Philosophi- 
 cal Transactions for 1708, he maintained that Newton 
 was " beyond all doubt" the first inventor of fluxions. 
 He referred for a direct proof of this to his letters 
 published by Wallis ; and he asserted " that the same 
 calculus was afterward published by Leibnitz, the 
 name and the mode of notation being changed." 
 If the reader is disposed to consider this passage 
 as retorting the charge of plagiarism upon Leibnitz, 
 he will readily admit that the mode of its expres- 
 sion is neither so coarse nor so insidious as that 
 which is used by the writer in the Leipsic Acts. 
 In a letter to Hans Sloane, dated March, 1711, Leib- 
 nitz complained to the Royal Society of the treat- 
 ment he had received. He expressed his conviction 
 that Keill had erred more from rashness of judgment 
 than from any improper motive, and that he did not 
 regard the accusation as a calumny; and he re- 
 quested that the society would oblige Mr. Keill to 
 disown publicly the injurious sense which his words 
 might bear. When this letter was read to thi
 
 188 am ISAAC NEWTON. 
 
 society, Keill justified himself to Sir Isaac Newton 
 and the other members by showing them the ob- 
 noxious review of the Quadrature of Curves in the 
 Leipsic Acts. They all agreed in attaching the same 
 injurious meaning to the passage which we formerly 
 quoted, and authorized Keill to explain and defend 
 his statement. He accordingly addressed a letter 
 to Sir Hans Sloane, which was read at the society 
 on the 24th May, 1711, and a copy of which was 
 ordered to be sent to Leibnitz. In this letter, which 
 is one of considerable length, he declares that he 
 never meant to state that Leibnitz knew either the 
 name of Newton's method or the form of notation, 
 and that the real meaning of the passage was, " that 
 Newton was the first inventor of fluxions or of the 
 differential calculus, and that he had given, in two 
 letters to Oldenburg, and which he had transmitted 
 to Leibnitz, indications of it sufficiently intelligible 
 to an acute mind, from which Leibnitz derived, or at 
 least might derive, the principles of his calculus." 
 
 The charge of plagiarism which Leibnitz thought 
 was implied in the former letter of his antagonist 
 is here greatly modified, if not altogether denied. 
 Keill expresses only an opinion that the letter seen 
 by Leibnitz contained intelligible indications of the 
 fluxionary calculus. Even if this opinion were cor- 
 rect, it is no proof that Leibnitz either saw these indi- 
 cations or availed himself of them, or if he did per- 
 ceive them, it might have been in consequence of his 
 having previously been in possession of the differential 
 calculus, or having enjoyed some distant view of it. 
 Leibnitz should, therefore, have allowed the dispute 
 to terminate here ; for no ingenuity on his part, and 
 no additional facts, could affect an opinion which 
 any other person as well as Keill was entitled to 
 maintain. 
 
 Leibnitz, however, took a different view of the 
 subject, and wrote a letter to Sir Hans Sloane, 
 dated December 19, 171 1 , which excited new feelings,
 
 HISTORY OF FLUXIONS. 189 
 
 and involved him in new embarrassments. Insensi- 
 ble to the mitigation which had been kindly impressed 
 upon the supposed charge against his honour, he 
 alleges that Keill had attacked his candour and sin- 
 cerity more openly than before; that he acted 
 without any authority from Sir Isaac Newton, who 
 was the party interested ; and that it was in vain 
 to justify his proceedings by referring to the provo- 
 cation in the Leipsic Acts, because in that journal 
 no injustice had been done to any party, but every one 
 had received what was his due. He branded Keill with 
 the odious appellation of an upstart, and one little 
 acquainted with the circumstances of the case ;* he 
 called upon the society to silence his vain and un- 
 just clamours,| which, he believed, were disapproved 
 by Newton himself, who was well acquainted with 
 the facts, and who, he was persuaded, would will- 
 ingly give his opinion on the matter. 
 
 This unfortunate letter was doubtless the cause 
 of all the rancour and controversy which so speedily 
 followed, and it placed his antagonist in a new and a 
 more favourable position. It may be correct, though 
 few will admit it, that Keill's second letter was more 
 injurious than the first; but it was not true that 
 Keill acted without the authority of Newton, be- 
 cause Keill's letter was approved of and trans- 
 mitted by the Royal Society, of which Newton was 
 the president, and therefore became the act of that 
 body. The obnoxious part, however, of Leibnitz's 
 letter consisted in his appropriating to himself the 
 opinions of the reviewer in the Leipsic Acts, by 
 declaring that, in a review which charged Newton 
 with plagiarism, every person had got what was 
 his due. The whole character of the controversy 
 was now changed : Leibnitz places himself in th 
 
 * Homine docto, sed novo, et parum perito rentm ants* actarnm c* 
 nitare. 
 
 t Vanae et injustse vociferationes. 
 P
 
 190 SIR ISAAC NEWTON. 
 
 position of the party who had first disturbed the 
 tranquillity of science by maligning its most disiin- 
 guished ornament ; and the Royal Society was im- 
 periously called upon to throw all the light they 
 could upon a transaction which had exposed their 
 venerable president to so false a charge. The so- 
 ciety, too, had become a party to the question, by 
 their approbation and transmission of KeilPs second 
 letter, and were on that account alone bound to vin- 
 dicate the step which they had taken. 
 
 When the letter of Leibnitz, therefore, w-as read, 
 Keill appealed to the registers of the society for 
 the proofs of what he had advanced-; Sir Isaac also 
 expressed his displeasure at the obnoxious passage 
 _in the Leipsic Review, and at the defence of it by 
 Leibnitz, and he left it to the society to act as they 
 thought proper. A committee was therefore ap- 
 pointed on the 1 1th March, consisting of Dr. Arbuth- 
 not, Mr. Hill, Dr. Halley, Mr. Jones, Mr. Machin, 
 and Mr. Burnet, who were instructed to examine 
 the ancient registers of the society, to inquire into 
 the dispute, and to produce such documents as they 
 should find, together with their own opinions on the 
 subject. On the 24th April the committee produced 
 the following report : 
 
 " We have consulted the letters and letter-books 
 in the custody of the Royal Society, and those 
 found among the papers of Mr. John Collins, dated 
 between the years 1669 and 1677, inclusive; and 
 showed them to such as knew and avouched the 
 hands of Mr. Barrow, Mr. Collins, Mr. Oldenburg, 
 and Mr. Leibnitz ; and compared those of Mr. 
 Gregory with one another, and with copies of some 
 of them taken in the hand of Mr. Collins ; and have 
 extracted from them w^hat relates to the matter re- 
 ferred to us ; all which extracts herewith delivered 
 to you we believe to be genuine and authentic. And 
 by these letters and papers we find, 
 
 " I. Mr. Leibnitz was in London in the beginning
 
 REPORT OF THE ROYAL SOCIETY. 191 
 
 of the year 1673; and went thence, in or about 
 March, to Paris, where he kept a correspondence 
 with Mr. Collins by means of Mr. Oldenburg, till 
 about September, 1676, and then returned by London 
 and Amsterdam to Hanover : and that Mr. Collins 
 was very free in communicating to able mathema- 
 ticians what he had received from Mr. Newton and 
 Mr. Gregory. 
 
 " II. That when Mr. Leibnitz was the first time in 
 London, he contended for the invention of another 
 differential method properly so called ; and, notwith- 
 standing that he was shown by Dr. Pell that it was 
 Newton's method, persisted in maintaining it to be 
 his own invention, by reason that he had found it by 
 himself without knowing what Newton had done 
 before, and had much improved it. And we find no 
 mention of his having any other differential method 
 than Newton's before his letter of the 21st of June, 
 1677, which was a year after a copy of Mr. Newton's 
 letter of the 10th of December, 1672, had been sent 
 to Paris to be communicated to him ; and above foui 
 years after, Mr. Collins began to communicate that 
 letter to his correspondent; in which letter the 
 method of fluxions was sufficiently described to any 
 intelligent person. 
 
 " III. That by Mr. Newton's letter of the 13th of 
 June, 1676, it appears that he had the method of 
 fluxions above five years before the writing of that 
 letter. And by his Analysis per ^Equationes numero 
 Terminorum Infinitas, communicated by Dr. Barrow 
 to Mr. Collins in July, 1669, we find that he had in- 
 vented the method before that time. 
 
 " IV. That the differential method is one and the 
 same with the method of fluxions, excepting the 
 name and mode of notation ; Mr. Leibnitz calling 
 those quantities differences which Mr. Newton calls 
 moments or fluxions ; and marking them with the 
 letter d a mark not used by Mr. Newton. 
 
 " And therefore we take the proper question to be
 
 192 SIR ISAAC NEWTON. 
 
 not who invented this or that method, but who was 
 the first inventor of the method. And we believe 
 that those who have reputed Mr. Leibnitz the first 
 inventor knew little or nothing of his correspondence 
 with Mr. Collins and Mr. Oldenburg long before, nor 
 of Mr. Newton's having that method above fifteen 
 vears before Mr. Leibnitz began to publish it in the 
 Acta Eruditorum of Leipsic. 
 
 " For which reason we reckon Mr. Newton the 
 first inventor ; and are of opinion that Mr. Keill, in 
 asserting the same, has been no ways injurious to 
 Mr. Leibnitz. And we submit to the judgment of 
 the society whether the extract and papers now pre- 
 sented to you, together with what is extant to the 
 same purpose in Dr. Wallis's third volume, may not 
 deserve to be made public." 
 
 This report being read, the society unanimously 
 ordered the collection of letters and manuscripts to 
 be printed, and appointed Dr. Halley, Mr. Jones, and 
 Mr. Machin to superintend the press. Complete 
 copies of it, under the title of Commercium Epistoli- 
 cum D. Johannis Collins et aliorum de analyst promota, 
 were laid before the society on the 8th January, 1713, 
 and Sir Isaac Newton, as president, ordered a copy 
 to be delivered to each person of the committee ap- 
 pointed for that purpose, to examine it before its 
 publication. 
 
 Leibnitz received information of the appearance 
 of the Commercium Epistolicum when he was at 
 Vienna; and "being satisfied," as he expresses it, 
 " that it must contain malicious falsehoods, I did not 
 think proper to send for it by post, but wrote to M. 
 Bernouilli to give me his sentiments. M. Bernoulli! 
 wrote me a letter dated at Basle, June 7th, 1713, in 
 which he said that it appeared probable that Sir Isaac 
 Newton had formed his calculus after hat-ing seen 
 mine."* This letter was published by a friend of 
 
 * Letter to Count Bothman in Des Maizeaux's Recueil de diver .
 
 COMMERCIUM EPISTOLICUM. 198 
 
 Leibnitz, with reflections, in a loose sheet entitled 
 Char la Volans, and dated July 29, 1713. It was 
 widely circulated without either the name of the 
 author, printer, or place of publication, and was 
 communicated to the Journal Literaire by another 
 friend of Leibnitz, who added remarks of his own, 
 and stated, that when Newton published the Principia 
 in 1687, he did not understand the true differential 
 method ; and that he took his fluxions from Leibnitz. 
 
 In this state of the controversy, Mr. Chamberlayne 
 conceived the design of reconciling the two distin- 
 guished philosophers ; and in a letter dated April 28, 
 1714,* he addressed himself to Leibnitz, who was 
 still at Vienna. In replying to this letter, Leibnitz 
 declared that he had given no occasion for the dis- 
 pute ; " that Newton procured a book to be published, 
 which was written purposely to discredit him, and 
 sent it to Germany, &c. as in the name of the 
 society ;" and he stated that there was room to doubt 
 whether Newton knew his invention before he had it of 
 him. Mr. Chamberlayne communicated this letter 
 to Sir Isaac Newton, who replied that Leibnitz had 
 attacked his reputation in 1705, by intimating that he 
 had borrowed from him the method of fluxftms; 
 that if Mr. C. could point out to him any thing in 
 which he had injured Mr. Leibnitz, he would give 
 him satisfaction ; that he would not retract things 
 which he knew to be true ; and that he believed that 
 the Royal Society had done no injustice by the publi- 
 cation of the Commercium Epistolicum. 
 
 The Royal Society, having learned that Leibnitz 
 complained of their having condemned him unheard, 
 inserted a declaration in their journals on the 20th 
 May, 1714, that they did not pretend that the report 
 of their committee should pass for a decision of the 
 society. Mr. Chamberlayne sent a copy of this to 
 Leibnitz, along with Sir Isaac's letter, and Dr. KeilPs 
 
 * See Des Maizeaux, torn. ii. p. 116.
 
 194 SIR ISAAC NEWTON. 
 
 answer to the papers inserted in the Journal Lite- 
 raire. After perusing these documents, M. Leibnitz 
 replied, " that Sir Isaac's letter was written with 
 very little civility; that he was not in a humour 
 to put himself in a passion against such people; 
 that there were other letters among those of Olden- 
 burg and Collins which should have been published ; 
 and that on his return to Hanover, he would be able 
 to publish a Commercium Epistolicum which would 
 be of service to the history of learning." When 
 this letter was read to-the Royal Society, Sir Isaac 
 remarked, that the last part of it injuriously accused 
 the society of having made a partial selection of 
 papers for the Commercium Epistolicum ; that he 
 did not interfere in any way in the publication of 
 that work, and had even withheld from the com- 
 mittee two letters, one from Leibnitz in 1693, and 
 another from Wallis in 1695, which were highly 
 favourable to his cause. He stated that he did not 
 think it right for M. Leibnitz himself, but that, if 
 he had letters to produce in his favour, that they 
 might be published in the Philosophical Transac- 
 tions, or hi Germany. 
 
 Atfout this time the Abbe Conti, a noble Vene- 
 tian, came to England. He was a correspondent of 
 Leibnitz, and hi a letter which he had received soon 
 after his arrival,* he enters upon his dispute with 
 Newton. He charges the English " with wishing 
 to pass for almost the only inventors." He declares 
 " that Bernouilli had judged rightly in saying that 
 Newton did not possess before him the infinitesimal 
 characteristic and algorithm." He remarks that 
 Newton preceded him only in series ; and he con- 
 fesses that during his second visit to England, " Col- 
 lins showed him part of his correspondence," or, as 
 lie afterward expresses it, he saw " some of the let- 
 ters of Newton at Mr. Collins's." He then attacks 
 
 * Written in November or December, 1715 .
 
 COMMERCIUM EPISTOLICUM. 195 
 
 Sir Isaac's philosophy, particularly his opinions 
 about gravity and vacuum, the intervention of God 
 for the preservation of his creatures ; and he accuses 
 him of reviving the occult qualities of the schools. 
 But the most remarkable passage in this letter is 
 the following : " I am a great friend of experimental 
 philosophy, but Newton deviates much from it when 
 he pretends that all matter is heavy, or that each par- 
 ticle of matter attracts every other particle." 
 
 The above letter to the Abbe Conti was generally 
 shown in London, and came to be much talked of at 
 court, in consequence of Leibnitz having been privy 
 counsellor to the Elector of Hanover when that 
 prince ascended the throne of England. Many 
 persons of distinction, and particularly the Abbe 
 Conti, urged Newton to. reply to Leibnitz's letter, 
 but he resisted all their solicitations. One day, 
 however, King George I. inquired when Sir Isaac 
 Newton's answer to Leibnitz would appear; and 
 when Sir Isaac heard this, he addressed a long reply 
 to the Abbe Conti, dated February 26th, O. S. 1715- 
 16. This letter, written with dignified severity, is 
 a triumphant refutation of the allegations of his ad- 
 versary ; and the following passage deserves to be 
 quoted, as connected with that branch of the dispute 
 which relates to Leibnitz's having seen part of 
 Newton's letters to Mr. Collins. " He complains 
 of the committee of the Royal Society, as if they 
 had acted partially in omitting what made against 
 me ; but he fails in proving the accusation. For he 
 instances in a paragraph concerning my ignorance, 
 pretending that they omitted it, and yet you will 
 find it in the Commercium Epistolicum, p. 547, lines 
 2, 3, and I am not ashamed of it. He saith that he 
 saw this paragraph in the hands of Mr. Collins when 
 he was in London the second time, that is in Octo- 
 ber, 1676. It is in my letter of the 24th of October, 
 1676, and therefore he then saw that letter. And
 
 196 SIR ISAAC NEWTON. 
 
 in that and some other letters writ before that time, 
 I described my method of fluxions ; and hi the same 
 letter I described also two general methods of series, 
 one of which is now claimed from me by Mr. Leib- 
 nitz." The letter concludes with the following 
 paragraph : " But as he has lately attacked me with 
 an accusation which amounts to plagiary ; if he goes 
 on to accuse me, it lies upon him by the laws of all 
 nations to prove his accusations, on pain of being 
 accounted guilty of calumny. He hath hitherto 
 written letters to his correspondents full of affirma- 
 tions, complaints, and reflections, without proving 
 any thing. But he is the aggressor, and it lies upon 
 him to prove the charge." 
 
 In transmitting this letter to Leibnitz, the Abbe 
 Conti informed him that he himself had read with 
 great attention, and without the least prejudice, the 
 Commercium Epistolicum, and the little piece* that 
 contains the extract ; that he had also seen at the 
 Royal Society the original papers of the Commer- 
 cium Epistolicum, and some other original pieces 
 relating to it. " From all this," says he, " 1 infer, 
 that, if all the digressions are cut off, the only point 
 is, whether Sir Isaac Newton had the method of 
 fluxions or infinitesimals before you, or whether you 
 had it before him. You published it first, it is true, 
 but you have owned also that Sir Isaac Newton had 
 given many hints of it in his letters to Mr. Olden- 
 burg and others. This is proved very largely in the 
 Commercium, and in the extract of it. What an- 
 swer do you give? This is still wanting to the 
 public, in order to form an exact judgment of the 
 affair." The Abbe adds, that Mr. Leibnitz's own 
 friends waited for his answer with great impatience, 
 and that they thought he could not dispense with 
 answering, if not Dr. Keill, at least Sir Isaac New- 
 
 * This is the Recensio Commercii Fpistolici, or rev'.ew of it, which 
 *as first published in the Phil. Trans. 1715.
 
 GENERAL VIEW OF THE CONTROVERSY. 197 
 
 ton himself, who had given him a defiance in express 
 terms. 
 
 Leibnitz was not long in complying with this 
 request. He addressed a letter to the Abbe Conti, 
 dated April 9th, 1716, but he sent it through M. Ra- 
 mond at Paris, to communicate it to others. When 
 it was received by the Abbe Conti, Newton wrote 
 observations upon it, which were communicated 
 only to some of his friends, and which, while they 
 placed his defence on the most impregnable basis, 
 at the same time threw much light on the early his- 
 lory of his mathematical discoveries. 
 
 The death of Leibnitz on the 14th November, 
 1716, put an end to this controversy, and Newton 
 some time afterward published the correspondence 
 with the Abbe Conti, which had hitherto been only 
 privately circulated among the friends of the dispu- 
 tants.* 
 
 In 1722, a new edition of the Commercium Epis- 
 tolicum was published, and there was prefixed to it 
 a general review of its contents, which has been 
 falsely ascribed to Newton.f When the third edi- 
 
 * M. Biot remarks, that the animosity of Newton was not calmed by 
 the death of Leibnitz, for he had no sooner heard of it than he caused to 
 be printed two manuscript letters of Leibnitz, written in the preceding 
 year, accompanying them with a very bitter refutation (en les accom- 
 pagnant d'un refutation tres-amere). Who that reads this sentence 
 does not believe that the bitter refutation was written after Leibnitz's 
 death 1 The animosity could not be shown by the simple publication 
 of the letters. It could reside only in the bitterness of the refutation. 
 The implied charge is untrue ; the bitter refutation was written before 
 Leibnitz's death, and consequently he showed no animosity over the 
 grave of his rival ; and in our opinion none even before his death. 
 
 T M.Biot states that Sir Isaac Newton caused this edition of the 
 Commercium Epistolicum to be printed ; that Sir Isaac placed at the 
 head of it a p&rtial abstract of the collection ; and that this abstract 
 appeared to have been written by himself. These groundless charges 
 maybe placed, without any refutation, beside the assertion of Montucla, 
 that Newton wrote the notes (les notes) on the Commercium Epis- 
 tolicum ; and the equally incorrect statement of La Croix, th- 
 Newton added to it notes (des notes), with his own hand. We shout 
 not hive noticed the charges of M. Biot, had he not adduced them a 
 proofs of Newton's animosity to Leibnitz after his death. See Mr. 
 Herschel's History of Mathematics in the Edinburgh Encyclopaedia, 
 rol. xiii. p. 368, note.
 
 XX' 
 
 198 tflR ISAAC NEWTON. 
 
 tion of the Principia was published in 1725, the 
 celebrated scholium which we have already quoted, 
 and in which Leibnitz's differential calculus was 
 mentioned, was struck out either by Newton or by 
 the editor. This step was perhaps rash and ill- 
 advised ; but as the scholium had been adduced by 
 Leibnitz and others as a proof that Newton acknow- 
 ledged him to be an independent inventor of the 
 calculus, an interpretation which it does not bear, 
 and which Newton expressly states he never in- 
 tended it to bear, he was justified in withdrawing 
 a passage which had been so erroneously inter- 
 preted, and so greatly misapplied. 
 
 In viewing this controversy, at the distance of 
 more than a century, when the passions of the in- 
 dividual combatants have been allayed, and national 
 jealousies extinguished, it is not difficult to form a 
 correct estimate of the conduct and claims of the 
 two rival analysts. By the unanimous verdict of 
 all nations, it has been decided that Newton invented 
 fluxions at least ten years before Leibnitz. Some 
 of the letters of Newton which bore reference to 
 this great discovery were perused by the German 
 mathematician ; but there is no evidence whatever 
 that he borrowed his differential calculus from these 
 letters. Newton was therefore the first inventor, 
 and Leibnitz the second. It was impossible that the 
 former could have been a plagiarist; but il was 
 possible for the latter. Had the letters of Newton 
 contained even stronger indications than they do of 
 the new calculus, no evidence short of proof could 
 have justified any allegation against Leibnitz's 
 honour. The talents which he displayed in the im- 
 provement of the calculus showed that he was 
 capable of inventing it; and his character stood 
 sufficiently high to repel every suspicion of his in- 
 tegrity. But if it would have been criminal to 
 charge Leibnitz with plagiarism, what must we 
 think of those who dared to accuse Newton of bor
 
 GENERAL VIEW OF THE CONTROVERSY. 199 
 
 rowing his fluxions from Leibnitz! This odious 
 accusation was made by Leibnitz himself, and by 
 Bernouilli ; and we have seen that the former re- 
 peated it again and again, as if his own good name 
 rested on the destruction of that of his rival. It was 
 this charge against Newton that gave rise to the at- 
 tack of Keill, and the publication of the Commercium 
 Epistolicum; and, notwithstanding this high provo- 
 cation, the committee of the Royal Society contented 
 themselves with asserting Newton's priority, with- 
 out retorting the charge of plagiarism upon his rival. 
 
 Although an attempt has been recently made to 
 place the conduct of Leibnitz on the same level with 
 that of Newton, yet the circumstances of the case 
 will by no means justify such a comparison. The 
 conduct of Newton was at all times dignified and 
 just. He knew his rights, and he boldly claimed 
 them. Conscious of his integrity, he spurned with 
 indignation the charge of plagiarism with which an 
 ungenerous rival had so insidiously loaded him ; and 
 if there was one step in his frank and unhesitating 
 procedure which posterity can blame it is his omis- 
 sion, in the third edition of the Principia, of the 
 references to the differential calculus of Leibnitz. 
 This omission, however, was perfectly just. The 
 scholium which he had left out was a mere historical 
 statement of the fact, that the German mathemati- 
 cian had sent him a method which was the same as 
 his own ; and when he found that this simple asser- 
 tion had been held by Leibnitz and others as a re- 
 cognition of his independent claim to the invention, 
 he was bound either to omit it altogether, or to 
 enter into explanations which might have involved 
 him in a new controversy. 
 
 The conduct of Leibnitz was not marked with the 
 same noble lineaments. That he was the aggressor 
 is universally allowed. That he first dared to 
 breathe the charge of plagiarism against Newton, 
 and that he often referred to it, has been sufficiently
 
 200 SIR ISAAC NEWTON. 
 
 apparent; and when arguments failed him he had 
 recourse to threats declaring that he would publish 
 another Commercium Epistolicum, though he had 
 no appropriate letters to produce. All this is now 
 matter of hietory ; and we may find some apology 
 for it in his excited feelings, and in the insinuations 
 which were occasionally thrown out against the 
 originality of his discovery ; but for other parts of 
 his conduct we seek in vain for an excuse. When 
 he assailed the philosophy of Newton in his letters 
 to the Abbe Conti, he exhibited perhaps only the 
 petty feelings of a rival ; but when he dared to ca- 
 lumniate that great man in his correspondence with 
 the Princess of Wales, by whom he was respected 
 and beloved; when he ventured to represent the 
 Newtonian philosophy as physically false, and as 
 dangerous to religion ; and when he founded these 
 accusations on passages in the Principia and the 
 Optics glowing with all the fervour of genuine 
 piety, he cast a blot upon his name, which all his 
 talents as a philosopher, and all his virtues as a man, 
 will never be able to efface. 
 
 CHAPTER XIII. 
 
 James II. attacks the Privileges of the University of Cambridge New- 
 ton chosen one of the Delegates to resist this Encroachment He is 
 elected a Member of the Convention Parliament Burning of his 
 Manuscripts His supposed Derangement of Mind View taken of 
 this by foreign Philosophers His Correspondence with Mr. Pepys 
 and Mr. Locke at the time of his Illness Mr. Millington's Letter to 
 Mr. Pepys on the subject of Newton's nines s Refutation of the 
 Statement that he laboured under Mental Derangement. 
 
 FROM the year 1669, when Newton was installed 
 in the Lucasian chair, till 1695, when he ceased to 
 reside in Cambridge, he seems to have been seldom 
 absent from his college more than three or four
 
 UNIVERSITY OF CAMBRIDGE. 201 
 
 yeeks in the year. In 1675, he received a dispensa- 
 tion from Charles II. to continue in his fellowship 
 of Trinity College without taking orders, and we 
 have already seen in the preceding chapter how his 
 time was occupied till the publication of the Principia 
 in 1687. 
 
 An event now occurred which drew Newton from 
 the seclusion of his studies, and placed him upon the 
 theatre of public life. Desirous of re-establishing 
 the Catholic faith in its former supremacy, King 
 James II. had begun to assail the rights and privi- 
 leges of his Protestant subjects. Among other illegal 
 acts, he sent his letter of mandamus to the University 
 of Cambridge to order Father Francis, an ignorant 
 monk of the Benedictine order, to be received as 
 master of arts, and to enjoy all the privileges of this 
 degree, without taking the oaths of allegiance and 
 supremacy. The university speedily perceived the 
 consequences which might arise from such a meas- 
 ure. Independent of the infringement of their rights 
 which such an order involved, it was obvious that 
 the highest interests of the university were endan- 
 gered, and that Roman Catholics might soon become 
 a majority in the convocation. They therefore 
 unanimously refused to listen to the royal order, and 
 they did this with a firmness of purpose which irri- 
 tated the despotic court. The king reiterated his 
 commands, and accompanied them with the severest 
 threatenings in case of disobedience. The Catho- 
 lics were not idle in supporting the views of the 
 sovereign. The honorary degree of M.A. which 
 conveys no civil rights to its possessor, having been" 
 formerly given to the secretary of the ambassador 
 from Morocco, it was triumphantly urged that the 
 University of Cambridge had a greater regard for a 
 Mahometan than for a Roman Catholic, and was 
 more obsequious to the ambassador from Morocco 
 than to their own lawful sovereign. Though this 
 reasoning might impose upon the ignorant, it pro-
 
 202 SIR ISAAC NEWTCM. 
 
 duced little effect upon the members of the univer- 
 sity. A few weak-minded individuals, however, 
 were disposed to yield a reluctant consent to the 
 royal wishes. They proposed to confer the degree, 
 and at the same time to resolve that it should not in 
 future be regarded as a precedent. To this it was 
 replied, that the very act of submission in one case 
 would be a stronger argument for continuing the 
 practice than any such resolution would be against 
 its repetition. The university accordingly remained 
 firm in their original decision. The vice-chancellor 
 was summoned before the ecclesiastical commission 
 to answer for this act of contempt. Newton was 
 among the number of those who resisted the wishes 
 of the court, and he was consequently chosen one 
 of the nine delegates ivho were appointed to defend 
 the independence of the university. These dele- 
 gates appeared before the High Court. They main- 
 tained that not a single precedent could be found to 
 justify so extraordinary a measure ; and they showed 
 that Charles II. had, under similar circumstances, 
 been pleased to withdraw his mandamus. This 
 representation had its full weight, and the king was 
 induced to abandon his design.* 
 
 The part which Newton had taken in this affair, 
 and the high character which he now held in the 
 scientific world, induced his friends to propose him 
 as member of parliament for the university. He 
 was accordingly elected in 1688, though by a very 
 narrow majority,! and he sat in the Convention 
 Parliament till its dissolution. In the year 1688 
 and 1689, Newton was absent from Cambridge during 
 the greater part of the year, owing, we presume, to 
 his attendance in parliament; but it appears from 
 
 * See Burnet's History of his own Times, vol. i p. 697. Lond. 1724. 
 1 Tre other candidates were Sir Robert Sawyer and Mr. Finch, am 
 the votes stood thus. 
 
 Sir Robert Sawyer, 125 
 Mr. Newton, 122 
 
 Mr. Finch, 117
 
 BURNING OF HIS MANUSCRIPTS. 203 
 
 the books of the University that from 1690 to 1695 
 he was seldom absent, ami must therefore have 
 renounced his parliamentary duties. 
 
 During his stay in London he had no doubt expe- 
 rienced the unsuitableness of his income to the new 
 circumstances in which he was placed, and it is 
 probable that this was the cause of the limitation 
 of his residence to Cambridge. His income was 
 certainly very confined, and but little suited to the 
 generosity of his disposition. Demands were doubt- 
 less made upon it by some of his less wealthy rela- 
 tives ; and there is reason to think that he himself, 
 as well as his influential friends, had been looking 
 forward to some act of liberality on the part of the 
 government. 
 
 An event however occurred which will ever form 
 an epoch in his history ; and it is a singular circum- 
 stance, that this incident has been for more than a 
 century unknown to his own countrymen, and has 
 been accidentally brought to light by the examina- 
 tion of the manuscripts of Huygens. This event 
 has been magnified into a temporary aberration of 
 mind, which is said to have arisen from a cause 
 scarcely adequate to its production. 
 
 While he was attending divine service in a winter 
 morning, he had left in his study a favourite little 
 dog called Diamond. Upon returning from chapel 
 he found that it had overturned a lighted taper on 
 his desk, which set fire to several papers on which 
 he had recorded the results of some optical experi- 
 ments. These papers are said to have contained the 
 labours of many years, and it has been stated that 
 when Mr. Newton perceived the magnitude of his loss, 
 he exclaimed, " Oh, Diamond, Diamond, little do you 
 know the mischief you have done me!" It is a 
 curious circumstance that Newton never refers to 
 the experiments which he is said to have lost on this 
 occasion, and his nephew, Mr. Conduit, makes no 
 allusion to the event itself. The distress, however
 
 204 SIR ISAAC NEWTON. 
 
 which it occasioned is said to have been so deep ae 
 to affect even the powers of his understanding. 
 
 This extraordinary effect was first communicated 
 to the world in the Life of Newton by M. Biot, who 
 received the following account of it from the cele- 
 brated M. Van Swinden. 
 
 " There is among the manuscripts of the cele- 
 brated Huygens a small journal in folio, in which 
 he used to note down different occurrences. It is 
 
 side No. 8, p. 112, in the catalogue of the library 
 of Leyden. The following extract is written by 
 Huygens himself, with whose handwriting I am well 
 
 acquainted, having had occasion to peruse several 
 of his manuscripts and autograph letters. ' On the 
 29th May, 1694, M. Colin,* a Scotsman, informed me 
 that eighteen months ago the illustrious geometer, Isaac 
 Newton, had become insane, either in consequence of 
 his too intense application to his studies, or from ex- 
 cessive grief at having lost, by fire, his chymical labora- 
 tory and several manuscripts. When he came to the 
 Archbishop of Cambridge, he made some observations 
 which indicated an alienation of mind. He icas imme- 
 diately taken care of by his friends, who confined him to 
 his house and applied remedies, by means of which he 
 had now so far recovered his health that he began to under- 
 stand the PrincipiaS " Huygens mentioned this cir- 
 cumstance to Leibnitz, in a letter dated 8th June, 
 1694, to which Leibnitz replies in a letter dated the 
 23d, " I am very glad that I received information of 
 the cure of Mr.'Newton, at the same time that I first 
 heard of his illness, which doubtless must have been 
 
 * This M. Colin was probably a young bachelor of arts whom New 
 ton seems afterward to have employed in some of his calculations. 
 These bachelors were distinguished by the title of Dominus, and it. was 
 usual to translate this word and torall thorn Sir. In a letter from New- 
 ton to Flamstead, dated Cambridge, June 29th, 1695, is the following 
 passage : " I want not your calculations, but your observations only, for 
 besides myself and my servant, Sir Collins (whom I can employ for a 
 little money, which I value not) tells me that he can calculate 'an eclips* 
 and work truly.
 
 STATE OF HIS MINI). 205 
 
 very alarming. ' It is to men like you and him, sir, 
 that I wish a long life.' " 
 
 The first publication of the preceding statement 
 produced a strong sensation among the friends and 
 admirers of Newton. They could not easily believe 
 in the prostration of that intellectual strength whic^ 
 had unbarred the strongholds of the universe. The 
 unbroken equanimity of Newton's mind, the purity 
 of his moral character, his temperate and abstemious 
 life, his ardent and unaffected piety, and the weak- 
 ness of his imaginative powers, all indicated a mind 
 which was not likely to be overset by any affliction 
 to which it could be exposed. The loss of a few 
 experimental records could never have disturbed the 
 equilibrium of a mind like his. If they were the 
 records of discoveries, the discoveries themselves 
 indestructible would have been afterward given to 
 the world. If they were merely the details of ex- 
 perimental results, a little time could have easily 
 reproduced them. Had these records contained the 
 first fruits of early genius of obscure talent, on 
 which fame had not yet shed its rays, we might have 
 supposed that the first blight of such early ambition 
 would have unsettled the stability of an untried 
 mind. But Newton was satiated with fame. His 
 mightiest discoveries were completed and diffused 
 over all Europe, and he must have felt himself 
 placed on the loftiest pinnacle of earthly ambition. 
 The incredulity which such views could not fail to 
 encourage was increased by the novelty of the in 
 formation. No English biographer had ever alluded 
 to such an event. History and tradition were equally 
 silent, and it was not easy to believe that the Luca- 
 sian Professor of Mathematics at Cambridge, a mem- 
 ber of the English parliament, and the first philoso- 
 pher in Europe could have lost his reason without 
 the dreadful fact being known to his own countrymen. 
 
 But if the friends of Newton were surprised by 
 the nature of the intelligence, they were distressed 
 Q
 
 <06 SIR ISAAC NEWTON. 
 
 at the view which was taken of it by foreign philoso- 
 phers. While one maintained that the intellectual 
 exertions of Newton had terminated with the publica- 
 tion of the Principia, and that the derangement of 
 his mind was the cause of his abandoning the sci- 
 ences, others indirectly questioned the sincerity of 
 his religious views, and ascribed to the aberration 
 of his mind those theological pursuits which gilded 
 his declining age. " But the fact," says M. Biot, 
 " of the derangement of his intellect, whatever may 
 have been the cause of it, will explain why, after the 
 publication of the Principia in 1687, Newton, though 
 only forty-five years old, never more published a 
 new work on any branch of science, but contented 
 himself with giving to the world those which he had 
 composed long before that epoch, confining himself 
 to the completion of those parts which might require 
 development. We may also remark, that even 
 these developments appear always to be derived 
 from experiments and observations formerly made, 
 such as the additions to the second edition of the 
 Principia, published in 1713, the experiments on 
 thick plates, those on diffraction, and the chymical 
 queries placed at the end of the Optics in 1704 ; for 
 in giving an account of these experiments Newton 
 distinctly says that they were taken from ancient 
 manuscripts which he had formerly composed ; and 
 he adds, that though he felt the necessity of extend- 
 ing them, or rendering them more perfect, he was 
 not able to resolve to do this, these matters being no 
 longer in his way. Thus it appears that though he 
 had recovered his health sufficiently to understand 
 all his researches, and even in some cases to make 
 additions to them, and useful alterations, as appears 
 from the second edition of the Principia, for which 
 he kept up a very active mathematical correspond- 
 ence with Mr. Cotes, yet he did not wish to under- 
 take new labours in those departments of science 
 where he had done so much, and where he so dis-
 
 STATE OF HIS MIND. 207 
 
 tinctly saw what remained to be done." Under the 
 influence of the same opinion, M. Biot finds " it ex- 
 tremely probable that his dissertation on the scale 
 of heat was written before the fire in his laboratory;" 
 he describes Newton's conduct about the longitude 
 bill as " almost puerile on so solemn an occasion, 
 and one which might lead to the strangest conclu- 
 sions, particularly if we refer it to the fatal accident 
 which Newton had suffered in 1695." 
 
 The celebrated Marquis de la Place viewed the 
 illness of Newton in a light still more painful to his 
 friends. He maintained that he never recovered the 
 vigour of his intellect, and he was persuaded that 
 Newton's theological inquiries did not commence 
 till after that afflicting epoch of his life. He even 
 commissioned Professor Gautier of Geneva to make 
 inquiries on this subject during his visit to England, 
 as if it concerned the interests of truth and justice 
 to show that Newton became a Christian and a 
 theological writer only after the decay of his 
 strength and the eclipse of his reason. 
 
 Such having been the consequences of the dis- 
 closure of Newton's illness by the manuscript of 
 Huygens, I felt it to be a sacred duty to the memory 
 of that great man, to the feelings of his countrymen, 
 and to the interests of Christianity itself, to inquire 
 into the nature and history of that indisposition 
 which seems to have been so much misrepresented 
 and misapplied. From the ignorance of so extraor- 
 dinary an event which has prevailed for such a long 
 period in England, it might have been urged with 
 some plausibility that Huygens had mistaken the 
 real import of the information that was conveyed to 
 him ; or that the Scotchman from whom he received 
 it had propagated an idle and a groundless rumour. 
 But we are, fortunately, not confined to this very 
 reasonable mode of defence. There exists at Cam- 
 bridge a manuscript journal written by Mr. Abraham 
 de la Pryme, who was a student in the university
 
 208 SIR ISAAC NEWTON. 
 
 while Newton was a fellow of Trinity. This manu- 
 script is entitled " Epkemeris Vita, or Diary of my 
 own Life, containing an account likewise of the most 
 observable and remarkable things that 1 have taken 
 notice of from my youth up hitherto." Mr. de la 
 Pryme was born in 1671, and begins the diary in 
 1685. This manuscript is in the possession of his 
 collateral descendant, George Pryme, Esq., Profes- 
 sor of Political Economy at Cambridge, to whom I 
 have been indebted for the following extract. 
 
 " 1692, February 3d. What I heard to-day I must 
 relate. There is one Mr. Newton (whom I have 
 very oft seen), Fellow of Trinity College, that is 
 mighty famous for his learning, being a most excel- 
 lent mathematician, philosopher, divine, &c. He 
 has been Fellow of the Royal Society these many 
 years; and among other very learned books and 
 tracts, he's written one upon the mathematical prin- 
 ciples of philosophy, which has got him a mighty 
 name, he having received, especially from Scotland, 
 abundance of congratulatory letters for the same ; 
 but of all the books that he ever wrote, there was 
 one of colours and light, established upon thousands 
 of experiments which he had been twenty years of 
 making, and which had cost him many hundred of 
 pounds. This book, which he valued so much, and 
 which was so much talked of, had the ill luck to 
 perish and be utterly lost just when the learned 
 author was almost at putting a conclusion at the 
 same, after this manner: In a winter's morning, 
 leaving it among his other papers on his study table 
 while he went to chapel, the candle, which he had 
 unfortunately left burning there too, catched hold 
 by some means of other papers, and they fired the 
 aforesaid book, and utterly consumed it and several 
 other valuable writings ; and, which is most wonder- 
 ful, did no further mischief. But when Mr. Newton 
 came from chapel, and had seen what was done, 
 every one thought he would have run inad, he wa
 
 STATE OF HIS MIND. 209 
 
 so troubled thereat that he was not himself for a 
 month after. A long account of this his system of 
 lio-ht and colours you may find in the Transactions 
 of the Royal Society, which he had sent up to them 
 long before this sad mischance happened unto him." 
 
 From this extract we are enabled to fix the ap- 
 proximate date of the accident by which Newton 
 lost his papers. It must have been previous to the 
 3d January, 1692, a month before the date of the 
 extract ; but if we fix it by the dates in Huygens's 
 manuscript, we should place it about the 29th No 
 vember, 1692, eighteen months previous to the 
 conversation between Collins and Huygens. The 
 manner in which Mr. Pryme refers to Newton's 
 state of mind is that which is used every day when 
 we speak of the loss of tranquillity which arises 
 from the ordinary afflictions of life ; and the meaning 
 of the passage amounts to nothing more than that 
 Newton was very much troubled by the destruction 
 of his papers, and did not recover his serenity, and 
 return to his usual occupations, for a month. The 
 very phrase that " every person thought he would 
 have run mad" is in itself a proof that no such effect 
 was produced ; and, whatever degree of indisposi- 
 tion may be implied in the phrase "he was not 
 himself for a month after," we are entitled to infer 
 that one month was the period of its duration, and 
 that previous to the 3d February, 1692, the date of Mr. 
 Pryme's memorandum, "Newton was himself again." 
 
 These facts and dates cannot be reconciled with 
 those in Huygens's manuscript. It appears from 
 that document, that, so late as May, 1694, Newton 
 had only so far recovered his health as to begin 
 to again understand the Principia. His supposed 
 malady, therefore, was in force from the 3d of 
 January, 1692, till the month of May, 1694, a 
 period of more than two years. Now, it is a most 
 important circumstance, which M. Biot ought to 
 have known, that in the very middle of this period^
 
 210 SIR ISAAC NEWTON. 
 
 Newton wrote his four celebrated letters to Dr. 
 Bentley on the Existence of a Deity, letters which 
 evince a power of thought and a serenity of mind 
 absolutely incompatible even with the slightest ob- 
 scuration of his faculties. No man can peruse these 
 letters without the conviction that their author then 
 possessed the full vigour of his reason, and was 
 capable of understanding the most profound parts 
 of his writings. The first of these letters was writ- 
 ten on the 10th December, 1692, the second on the 
 17th January, 1693, the third on the 25th February, 
 and the 4th "on the llth* February, 1693. His mind 
 was, therefore, strong and vigorous on these four 
 occasions ; and as the letters were written at the 
 express request of Dr. Bentley, who had been ap- 
 pointed to deliver the lecture founded by Mr. Boyle 
 for vindicating the fundamental principles of natural 
 and revealed religion, we must consider such a re- 
 quest as showing his opinion of the strength and 
 freshness of his friend's mental powers. 
 
 In 1692, Newton, at the request of Dr. Wallis, 
 transmitted to him the first proposition of his book 
 on quadratures, with examples of it in first, second, 
 and third fluxions, f These examples were written 
 in consequence of an application from his friend; 
 and the author of the review of the Commercium 
 Epistolicum, in which this fact is quoted, draws the 
 conclusion, that he had not at that time forgotten 
 his method of second fluxions. It appears, also, 
 from the second book of the Optics,^ that in the 
 month of June, 1692, he had been occupied with the 
 subject of haloes, and had made accurate observations 
 both on the colours and the diameters of the rings 
 in. a halo which he had then seen around the sun. 
 
 * They are thus dated in Horsley's edition of Newton's Works, the 
 fourth letter having an earlier date than the third. 
 
 t See Newtoni Opera, torn. iv. p. 480, and Wallasii Opera, 1693, took 
 I p. 3&1-396. 
 
 J Optics, part iv. obs. 13.
 
 8TATB OF HIS MIND. 211 
 
 But though, these facts stand in direct contradic- 
 tion to the statement recorded by Huygens, the 
 reader will be naturally anxious to know the real 
 nature and extent of the indisposition to which it 
 refers. The following letters,* written by Newton 
 himself, Mr. Pepys, Secretary to the Admiralty, and 
 Mr. Millington of Magdalene College, Cambridge, 
 will throw much light upon the subject. 
 
 Newton, as will be presently seen, had fallen into 
 a bad state of health some time in 1692, in conse- 
 quence of which both his sleep and his appetite 
 were greatly affected. About the middle of Sep- 
 tember, 1693, he had been kept awake for five nights 
 by this nervous disorder, and in this condition he 
 wrote the following letter to Mr. Pepys : 
 
 " SIR, Sept. 13, 1693. 
 
 " Some time after Mr. Millington had delivered 
 your message, he pressed me to see you the next 
 time I went to London. I was averse ; but upon 
 his pressing consented, before I considered what I 
 did, for 1 am extremely troubled at the embroilment 
 I am in, and have neither ate nor slept well this 
 twelvemonth, nor have my former consistency of 
 mind. I never designed to get any thing by your 
 interest, nor by King James's favour, but am now 
 sensible that I must withdraw from your acquaint- 
 ance, and see neither you nor the rest of my friends 
 any more, if I may but leave them quietly. I beg 
 your pardon for saying I would see you again, and 
 rest your most humble and most obedient servant, 
 " I s . NEWTON." 
 
 From this letter we learn, on his own authority, 
 that his complaint had lasted for a twelvemonth, 
 and that during that twelvemonth he neither ate nor 
 slept well, nor enjoyed his former consistency of 
 
 * For these letters I have been indebted to the kindness of Lord Bray- 
 brooke.
 
 212 SIR ISAAC NEWTON 
 
 mind. It is not easy to understand exactly what is 
 meant by not enjoying his former consistency of 
 mind ; but whatever be its import, it is obvious that 
 he must have been in a state of mind so sound as to 
 enable him to compose the four letters to Bentley, 
 all of which were written during the twelvemonth 
 here referred to. 
 
 On *he receipt of this letter, his friend Mr. Pepys 
 seems to have written to Mr. Millington of Magda- 
 lene College to inquire after Mr. Newton's health ; 
 but the inquiry having been made in a vague man- 
 ner, an answer equally vague was returned. Mr. 
 Pepys, however, who seems to have been deeply 
 anxious about Newton's health, addressed the fol- 
 lowing more explicit letter to his friend Mr. Mil- 
 lington : 
 
 " SIR, Septemb. 26, 1693. 
 
 "After acknowledging your many old favours, 
 give me leave to do it a little more particularly upon 
 occasion of the new one conveyed to me by my 
 nephew Jackson. Though, at the same time, I 
 must acknowledge myself not at the ease I would 
 be glad to be at in reference to the excellent Mr. 
 Newton ; concerning whom (methinks) your answer 
 labours under the same kind of restraint wiiich (to 
 tell you the truth) my asking did. For I was loth 
 at first dash to tell you that I had lately received a 
 letter from him so surprising to me for the incon- 
 sistency of every part of it, as to be put into great 
 disorder by it, from the concernment I have for him, 
 lest it should arise from that which of all mankind I 
 should least dread from him and most lament for, I 
 mean a discomposure in head, or mind, or both. Let 
 me therefore beg you, sir, having now told you the true 
 ground of the trouble I lately gave you, to let me 
 know the very truth of the matter, as far at least as 
 comes within your knowledge. For I own too great 
 an esteem for Mr. Newton, as for a public good, to
 
 STATE OF HIS MIND. 213 
 
 be able to let any doubt in me of this kind concern- 
 ing him lie a moment uncleared, where I can nave 
 any hopes of helping it. I am, with great truth and 
 respect, dear sir, your most humble, and most af- 
 fectionate servant, 
 
 "S. PEPYS." 
 
 To this letter Mr. Millington made the following 
 reply : 
 
 Coll. Magd. Canib. 
 
 " HONOR'D SIR, Sept. the 30, 1693. 
 
 " Coming home from a journey on the 28th instant 
 at night, I met with your letter which you were 
 pleased to honour me with of the 26th. I am much 
 troubled I was not at home in time for the post, 
 that I might as soon as possible put you out of your 
 generous payne that you are in for the worthy Mi 
 Newton. I was, I must confess, very much surprised 
 at the inquiry you were pleased to make by your 
 nephew about the message that Mr. Newton made 
 the ground of his letter to you, for I was very sure 
 I never either received from you or delivered to him 
 any such, and therefore I went immediately to wayt 
 upon him, with a design to discourse him about the 
 matter, but, he was out of town, and since I have 
 not seen him, till upon the 28th I met him at Hunt- 
 ingdon, where, upon his own accord, and before I 
 had time to ask him any question, he told me that 
 he had writt to you a very odd letter, at which he 
 was much concerned ; added, that it was in a dis- 
 temper that much seized his head, and that kept him 
 awake for above five nights together, which upon 
 occasion he desired I would represent to you, and 
 beg your pardon, he being very much ashamed he 
 should be so rude to a person for whom he hath so 
 great an honour. He is now very well, and, though 
 I fear he is under some small degree of melancholy, 
 yet I think there is no reason to suspect, it hath afc 
 R
 
 214 SIR ISAAC NEWTON. 
 
 all touched his understanding, and I hope never will ; 
 ancl so I am sure all ought to wish that love learning 
 or the honour of our nation, which it is a sign how 
 much it is looked after, when such a person as Mr. New- 
 ton lyes so neglected by those in power. And thus, hon- 
 oured sir, I have made you acquainted with all I 
 know of the cause of such inconsistency's in the 
 letter of so excellent a person ; and I hope it will 
 remove the doubts and fears you are, with so much 
 compassion and publickness of spirit, pleased to 
 entertain about Mr. Newton ; but if I should have 
 been wanting in any thing tending to the more full 
 satisfaction, I shall, upon the least notice, endeav- 
 our to amend it with all gratitude and truth. 
 Honored sir, your most faithfull and most obedient 
 servant, 
 
 "JOH. MlLLINGTON." 
 
 Mr. Pepys was perfectly satisfied with this answer, 
 as appears from the following letter : 
 
 " SIR, October 3d, 1693. 
 
 " You have delivered me from a fear that indeed 
 gave me much trouble, and from my very heart I 
 thank you for it ; an evil to Mr. Newton being what 
 every good man must feel for his own sake as well 
 as his. God grant it may stopp here. And for the 
 kind reflection hee has since made upon his letter to 
 mee, I dare not take upon mee to judge what an- 
 swer I should make him to it, or whether any or no ; 
 and therefore pray that you will bee pleased either 
 to bestow on mee what directions you see fitt for 
 my own guidance towards him in it, or to say to 
 him in my name, but your own pleasure, whatever 
 you think may be most welcome to him upon it, 
 and most expressive of my regard and affectionate es- 
 teem of him, and concernment for him. * 
 * * * Dear sir, youi 
 
 most humble and most faithful servant, 
 
 " S. PEPYS."
 
 CORRESPONDENCE WITH LOCKE. 215 
 
 It does not appear from the memoirs of Mr 
 Pepys whether he ever returned any answer to the 
 letter of Mr. Newton which occasioned this corres- 
 pondence ; but we find that in less than two months 
 aftei the date of the preceding letter, an oppor- 
 tunity occurred of introducing to him a Mr. Smith, 
 who wished to have his opinion on some pfbblem in 
 the doctrine of chances. This letter from Pepys is 
 dated November 22d, 1693. Sir Isaac replied to it 
 on the 26th November, and wrote to Pepys again 
 on the 16th December, 1693; and in both these 
 letters he enters fully into the discussion of the 
 mathematical question which had been submitted to 
 his judgment.* 
 
 It is obvious, from Newton's letter to Mr. Pepys, 
 that the subject of his receiving some favour from 
 the government had been a matter of anxiety with 
 himself, and of discussion among his friends. f Mr. 
 Millington was no doubt referring to this anxiety, 
 when he represents Newton as an honour to the 
 nation, and expresses his surprise " that such a per- 
 son should lye so neglected by those in power." And 
 we find the same subject distinctly referred to in 
 two letters written to Mr. Locke during the pre- 
 ceding year. In one of these, dated January 26th, 
 1691-2, he says, " Being fully convinced that Mr. 
 Montague, upon an old grudge which I thought had 
 been worn out, is false to me, I have done with him, 
 and intend to sit still, unless my Lord Monmouth be 
 still my friend." Mr. Locke seems to have assured 
 him of the continued friendship of this nobleman, 
 and Mr. Newton, still referring to the same topic, 
 in a letter dated February 16th, 1691-2, remarks, 
 
 * These three letters have been published by Lord Braybrooke in the 
 Life and Correspondence of Mr. Pepys. 
 
 t This anxiety will be understood from the fact that, by an order of 
 council dated January 28th, 1674-5, Mr. Newton was excused from 
 making the usual payments of one shilling per week, "on account of hi* 
 low circumstances, as he representpd "
 
 216 SIR ISAAC NEWTON. 
 
 ** I am very glad Lord MonmoutTi is still my friend, 
 but intend not to give his lordship and you any far- 
 ther trouble. My inclinations are to sit still." In 
 a later letter to Mr. Locke, dated September, 1693, 
 and given below, he asks his pardon for saying or 
 thinking % that there was a design to sell him an 
 office. In these letters Mr. Newton no doubt re- 
 ferred to some appointment in London which he was 
 solicitous to obtain, and which Mr. Montague and 
 his other friends may have failed in procuring. 
 This opinion is confirmed by the letter of Mr. Mon- 
 tague announcing to him his appointment to the 
 wardenship of the mint, in which he says that he is 
 very glad he can at last give him good proof of his 
 friendship. 
 
 In the same month in which Newton wrote to Mr. 
 Pepys, we find him in correspondence with Mr. 
 Locke. Displeased with his opinions respecting 
 innate ideas, he had rashly stated that they struck 
 at the root of all morality ; and that he regarded 
 the author of such doctrines as a Hobbist. Upon 
 reconsidering these opinions, he addressed the fol- 
 lowing remarkable letter to Locke, written three 
 days after m his letter to Mr. Pepys, and conse- 
 quently during the illness under which he then 
 laboured. 
 
 " SIR, 
 
 " Being of opinion that you endeavoured to em- 
 broil me with w^omen, and by other means, I was so 
 much affected with it, as that when one told me you 
 were sickly and would not live, I answered, 'twere 
 better if you were dead. I desire you to forgive me 
 this uncharitableness ; for I am now satisfied that 
 what you have done is just, and I beg your pardon 
 for my having hard thoughts of you for it, and for 
 representing that you struck at the root of morality, 
 in a principle you laid in your book of ideas, and 
 designed to pursue in another book, and that 1 took
 
 CORRESPONDENCE WITH LOCKE. 217 
 
 you for a Hobbist.* I beg your pardon also fa- 
 saying or thinking that there was a design to sell m 
 an office, or to embroil me. I am your most hu** 
 ble and unfortunate servant, 
 
 " I s . NEWTON. 
 
 " 4.t the Bull, in Shoreditch, London, 
 Sept. IQth, 1693." 
 
 To this letter Locke returned the following an- 
 swer, so nobly distinguished by philosophical mag- 
 nanimity and Christian charity : 
 
 " SIR, Gates, Oct. 5th, 1693. 
 
 " I have been, ever since I first knew you, so en 
 tirely and sincerely your friend, and thought you so 
 much mine, that I could not have believed what you 
 tell me of yourself had I had it from anybody else. 
 And, though I cannot but be mightily troubled that 
 you should have had so many wrong and unjust 
 thoughts of me, yet next to the return of good 
 offices, such as from a sincere good-will I have ever 
 done you, I receive your acknowledgment of the 
 contrary as the kindest thing you have done me, 
 since it gives me hopes I have not lost a friend I so 
 much valued. After what your letter expresses, I 
 shall not need to say any thing to justify myself to 
 you. I shall always think your own reflection on 
 my carriage, both to you and all mankind, will suffi 
 ciently do that. Instead of that, give me leave to 
 assure you that I am more ready to forgive you than 
 you can be to desire it; and I do it so freely and fully, 
 that I wish for nothing more than the opportunity 
 to convince you that I truly love and esteem you, 
 and that I have the same good-will for you as if 
 
 * The system of Hobbes was at this time very prevalent. According 
 M Dr. Bentiey, " the taverns and coffee-houses, nay, Westminster Hall 
 and the very churches, were full of it ;" and he was convinced from 
 personal observation, that " not one English infidel in a hundred was 
 other than a Hobbist." Monkte Life of Bentiey, p. 31;
 
 218 SIR ISAAC NEWTON. 
 
 nothing of this had happened. To confirm this to 
 you more fully, I should be glad to meet you any 
 where, and the rather, because the conclusion of 
 your letter makes me apprehend it would not be 
 wholly useless to you. But whether you think it 
 fit or not, I leave wholly to you. I shall always be 
 ready to serve you to "my utmost, hi any way you 
 shall like, and shall only need your commands or 
 permission to do it. 
 
 " My book is going to press for a second edition ; 
 . and, though I can answer for the design with which 
 I write it, yet, since you have so opportunely given 
 me notice of what you have said of it, I should take 
 it as a favour if you would point out to me the 
 places that gave occasion to that censure, that, by 
 explaining myself better, I may avoid being mis- 
 taken by others, or unawares doing the least preju- 
 dice to truth or virtue. I am sure you are so much 
 a friend to them both, that, were you none to me, I 
 could expect this from you. But I cannot doubt but 
 you would do a great deal more than this for my 
 sake, who, after all, have all the concern of a friend 
 for you, wish you extremely well, and am, without 
 compliment, &c."* 
 
 To this letter Newton made the following reply: 
 
 " SIR, 
 
 " The last winter, by sleeping too often by my 
 fire, I got an ill habit of sleeping ; and a distemper, 
 which this summer has been epidemical, put me 
 farther out of order, so that when I wrote to you, I 
 had not slept an hour a night for a fortnight together, 
 and for five days together not a wink. 1 remember. 
 I wrote to you, but what I said of your book I re- 
 member not. If you please to send me a transcript 
 
 * Tht draft of this letter is endorsed " J. L. to I. Newton."
 
 CORRESPONDENCE WITH LOCKE. 219 
 
 of that passage, I will give you an account of it if I 
 can. I am your most humble servant, 
 
 " I s - NEWTON. 
 " Cambridge, Oct. 5th, 1693." 
 
 Although the first of these letters evinces the 
 existence of a nervous irritability which could not 
 fail to arise from want of appetite and of rest, yet it 
 is obvious that its author was in the full possession 
 of his mental powers. The answer of Mr. Locke, 
 indeed, is written upon that supposition ; and it de- 
 serves to be remarked, that Mr. Dugald Stewart, 
 who first published a portion of these letters, never 
 imagines for a moment that Newton was labouring 
 under any mental alienation. 
 
 The opinion entertained by Laplace, that Newton 
 devoted his attention to theology only in the latter 
 part of his life, may be considered as deriving some 
 countenance from the fact, that the celebrated gene- 
 ral scholium at the end of the second edition of the 
 Principia, published in 1713, did not appear in the 
 first edition of that work. This argument has been 
 ably controverted by Dr. J. C. Gregory of Edinburgh, 
 on the authority of a manuscript of Newton, which 
 seems to have been transmitted to his ancestor, Dr. 
 David Gregory, between the years 1687 and 1698. 
 This manuscript, which consists of twelve folio 
 pages in Newton's handwriting, contains, in the 
 form of additions and scholia to some propositions 
 in the third book of the Principia, an account of the 
 opinions of the ancient philosophers on gravitation 
 and motion, and on natural theology, with various 
 quotations from their works. Attached to this 
 manuscript are three very curious paragraphs. The 
 first two appear to have been the original draught 
 of the general scholium already referred to ; and 
 the third relates to the subject of an ethereal me- 
 dium, respecting which he maintains an opinion 
 diametrically opposite to that which he afterward
 
 220 SIR ISAAC NEWTON. 
 
 published at the end of his Optics.* The first para- 
 graph expresses nearly the same ideas as some 
 sentences in the scholium beginning " Deus summus 
 est ens aeternum, infinitum, absolute perfectum ;"| 
 and it is remarkable that the second paragraph is 
 found only in the third edition of the Principia, 
 which appeared in 1726, the year before Newton's 
 death. 
 
 In the middle of the year 1694, about the time 
 when our author is said to be beginning to under- 
 stand the Principia, we find him occupied with the 
 difficult and profound subject of the lunar theory. 
 In order to procure observations for verifying the 
 equations which he had deduced from the theory of 
 gravity, he paid a visit to Flamstead, at the Royal 
 Observatory of Greenwich, on the 1st September, 
 1694, when he received from him a series of lunar 
 observations. On. the 7th of October he wrote to 
 Flamstead that he had compared the observations 
 with his theory, and had satisfied himself that by 
 both together " the moon's theory may be reduced 
 to a good degree of exactness, perhaps to the exact- 
 ness of two or three minutes." He wrote him again 
 on the 24th October, and the correspondence was 
 continued till 1698, Newton making constant appli- 
 cation for observations to compare with his theory 
 
 * Dr. Gregory concludes his account of this manuscript, which he has 
 kindly permitted me to read, in the following words : " I do not know 
 whether it is true, as stated by Huygens, 'Newtonian incidisse in Phre- 
 nitim ;' but I think every gentleman who examines this manuscript will 
 be of opinion that he must have thoroughly recovered from his phrenitia 
 before he wrote either the Commentary on the Opinions of the Ancients, 
 or the Sketch of his own Theological and Philosophical Opinions which 
 it contains." 
 
 t This paragraph is as follows: " Deum esse ens summe perfectum 
 concedunt omnes. Entis autem summe perfecti Idea est ut sit substan- 
 tia, una, simplex, indivisibilis, viva et vivifica, unique semper necessario 
 existens, summe inteMigens omnia, libere volens bona, voluutate efficiens 
 possibilia, effectibus nobilioribus similitudinem propriam quantum fieri 
 potcst coramunicans, omnia in se continens tanquam eorum principiunj 
 et locus, omnia per presentiam substantialem cernens et regens, et cum 
 rebus omnibus, secundum leges accuratas ut naturae totius fundamen 
 turn et causa constanter co-operans, nisi ubi aliter agere bonum eat *
 
 CORRESPONDENCE WITH FLAMSTEAD. 221 
 
 of the planetary motions ; while Flamstead, riot suffi- 
 ciently aAvare of the importance of the inquiry, re- 
 ceived his requests as if they were idle intrusions in 
 which the interests of science were but slightly con- 
 cerned.* 
 
 In reviewing the details which we have now given 
 respecting the health and occupations of Newton 
 from the beginning of 1692 till 1695, it is impossible 
 to draw any other conclusion than that he possessed 
 a sound mind, and was perfectly capable of carrying 
 on his mathematical, his metaphysical, and his astro- 
 nomical inquiries. His friend and admirer, Mr. 
 Pepys, residing within fifty miles of Cambridge, had 
 never heard of his being attacked with any illness 
 till he inferred it from the letter to himself written 
 in September, 1693. Mr. Millington, who lived in 
 the same university, had been equally unacquainted 
 with any such attack, and, after a personal inter- 
 view with Newton, for the express purpose of ascer- 
 taining the state of his health, he assures Mr. Pepys 
 "that he is very well, that he fears he is under 
 some small degree of melancholy, but that there is 
 
 * The following extract, characteristic of Flamstead's manner, is from 
 a letter to Newton dated January 6, 1698-9. 
 
 " Upon hearing occasionally that you had sent a letter to Dr. Wallis 
 about the parallax of the fixed stars to be printed, and that you had men- 
 tioned me therein with respect to the theory of the moon, I was con- 
 cerned to be publicly brought upon the state about what, perhaps, will 
 never be fitted for the public, and thereby the world put into an expecta 
 tion of what perhaps they are never likely to have. I do not luve to be 
 printed upon every occasion, much less to be dunned and teased by 
 foreigners about mathematical things, or to be thought by your own people 
 to be trifling away my time when I should be about the king's business." 
 On the first of the above passages in italics Flamstead has the follow- 
 ing memorandum: *' When Mr. Halley boasts 'tis done, and given to 
 him as a secret, tells the Society so and foreigners.' In the second pas- 
 sage in italics, Mr. Flamstead refers, in a note, to Mr. Colson's letter to 
 him, in which he seems to have represented practical astronomy as 
 trifling. Mr. Flamstead adds, " Was Mr. Newton a trifler when he read 
 mathematics for a salary at Cambridge : surely, then, astronomy is of 
 some good use, though his place be more beneficial." For these extracts 
 from the original manuscript in the collection of Corpus Christi College, 
 Oxford, I have been indebted to the kindness of Professor Rigaud of 
 Oxford.
 
 222 SIR ISAAC NEWTON. 
 
 no reason to suspect that it hath at all touched his 
 understanding." 
 
 During this period of bodily indisposition, his 
 mind, though in a state of nervous irritability, and 
 disturbed by want of rest, was capable of putting 
 forth its highest powers. At the request of Dr. 
 Wallis he drew up an example of one of his pro- 
 positions on the quadrature of curves in second 
 fluxions. He composed, at the desire of Dr. Bentley, 
 his profound and beautiful letters on the existence 
 of the Deity. He was requested by Locke to re- 
 consider his opinions on the subject of innate ideas ; 
 and we find him grappling with the difficulties of the 
 lunar theory. 
 
 But with all these proofs of vigorous mind, a 
 diminution of his mental powers has been rashly 
 inferred from the cessation of his great discoveries, 
 and from his unwillingness to enter upon new in- 
 vestigations. The facts, however, here assumed 
 are as incorrect as the inference which is drawn 
 from them. The ambition of fame is a youthful 
 passion, which is softened, if not subdued,' by age. 
 Success diminishes its ardour, and early pre-emi- 
 nence often extinguishes it. Before the middle 
 period of life Newton was invested with all the 
 insignia of immortality ; but endowed with a native 
 humility of mind, and animated with those hopes 
 which teach us to form an humble estimate of human 
 greatness, he was satisfied with the laurels which 
 he had won, and he sought only to perfect and com- 
 plete his labours. His mind was principally bent on 
 the improvement of the Principia ; but he occasion- 
 ally diverged into new fields of scientific research, 
 he solved problems of great difficulty which had 
 been proposed to try his strength, and he devoted 
 much of his time to profound inquiries in chronology 
 and in theological literature. 
 
 The powers of his mind were therefore in full 
 requisition; and, when we consider that he was
 
 MERITS NEGLECTED. 223 
 
 called to the discharge of high official functions 
 which forced him into public life, and compelled 
 him to direct his genius into new channels, we can 
 scarcely be surprised that he ceased to produce any 
 original works on abstract science. In the direc- 
 tion of the affairs of the mint, and of the Royal So- 
 ciety, to which we shall now follow him, he found 
 ample occupation for his time ; while the leisure of 
 his declining years was devoted to those exalted 
 studies in which philosophy yields to the supremacy 
 of faith, and hope administers to the aspirations of 
 genius. 
 
 CHAPTER XIV. 
 
 No Mark of National Gratitude conferred upon Newton Friendship 
 between him and Charles Montague, afterward Earl of Halifax Mr 
 Montague appointed Chancellor of the Exchequer in 1694 He resolves 
 upon a Recoinage Nominates Mr. Newton Warden of the Mint in 
 1695 Mr. Newton appointed Master of the Mint, in 1699 Notice of 
 the Earl of Halifax Mr. Newton elected Associate of the Academy 
 of Sciences in 1699 Member for Cambridge in 1701 and President 
 of the Royal Society in 1703 Queen Anne confers upon him the 
 Honour of Knighthood in 1705 Second Edition of the Principia, 
 edited by' Cotes His Conduct respecting Mr. Dittoris Method of find- 
 ing the Longitude. 
 
 HITHERTO we have viewed Newton chiefly as a 
 philosopher leading a life of seclusion within the 
 walls of a college, and either engaged in the duties 
 of his professorship, or ardently occupied in mathe- 
 matical and scientific inquiries. He had now reached 
 the fifty-third year of his age, and while those of his 
 own standing at the university had been receiving 
 high appointments in the church, or lucrative offices 
 in the state, he still remained without any mark of 
 the respect or gratitude of his country. All Europe 
 indeed had been offering incense to his name, and
 
 224 SIR ISAAC NEWTON. 
 
 Englishmen themselves boasted of him as the pride 
 of their country and the ornament of their species, 
 but he was left in comparative poverty,* with no 
 other income than the salary of his professorship, 
 eked out with the small rental of his paternal in- 
 heritance. Such disregard of the highest genius, 
 dignified by the highest virtue, could have taken 
 place only in England, and we should have ascribed 
 it to the turbulence of the age in which he lived 
 had we not seen, in the history of another century, 
 that the successive governments which preside over 
 the destinies of our country have never been able 
 either to feel or to recognise the true nobility of 
 genius. 
 
 Among his friends at Cambridge Newton had the 
 honour of numbering Charles Montague, grandson 
 of Henry Earl of Manchester, a young man of high 
 promise, and every way worthy of his friendship. 
 Though devoted to literary pursuits, and twenty 
 years younger than Newton, he cherished for the 
 philosopher all the veneration of a disciple, and his 
 affection for him gathered new strength as he rose 
 to the highest honours and offices of the state. In 
 the year 1684 we find him co-operating with Newton 
 in the establishment of a philosophical society at 
 Cambridge ; but though both of them had made per- 
 sonal application to different individuals to become 
 members, yet the plan failed, from the want, as 
 Newton expresses it, of persons willing to try ex- 
 periments. 
 
 Mr. Montague sat along with Newton in the con- 
 vention parliament, and such were the powers which 
 he displayed in that assembly as a public speaker, 
 that he was appointed a commissioner of the treasury, 
 and soon afterward a privy counsellor. In these 
 situations his talents and "knowledge of business 
 were highly conspicuous, and in 1694 he was ap- 
 
 * See page 215, note.
 
 WARDEN OF THE MINT. 225 
 
 pointed chancellor of the exchequer. The current 
 coin of the nation having been adulterated and de- 
 based, one of his earliest designs was to recoin it 
 and restore it to its intrinsic value. This scheme, 
 however, met with great opposition. It was char- 
 acterized as a wild project, unsuitable to a period 
 of war, as highly injurious to the interests of com- 
 merce, and as likely to sap the foundation of the 
 government. But he had weighed the subject too 
 deeply, and had intrenched himself behind opinions 
 too impartial and too well-founded, to be driven from 
 a measure which the best interests of his country 
 seemed to require. 
 
 The persons whom Mr. Montague had consulted 
 about the recoinage were Newton, Locke, and Hal- 
 ley, and in consequence of Mr. Overton, the warden 
 of the mint, having been appointed a commissioner 
 of customs, he embraced the opportunity which was 
 thus offered of serving his friend and his country by 
 recommending Newton to that important office. 
 The notice of this appointment was conveyed in the 
 following letter to Newton. 
 
 " SIR, London, 19 th March, 1695. 
 
 " I am very glad that, at last, I can give you a 
 good proof of my friendship, and the esteem the 
 king has of your merits. Mr. Overton, the warden 
 of the mint, is made one of the commissioners of 
 the customs, and the king has promised me to make 
 Mr. Newton warden of the mint. The office is the 
 most proper for you. 'Tis the chief office in the mint, 
 'tis worth five or six hundred pounds per annum, and 
 has not too much business to require more attendance 
 than you can spare. I desire that you will come up 
 as soon as you can, and I will take care of your 
 warrant in the mean time. Let me see you as soon 
 as you come to town, that I may carry you to kiss 
 the king's hand. I believe you may have a lodging 
 near me. I am, &c. CHARLES MONTAGUE."
 
 226 SIR ISAAC NEWTON. 
 
 Iii this new situation the mathematical and chy- 
 mical knowledge of our author was of great service 
 to the nation, and he became eminently useful in 
 carrying on the recoinage, which was completed in 
 the short space of two years. In the year 1699, he 
 was promoted to the mastership of the mint, an 
 office which was worth twelve or fifteen hundred 
 pounds per annum, and which he held during the 
 remainder of his life. In this situation he wrote an 
 official report on the Coinage, which has been pub- 
 lished ; and he drew up a table of Assays of Foreign 
 Coins, which is printed at the end of Dr. Arbuthnot's 
 Tables of Ancient Coins, Weights, and Measures, 
 which appeared in 1727. 
 
 While our author filled the inferior office of warden 
 of the mint, he retained his professorship at Cam- 
 bridge ; but upon his promotion in 1699, he appointed 
 Mr. Whiston to be his deputy, with all the emolu- 
 ments of the office ; and when he resigned the chaii 
 in 1703, he succeeded in getting him nominated his 
 successor. 
 
 The appointment of Newton to the mastership of 
 the mint must have been peculiarly gratifying to 
 the Royal Society, and it was probably from a feel- 
 ing of gratitude to Mr. Montague, as much as from 
 a regard for his talents, that this able statesman was 
 elected president of that learned body on the 30th 
 November, 1695. This office he held for three 
 years, and on the 30th January, 1697, Newton had 
 the satisfaction of addressing to Mm his solution of 
 the celebrated problems proposed by John Bernouilli 
 
 This accomplished nobleman was created Earl of 
 Halifax in 1700, and after the death of his first wifa 
 he conceived a strong attachment for Mrs. Catharine 
 Barton, the widow of Colonel Barton, and the niece 
 of Newton. This lady was young, gay, and beau- 
 tiful, and though she did not escape the censures of 
 her contemporaries, she was regarded by those who 
 knew her as a woman of strict honour and virtue.
 
 PRESIDENT OF THE ROYAL SOCIETY. 227 
 
 We are not acquainted with the causes which pre- 
 vented her union with the Earl of Halifax, but so 
 great was the esteem and affection which he bore 
 her, that in the will in which he left 100Z. to Mr. 
 Newton, he bequeathed to his niece a very large 
 portion of his fortune. This distinguished states- 
 man died in 1715, in the fifty-fourth year of his age. 
 Himself a poet and an elegant writer, he was the 
 liberal patron of genius, and he numbered among 
 his intimate friends Congreve, Halley, Prior, Tickell, 
 Steele, and Pope. His conduct to Newton will be 
 for ever remembered in the annals of science. The 
 sages of every nation and of every age will pronounce 
 with affection the name of Charles Montague, and 
 the persecuted science of England will continue to 
 deplore that he was the first and the last English 
 minister who honoured genius by his friendship and 
 rewarded it by his patronage. 
 
 The elevation of Mr. Newton to the highest offices 
 in the mint was followed by other marks of honour. 
 The Royal Academy of Sciences at Paris having 
 been empowered by a new charter granted in 1699, 
 to admit a very small number of foreign associates, 
 Newton was elected a member of that distinguished 
 body. In the year 1701, on the assembling of a new 
 parliament, he was re-elected one of the members 
 for the University of Cambridge.* In 1703 he was 
 chosen President of the Royal Society of London, 
 aiK he was annually re-elected to this office during 
 the remaining twenty-five years of his life. On the 
 16th of April, 1705, when Queen Anne was living at 
 the royal residence of Newmarket, she went with 
 Prince George of Denmark and the rest of the court 
 to visit the University of Cambridge. After the 
 meeting of the Regia Consilia, her majesty held a 
 
 * The candidates in 1701 were as follows ; 
 
 Mr. Henry Boyle, afterward Lord Carleton, 180 > Both of Trinity 
 Mr. Newton . . . ... 161 I College. 
 
 Mr. Hammond .... 64
 
 228 SIR^ ISAAC NEWTON. 
 
 court at Trinity Lodge, the residence of Dr. Bent 
 then master of Trinity ; where the honour of knight- 
 hood was conferred upon Mr. Newton, Mr. John Ellis, 
 the vice-chancellor, and Mr. James Montague, the 
 university counsel.* 
 
 On the dissolution of the parliament, which took 
 place in 1705, Sir Isaac was again a candidate for 
 the representation of the University, but notwith- 
 standing the recent expression of the royal favour, 
 he lost his election by a very great majority.! 
 This singular result was perhaps owing to the loss 
 of that personal influence which his residence in the 
 university could not fail to command, though it is 
 more probable that the ministry preferred the candi- 
 dates of a more obsequious character, and that the 
 electors looked for advantages which Sir Isaac New 
 ton was not able to obtain for them. 
 
 Although the first edition of the Principiahad been 
 for some time sold off, and copies of it had become 
 extremely rare, yet Sir Isaac's attention was so 
 much occupied with his professional avocations that 
 he could not find leisure for preparing a new edition. 
 Dr. Bentley, who had repeatedly urged him to this 
 task, at last succeeded, by engaging Roger Cotes, 
 Plumian Professor of Astronomy at Cambridge, to 
 superintend its publication at the university press. 
 In June, 1709, Sir Isaac committed this important 
 trust to his young friend; and about the middle of 
 July he promised to send him in the course of a fort- 
 night his own revised copy of the work. Business, 
 however, seems to have intervened, and Mr. Cotes 
 was obliged to remind Sir Isaac of his promise, which 
 he did in the following letter : 
 
 * The banquet which was on this occasion given in the college hU 
 to the royal visiter seems to have cost about 1000Z., and the university 
 was obliged to borrow 500/., to defray the expense of it. Monk's Ltf 
 of Bentley, p. 143, 144. 
 
 t The candidates in 1705 were as follows : 
 
 The Hon. Arthur Annesley 182 
 Hon. Dixie Windsor . 170 
 Mr. Godolphin . . .162 
 Sir Isaac Newton 117
 
 SECOND EDITION OF THE PRINCIPIA. 229 
 
 " SIR, Cambridge, Aug. 18th, 1709. 
 
 " The earnest desire I have to see a new edition 
 of your Principia makes me somewhat impatient 
 till we receive your copy of it, which you were 
 pleased to promise me about the middle of last month 
 you would send down in about a fortnight's time. 
 5 hope you will pardon me for this uneasiness^ from 
 which I cannot free myself, and for giving you this 
 trouble to let you know it. I have been so much 
 obliged by yourself and by your book, that (I desire 
 you to believe me) I think myself bound in gratitude 
 to take all the care I possibly can that it shall be 
 correct. Your obliged servant, 
 
 " ROGER COTES. 
 
 " For Sir Isaac Newton, at his house in 
 
 Jermyn-street, near St. Jameses 
 
 Church, Westminster." 
 
 This was the first letter of that celebrated corres- 
 pondence, consisting of nearly three hundred letters, 
 in which Sir Isaac and Mr. Cotes discussed the various 
 improvements which were thought necessary in a 
 new edition of the Principia. This valuable collec- 
 tion of letters is preserved in the library of Trinity 
 College ; and we cannot refrain from repeating the 
 wish expressed by Dr. Monk, " that one of the many 
 accomplished Newtonians who are resident in that 
 society would favour the world by publishing the 
 whole collection." 
 
 When the work was at last printed, Mr. Cotes ex- 
 pressed a wish that Dr. Bentley should write the pre- 
 face to it, but it was the opinion both of Sir Isaac 
 and Dr. Bentley that the preface should come from 
 the pen of Mr. Cotes himself. This he accordingly 
 undertook; but previous to its execution he ad- 
 dressed the following letter to Dr. Bentley, in order 
 to learn from Sir Isaac the particular view with 
 which it should be written* 
 S
 
 230 SIR ISAAC NEWTON. 
 
 "SiR, March 10M, 1712-13. 
 
 " I received what you wrote to me in Sir Isaac's 
 letter. I will set about the index in a day or two. 
 As for the preface, I should be glad to know from 
 Sir Isaac with what view he thinks proper to have 
 it written. You know the book has been received 
 abroad with some disadvantage, and the cause of it 
 may be easily guessed at. The Commercium Episto- 
 licum, lately published by order of the Royal Society, 
 gives such indubitable proofs of Mr. Leibnitz's want of 
 candour, that I shall not scruple in the least to speak 
 out the full truth of the matter, if it be thought 
 convenient. There are some pieces of his looking 
 this way which deserve a censure, as his Tentamen 
 de motuum ccdestium causis. If Sir Isaac is willing 
 that something of this nature may be done, I should 
 be glad if, while I am making the index, he would 
 consider of it, and put down a few notes of what he 
 thinks most material to be insisted on. This I say 
 upon supposition that I write the preface myself. 
 But I think it will be much more advisable that you, 
 or he, or both of you should write it while you are 
 in town. You may depend upon it I will own it, 
 and defend it as well as I can, if hereafter there be 
 occasion. I am sir, &c." 
 
 We are not acquainted with the instructions which 
 were given to Mr. Cotes in consequence of this ap- 
 plication; but it appears from the preface itself, 
 which contains a long and able summary of the New- 
 tonian philosophy, that Sir Isaac had prohibited any 
 personal reference to the conduct of Leibnitz. 
 
 The general preface is dated 12th May, 1713, and 
 in a subsidiary preface of only a few lines, dated 
 March s*8th, 1713, Sir Isaac mentions the leading 
 alterations which had been made in this edition 
 The determination of the forces by which bodies 
 may revolve in given orbits was simplified and en- 
 larged. The theory of the resistance of fluids was
 
 LONGITUDE AT SEA. 231 
 
 more accurately investigated, and confirmed by new 
 experiments. The theory of the moon and the pre- 
 cession of the equinoxes were more fully deduced 
 from their principles ; and the theory of comets was 
 confirmed by several examples of their orbits more 
 accurately computed. 
 
 In the year 1714, several captains and owners of 
 merchant vessels petitioned the House of Commons 
 to consider the propriety of bringing in a bill to 
 reward inventions for promoting the discovery of 
 the longitude at sea. A committee was appointed to 
 investigate the subject, and Mr. Ditton and Mr. 
 Whiston, having thought of a new method of finding 
 the longitude, submitted it to the committee. Four 
 members of the Royal Society, viz. Sir Isaac New- 
 ton, Dr. Halley, Mr. Cotes, and Dr. Clarke, were 
 examined on the subject, along with Mr. Ditton and 
 Mr. Whiston. The last three of these philosophers 
 stated their opinions verbally. Mr. Cotes considered 
 the proposed scheme as correct in theory and on 
 shore, and both he and Dr. Halley were of opinion 
 that expensive experiments would be requisite. 
 Newton, when called upon for his opinion, read the 
 following memorandum, which deserves to be re- 
 corded. 
 
 " For determining the longitude at sea there have 
 been several projects, true in theory, but difficult to 
 execute. 
 
 " 1. One is by a watch to keep time exactly; but 
 by reason of the motion of the ship, the variation 
 of heat and cold, wet or dry, and the difference of 
 gravity in different latitudes, such a watch hath not 
 yet been made. 
 
 " 2. Another is by ihe eclipses of Jupiter's satel- 
 lites; but by reason of the length of telescopes 
 requisite to observe them, and the motion of a ship 
 at sea, those eclipses cannot yet be there observed. 
 
 " 3. A third is by the place of the moon ; but her 
 theory is not yet exact enough for that purpose ; it
 
 232 SIR ISAAC NEWTON. 
 
 is exact enough to determine the longitude within 
 two or three degrees, but not within a degree. 
 
 " 4. A fourth is Mr. Ditton's project, and this is 
 rather for keeping an account of the longitude at 
 sea than for finding it, if at any time it should be 
 lost, as it may easily be in cloudy weather. How far 
 this is practicable, and with what charge, they that 
 are skilled in sea affairs are best able to judge. In 
 sailing by this method, whenever they are to pass 
 over very deep seas, they must sail due east or west ; 
 they must first sail into the latitude of the next place 
 to which they are going beyond it, and then keep 
 due east or west till they come at that place. In 
 the first three ways there must be a watch regulated 
 by a spring, and rectified every visible sunrise and 
 sunset, to tell the hour of the day or night. In the 
 fourth way such a watch is not necessary. In the 
 first way there must be two watches, this and the 
 other above mentioned. In any of the first three 
 ways, it may be of some service to find the longitude 
 within a degree, and of much more service to find it 
 within forty minutes, or half a degree if it may, and 
 the success may deserve rewards accordingly. In 
 the fourth way, it is easier to enable seamen to 
 know their distance and bearing from the shore 40, 
 60, or 80 miles off, than to cross the seas ; and some 
 part of the reward may be given when the first is 
 performed on the coast of Great Britain for the safety 
 of ships coming home ; and the rest when seamen 
 shall be enabled to sail to an assigned remote har- 
 bour without losing their longitude if it may be." 
 
 The committee brought up their report on the 1 1th 
 June, and recommended that a bill should be intro- 
 duced into parliament for the purpose of rewarding 
 inventions or discoveries connected with the deter- 
 mination of the longitude. The bill passed the 
 House of Commons on the 3d July, and was agreed 
 to by the Lords on the 8th of the same month.* 
 
 * Joarnals of the House cf Commons ^ol xvii.p. 677, 716
 
 LONGITUDE AT SEA. 233 
 
 In ghing an account of this transaction,* Mr. 
 Whiston states, that nobody understood Sir Isaac's 
 paper, and that after sitting down he obstinately 
 kept silence, though he was much pressed to explain 
 himself more distinctly. At last, seeing that the 
 scheme was likely to be rejected, Whiston ventured 
 to say that Sir Isaac did not wish to explain more 
 through fear of compromising himself, but that he 
 really approved of the plan. Sir Isaac, he goes on 
 to say, repeated word for word what Whiston had 
 said. This is the part of Mr. Newton's conduct 
 which M. Biot has described as puerile, and " tend- 
 ing to confirm the fact of the aberration of his intel- 
 lect in 1693." Before we can admit such a censure 
 we must be satisfied with the correctness of Whis- 
 ton's statement. Newton's paper is perfectly intel- 
 ligible, and we may easily understand how he might 
 have approved of Mr. Ditton's plan as ingenious and 
 practicable under particular circumstances, though 
 he did not think it of that paramount importance 
 which would have authorized the House of Com- 
 mons to distinguish it by a parliamentary reward. 
 The conflict between public duty and a disposition 
 to promote the interests of Mr. Whiston and Mr. 
 Ditton was no doubt the cause of that embarrass, 
 ment of manner which the former of these mathe- 
 maticians has so unkindly brought before the public. 
 
 * Winston's " Longitude Discovered." Lond 1738.
 
 234 sm ISAAC NEWTON. 
 
 CHAPTER XV. 
 
 Respect in which Newton was held at the Court of George I. The Prin- 
 cess of Wales delighted with his Conversation Leibnitz r*. eavourt 
 to prejudice the Princess against Sir Isaac and Locke Controversy 
 occasioned by his Conduct The Princess obtains a Manuscript Ab- 
 stract of hit System of Chronology The Abbe Conti is, at her request, 
 allowed to take a Copy of it on the promise of Secresy He prints it 
 surreptitiously in French, accompanied with a Refutation by M. Freret 
 Sir Isaac's Defence of his System Father Souciet attacks it and 
 is answered by Dr. Halley Sir Isaac's larger Work on Chronology 
 published after his Death Opinions respecting it Sir Isaac's Paper 
 on the Form of the most ancient Year. 
 
 ON the accession of George I. to the British throne 
 in 1714, Sir Isaac Newton became an object of in- 
 terest at court. His high situation under govern- 
 ment, his splendid reputation, his spotless charac- 
 ter, and, above all, his unaffected piety attracted 
 tke attention of the Princess of Wales, afterward 
 queen-consort to George II. This lady, who pos- 
 sessed a highly cultivated mind, derived the greatest 
 pleasure from conversing with Newton and corres- 
 ponding with Leibnitz. In all her difficulties, she 
 received from Sir Isaac that information and assist- 
 ance which she had elsewhere sought in vain, and 
 she was often heard to declare in public that she 
 thought herself fortunate in living at a time which 
 enabled her to enjoy the conversation of so great a 
 genius. But while Newton was thus esteemed by 
 the house of Hanover, Leibnitz, his great rival, en- 
 deavoured to weaken and undermine his influence. 
 In his correspondence with the princess, he repre- 
 sented the Newtonian philosophy, not only as phy- 
 sically false, but as injurious to the interests of 
 religion. He asserted that natural religion was 
 rapidly declining in England, and he supported this 
 nosition by referring to the works of Locke, and to
 
 CHRONOLOGY. 235 
 
 the beautiful and pious sentiments contained in the 
 28th query at the end of the Optics. He represented 
 the principles of these great men as precisely the 
 same with those of the materialists, and thus endea- 
 voured to degrade the character of English philoso- 
 phers. 
 
 These attacks of Leibnitz became subjects of con- 
 versation at court, and when they reached the ear of 
 the king, his majesty expressed his expectation that 
 Sir Isaac Newton would draw up a reply. He ac- 
 cordingly entered the lists on the mathematical part 
 of the controversy, and left the philosophical part 
 of it to Dr. Clarke, who was a full match for the 
 German philosopher. The correspondence which 
 thus took place was carefully perused by the prin- 
 cess, and from the estimation in which Sir Isaac 
 continued to be held, we may infer that the views of 
 the English philosopher were not very remote from 
 her own. 
 
 When Sir Isaac was one day conversing with her 
 royal highness on some points of ancient history, 
 he was led to mention to her, and to explain, a new 
 system of chronology which he composed during his 
 residence at Cambridge, where he was in the habit, 
 as he himself expresses it, " of refreshing himself 
 with history and chronology when he was weary 
 with other studies." The princess was so much 
 pleased with his ingenious system, that she subse- 
 quently, in the year 1718, sent a message by the Abb6 
 Conti to Sir Isaac, requesting him to speak with her, 
 and she, on this occasion, requested a copy of the 
 interesting work which contained his system of chro- 
 nology. Sir Isaac informed her that it existed merely 
 in separate papers, which were not only in a state 
 of confusion, but which contained a very imperfect 
 view of the subject, and he promised, in a few days, 
 to draw up an abstract of it for her own private use, 
 and on the condition that it should not be communi- 
 cated to any other person. Some time after the
 
 236 SIR ISAAC NEWTON. 
 
 princess received the manuscript, she requested that 
 the Abbe Conti might be allowed to have a copy of 
 it. Sir Isaac granted this request, and the Abbe was 
 informed that he received a copy of the manuscript 
 with Sir Isaac's leave, and at the princess's request, 
 and that it was to be kept secret.* The manuscript 
 which was thus rashly put into the hands of a 
 foreigner was entitled " A Short Chronicle from the 
 First Memory of Things in Europe to the Conquest 
 of Persia by Alexander the Great." It consists of 
 about twenty-four quarto printed pages,f with an 
 introduction of four pages, in which Sir Isaac states 
 that he " does not pretend to be exact to a year, that 
 there may be errors of five or ten years, and some- 
 times twenty, but not much above." 
 
 The Abbe Cpnti kept his promise of secrecy during 
 his residence in England, but he no sooner reached 
 Paris than he communicated it to M. Freret, a 
 learned antiquarian, who not only translated it, but 
 drew up observations upon it for the purpose of re- 
 futing some of its principal results. Sir Isaac was 
 unacquainted with this transaction till he was in- 
 formed of it by the French bookseller, M. Cavalier, 
 who requested his leave to publish it, and charged 
 one of his friends in London to procure Sir Isaac's 
 answer, which was as follows : 
 
 " I remember that I wrote a Chronological index 
 for a particular friend, on condition that it should not 
 be communicated. As I have not seen the manu- 
 script which you have under my name, I know not 
 whether it be the same. That which I wrote was 
 not at all done with design to publish it. I intend 
 not to meddle with that which hath been given you 
 
 * This anecdote concerning the Chronological manuscript is not cor- 
 rectly given in the Biographia Britannica, and in some of the other livea 
 of Newton. I have followed implicitly Newton's own account of it in 
 the Phil. Trans. 1725, vol. xxxiii. No. 389, p. 315. 
 
 t M. Biot has supposed that this abstract was an imperfect edition of 
 Newton's work on Chronology
 
 CHRONOLOGY. 237 
 
 under my name, nor to give any consent to the pub- 
 lishing of it. I am your very humble servant, 
 
 "ISAAC NEWTON. 
 "London, May 27th, 1725, 0. S." 
 
 Before this letter was written, viz. on the 21st 
 May, the bookseller had received the royal privilege 
 for printing the work ; and when it was completed, 
 he sent a copy in a present to Sir Isaac, who received 
 it on the llth November, 1725. It was entitled, 
 Abrege de Chronologic de M. Le Chevalier Neivton, 
 fait par lui-meme, et traduit sur le manuscript Anglais, 
 and was accompanied with observations by M. Fre- 
 ret,* the object of which was to refute the leading 
 points of the system.f An advertisement was pre- 
 fixed to it, in which the bookseller defends himself 
 for printing it without the author's leave, on the 
 ground that he had written three letters to obtain 
 permission, and had declared that he would take Sii 
 Isaac's silence for consent. When Sir Isaac received 
 this work, he drew up a paper entitled, Remarks on 
 the Observations made on a Chronological Index of Sir 
 Isaac Newton, translated into French by the Observator, 
 and published at Paris, which was printed in the Phi- 
 losophical Transactions for 1725.J In this paper Sir 
 Isaac gives a history of the transaction, charges 
 the Abbe Conti with a breach of promise, and blames 
 the publisher for having asked his leave to print the 
 translation without sending him a copy for his peru- 
 sal, without acquainting him with the name of the 
 translator, and without announcing his intention of 
 printing along with it a refutation of the original. 
 
 * Father Souciet was supposed by Halley and others to have been the 
 author of these observations, but there is no doubt that they were written 
 by M. Freret. 
 
 t It is stated in the Biogr. Britannica, Art. Newton, that the copy of 
 the French translation was not accompanied with the refutation. Though 
 the reverse of this is not distinctly stated by Sir Isaac himself, yet it 
 may be inferred from his observations. 
 
 J Vol. xxxiii. No. 389, p. 315.
 
 238 SIR ISAAC NEWTON. 
 
 The observations made by the translator against the 
 conclusions deduced by the author were founded on 
 an imperfect knowledge of Sir Isaac's system ; and 
 they are so specious, that Halley himself confesses 
 that he was at first prejudiced in favour of the obser- 
 vations, taking the calculations for granted, and not 
 having seen Sir Isaac's work. 
 
 To all the observations of M. Freret Sir Isaac re- 
 turned a triumphant answer. This presumptuous 
 antiquary had ventured to state at the end of his 
 observations, " that he believed he had stated enough 
 concerning the epochs of the Argonauts, and the 
 length of generations, to make people cautious about 
 the rest ; for these are the two foundations of all this 
 new system of chronology." He founds his argu- 
 ments against the epochs of the Argonauts, as fixed 
 by our author, on the supposition that Sir Isaac 
 places the vernal equinox at the time of the Argo- 
 nautic expedition in the middle of the sign of Aries, 
 whereas Sir Isaac places it in the middle of the con- 
 stellation, a point corresponding with the middle of 
 the back of Aries, or 8 from the first star of Aries. 
 This position of the colure is assigned on the author- 
 ity of Eudoxus, as given by Hipparchus, who says 
 that the colure passed over the back of Aries. Set- 
 ting out with this mistake, M. Freret concludes that 
 the Argonautic expedition took place 532 years 
 earlier than Sir Isaac made it. His second objection 
 to the new system relates to the length of genera 
 tions, which he says is made only 18 or 20 years. 
 Sir Isaac, on the contrary, reckons a generation at 
 33 years, or 3 generations at 100 ; and it was the 
 lengths of the reigns of kings that he made 18 or 20 
 years. This deduction he founds on the reigns of 
 64 French kings. Now, the ancient Greeks and 
 Egyptians reckoned the length of a reign equal to 
 that of a generation ; and it was by correcting this 
 mistake, and adopting a measure founded on fact, 
 that Sir Isaac placed the Argonautic expedition fortv-
 
 CHRONOLOGY. 239 
 
 four years after the death of Solomon, and fixed some 
 of the other points of his system. 
 
 This answer of Sir Isaac's to the objections of 
 Freret called into the field a fresh antagonist, Father 
 Souciet, who published five dissertations on the new 
 chronology. These dissertations were written in 
 a tone highly reprehensible ; and the friends of Sir 
 Isaac, being apprehensive that the manner in which 
 his system was attacked would affect him more than 
 the arguments themselves, prevailed upon a friend to 
 draw up an abstract of Souciet's objections, stripped 
 of the " extraordinary ornaments with which they 
 were clothed." The perusal of these objections had 
 no other effect upon him than to convince him of 
 the ignorance of their author ; and he was induced 
 to read the entire work, which produced no change 
 in his opinion. 
 
 In consequence of these discussions, Sir Isaac 
 was prevailed upon to prepare his larger work for 
 the press. He had nearly completed it at the time 
 of his death, and it was published in 1728, under the 
 title of The Chronology of Ancient Kingdoms amended, 
 to which is prefixed a short Chronicle, from the first 
 memory of Things in Europe to the Conquest of Per- 
 sia by Alexander the Great. It was dedicated to the 
 queen by Mr. Conduit, and consists of six chapters : 
 1. On the Chronology of the Greeks ;* 2. Of the 
 Empire of Egypt ; 3. Of the Assyrian Empire ; 4. 
 Of the two contemporary Empires of the Baby- 
 lonians and Medes ; 5. A Description of the Temple 
 of Solomon; 6. Of the Empire of the Persians. 
 The sixth chapter was not copied out with the other 
 five, which makes it doubtful whether or not it was 
 intended for publication ; but as it was found among 
 his papers, and appeared to be a continuation of the 
 
 * According to Whiston, Sir Isaac wrote out eighteen copies of thia 
 chapter with 'his own hand, differing little from one another Whit 
 '
 
 240 SIR ISAAC NEWTON. 
 
 same work, it was thought right to add it to the 
 other five chapters.* 
 
 After the death of Newton, Dr. Halley, who had 
 not yet seen the larger work, felt himself called upon, 
 both as astronomer-royal and as the friend of the 
 author, to reply to the first and last dissertations of 
 Father Souciet, which were chiefly astronomical; 
 and in two papers printed in the Philosophical Trans- 
 actions for I727,f he has done this in a most con- 
 vincing and learned argument. 
 
 Among the supporters of the views of Newton, 
 we may enumerate Dr. Reid, Nauze, and some other 
 writers ; and among its opponents, M. Freret, who 
 left behind him a posthumous work on the subject, 
 M. Fourmond, Mr. A. Bedford, Dr. Shuckford, Dr. 
 Middleton, Whiston, and the late M. Delambre. The 
 object of M. Fourmond is to show the uncertainty 
 of the astronomical argument, arising on the one 
 hand from the vague account of the ancient sphere 
 as given by Hipparchus ; and, on the other, from the 
 extreme rudeness of ancient astronomical observa- 
 tions. Delambre has taken a similar view of the 
 subject: he regards the observations of ancient 
 astronomers as too incorrect to form the basis of a 
 system of chronology ; and he maintains, that if we 
 admit the accuracy of the details in the sphere of 
 Eudoxus, and suppose them all to belong to the 
 same epoch, all the stars which it contains ought at 
 that epoch to be found in the place where they are 
 marked, and we might thence verify the accuracy, 
 and ascertain the state of the observations. It fol- 
 lows, however, from such an examination, that the 
 
 * This work is the first article in the fifth volume of Dr. Horsley's 
 edition of Newton's works. The next article in the volume is entitled, 
 " A Short Chronicle from a MS., the property of the Reverend Dr. 
 Ekins, Dean of Carlisle ;" which is nothing more than the abstract of 
 the Chronology already printed in the same volume. We cannot even 
 conjecture the" reasons for publishing it, especially as it is less perfect 
 than the abstract, two or three dates being wanting. 
 
 1 See vol. xxxiv. p. 205. and vol. xxxv. p. 296
 
 CHRONOLOGY. 241 
 
 sphere would indicate almost as many different 
 epochs as it contains stars. Some of them even 
 had not, in the time of Eudoxus, arrived at the po- 
 sition which had been fur a long time attributed to 
 them, and will not even reach it for three hundred 
 years to come, and on this account he considers it 
 impossible to deduce any chronological conclusions 
 from such a rude mass of errors. 
 
 But however wtil-founded these observations may 
 be, we agree in opinion with M. Daunou,* " that 
 they are not sufficient to establish a new system, 
 and we must regard the system of Newton as a 
 great fact in the history of chronological science, 
 and as confirming the observation of Varro, that the 
 stage of history does not commence till the first 
 Olympiad." 
 
 Among the chronological writings of Sir Isaac 
 Newton we must enumerate his letter to a person 
 of distinction who had desired his opinion pf the learned 
 Bishop Lloyd *s hypothesis concerning the form of the 
 most ancient year. This hypothesis was sent by the 
 Bishop of Worcester to Dr. Prideaux. Sir Isaac 
 remarks, that it is filled with many excellent obser- 
 vations on the ancient year ; but he does not " find 
 it proved that any ancient nations used a year of 
 twelve months and 360 days without correcting it 
 from time to time by the luminaries, to make the 
 months keep to the course of the moon, and the year 
 to the course of the sun, and returns of the seasons 
 and fruits of the earth." After examining the years 
 of all the nations of antiquity, he concludes, " that no 
 other years are to be met with among the ancients 
 but such as were either luni-solar, or solar or lunar, 
 or the calendars of these years." A practical year, 
 he adds, of 360 days is none of these. The begin- 
 ning of such a year would have run round the four 
 
 * See an excellent view of this chronological controversy In an able 
 note by M. Daunoa, attached to Biot's Life of Newton in the Biog. Uni 
 vvrsetle, torn xxxi. pi 180
 
 242 SIR ISAAC NEWTON. 
 
 seasons in seventy years, and such a notable revolu 
 tion would have been mentioned in history, and is 
 not to be asserted without proving it.* 
 
 CHAPTER XVI. 
 
 Cheological Studies of Sir Isaac Their Importance to Christianity- 
 Motives to which they have been ascribed Opinions of Biot and La- 
 place considered his Theological Researches begun before his sup- 
 posed Mental Illness The Date of these Works fixed Letters to Locke 
 Account of his Observations on Prophecy His Historical Account 
 of two notable Corruptions of Scripture His Lexicon Propheticum 
 His Four Letters to Dr. Bentley Origin of Newton's Theological 
 Studies Analogy between the Book of Nature and that of Revelation 
 
 THE history of the theological studies of Sir Isaac 
 Newton will ever be regarded as one of the most 
 interesting portions of his life. That he who among 
 all the individuals of his species possessed the high- 
 est intellectual powers was not only a learned and 
 profound divine, but a firm believer in the great doc- 
 trines of religion, is one of the proudest triumphs 
 of the Christian faith. Had he distinguished him- 
 self only by an external respect for the offices and 
 duties of religion ; and had he left merely in his last 
 words an acknowledgment of his faith, his piety 
 would have been regarded as a prudent submission 
 to popular feeling, and his last aspirations would 
 have been ascribed to the decay or to the extinction 
 of his transcendent powers. But he had been a 
 Christian from his youth, and though never intended 
 for the church, yet he interchanged the study of the 
 Scriptures with that of the laws of the material 
 universe ; and from the examination of the works 
 of the Supreme Creator he found it to be no abrupt 
 
 * This letter is published without any date in the Gentleman's Maga* 
 tine for 1755,>,vol. xxv. p. 3. It bears internal evidence of being genuine
 
 THEOLOGICAL STUDIES. 243 
 
 transition to investigate the revelation of his will, 
 and to contemplate the immortal destinies of man- 
 kind. 
 
 But when the religious habits of Sir Isaac Newton 
 could not be ascribed to an ambition of popularity, 
 to the influence of weak health, or to the force of 
 professional impulse, it became necessary for the 
 apostles of infidelity to refer it to some extraordi- 
 nary cause. His supposed insanity was therefore 
 eagerly seized upon by some as affording a plausible 
 origin for his religious principles; while others, 
 without any view of supporting the cause of skep- 
 ticism, ascribed his theological researches to the 
 habits of the age in which he lived, and to a desire 
 of promoting political liberty, by turning against the 
 abetters of despotism those powerful weapons which 
 the Scriptures supplied. The anxiety evinced by 
 M. de Laplace to refer his religious writings to a 
 late period of his life seems to have been felt also 
 by M. Biot, who has gone so far as to fix the very 
 date of one of his most important works, and thus 
 to establish the suspicions of his colleague. 
 
 " From the nature of the subject,"* says he, " and 
 from certain indications which Newton seems to 
 give at the beginning of his dissertation, we may 
 conjecture with probability that he composed it at 
 the time when the errors of Whiston, and a work 
 of Dr. Clarke on the same subject, drew upon them 
 the attacks of all the theologians of England, which 
 would place the date between the years 1712 and 
 1719. It would then be truly a prodigy to remark, 
 that a man of from seventy-two to seventy-five 
 years of age was able to compose, rapidly, as he 
 leads us to believe, so extensive a piece of sacred 
 criticism, of literary history, and even of bibliogra- 
 phy, where an erudition the most vast, the most 
 
 * His Historical Account of two notable Corruptions of the Serif 
 tures 50 pp quarto.
 
 444 SIR ISAAC NEWTON. 
 
 varied, and the most ready always supports an argu- 
 ment well arranged and powerfully combined. * * * 
 A.t this epoch of the life of Newton the reading ot 
 religious books had become one of his most habitual 
 occupations, and after he had performed the duties 
 of his office, they formed, along with the conversa- 
 tion of his friends, his principal amusement. He 
 had then almost ceased to care for the sciences, and, 
 in we have already remarked, since the fatal epoch 
 Df 1693, he gave to the world only three really new 
 scientific productions." 
 
 Notwithstanding the prodigy which it involves, M. 
 Biot has adopted 1712-1719 as the date of this criti- 
 cal dissertation ; it is regarded as the composition 
 of a man of seventy-two or seventy-five ; the read- 
 ing of religious works is stated to have become one of 
 his most habitual occupations, and such redding is 
 said to have been one of his principal amusements ; 
 md all this is associated with " the fatal epoch of 
 1693," as if his illness at that time had been the 
 lause of his abandoning science and bet<iking him- 
 self to theology. Carrying on the same views, M. 
 Biot asks, in reference to Sir Isaac's work on Pro- 
 phecy, " How a mind of the character and force of 
 Newton's, so habituated to the severity of mathe 
 matical considerations, so exercised in the observa- 
 tion of real phenomena, and so weU aware of the 
 conditions by which truth is to be discovered, could 
 out together such a number of conjectures without 
 noticing the extreme improbability of his interpreta- 
 tions from the infinite number of arbitrary postulates 
 HI which he has founded them V We would apply 
 JIP same question to the reasoning by which M. Biot 
 fixes the date of the critical dissertation ; and we 
 would ask how so eminent a philosopher could haz- 
 drd such frivolous conjectures upon a subject on 
 kvliich he had not a single fact to guide his inquiries. 
 Phe obvious tendency, though not the design, of the 
 .'-oiKrCusion at which he arrives is injurious to the
 
 LETTERS TO LOCKE. 245 
 
 memory of Newton, as well as to the interests of 
 religion; and these considerations might have 
 checked the temerity of speculation, even if it had 
 been founded on better data. The Newtonian inter- 
 pretation of the Prophecies, and especially that part 
 which M. Bipt characterizes as unhappily stamped 
 with the spirit of prejudice, has been adopted by men 
 of the soundest and most unprejudiced minds ; and 
 in addition to the moral and historical evidence by 
 which it is supported, it may yet be exhibited in all 
 the fulness of demonstration. But the speculation 
 of Biot respecting the date of Newton's theological 
 works was never maintained by any other person 
 than himself, and is capable of being disproved by 
 the most incontrovertible evidence. 
 
 We have already seen, in the extract from Mr. 
 Pryme's manuscript, that previous to 1692, when a 
 shade is supposed to have passed over his gifted 
 mind, Newton was well known by the appellation 
 of an " excellent divine," a character which could 
 not have been acquired without the devotion of many 
 years to theological researches ; but, important as 
 this argument would have been, we are fortunately 
 not left to so general a defence. The correspond- 
 ence of Newton with Locke, recently published by 
 Lord King, places it beyond a doubt that he had be- 
 gun his researches respecting the Prophecies before 
 the year 1691, before the forty-ninth year of his 
 age, and before the " fatal epoch of 1693." The 
 following letter shows that he had previously dis- 
 cussed this subject with his friend : 
 
 "SiR, Cambridge, Feb. 7, 1690-1. 
 
 "I am sorry your journey proved to so little pur- 
 pose, though it delivered you from the trouble of the 
 company the day after. You have obliged me by 
 mentioning me to my friends at London, and I must 
 thank both you and my Lady Masham for your 
 civilities at Gates, and for not thinking that I made 
 T
 
 246 SIR ISAAC NEWTON. 
 
 a long stay there. I hope we shall meet again in 
 due time, and then I should be glad to have your 
 judgment upon some of my mystical fancies. "The 
 Son of Man, Dan. vii. I take to be the same with the 
 Word of God upon the White Horse in Heaven, 
 Apoc. xii., for both are to rule the nations with a rod 
 of iron ; but whence are you certain that the Ancient 
 of Days is Christ 1 Does Christ anywhere sit upon 
 the throne? If Sir Francis Masham be at Gates, 
 present, I pray, my service to him, with his lady, 
 Mrs. Cudworth, and Mrs. Masham. Dr. Covel is 
 not in Cambridge. I am your affectionate and 
 humble servant, " Is. NEWTON 
 
 * Know you the meaning of Dan. x. 21. There 
 is none that holdeth with me in these things but 
 Mich, the prince." 
 
 Having thus determined the date of those investi- 
 gations which constitute his observations on the pro- 
 phecies of holy writ, particularly the prophecies of 
 Daniel and the Apocalypse, we shall proceed to fix 
 the latest date of his historical account of two notable 
 corruptions of the Scripture, in a letter to a friend. 
 
 This work seems to have been a very early pro- 
 duction of our author. It was written in the form 
 of a letter to Mr. Locke, and at that time Sir Isaac 
 seems to have been anxious for its publication. 
 Afraid, however, of being again led into a contro- 
 versy, and dreading the intolerance to which he 
 might be exposed, he requested Mr. Locke, who 
 was at that time meditating a voyage to Holland, 
 to get it translated into French, and published on 
 ihe Continent. Having abandoned his design of 
 visiting Holland, Locke transmitted the manuscript, 
 without Newton's name, to his learned friend M. Le 
 Clerc, in Holland ; and it appears, from a letter of 
 Le Clerc's to Locke, that he must have received it 
 before the llth April, 1691. M. Le Clerc delayed
 
 LETTERS TO LOCKE. 247 
 
 for a long time to take any steps regarding its pub- 
 lication ; but in a letter dated January 20th, 1692, he 
 announced to Locke his intention of publishing the 
 tract in Latin. When this plan was communicated 
 to Sir Isaac, he became alarmed at the risk of de- 
 tection, and resolved to stop the publication of his 
 manuscript. This resolution was intimated to Mr. 
 Locke in the following letter : 
 
 " SIR, Cambridge, Feb. 16th, 1691-2. 
 
 " Your former letters came not to my hand, but 
 this I have. I was of opinion my papers had lain 
 still, and am sorry to hear there is news about them. 
 Let me entreat you to stop their translation and im- 
 pression so soon as you can ; for I design to suppress 
 them. If your friend hath been at any pains and 
 charge, I will repay it, and gratify him. I am very 
 glad my Lord Monmouth is till my friend, but intend 
 not to give his lordship and you any farther trouble. 
 My inclinations are to sit still. I am to beg his 
 lordship's pardon for pressing into his company the 
 last time I saw him. I had not done it, but that Mr. 
 Paulin pressed me into the room. Miracles, of 
 good credit, continued in the church for about two 
 or three hundred years. Gregorius Thaumaturgus 
 had his name from thence, and was one of the latest 
 who was eminent for that gift ; but of their number 
 and frequency I am not able to give you a just ac- 
 count. The history of those ages is very imperfect. 
 Mr. Paulin told me you had writ for some of Mr 
 Boyle's red earth, and by that I knew you had the 
 receipt. Your most affectionate and humble servant, 
 " Is. NEWTON." 
 
 Hence we see that this celebrated treatise, v hich 
 Biot alleges to have been written between 1712 and 
 1719, was actually in the hands of Le Clerc in Hol- 
 land previous to the llth April, 1691, and conse- 
 quently previous to the time of the supposed insanity
 
 248 SIR ISAAC NEWTON. 
 
 of its author. Mr. Locke lost no time in obeying the 
 request of his friend. Le Clerc instantly stopped the 
 publication of the letter, and, as he had never learned 
 the name of the author, he deposited the manuscript, 
 which was in the handwriting of Mr. Locke, in the 
 library of the Remonstrants, where it was afterwaid 
 found, and was published at London in 1754, under 
 the title of Two letters from Sir Isaac Newton to M. 
 Le Clerc, a form which had never been given to it 
 by its author. The copy thus published was a very 
 imperfect one, wanting both the beginning* and the 
 end, and erroneous in many places ; but Dr. Horsley 
 has published a genuine edition, which has the form 
 of a single letter to a friend, and was copied from a 
 manuscript in Sir Isaac Newton's handwriting, in the 
 possession of the Rev. Dr. Ekins, Dean of Carlisle. 
 
 Having thus determined as accurately as possible 
 the dates of the principal theological writings of Sir 
 Isaac, we shall now proceed to give some account 
 of their contents. 
 
 The Observations on the Prophecies of Daniel ana 
 the Apocalypse of St. John were published in London 
 in 1733, in one volume 4to. The work is divided 
 into two parts, the first of which treats of the Pro- 
 phecies of Daniel, and the second of the Apocalypse 
 of St. John. It begins with an account of the dif- 
 ferent books which compose the Old Testament ; and 
 as the author considers Daniel to be the most dis- 
 tinct in the order of time, and the easiest to be un- 
 derstood, he makes him the key to all the prophetic 
 books in those matters which relate to the "last time." 
 He next considers the figurative language of the 
 prophets, which he regards as taken " from the 
 analogy between the world natural and an empire 
 or kingdom considered as a world politic ;" the hea- 
 vens and the things therein representing thrones and 
 dynasties; the earth, with the things therein, the 
 
 * The editor supplied the beginning down to the 13th page, where be 
 mentions in a note that " thus far is not Sir Isaac's,"
 
 OBSERVATIONS ON PROPHECY. 249 
 
 inferior people ; and the lowest parts of the earth 
 the most miserable of the people. The sun is put 
 for the whole race of kings, the moon for the body 
 of the common people, and the stars for subordinate 
 princes and rulers. In the earth, the dry land and 
 the waters are put for the people of several nations. 
 Animals and vegetables are also put for the people 
 of several regions. When a beast or man is put for 
 a kingdom, his parts and qualities are put for the 
 analogous parts and qualities of the kingdom ; and 
 when a man is taken in a mystical sense, his quali- 
 ties are often signified by his actions, and by the 
 circumstances and things about him. In applying 
 these principles he begins with the vision of the 
 image composed of four different metals. This 
 image he considers as representing a body of four 
 great nations which should reign in succession over 
 the earth, viz. the people of Babylonia, the Persians, 
 the Greeks, and the Romans ; while the stone cut out 
 without hands is a new kingdom which should arise 
 after the four, conquer all those nations, become very 
 great, and endure to the end of time. 
 
 The vision of the four beasts is the prophecy of the 
 four empires repeated, with several new additions. 
 The lion with eagles' wings was the kingdom of 
 Babylon and Media, which overthrew the Assyrian 
 power. The beast like a bear was the Persian em- 
 pire, and its three ribs were the kingdoms of Sardis, 
 Babylon, and Egypt. The third beast, like a leopard, 
 was the Greek empire, and its four heads and four 
 wings were the kingdoms of Cassander, Lysimachus, 
 Ptolemy, and Seleucus. The fourth beast, with its 
 great iron teeth, was the Roman empire, and its ten 
 horns were the ten kingdoms into which it was 
 broken in the reign of Theodosius the Great. 
 
 In the fifth chapter Sir Isaac treats of the king- 
 doms represented by the feet of the image composed 
 of iron and clay which did not stick to one another, 
 and which were of different strength. These were
 
 250 sm ISAAC NEWTON. 
 
 the Gothic tribes called Ostrogoths, Visigoths, Van- 
 dals, Gepidae, Lombards, Burgundians, Alans, &c. ; 
 all of whom had the same manners and customs, 
 and spoke the same language, and who, about the 
 year 416 A. C. were all quietly settled in several 
 kingdoms within the empire, not only by conquest, 
 but by grants of emperor. 
 
 In the sixth chapter he treats of the ten kingdoms 
 represented by the ten horns'of the fourth beast, into 
 which the western empire became divided about the 
 time when Rome was besieged and taken by the 
 Goths. These kingdoms were, 
 
 1. The kingdom of the Vandals and Alans in Spain 
 and Africa. 
 
 2. The kingdom of Suevians in Spain. 
 
 3. The kingdom of the Visigoths. 
 
 4. The kingdom of the Alans in Gaul. 
 
 5. The kingdom of the Burgundians. 
 
 6. The kingdom of the Franks. 
 
 7. The kingdom of the Britains. 
 
 8. The kingdom of the Huns. 
 
 9. The kingdom of the Lombards. 
 10. The kingdom of Ravenna. 
 
 Some of these kingdoms at length fell, and new 
 ones sprung up ; but whatever was their subsequent 
 number, they still retain the name of the ten kings 
 from their first number. 
 
 The eleventh horn of Daniel's fourth beast is shown 
 in chapter vii. to be the Church of Rome in its triple 
 character of a seer, a prophet, and a king ; and its 
 power to change times and laws is copiously illus- 
 trated in chapter viii. 
 
 In the ninth chapter our author treats of the king- 
 dom represented in Daniel by the ram and he-goat, 
 ',he ram indicating the kingdom of the Medes and 
 Persians from the beginning of the four empires, and 
 the he-goat the kingdom of the Greeks to the end 
 of them. 
 
 The prophecy of the seventy weeks, which had
 
 OBSERVATIONS ON PROPHECY. 251 
 
 hitherto been restricted to the first coming of our 
 Saviour, is shown to be a prediction of all the main 
 periods relating to the coming of the Messiah, the 
 times of his birth and death, the time of his rejection 
 by the Jews, the duration of the Jewish war by which 
 he caused the city and sanctuary to be destroyed, 
 and the time of his second coming. 
 
 In the eleventh chapter Sir Isaac treats 'vith great 
 sagacity and acuteness of the time of our Saviour's 
 birth and passion, a subject which had perplexed 
 all preceding commentators. 
 
 After explaining in the twelfth chapter the last 
 prophecy of Daniel, namely, that of the scripture of 
 truth, which he considers as a commentary on the 
 vision of the ram and he-goat, he proceeds in the 
 thirteenth chapter to the prophecy of the king who 
 did according to his will, and magnified himself above 
 every god, and honoured Mahuzzims, and regarded 
 not the desire of women. He shows that the Greek 
 empire, after the division of the Roman empire into 
 the Greek and Latin empires, became the king who 
 in matters of religion did according to his will, and 
 in legislation exalted and magnified himself above 
 every god. 
 
 In the second part of his work on the Apocalypse 
 of St. John, Sir Isaac treats, 1st, Of the time when 
 the prophecy was written, which he conceives to 
 have been during John's exile in Patmos, and before 
 the epistle to the Hebrews and the epistles of Peter 
 were written, which in his opinion have a reference 
 to the Apocalypse ; 2dly, Of the scone of the vision, 
 and the relation which the Apocalypse has to the 
 book of the law of Moses, and to the worship of God 
 in the temple ; and, 3d7y, Of the relation which the 
 Apocalypse has to the prophecies of Daniel, and of 
 the subject of the prophecy itself. 
 
 Sir Isaac regards the prophecies of the Old and 
 New Testaments, not as given to gratify men's curi 
 osities, by enabling them to foreknow things, but tha
 
 252 SIR ISAAC NEWTON. 
 
 after they were fulfilled, they might be interpreted 
 by the event, and afford convincing arguments that 
 the woild is governed by Providence. He considers 
 that there is so much of this prophecy already ful- 
 filled as to afford to the diligent student sufficient 
 instances of God's providence; and he adds, that 
 " among the interpreters of the last age, there is 
 scarce one of note who hath not made some discovery 
 worth knowing, and thence it seems one may gather 
 that God is about opening these mysteries. The 
 success of others," he continues, " put me upon con- 
 sidering it, and if I have done any thing which may 
 be useful to following writers, I have my design." 
 
 Such is a brief abstract of this ingenious work, 
 which is characterized by great learning, and marked 
 with the sagacity of its distinguished author. The 
 same qualities of his mind are equally conspicuous 
 in his Historical Account of Two Notable Corruptions 
 of Scripture. 
 
 This celebrated treatise relates to two texts in the 
 Epistles of St. John and St. Paul. The first of these 
 is in 1 John v. 7. " For there are three that bear 
 record in heaven, the Father, the Son, and the Holy 
 Ghost, and these three are one." This text he con- 
 siders as a gross corruption of Scripture, which had 
 its origin among the Latins, who interpreted the 
 Spirit, Water, and Blood to be the Father, Son, and 
 Holy Ghost, in order to prove them one. With the 
 same view Jerome inserted the Trinity in express 
 words in his version. The Latins marked his varia- 
 tions in the margins of their books; and in the 
 twelfth and following centuries, when the disputa- 
 tions of the schoolmen were at their height, the 
 variation began to creep into the text in transcribing. 
 After the invention of printing, it crept out of the 
 Latin into the printed Greek, contrary to the author- 
 ity of all the Greek manuscripts and ancient ver- 
 sions; and from the Venetian press it went soon 
 after into Greece. After proving these positions
 
 CORRUPTIONS OF SCRIPTURE. 253 
 
 Sir Isaac gives the following paraphrase of this re- 
 markable passage, which is given in italics. 
 
 " Who is he that overcometh the world, but he that 
 believeth that Jesus is the Son of God, that Son spoken 
 of in the Psalms, where he saith, * thou art my Son ; 
 this day have 1 begotten thee.' This is he that, after 
 the Jews had long expected him, came, first in a mor- 
 tal body, by baptism of water, and then in an immor- 
 tal one, by shedding his blood upon the cross and 
 rising again from the dead ; not by water only, but 
 by water and blood ; being the Son of God, as well 
 by his resurrection from the dead (Acts xiii. 33), as 
 by his supernatural birth of the virgin (Luke i. 35). 
 And it is the Spirit also that, together with the water 
 and blood, beareth ivitness of the truth of his coming ; 
 because the Spirit is truth; and so a fit and unexcep- 
 tionable witness. For there are three that bear record 
 of his coming ; the Spirit, which he promised to send, 
 and which was since shed forth upon us in the form 
 of cloven tongues, and in various gifts ; the baptism 
 of water, wherein God testified ' this is my beloved 
 Son ;' and the shedding of his blood, accompanied with 
 his resurrection, whereby he became the most faith- 
 ful martyr, or witness, of this truth. And these three, 
 the spirit, the baptism, and passion of Christ, agree 
 in witnessing one and the same thing (namely, that 
 the Son of God is come) ; and, therefore, their evi- 
 dence is strong : for the law requires but two con- 
 senting witnesses, and here we have three : and if 
 we receive the witness of men, the threefold witness of 
 God, which he bare of his Son, by declaring at his 
 baptism 'this is my beloved Son,' by raising him 
 from the dead, and by pouring out his Spirit on us 
 is greater ; and, therefore, ought to be more readily 
 received." 
 
 While the Latin Church was corrupting the pre- 
 ceding text, the Greek Church was doing the same 
 to St. Paul's 1st Epistle to Timothy iii. 16. Great 
 is the mystery of godliness, God manifest in the flesh,
 
 254 SIR ISAAC NEWTON. 
 
 According to Sir Isaac, this reading was effected by 
 changing & into ec, the abbreviation of 00f, and after 
 proving this by a learned and ingenious examination 
 of ancient manuscripts, he concludes that the read- 
 ing should be Great is the mystery of Godliness who 
 (viz. our Saviour) was manifest in the flesh. 
 
 As this learned dissertation had the effect of de- 
 priving the defenders of the doctrine of the Trinity 
 of the aid of two leading texts, Sir Isaac Newton has 
 been regarded as an Antitrinitarian ; but such a con- 
 clusion is not warranted by any thing which he has 
 published ;* and he distinctly warns us, that his ob- 
 ject was solely to "purge the truth of things spu- 
 rious." We are disposed, on the contrary, to think 
 that he declares his belief in the doctrine of the 
 Trinity when he says, " In the eastern nations, and 
 for a long time in the western, the faith subsisted 
 without this text ; and it is rather a danger to reli- 
 gion than an advantage, to make it now lean upon a 
 bruised reed. There cannot be better service done 
 to the truth than to purge it of things spurious ; and 
 therefore, knowing your prudence and calmness of 
 temper, I am confident I shall not offend you by tell- 
 ing you my mind plainly ; especially since it is no 
 article of faith, no point of discipline, nothing but a 
 criticism concerning a text of Scripture which I am 
 going to write about." The word faith in the pre- 
 ceding passage cannot mean faith in the Scriptures in 
 general, but faith in the particular doctrine of the 
 Trinity ; for it is this article of faith only to which 
 the author refers when he deprecates its leaning on 
 a bruised reed. But, whatever be the meaning of 
 this passage, we know that Sir Isaac was greatly 
 
 * M. Biot has well remarked that there is absolutely nothing in th 
 writings of Newton to justify, or even to authorize, the idea that he was 
 an Antitrinitarian. This passage is strangely omitted in the English 
 translation of Blot's Life of Newton. We do not know upon what au- 
 thority Dr. Thomson states, in his History of the Royal Society, that 
 Newton " did not believe in the Trinity," and that Dr. Horsley considered 
 Newton's papers unfit for publication, because they contained proofs of 
 his hostility to that doctrine.
 
 LEXICON PROPHETICTJM. 255 
 
 offended at Mr. Whiston for having represented him 
 as an Arian ; and so much did he resent the conduct 
 of his friend in ascribing to him heretical opinions, 
 that he would not permit him to be elected a Fellow 
 of the Royal Society while he was President.* 
 
 The only other religious works which were com- 
 posed by Sir Isaac Newton were his Lexicon Pro- 
 pheticum, to which was added a Dissertation on the 
 sacred cubit of the Jews, and Four Letters addressed 
 to Dr. Bentley, containing some arguments in proof of 
 a Deity. 
 
 The Lexicon Propheticum was left incomplete, and 
 has not been published ; but the Latin Dissertation 
 which was appended to it, in which he shows that 
 the cubit was about 26i Roman unciae, was published 
 in 1737 among the Miscellaneous Works of Mr. John 
 Greaves. 
 
 Upon the death of the Honourable Robert Boyle, 
 on the 30th of December, 1691, it was found, by a 
 codicil to his will, that he had left a revenue of 507. 
 per annum to establish a lectureship, in which eight 
 discourses were to be preached annually in one of 
 the churches of the metropolis, in illustration of the 
 evidences of Christianity, and in opposition to the 
 principles of infidelity. Dr. Bentley, though a very 
 young man, was appointed to preach the first course 
 of sermons, anri the manner in which he discharged 
 this important duty gave the highest satisfaction, not 
 only to the trustees of the lectureship, but to the 
 public in general. In the first six lectures Bentley 
 exposed the folly of atheism even in reference to the 
 present life, and derived powerful arguments for the 
 existence of a Deity from the faculties of the soul, 
 and the structure and functions of the human frame 
 In order to complete his plan, he proposed to devote 
 his seventh and eighth lectures to the demonstration 
 of a Divine Providence from the physical constitu- 
 
 * Whiston's Memoirs of his own Life, p. 178, 249, 250 Edit ^3
 
 256 SIR ISAAC NEWTON. 
 
 tion of the universe, as established in the Principia. 
 In order to qualify himself for this task, he received 
 from Sir Isaac written directions respecting a list of 
 books necessary to be perused previous to the study 
 of that work ;* and having made himself master of 
 the system which it contained, he applied it with 
 irresistible force of argument to establish the ex- 
 istence of an overruling mind. Previous to the pub- 
 lication of these lectures, Bentley encountered a 
 difficulty which he was not able to solve, and he 
 prudently transmitted to Sir Isaac during 1692 a 
 series of queries on the subject. This difficulty oc- 
 curred in an argument urged by Lucretius, to prove 
 the eternity of the world from an hypothesis of de- 
 riving the frame of it by mechanical principles from 
 matter endowed with an innate power of gravity, and 
 evenly scattered throughout the heavens. Sir Isaac 
 willingly entered upon the consideration of the sub- 
 x'ct, and transmitted his sentiments to Dr. Bentley 
 in the four letters which have been noticed hi a pre- 
 ceding chapter. 
 
 In the firstf of these letters Sir Isaac mentions 
 that when he wrote his treatise about our system, 
 viz. the Third Book of the Principia, " he had an 
 eye upon such principles as might work, with con- 
 sidering men, for the belief of a Deity, and he ex- 
 presses his happiness that it has been found useful 
 for that purpose. In answering the first query of 
 Dr. Bentley, the exact import of which we do not 
 know, he states, that, if matter were evenly diffused 
 through a finite space, and endowed with innate 
 gravity, it would fall down into the middle of the 
 space, and form one great spherical mass ; but if it 
 were diffused through an infinite space, some of it . 
 would collect into one mass, and some into another, 
 
 * Dr. Monk's Life of Bentley. p. 31. 
 
 f Dated December 10th, 1692. ' This letter is endorsed, in Bentley'8 
 hand, "Mr. Newton's answer to some queries sent by rne e^er I had 
 preached my two last sermons." Monk's Life of Bentley, p. 34. ~iote.
 
 LETTERS TO DR. BENTLEY. 257 
 
 so as to form an infinite number of great masses. 
 In this manner the sun and stars might be formed if 
 the matter were of a lucid nature. But he thinks it 
 inexplicable by natural causes, and to be ascribed to 
 the counsel and contrivance of a voluntary Agent, 
 that the matter should divide itself into two sorts, 
 part of it composing a shining body like the sun, and 
 part an opaque body like the planets. Had a natural 
 and blind cause, without contrivance and design, 
 placed the earth in the centre of the moon's orbit, 
 and Jupiter in the centre of his system of satellites, 
 and the sun in the centre of the planetary system, 
 the sun would have been a body like Jupiter and the 
 earth, that is, without light and heat, and conse- 
 quently he knows no reason why there is only one 
 body qualified to give light and heat to all the rest, 
 but because the Author of the system thought it con- 
 venient, and because one was sufficient to warm 
 and enlighten all the rest. 
 
 To the second query of Dr. Bentley, he replies 
 that the motions which the planets now have could 
 not spring from any natural cause alone, but were 
 impressed by an intelligent Agent* " To make such 
 a system with all its motions required a cause which 
 understood and compared together the quantities of 
 matter in the several bodies of the sun and planets, 
 and the gravitating powers resulting from thence ; 
 the several distances of the primary planets from 
 the sun, and of the secondary ones from Saturn Ju- 
 piter, and the earth, . and the velocities with which 
 those planets could revolve about those quantities 
 of matter in the central bodies ; and to compare and 
 adjust all these things together in so great a variety 
 of bodies, argues that cause to be not blind and for- 
 tuitous, but very well skilled in mechanics and geo- 
 metry." 
 
 In'the second* letter, he admits that the spherical 
 
 Dated Jan. 17th, 1692-3
 
 258 SIR ISAAC NEWTON. 
 
 mass formed by the aggregation of particles would 
 affect the figure of the space in which the matter 
 was diffused, provided the matter descends directly 
 downwards to that body, and the body has no diurnal 
 rotation ; but he states, that by earthquakes loosen- 
 ing the parts of this solid, the protuberance might 
 sink a little by their weight, and the mass by degrees 
 approach a spherical figure. He then proceeds to 
 correct an error of Dr. Bentley's in supposing that 
 all infinites are equal. He admits that gravity might 
 put the planets in motion, but he maintains that, 
 without the Divine power, it could never give them 
 such a circulating motion as they have about the 
 sun, because a proper quantity of a transverse mo- 
 tion is necessary for this purpose ; and he concludes 
 that he is compelled to ascribe the frame of this 
 system to an intelligent Agent. 
 
 The third letter contains opinions confirming or 
 correcting several positions which Dr. Bentley had 
 laid down, and he concludes it with a curious exam- 
 ination of the opinion of Plato, that the motion of 
 the planets is such as if they had been ail created 
 by God in some region very remote from our sys- 
 tem, and let fall from thence towards the sun, their 
 falling motion being turned aside into a transverse 
 one whenever they arrived at their several orbits. 
 Sir Isaac shows that there is no common place such 
 as that conjectured by Plato, provided the gravi- 
 tating power of the sun remains constant ; but that 
 Plato's affirmation is true if we suppose the gravi 
 tating power of the sun to be doubled at that mo- 
 ment of time when they all arrive at their several 
 orbits. " If we suppose," says he, " the gravity of 
 all the planets towards the sun to be of such a quan-- 
 tity as it really is, and that the motions of the 
 planets are turned upwards, every planet will ascend 
 to twice its height from the sun. Saturn will as- 
 cend till he be twice as high from the sun as he is 
 at present, and no higher; Jupiter will ascend as
 
 LETTERS TO DR. BENTLEY. 259 
 
 high again as at present, that is, a little above the 
 orb of Saturn ; Mercury will ascend to twice his 
 present height, that is, to the orb of Venus ; and so 
 of the rest ; and then, by falling down again from 
 the places to which they ascended, they will arise 
 again at their several orbs with the same velocities 
 they had at first, and with which they now revolve- 
 " But if so soon as their motions by which the} 
 revolve are turned upwards, the gravitating powei 
 of the sun, by which their ascent is perpetually re 
 tarded, be diminished by one-half, they will now 
 ascend perpetually, and all of them, at all equal dis- 
 tances from the sun, will be equally swift. Mer- 
 cury, when he arrives at the orb of Venus, will be 
 as swift as Venus ; and he and Venus, when they 
 arrive at the orb of the earth, will be as swift as the 
 earth ; and so of the rest. If they begin all of them 
 to ascend at once, and ascend in the same line, they 
 will constantly, in ascending, become nearer and 
 nearer together, and their motions will constantly 
 approach to an equality, and become at length 
 slower than any motion assignable. Suppose, there- 
 fore, that they ascended till they were almost con- 
 tiguous, and their motions inconsiderably little, and 
 that all their motions were at the same moment of 
 time turned back again, or, which comes almost to 
 the same thing, that they were only deprived of their 
 motions, and let fall at that time, they would all at 
 once arrive at their several orbs, each with the ve- 
 locity it had at first ; and if their motions were then 
 turned sideways, and at the same time the gravi 
 tating power of the sun doubled, that it might be 
 strong enough to retain them in their orbs, they 
 would revolve in them as before their ascent. But 
 if the gravitating power of the sun was not doubled, 
 they would go away from their orbs into the highest 
 heavens in parabolical lines."* 
 
 * " These things," says he, " follow from my Princip. Math. lib. i, 
 Drop. 33, 34, 35, 36 "
 
 260 SIR ISAAC NEWTON. 
 
 In the fourth letter* he states, that the hypothesis 
 that matter is at first evenly diffused through the 
 universe is in his opinion inconsistent with the 
 hypothesis of innate gravity without a supernatural 
 power to reconcile them, and therefore it infers a 
 Deity. " For if there be innate gravity, it is impos- 
 sible now for the matter of the earth and all the 
 planets and stars to fly up from them, and become 
 evenly spread throughout all the heavens without a 
 supernatural power ; and certainly that which can 
 never be hereafter without a supernatural power, 
 could never be heretofore without the same power." 
 
 These letters, of which we have endeavoured to 
 give a brief summary, will well repay the most 
 attentive perusal by the philosopher as well as the 
 divine. They are written with much perspicuity of 
 language and great power of thought, and they 
 contain results which inconte stably prove that their 
 author was fully master of his noblest faculties, 
 and comprehended the profoundest parts of his own 
 writings.! 
 
 The logical acuteness, the varied erudition, and 
 the absolute freedom from all prejudice which shine 
 throughout the theological writings of Newton, 
 might have protected them from the charge of hav- 
 ing been written in his old age, and at a time when 
 a failure of mind was supposed to have unfitted him 
 for his mathematical investigations. But it is fortu- 
 nate for his reputation, as well as for the interests 
 of Christianity, that we have been able to prove the 
 incorrectness of such insinuations, and to exhibit 
 the most irrefragable evidence that all the theological 
 
 * Dated February llth, 1693. 
 
 t The originals of these four letters to Bentley " were given by Dr. 
 Richard Bentley to Cumberland, his nephew, and executor, while a stu- 
 dent at Trinity College, and were printed by him in a separate pamphlet 
 in 1756. This publication was reviewed by Dr. Samuel Johnson in the 
 Literary Magazine, vol. i. p. 89. See Johnson's Works, vol. ii. p. 328. 
 The original letters are preserved in Trinity College, to which society 
 they were given by Cumberland a short time before his death." Monk'* 
 Life of Bentley, p. 33, note.
 
 THEOLOGICAL STUDIES. 261 
 
 writings of Newton were composed in the vigom 
 of his life, and before the crisis of that bodily dis- 
 order which is supposed to have affected his reason. 
 The able letters to Dr. Bentley were even written 
 in the middle of that period when want of sleep and 
 appetite had disturbed the serenity of his mind, and 
 enable us to prove that this disturbance, whatever 
 was its amount, never affected the higher functions 
 of his understanding. 
 
 When a philosopher of distinguished eminence, 
 and we believe not inimical to the Christian faith, 
 has found it necessary to make a laboured apology 
 for a man like Newton writing on theological sub- 
 jects, and has been led to render that apology more 
 complete by referring this class of his labours to a 
 mind debilitated by age and weakened by its pre- 
 vious aberrations, it may be expected from an Eng- 
 lish biographer, and one who acknowledges the 
 importance of revealed truth, and the paramount 
 interest of such subjects above all secular studies, 
 to suggest the true origin of Newton's theological 
 inquiries. 
 
 When a mind of great and acknowledged power 
 first directs its energies to the study of the material 
 universe, no indications of order attract his notice, 
 and no proofs of design call forth his admiration. 
 In the starry firmament he sees no bodies of stupen- 
 dous magnitude, and no distances of immeasurable 
 span. The two great luminaries appear vastly in- 
 ferior in magnitude to many objects around him, and 
 the greatest distances in the heavens seem even in- 
 ferior to those which his own eye can embrace on 
 the surface of the earth. The planets, when ob- 
 served with care, are seen to have a motion among 
 the fixed stars, and to vary in their magnitude and 
 distances, but these changes appear to follow no 
 law. Sometimes they move to the east, sometimes 
 to the west, sometimes towards the north, and 
 sometimes towards the south, and at other times
 
 262 SIR ISAAC NEWTON. 
 
 they are absolutely stationary. No system, in short, 
 appears, and no general law seems to direct their 
 motions. By the observations and inquiries of 
 astronomers, however, during successive ages, a 
 regular system has been "recognised in this chaos of 
 moving bodies, and the magnitudes, distances, and 
 revolutions of every planet which composes it has 
 been determined with the most extraordinary accu- 
 racy. Minds fitted and prepared for this species of 
 inquiry are capable of understanding the great 
 variety of evidence by which the truth of the plan- 
 etary system is established ; but thousands of indi 
 viduals who are even distinguished in other branches 
 of knowledge are incapable of such researches, and 
 view with a skeptical eye the great and irrefragable 
 truths of astronomy. 
 
 That the sun is stationary in the centre of our 
 system, that the earth moves round the sun, and 
 round its own axis, that the earth is 8000 miles in 
 diameter, and the sun one hundred and ten times as 
 large, that the earth's orbit is 190 millions of miles 
 in breadth, and that if this immense space were 
 filled with light, it would appear only like a luminous 
 point at the nearest fixed star, are positions abso- 
 lutely unintelligible and incredible to all who have 
 not carefully studied the subject. To millions of 
 our species, then, the great book of nature is ab- 
 solutely sealed, though it is in the power of all to 
 unfold its pages, and to peruse those glowing pas- 
 sages which proclaim the power and wisdom of its 
 mighty Author. 
 
 The book of revelation exhibits to us the same 
 peculiarities as that of nature. To the ordinary 
 eye it presents no immediate indications of its 
 Divine origin. Events apparently insignificant 
 supernatural interferences seemingly unnecessary 
 doctrines almost contradictory and prophecies 
 nearly unintelligible occupy its pages. The history 
 of the fall of man of the introduction of moral
 
 THEOLOGICAL STUDIES. 203 
 
 and physical evil the prediction of a Messiah the 
 actual advent of our Saviour his instructions his 
 miracles his death his resurrection and the sub- 
 sequent propagation of his religion by the unlettered 
 fishermen of Galilee, are each a stumblingblock to 
 the wisdom of this world. The youthful and vigor- 
 ous mind, when first summoned to peruse the Scrip- 
 tures, turns from them with disappointment. It 
 recognises in them no profound science no secular 
 wisdom no Divine eloquence no disclosures of 
 nature's secrets no direct impress of an Almighty 
 hand. But, though the system of revealed truth 
 which this book contains is, like that of the universe, 
 concealed from common observation, yet the labours 
 of centuries have established its Divine origin, and 
 developed in all its order and beauty the great plan 
 of human restoration. In the chaos of its incidents 
 we discover the whole history of our species, 
 whether it is delineated in events that are past or 
 shadowed forth in those which are to come, from 
 the creation of man and the origin of evil, to the 
 extinction of his earthly dynasty and the commence- 
 ment of his immortal career. 
 
 The antiquity and authenticity of the books which 
 compose the sacred canon, the fulfilment of its 
 prophecies, the miraculous works of its founder, 
 his death and resurrection, have been demonstrated 
 to all who are capable of appreciating the force of 
 historical evidence; and in the poetical and prose 
 compositions of the inspired authors we discover a 
 system of doctrine and a code of morality traced in 
 characters as distinct and legible as the most unerr- 
 ing truths in the material world. False systems of 
 religion have indeed been deduced from the sacred 
 record, as false systems of the universe have 
 sprung from the study of the book of nature, but 
 the very prevalence of a false system proves the 
 existence of one that is true ; and though the two 
 classes of facts necessarily depend on different
 
 264 SIR ISAAC NEWTON. 
 
 kinds of evidence, yet we scruple not to say thnl 
 the Copernican system is not more demonstrably 
 true than the system of theological truth contained 
 in the Bible. If men of high powers, then, are still 
 found, who are insensible to the evidence which 
 sustains the system of the universe, need we won- 
 der that there are others whose minds are shut 
 against the effulgent evidence which intrenches the 
 strongholds of our faith. 
 
 If such, then, is the character of the Christian 
 faith, we need not be surprised that it was embraced 
 and expounded by such a genius as Sir Isaac New 
 ton. Cherishing its doctrines, and leaning on its 
 promises, he felt it his duty, as it was his pleasure, 
 to apply to it that intellectual strength which had 
 successfully surmounted the difficulties of the ma- 
 terial universe. The fame which that success pro- 
 cured him he could not but feel to be the breath of 
 popular applause, which administered only to his 
 personal feelings ; but the investigation of the sacred 
 mysteries, while it prepared his own mind for its 
 final destiny, was calculated to promote the spiritual 
 interests of thousands. This noble impulse he did 
 not hesitate to obey, and by thus uniting philosophy 
 with religion, he dissolved the league which genius 
 had formed with skepticism, and added to the cloud 
 of witnesses the brightest name of ancient or o f 
 modern times.
 
 HIS SCALE OF HEAT. 265 
 
 CHAPTER XVII. 
 
 Tfie minor Discoveries and Inventions of Newton His Researches on 
 Heat On Fire and Flame On Elective AttractionOn the Struc- 
 ture of Bodies His supposed Attachment to AlchymyHis Hypothe- 
 sis respecting Ether as the Cause of Light and Gravity On the Ex- 
 citation of Electricity in Glass His Rejecting Sextant invented 
 before 1700 His Reflecting Microscope His Prismatic Reflector as a 
 Substitute for the small Speculum of Reflecting Telescopes His 
 Method of varying the Magnifying Power of Newtonian Telescope* 
 His Experiments on Impressions on the Retina, 
 
 IN the preceding chapters we have given an ac 
 count of the principal labours of Sir Isaac Newton ; 
 but there still remain to be noticed several of his 
 minor discoveries and inventions, which could not 
 properly be introduced under any general head. 
 
 The most important of these, perhaps, are his 
 chymical researches, which he seems to have pur- 
 sued with more or less diligence from the time 
 when he first witnessed the practical operations of 
 chymistry during his residence at the apothecary's 
 at Grantham. His first chymical experiments were 
 probably made on the alloys of metals, for the pur- 
 pose of obtaining a good metallic composition for 
 the specula of reflecting telescopes. In his paper 
 on thin plates he treats of the combinations of solids 
 and fluids ; but he enters more largely on these and 
 other subjects in the queries published at the end 
 of his Optics. 
 
 One of his most important chymical papers is 
 his Tabula quantilatwn et graduum caloris, which 
 was published in the Philosophical Transactions. 
 This short paper contains a comparative scale of 
 temperature from that of melting" ice to that of a 
 small kitchen coal-fire. The following are the 
 principal points of the scale, the intermediate
 
 266 SIR ISAAC NEWTON. 
 
 degrees of heat having been determined with great 
 care. 
 
 'terrees Equal Parts 
 
 of Ht of Heat. 
 
 Freezing point of water. 
 
 1 12 Blood-heat. 
 
 2 24 Heat of melting wax. 
 
 3 48 Melting point of equal parts of tin 
 
 and bismuth. 
 
 4 96 Melting point of lead. 
 
 5 192 Heat of a small coal-fire. 
 
 The first column of this table contains the degrees 
 of heat in arithmetical progression, and the second 
 in geometrical progression, the second degree being 
 twice as great as the first, and so on. It is obvious 
 from this table, that the heat at which equal parts 
 of tin and bismuth melt is four times greater than 
 that of blood-heat, the heat of melting lead eight 
 times greater, and the heat of a small coal-fire six- 
 teen times greater. 
 
 This table was constructed by the help of a ther- 
 mometer, and of red-hot iron. By the former he 
 measured all heats as far as that of melting tin ; 
 and by the latter he measured all the higher heats. 
 For the heat which heated iron loses in a given time 
 is as the total heat of the iron ; and therefore, if the 
 times of cooling are taken equal, the heats will be 
 in a geometrical progression, and may therefore be 
 easily found by a table of logarithms. 
 
 He found by a thermometer constructed with lin- 
 seed oil, that if the oil, when the thermometer was 
 placed in melting snow, occupied a space of 1000 
 parts, the same oil, rarefied with one degree of heat,- 
 or that of the human body, occupied a space of 
 10256; in the heat of water beginning to boil, a 
 space of 10705 ; in the heat of water boiling vio 
 lently, 10725 ; in the heat of melted tin beginning tc 
 cool, and putting on the consistency of an amalgam
 
 HIS SCALE OF HEAT. 267 
 
 11516, and when the tin had become solio, 11496. 
 Hence the oil was rarefied in the ratio of 40 to 39 
 by the heat of the human body ; of 15 to 14 by the 
 heat of boiling water; of 15 to 13 in the heat of 
 melting tin beginning to solidify ; and of 23 to 20 in 
 the same tin when solid. The rarefaction of air 
 was, with the same heat, ten times greater than that 
 of oil, and the rarefaction of oil fifteen times greater 
 than that of spirit of wine. By making the heats 
 of oil proportional to its rarefaction, and by calling 
 the heat of the human body 12 parts, we obtain the 
 heat of water beginning to boil, 33 ; of water boil- 
 ing violently, 34 ; of melted tin beginning to solidify, 
 72 ; and of the same become solid, 70. 
 
 Sir Isaac then heated a sufficiently thick piece 
 of iron till it was red-hot ; and having fixed it in a 
 cold place, where the wind blew uniformly, he put 
 upon it small pieces of different metals and other 
 fusible bodies, and noted the times of cooling, till 
 all the particles, having lost their fluidity, grew cold, 
 and the heat of the iron was equal to that of the 
 human body. Then, by assuming that the excesses 
 of the heats of the iron and of the solidified par- 
 ticles of metal above the heat of the atmosphere, 
 were in geometrical progression when the times 
 were in arithmetical progression, all the heats were 
 obtained. The iron was placed in a current of air, 
 in order that the air heated by the iron might always 
 be carried away by the wind, and that cold air 
 might replace it with a uniform motion; for thus 
 equal parts of the air were heated in equal times, 
 and received a heat proportional to that of the iron. 
 But the heats thus found had the same ratio to one 
 another with the heats found by the thermometer ; 
 and hence he was right in assuming that the rare- 
 factions of the oil were proportional to its heats. 
 
 Another short chymical paper by Sir Isaac New- 
 ton has been published by Dr. Horsley. It is enti-
 
 268 SIR ISAAC NEWTON. 
 
 tied De Natura Acidorum, but is principally occupied 
 with a number of brief opinions on chymical sub- 
 jects. This paper was written later than 1687, as it 
 bears a reference to the Principia; and the most im- 
 portant facts which it contains seem to have been 
 more distinctly reproduced in the queries at the end 
 of the Optics. 
 
 The most important of these queries relate to fire, 
 flame, and electric attractions, and as they were re- 
 vised in the year 1716 and 1717, they may be regarded 
 as containing the most matured opinions of their 
 author. Fire he regards as a body heated so hot as 
 to emit light copiously, and flame as a vapour, fume, 
 or exhalation heated so hot as to shine. In his long 
 query on elective attractions, he considers the small 
 particles of bodies as acting upon one another at 
 distances so minute as to escape observation. When 
 salt of tartar deliquesces, he supposes that this arises 
 from an attraction between the saline particles and 
 the aqueous particles held in solution in the atmos- 
 phere, and to the same attraction he ascribes it that 
 the water will not distil from the salt of tartar with- 
 out great heat. For the same reason sulphuric acid 
 attracts water powerfully, and parts with it with 
 great difficulty. When this attractive force becomes 
 very powerful, as in the union between sulphuric 
 acid and water, so as to make the particles " coalesce 
 with violence," and rush towards one another with 
 an accelerated motion, heat is produced by the mix- 
 ture of the two fluids. In like manner, he explains 
 the production of flame from the mixture of cold 
 fluids, the action of fulminating powders, the com- 
 bination of iron filings with sulphur, and all the 
 other chymical phenomena of precipitation, combi- 
 nation, solution, and crystallization, and the mechan- 
 ical phenomena of cohesion and capillary attrac- 
 tion. He ascribes hot springs, volcanoes, fire-damps, 
 mineral coruscations, earthquakes, hot suffocating
 
 ELECTIVE ATTRACTION. 260 
 
 exhalations, hurricanes, lightning, thunder, fiery 
 meteors, subterraneous explosions, land-slips, ebul- 
 litions of the sea, and waterspouts, to sulphureous 
 steams abounding in the bowels of the earth, and 
 fermenting with minerals, or escaping into the atmos- 
 phere, where they ferment with acid vapours fitted 
 to promote fermentation. 
 
 In explaining the structure of solid bodies, he is 
 of opinion, "that the smallest particles of matter 
 may cohere by the strongest attractions, and com- 
 pose bigger particles of weaker virtue ; and many 
 of these may cohere and compose bigger particles 
 whose virtue is still weaker ; and so on for divers 
 successions, until the progression end in the biggest 
 particles, on which the operations in chymistry and 
 the colours of natural bodies depend, and which, by 
 adhering, compose bodies of a sensible magnitude. 
 If the body is compact, and bends or yields inward 
 to pression, without any sliding of its parts, it is hard 
 and elastic, returning to its figure with a force rising 
 from the mutual attraction of its parts. If the parts 
 slide upon one another, the body is malleable or soft. 
 If they slip easily, and are of a fit size to be agitated 
 by heat, and the heat is big enough to keep them in 
 agitation, the body is fluid ; and if it be apt to stick 
 to things, it is humid ; and the drops of every fluid 
 affect a round figure, by the mutual attraction of their 
 parts, as the globe of the earth and sea affects a 
 round figure, by the mutual attraction of its parts, by 
 gravity." 
 
 Sir Isaac then supposes, that, as the attractive 
 force of bodies can reach but to a small distance from 
 them, " a repulsive virtue ought to succeed ;" and he 
 considers such a virtue as following from the reflec- 
 tion of the rays of light, the rays being repelled with- 
 out the immediate contact of the reflecting body, and 
 also from the emission of light, the ray, as soon as 
 it is shaken off from a shining body by the vibrating 
 motion of the parts of the body, getting beyond the 
 X
 
 270 SIR ISAAC NEWTON. 
 
 reach of attraction, and being driven away with ex- 
 ceeding great velocity by the force of reflection.* 
 
 Many of the chymical views which Sir Isaac thus 
 published in the form of queries were in his own 
 lifetime illustrated and confirmed by Dr. Stephen 
 Hales, in his book on Vegetable Statics, a work of 
 great originality, which contains the germ of some 
 of the finest discoveries in modern chynustry. 
 
 Although there is no reason to suppose that Sir 
 Isaac Newton was a believer in the" doctrines of 
 alchymy, yet we are informed by the Reverend Mr. 
 Law that he had been a diligent student of Jacob 
 Behmen's writings, and that there were found among 
 his papers copious abstracts from them in his own 
 handwriting.! He states also that Sir Isaac, together 
 with one Dr. Newton, his relation, had, in the earlier 
 part of his life, set up furnaces, and were for several 
 months at work in quest of the philosopher's tinc- 
 ture. These statements may receive some confir- 
 mation from the fact, that there exist among the 
 Portsmouth papers many sheets, in Sir Isaac's own 
 writing, of FlammePs Explication of Hieroglyphic 
 Figures, and in another hand, many sheets of Wil- 
 liam Yworth's Processus Mysterii Magni Philosophi- 
 cits, and also from the manner in which Sir Isaac 
 requests Mr. Aston to inquire after one Bony in 
 Holland, who always went clothed in green, and who 
 was said to possess valuable secrets ; but Mr. Law 
 has weakened the force of his own testimony, when 
 
 * Mr. Herschel, in his Treatise on Light, 553, has maintained that 
 Newton's Doctrine of Reflection is accordant with I he idea that the 
 attractive force extends beyond the repulsive or reflecting force. In the 
 query above referred to, Sir Isaac, in the most distinct manner, places 
 the sphere of the reflecting force without that of the attractive one. 
 
 t In a tract annexed to his Appeal to all that doubl or disbelieve the 
 truths of the Gospel. See Gent. Mag. 1782, vol. lii. p. 227, 239. 
 
 It is stated in a letter of Mr. Law's, quoted in this magazine, that 
 Charles I. was a diligent reader and admirer of Jacob Behmen ; that he 
 sent a well-qualified person from England to Goerlitz, in Upper Lusatia, 
 to acquire the German language, and to collect every anecdote he could 
 meet with there relative to this great alchyrnist.
 
 HYPOTHESIS OF ETHER. 271 
 
 he asserts that Newton borrowed the doctrine of 
 attraction from Behmen's first three propositions of 
 eternal nature. 
 
 On the 7th December, 1675, Sir Isaac Newton com- 
 municated to the Royal Society a paper entitled 
 An hypothesis explaining properties of light, in which 
 he, for the first time, introduces his opinions respect- 
 ing ether, and employs them to explain the nature 
 of light, and the cause of gravity. "He was in- 
 duced," he says, "to do this, because he had observed 
 the heads of some great virtuosos to run much upon 
 hypotheses, and he therefore gave one which he was 
 inclined to consider as the most probable, if he were 
 obliged to adopt one."* 
 
 This hypothesis seems to have been afterward a 
 subject of discussion between him and Mr. Boyle, to 
 whom he promised to communicate his opinion more 
 fully in writing. He accordingly addressed to him a 
 long letter, dated February 28th, 1678-9, in which 
 he explains his views respecting ether, and employs 
 them to account for the refraction of light, the co- 
 hesion of two polished pieces of metal in an exhausted 
 receiver, the adhesion of quicksilver to glass tubes, 
 the cohesion of the parts of all bodies, the cause 
 of filtration, the phenomena of capillary attraction, 
 the action of menstrua on bodies, the transmu- 
 tation of gross compact substances into aerial ones, 
 and the cause of gravity. From the language used 
 in this paper, we should be led to suppose that Sir 
 Isaac had entirely forgotten that he had formerly- 
 treated the general subject of ether, and applied it 
 to the explanation of gravity. " I shall set down," 
 says he, " one conjecture more which came into my 
 mind now as I was writing this letter ; it is about the 
 cause of gravity" which he goes on to explain ;f and 
 
 * In a letter to Dr. Halley, dated June 20th, 1686, Sir Isc refers to 
 this paper, and observes, that it is only to be looked upo . *(0 *f bis 
 guesses that he did not rely upon. 
 
 t See page 273.
 
 272 SIR ISAAC NEWTON. 
 
 he concludes by saying, that " he has so little fancy 
 to things of this nature, that, had not your encourage- 
 ment moved me to it, I should never, I think, thus far 
 have set pen to paper about them." 
 
 These opinions, however, about the existence of 
 ether, Newton seems to have subsequently re- 
 nounced; for in the manuscript in the possession 
 of Dr. J. C. Gregory, which we have already men- 
 tioned, and which was written previous to 1702, he 
 states, that ether is neither obvious to our senses, 
 nor supported by any arguments, but is a gratuitous 
 assumption, which, if we are to trust to reason and 
 to our senses, must be banished from the nature of 
 things ; and he goes on to establish, by various argu- 
 ments, the validity of this opinion. This renuncia- 
 tion of his former hypothesis probably arose from 
 his having examined more carefully some of the 
 phenomena which he endeavoured to explain by it. 
 Those of capillary attraction, for example, he had 
 ascribed to the ether " standing rarer in the very sen- 
 sible cavities of the capillary tubes than without 
 them," whereas he afterward discovered their true 
 cause, and ascribed them to the reciprocal attraction 
 of the tube and the fluid. But, however this may 
 be, there can be no doubt that he resumed his early 
 opinions before the publication of his Optics, which 
 may be considered as containing his views upon this 
 subject. 
 
 The queries which contain these opinions are the 
 18th-24th, all of which appeared for the first time in 
 the second English edition of the Optics. If a body 
 is either heated or loses its heat when placed in 
 vacuo, he ascribes the conveyance of the heat in 
 both cases " to the vibration of a much subtiler me- 
 dium than air ;" and he considers this medium as the 
 same with that by which light is refracted and re- 
 flected, and by whose vibrations light communicates 
 heat to bodies, and is put into fits of easy reflection 
 and transmission.
 
 HYPOTHESIS OF ETHER. 273 
 
 This ethereal medium, according to our author, is 
 exceedingly more rare and more elastic than air. 
 It pervades all bodies, and is expanded through all 
 the heavens. It is much rarer within the dense 
 bodies of the sun, stars, planets, and comets, than 
 in the celestial spaces between them, and also more 
 rare within glass, water, &c. than in the free ana 
 open spaces void of air and other grosser bodies. 
 In passing out of glass, water, &c. and other dense 
 bodies into empty space, it grows denser and denser 
 by degrees, and this gradual condensation extends 
 to some distance from the bodies. Owing to its 
 great elasticity, and, consequently, its efforts to 
 spread in all directions, it presses against itself, and, 
 consequently, against the solid particles of bodies, 
 so as to make them continually approach to one 
 another, the body being impelled from the denser 
 parts of the medium towards the rarer with all that 
 power which we call gravity. 
 
 In employing this medium to explain the nature 
 of light, Newton does not suppose, with Descartes, 
 Hooke, Huygens, and others, that light is nothing 
 more than the impression of those undulations on 
 the retina. He regards light as a peculiar substance, 
 composed of heterogeneous particles thrown off with 
 great velocity, and in all directions, from luminous 
 bodies ; and he supposes that these particles while 
 passing through the ether, excite in it vibrations or 
 pulses which accelerate or retard the particles of 
 light, and thus throw them into their alternate fits 
 of easy reflection and transmission. 
 
 Hence, if a ray of light falls upon a transparent 
 body, in which the ether consists of strata of varia- 
 ble density, the particles of light acted upon by the 
 vibrations which they create will be urged with an 
 accelerated velocity in entering the body, while their 
 velocity will be retarded in quitting it. In this man- 
 ner he conceives the phenomena of refraction to be 
 produced, and he shows how in such a case the
 
 274 SIR ISAAC NEWTON. 
 
 refraction would be regulated by the law of the 
 sines. 
 
 In order that the ethereal medium may produce 
 the fits of easy reflection and transmission, he con- 
 ceives that its vibrations must be swifter than light. 
 He computes its elasticity to be 490,000,000,000 
 times greater than that of air, in proportion to its 
 density, and about 600,000,000 times more rare than 
 water, from which he infers that the resistance 
 which it would oppose to the motions of the planets 
 would not be sensible in 10,000 years. He considers 
 that the functions of vision and hearing may be per- 
 formed chiefly by the vibrations of this medium, 
 executed in the bottom of the eye, or in the auditory- 
 nerve by the rays of light, and propagated through 
 the 'solid, pellucid, and uniform capillamenta of the 
 optic or auditoiy nerves into the place of sensation ; 
 and he is of opinion that animal motion may be 
 performed by the vibrations of the same medium, 
 excited in the brain by the power of the will, and 
 propagated from thence by the solid, pellucid, and 
 uniform capillamenta of the nerves into the muscles 
 for contracting and dilating them. 
 
 In the registers of the Royal Society there exist 
 several letters* on the excitation of electricity in 
 glass, which were occasioned by an experiment of 
 this kind having been mentioned in Sir Isaac's 
 hypothesis of light. The society had ordered the 
 experiment to be tried at their meeting of the 16th 
 December, 1675 ; but, in order to secure its success, 
 Mr. Oldenburg wrote to Sir Isaac for a more par- 
 ticular account of it. Sir Isaac being tnus "put 
 upon recollecting himself a little farther about it," 
 remembers that he made the experiment with a 
 glass fixed at the distance of the |d of an inch from 
 one end of a brass hoop, and only the ^th of an inch 
 from the other. Small pieces of thin paper were 
 
 * See Newtoni Opera, by Horsley, vol. iv. p. 375-382
 
 REFLECTING SEXTANT. 275 
 
 then laid upon the table ; when the glass was laid 
 above them and rubbed, the pieces of paper leaped 
 from the one part of the glass to the other, and 
 twirled about in the air. Notwithstanding this ex- 
 plicit account of the experiment, it entirely failed 
 at the Royal Society, and the secretary was de- 
 sired to request the loan of Sir Isaac's apparatus, 
 and to inquire whether or not he had secured the 
 papers from being moved by the air, which might 
 have somewhere stole in. In a letter, dated 21st 
 December, Sir Isaac recommended to the society to 
 rub the glass " with stuff whose threads may rake 
 its surface, and, if that will not do, to rub it with 
 the fingers' ends to and fro, and knock them as 
 often upon the glass." These directions enabled 
 the society to succeed with the experiment on the 
 13th January, 1676, when they used a scrubbing 
 brush of short hog's bristles, and the heft of a knife 
 made with whalebone. 
 
 Among the minor inventions of Sir Isaac Newton, 
 we must enumerate his reflecting instrument for 
 observing the moon's distance from the fixed stars 
 at sea. The description of this instrument was com- 
 municated to Dr. Halley in the year 1700 ; but, either 
 from having mislaid the manuscript, or from attach- 
 ing no value to the invention, he never communi- 
 cated it to the Royal Society, and it remained among 
 his papers till after his death in 1742, when it was 
 published in the Philosophical Transactions. The 
 following is Sir Isaac's own description of -it as 
 communicated to Dr. Halley. 
 
 " In the annexed figure PQRS denotes a plate of 
 brass, accurately divided in the limb DQ, into de- 
 grees, 2 minutes, and yV minutes, by a diagonal 
 scale; and the i degrees, and i minutes, and - 
 minutes, counted for degrees, minutes, and minutes". 
 A.B is a telescope three or four feet long, fixed on 
 the eige of that brass plate. G is a speculum fixed
 
 276 SIR ISAAC NEWTON. 
 
 on the brass plate perpendicularly as near as 
 may be to the object-glass of the telescope, so a 
 
 Piff. 12. 
 
 to be inclined forty-five degrees to the axis ot 
 the telescope, and intercept half the light which 
 would otherwise come through the telescope to the 
 eye. CD is a moveable index turning about the 
 centre C, and, with its fiducial edge, showing the 
 degrees, minutes, and minutes on the limb of the 
 brass plate PQ ; the centre C must be over against 
 the middle of the speculum G. H is another specu- 
 lum, parallel to the former, when the fiducial edge 
 of index falls on 0' 0" ; so that the same star may 
 then appear through the telescope in one and the 
 same place, both by the direct rays and by the re- 
 flexed ones ; but if the index be turned, the star shall 
 appear in two places, whose distance is showed on 
 the brass limb by the index. 
 
 "By this instrument the distance of the moon 
 from any fixed star is thus observed : view the star
 
 REFLECTING MICROSCOPE. 277 
 
 through the perspicil by the direct light, and the 
 moon by the reflexed (or on the contrary); and 
 turn the index till the star touch the limb of the 
 moon, and the index shall show on the brass limb 
 of the instrument the distance of the star from the 
 moon's limb ; and though the instrument shake by 
 the motion of the ship at sea, yet the moon and star 
 will move together as if they did really touch one 
 another in the heavens ; so that an observation may 
 be made as exactly at sea as at land. 
 
 " And by the same instrument may be observed 
 exactly the altitudes of the moon and stars, by 
 bringing them to the horizon ; and thereby the lati- 
 tude and times of observation may be determined 
 more exactly than by the ways now in use. 
 
 " In the time of the observation, if the instrument 
 move angularly about the axis of the telescope, the 
 star will move in a tangent of the moon's limb,, or 
 of the horizon ; but the observation may notwith- 
 standing be made exactly, by noting when the line 
 described by the star is a tangent to the moon's 
 limb, or to the horizon. 
 
 "To make the instrument useful, the telescope 
 ought to take in a large angle ; and to make the 
 observation true, let the star touch the moon's limb, 
 not on the outside, but on the inside." 
 
 This ingenious contrivance is obviously the very 
 same invention as that which ]VIr. Hadley produced 
 in 1731, and which, under the name of Hadley's 
 Quadrant, has been of so great service in navigation. 
 The merit of its first invention must therefore be 
 transferred to Sir Isaac Newton. 
 
 In the year 1672, Sir Isaac communicated to 
 Mr. Oldenburg his design for a microscope, which 
 he considered to be as capable of improvement as 
 the telescope, and perhaps more so, because it 
 requires only one speculum. This microscope is 
 shown in the annexed diagram, where AB is the 
 object-metal, CD the eye-glass, F their common
 
 278 SIR ISAAC NEWTON. 
 
 focus, and O the other focus of the metal in which 
 the object is placed. This ingenious idea has been 
 
 Fig. 13. 
 
 greatly improved in modern times by Professor 
 Amici, who makes AB a portion of an ellipsoid, 
 whose foci are O and F, and who places a small 
 plain speculum between O and AB, in order to re- 
 flect the object, which is placed on one side AP, for 
 the purpose of being illuminated. 
 
 In another letter to Mr. Oldenburg, dated July 
 llth in the same year, he suggests another improve- 
 ment in microscopes, which is to "illuminate the 
 object in a darkened room with the light of any 
 convenient colour not too much compounded : for 
 by that means the microscope will, with distinct- 
 ness, bear a deeper charge and larger aperture, 
 especially if its construction be such as I may here- 
 after describe."* This happy idea I have some 
 years ago succeeded in realizing, by illuminating 
 microscopic objects with the light of a monochro- 
 matic lamp, which discharges a copious flame of 
 pure yellow light of definite refrangibility.f 
 
 In order to remedy the evils arising from the 
 weak reflecting power of speculum metal, and from 
 its tarnishing by exposure to the air, Sir Isaac pro- 
 posed to substitute for the small oval speculum a 
 triangular prism of glass or crystal ABC. Its side 
 
 * Sir Isaac does not seem to have afterward described this construe 
 lion. 
 
 t See Edinburgh Transactions, vol. ix. p. 433, and the 
 Taurnal of Science, July, 1829, No. I. New Series, p. 108.
 
 PRISMATIC REFLECTOR. 
 
 279 
 
 AB la he supposes to perform the office of that metal, 
 by reflecting towards the eye-glass the light which 
 comes from the concave speculum DF, fig. 13, 
 whose light he supposes to enter into this prism at 
 its side CB be, and lest any colours should be pro- 
 duced by the refraction of these planes, it is requisite 
 that the angles of the Fig. 14. 
 
 prism at Aa and Bi be 
 precisely equal. This 
 maybe done most conve- 
 niently, by making them 
 half right angles, and con- 
 sequently the third angle A < 
 at Cc a right one. The 
 plane AB la will reflect 
 all the light incident upon 
 it ; but in order to ex- 
 clude unnecessary light, 
 it will be proper to cover 
 it all over with some black subetance excepting two 
 circular spaces of the planes Ac and Be, through 
 which the useful light may pass. The length of the 
 
 Fig. 15 
 
 prism should be such that its sides Ac and Be may 
 be square, and so much of the angles B and I as are
 
 280 
 
 SIR ISAAC NEWTON. 
 
 superfluous ought to be ground off, to give passage 
 for as much light as is possible from the object to 
 the speculum. 
 
 One great advantage of this prism, which cannot 
 be obtained from the oval metal, is, that without 
 using two glasses the object may be erected, and 
 the magnifying power of the telescope varied at 
 pleasure, by merely varying the distances of the 
 speculum, the prism, and the eye-glass. This will 
 be understood from fig. 16, where AI represents 
 
 Fig. 1C. 
 
 the great concave speculum, EF the eye-glass, and 
 BCD the prism of glass, whose sides BC and CD 
 are not flat, but spherically convex. The rays which 
 come from G, the focus of the great speculum AI, 
 will, by the refraction of the first side BC, be re- 
 duced to parallelism, and after reflection from the 
 base CD, will be made by the refraction of the next 
 side BD to converge to the focus H of the eye-glass 
 EF. If we now bring the prism BCD nearer the 
 image at G, the point H will recede from BD, and 
 the image formed there will be greater than that at 
 C>, and if we remove the prism BCD from G, the 
 point H will approach to BD, and the image at H
 
 IMPRESSIONS ON THE RETINA. ^81 
 
 will be less than that at G. The prism BCD per- 
 forms the same part as a convex lens, G and H 
 being its conjugate foci, and the relative size of the 
 images formed at these points being proportional to 
 their distance from the lens. This construction 
 would be a good one for varying optically the angu- 
 lai distance of a pair of wires placed in the focus of 
 the eye-glass EF; and by bisecting the lenticular 
 prism BCD, and giving the halves a slight inclina- 
 tion, we should be able to separate and to close the 
 two images or disks which would thus be produced, 
 and thus -form a double image micrometer. 
 
 Among the minor and detached labours of Sir 
 Isaac, we must not omit his curious experiments on 
 the action of light upon the retina. Locke seems 
 to have wished his opinion respecting a fact stated 
 in Boyle's Book on Colours, and in a letter from 
 Cambridge, dated June 3pth, 1691, he communicated 
 to his friend the following very remarkable obser- 
 vations made by himself. 
 
 "The observation you mention in Mr. Boyle's 
 book of colours I once made upon myself with the 
 hazard of my eyes. The manner was this ; I looked 
 a very little while upon the sun in the looking-glass 
 with my right eye, and then turned my eyes into a 
 dark corner of my chamber, and winked, to observe 
 the impression made, and the circles of colours 
 which encompassed it, and how they decayed by 
 degrees, and at last vanished. This I repeated a 
 second and a third time. At the third time, when 
 the phantasm of light and colours about it were 
 almost vanished, intending my fancy upon them to 
 see their last appearance, I found, to my amaze- 
 ment, that they began to return, and by little and 
 little to become as lively and vivid as when I had 
 newly looked upon the sun. But when I ceased to 
 intend my fancy upon them, they vanished again. 
 After this, I found, that as often as I went into the 
 dark, and intended my mind upon them, as when
 
 282 SIR ISAAC NEWTON. 
 
 a man looks earnestly to see any thing wnic>. 2s 
 difficult to be seen, I could make the phantasm re- 
 turn without looking any more upon the sun ; and 
 the oftener I made it return, the more easily I could 
 make it return again. And at length, by repeating 
 this without looking any more upon the sun, I made 
 such an impression on my eye, that, if I looked upon 
 the clouds, or a book, or any bright object, I saw 
 upon it a round bright spot of light like the sun. 
 and, which is still stranger, though I looked upon 
 the sun with my right eye only, and not with my 
 left, yet my fancy began to make an impression 
 upon my left eye, as well as upon rny right. For if 
 I shut my right eye, or looked upon a book or the 
 clouds with "my left eye, I could see the spectrum 
 of the sun almost as plain as with my right eye, if I 
 did but intend my fancy a little while upon it ; for 
 at first, if I shut my right eye, and looked with my 
 left, the spectrum of the sun did not appear till I in- 
 tended my fancy upon it ; but by repeating, this ap- 
 peared every time more easily. And now, in a few 
 hours' time, I had brought my eyes to such a pass, 
 that I could look upon no bright object with either 
 eye but I saw the sun before me, so that I durst 
 neither write nor read ; but to recover the use of my 
 eyes, shut myself up in my chamber made dark, for 
 three days together, and used all means to divert 
 my imagination from the sun. For if I thought 
 upon him, I presently saw his picture, though I was 
 in the dark. But by keeping in the dark, and em- 
 ploying my mind about other things, I began in 
 three or four days to have some use of my eyes 
 again ; and, by forbearing to look upon bright ob- 
 jects, recovered them pretty well, though not so 
 well but that, for some months after, the spectrum 
 Df the sim began to return as often as I began to 
 meditate upon tha phenomena, even though I lay in 
 bed at midnight \vith my curtains drawn. But now 
 I have been ver v well for manv years, though I am
 
 IMPRESSIONS ON THE RETINA. 283 
 
 apt to think, if I durst venture my eyes, I could still 
 make the phantasm return by the power of my 
 fancy. This story I tell you, to let you understand, 
 that in the observation related by Mr. Boyle, the 
 man's fancy probably concurred with the impression 
 made by the sun's light to produce that phantasm 
 of the sun which he constantly saw in bright objects. 
 And so your question about'the cause of this phan- 
 tasm involves another about the power of fancy, 
 which I must confess is too hard a knot for me to 
 untie. To place this effect in a constant motion is 
 hard, because the sun ought then to appear per- 
 petually. It seems rather to consist in a disposition 
 of the sensorium to move the imagination strongly, 
 and to be easily moved, both by the imagination 
 and by the light, as often as bright objects are looked 
 upon." 
 
 These observations possess in many respects a high 
 degree of interest. The fact of the transmission 
 of the impression from the retina of the one eye to 
 that of the other is particularly important ; and it 
 deserves to be remarked, as a singular coincidence, 
 that I had occasion to observe and to describe the 
 same phenomena above twenty years ago,* and long 
 oefore the observations of Sir Isaac were commit* 
 nicated to the scientific world. 
 
 * Art. Accidental Colours in the Edinburgh Encyclopedia.
 
 SIR ISAAC NEWTOV 
 
 CHAPTER XVIII. 
 
 Sis Acquaintance, with Dr. Pemberton, who edits the Third Edition of 
 ike PrincipiaHis first Attack of ill Health His Recovery- He it 
 taken ill in consequence of attending the Royal Society His Death 
 on the 20*A March, 1727 His Body lies in state His Funeral He 
 is. buried in Westminster Abbey His Monument described His Epi- 
 taph A Medal struck in honour of him Roubiliac's full-length 
 Statue of him erected in Cambridge Division of his Property His 
 Successors. 
 
 ABOUT the year 1722, Sir Isaac was desirous o/ 
 publishing- a third edition of his Principia, and the 
 premature death of Mr. Cotes having deprived him 
 of his valuable aid, he had the good fortune to be- 
 come acquainted with Dr. Henry Pemberton, a young 
 and accomplished physician, who had cultivated 
 mathematical learning with considerable success. 
 M. Poleni, an eminent professor in the University 
 of Padua, having endeavoured, on the authority of 
 a new experiment, to overturn the common opinion 
 respecting the force of bodies in motion, and to es- 
 tablish that of Leibnitz in its place, Dr. Pemberton 
 transmitted to Dr. Mead a demonstration of its 
 inaccuracy. Dr. Mead communicated this paper to 
 Sir Isaac, who not only highly approved of it, but 
 added a demonstration of his own, drawn from 
 another consideration of the subject ; and this was 
 printed without his name, as a postscript to Pem- 
 berton's paper, when it appeared in the Transac- 
 tions.* 
 
 In a short time after the commencement of their 
 acquaintance, Sir Isaac engaged Dr. Pemberton to 
 superintend the new edition of the Principia. In 
 discharging this duty, Dr. Pemberton had occasion 
 to make many remarks on this work, which Sir Isaac 
 
 * Bee Phil. Trans. 1722, vol. xxxiii. p. 57.
 
 ILL HEALTH 285 
 
 always received with the utmost goodness, and the 
 new edition appeared with numerous alterations in 
 1726. On the occasions upon which he had per- 
 sonal intercourse with Sir Isaac, and which were 
 necessarily numerous, he endeavoured to learn his 
 opinions on various mathematical subjects, and to 
 obtain some historical information respecting his 
 inventions and discoveries. Sir Isaac entered freely 
 into all these topics ; and during the conversations 
 which took place, and while they were reading 
 together Dr. Pemberton's popular account of Sir 
 Isaac's discoveries, he oHained the most perfect 
 evidence that, though his memory was much de- 
 cayed, yet he was fully able to understand his own 
 writings. 
 
 During the last twenty years of his life, which he 
 spent in London, the charge of his domestic con- 
 cerns devolved upon his beautiful and accomplished 
 Diece, Mrs. Catharine Barton, the wife of Colcne! 
 Barton, for whom, as we have already seen, the 
 Earl of Halifax had conceived the warmest affec- 
 tion. This lady, who had been educated at her 
 uncle's expense, married Mr. Conduit, and continued 
 to reside with her husband in Sir Isaac's house til/ 
 the time of his death. 
 
 In the year 1722, when he had reached the 
 eightieth year of his age, he was seized with an 
 incontinence of urine, which was ascribed to stone 
 in the bladder, and was considered incurable. By 
 means of a strict regimen, however, and other pre- 
 cautions, he was enabled to alleviate his complaint, 
 and to procure long intervals of ease. At this time 
 he gave up the use of his carriage, and always went 
 out in a chair. He declined all invitations to dinner, 
 and at his own house he had only small parties. In 
 his diet he was extremely temperate. Though he 
 took a little butcher meat, yet the principal articles 
 of his food were broth, vegetables, and fruit, of 
 which he always ate very heartily. In spite of all
 
 286 SHI ISAAC NEWTON. 
 
 his precautions, however, he experienced a return 
 of his old complaint, and in August, 1724,' he passed 
 a stone the size of a pea, which came away in two 
 pieces, the one at the distance of two days from the 
 other. After some months of tolerable good health, 
 he was seized in January, 1725, with a violent cough 
 and inflammation of the lungs ; and in consequence 
 of this attack, he was prevailed upon, with some 
 difficulty, to take up his residence at Kensington, 
 where his health experienced a decided improve- 
 ment. In February, 1725, he was -attacked in both 
 his feet with a fit of the gout, of which he had re- 
 ceived a slight warning a few years before, and the 
 effect of this new complaint was to produce a great 
 and beneficial change in his general health. On 
 Sunday the 7th March, when his head was clearer 
 and his memory stronger than Mr. Conduit had 
 known it to be for some time, he entered into a long 
 conversation on various subjects in astronomy. He 
 explained to Mr. Conduit how comets might be 
 formed out of the light of vapours discharged from 
 the sun and the fixed stars as the centres of sys- 
 tems. He conceived that these luminaries were 
 replenished by the same comets being again returned 
 to them ; and upon this principle he explained the 
 extraordinary lights which were seen among the 
 fixed stars by Hipparchus, Tycho Brahe, and Kepler's 
 disciples, and which he supposed to arise from the 
 additional fuel which they received.* 
 
 Notwithstanding the improvement which his health 
 had experienced, his indisposition was still suffi- 
 ciently severe to unfit him for the discharge of his 
 duties at the mint ; and as his old deputy was con- 
 fined with the dropsy, he was desirous in 1725 of 
 resigning his office to Mr. Conduit. Difficulties 
 probably were experienced in making this arrange- 
 ment, but his nephew discharged for him all the 
 
 * This conversation, originally copied from Mr. Conduit's handwriting, 
 te given in the Appendix, No. ill. p. 320.
 
 DEATH. 287 
 
 duties of his office ; and during the last year of his 
 life he hardly ever went to the mint. 
 
 But though every kind of motion was calculated 
 to aggravate his complaint, and though he had de- 
 rived from absolute rest and from the air at Ken- 
 sington the highest benefit, yet great difficulty was 
 experienced in preventing him from occasionally 
 going to town. Feeling himself able for the jour- 
 ney, he- went to London on Tuesday the 28th of 
 February, 1727, to preside at a meeting of the Royal 
 Society. On the following day Mr. Conduit con- 
 sidered him better than he had been for many years, 
 and Sir Isaac was himself so sensible of this im- 
 provement in his health, that he assured his nephew 
 that on the Sunday preceding, he had slept from 
 eleven o'clock at night till eight o'clock next morn- 
 ing without waking. He had undergone, however, 
 great fatigue in attending the meeting of the Royal 
 Society, and in paying and receiving visits, and the 
 consequence of this was a violent return of his 
 former complaint. He returned to Kensington on 
 Saturday the 4th March, and was attended by Dr. 
 Mead and Dr. Cheselden, who pronounced his dis- 
 ease to be stone, and held out no hopes of his 
 recovery. From the time of his last journey to 
 London he had experienced violent fits of pain with 
 very short intermissions ; and though the drops of 
 sweat ran down his face during these severe parox- 
 ysms, yet he never uttered a cry or a complaint, or 
 displayed the least marks of peevishness or impa 
 tience ; but during the short intervals of relief which 
 occurred, he smiled and conversed with his usual 
 gayety and cheerfulness. On Wednesday the 15th 
 of March he seemed a little better; and slight, 
 though groundless hopes were entertained of his 
 recovery. On the morning of Saturday the 18th 
 he read the newspapers, and carried on a pretty long 
 conversation with Dr. Mead, when all his senses and 
 faculties were strong and vigorous ' ut at six o'clock
 
 288 SIR ISAAC NEWTON. 
 
 of the same evening he became insensible, and he 
 continued in that state during the whole of Sunday, 
 and till Monday the 20th, when he expired between 
 one and two o'clock in the morning, in the eighty- 
 fifth year of his age. 
 
 His body was removed from Kensington to Lon- 
 don, and on Tuesday the 28th March it lay in state 
 in the Jerusalem Chamber, and was thence conveyed 
 to Westminster Abbey, where it was buried near the 
 entrance into the choir on the left-hand. The pall 
 was supported by the Lord High Chancellor, the 
 Dukes of Roxburghe and Montrose, and the Earls 
 of Pembroke, Sussex, and Macclesfield, who were 
 Fellows of the Royal Society. The Hon. Sir Mi- 
 chael Newton, Knight of the Bath, was chief 
 mourner, and was followed by some other relations, 
 and several distinguished characters who were inti- 
 mately acquainted with the deceased. The funeral 
 service was performed by the Bishop of Rochester, 
 attended by the prebend and choir. 
 
 Sensible of the high honour which they derived 
 from their connexion with so distinguished a phi- 
 losopher, the relations of Sir Isaac Newton who 
 inherited his personal estate,* agreed to devote 500/. 
 to the erection of a monument to his memory, and 
 the deaD and chapter of Westminster appropriated 
 for it a place in the most conspicuous part of the 
 Abbey, which had often been refused to the greatest 
 of our nobility. This monument was erected in 
 1731. On the front of a sarcophagus resting on a 
 pedestal are sculptured in basso-relievo youths bear- 
 ing in their hands the emblems of Sir Isaac's prin- 
 cipal discoveries. One carries a prism, another a 
 reflecting telescope, a third is weighing the sun and 
 
 * These were the three children of his half-brother Smith, the three 
 children of his half-sister Pilkington, and (he two daughters of his half- 
 sister Barton, all of whom survived Sir Isaac. New Anecdotes nf Sir 
 Isaac Newton, by J. H., a Gentleman of his Mother's Family. See An 
 nual Register, 1776, vol. xix. p. 25 of Characters. The author of this 
 paper was Janies Button, Esq. of Pimlico.
 
 MONUMENT. 289 
 
 planets with a steelyard, a fourth is employed about 
 a furnace, and two others are loaded with money 
 newly coined. On the sarcophagus is placed the 
 figure of Sir Isaac in a cumbent posture, with his 
 elbow resting on several of his works. Two youths 
 stand before him with a scroll, on wh ?h is drawn a 
 remarkable diagram relative to the solar system, and 
 above that is a converging series. Behind the sar- 
 cophagus is a pyramid, from the middle of which 
 rises a globe in mezzo-relievo, upon which several 
 of the constellations are drawn, in order to show 
 the path of the comet of 1681, whose period Sir 
 Isaac had determined, and also the position of the 
 solstitial colure mentioned by Hipparchus, and by 
 means of which Sir Isaac had, in his Chronology, 
 fixed the time of the Argonautic expedition. A figure 
 of 'Astronomy as Queen of the Sciences sits weep- 
 ing on the Globe with a sceptre in her hand, and a 
 star surmounts the summit of the pyramid. The 
 following epitaph is inscribed on the monument. 
 
 Hie situs est 
 
 Isaacus Newton, Eques Auratus, 
 
 Qui Animi Vi prope divina, 
 
 Planetarum Motus, Figuras, 
 
 Cometarum Semitas, Oceanique JSstus, 
 
 Sua Mathesi facem preferente, 
 
 Primus demonstravit. 
 
 Radiorum Lucis dissimilitudines, 
 
 Colorumque inde nascentium Proprietates, 
 
 Q,uas nemo aniea vel suspicatus erat, pervestigavit, 
 
 Naturae, Antiquitates, S. Scripturae, 
 
 Sedulus, sagax, fidns Interpres, 
 Dei Opt. Max. Majestatem Philosophia asseruit, 
 
 Evangelii simplicitatem moribus expressit. 
 Sibi gratulentur Mortales, tale tantumque extitisse, 
 
 HtTMAM GENERIS DECUS. 
 
 Natus xxv. Decemb. MDCXLII. Obiit. xx. Mar. 
 
 MDCCXXVII. 
 
 Of which the following is a literal translation i 
 
 Here lies 
 
 Isaac Newton, Knight, 
 Who, by a Vigour of Mind almost supernatural, 
 
 First demonstrated 
 The Morions and Figures of the Planets,
 
 290 SIR ISAAC NEVPTON. 
 
 The Paths of the Comets, and the Tides of tie Ocean 
 
 He diligently investigated 
 
 The different Refrdngibiiihes of the Rays of Light, 
 
 And the Properties of the Colours to which they give rise 
 
 AH assiduous, sagacious, and faithful Interpreter 
 
 Of Nature, Antiquity, and the Holy Scriptures, 
 
 He asserted in his Philosophy the Majesty of God, 
 
 And exhibited in his conduct the Simplicity of the GospeJ. 
 
 Let Mortals rejoice 
 That there has existed such and so great 
 
 AN ORNAMENT OF HOIAN NATTRE. C\y 
 
 Born 25th Dec. 1642, Died 20th March, 1727. 
 
 In the beginning of 1731, a medal was struck at 
 the Tower in honour of Sir Isaac Newton. It had 
 on one side the head of the philosopher, with the 
 motto, Felix cognoscere causas, and on the reverse a 
 figure representing the mathematics. 
 
 On the 4th February, 1755, a magnificent full- 
 length statue of Sir Isaac Newton in Vhite marble 
 was erected in the antechapel of Trinity College. 
 He is represented standing on a pedestal in a loose 
 gown, holding a prism, and looking upwards with an 
 expression of the deepest thought. On the pedestal 
 is the inscription, 
 
 Qui genus humanum ingenio superavit. 
 Who surpassed all men in genius. 
 
 This statue, executed by Roubiliac, was erected 
 at the expense of Dr. Robert Smith, the author of 
 the Compleat System of Optics, and professor of as- 
 tronomy and experimental philosophy at Cambridge. 
 It has been thus described by a modern poet : 
 
 Hark where the organ, full and clear, 
 With loud hosannas charms the ear ; 
 Behold, a prism within his hands, 
 Absorbed in thought great Newton stands 
 Such was his brow, and looks serene, 
 His serious gait and musing mien, 
 When taught on eagle wings to fly, 
 He traced the wonders of the sky ; 
 The chambers of the sun explored. 
 Where tints of thousand hues were stored. 
 
 Dr. Smith likewise bequeathed the sum of 500/.
 
 PROPERTY SUCCESSORS. 291 
 
 for executing a painting on glass for the window at 
 " 'he south end of Trinity College, Cambridge. The 
 subject represents jthe presentation of Sir Isaac 
 Newton to his majesty George III., who is seated 
 under a canopy with a laurel chaplet in his hand, and 
 attended by the British Minerva, apparently advising 
 him to reward merit in the person of the great phi- 
 losopher. Below the throne, the Lord Chancellor 
 Bacon is proposing to register the reward about to 
 be conferred upon Sir Isaac. The original drawing 
 of this absurd picture was executed by Cypriani, 
 and cost one hundred guineas. 
 
 The personal estate of S:',r Isaac Newton, which 
 was worth about 32,000/., was divided among his 
 four nephews and four nieces of the half-blood, the 
 grandchildren of his mother by the Reverend Mr. 
 Smith. The family estates of Woolsthorpe and 
 Sustern he bequeathed to John Newton, the heir-at- 
 law, whose great-grandfather was Sir Isaac's uncle. 
 This gentleman does not seem to have sufficiently 
 valued the bequest, for he sold them in 1732, to Ed- 
 mund Turnor of Stoke Rocheford.* A short time 
 before his death, Sir Isaac gave away an estate in 
 Berkshire to the sons and daughter of a brother of 
 Mrs. Conduit, who, in consequence of their father 
 dying before Sir Isaac, had no share in the personal 
 estate ; and he also gave an estate of the same value, 
 which he bought at Kensington, to Catharine, the 
 only daughter of Mr. Conduit, who afterward mar- 
 tied Mr. Wallop, the eldest son of Lord Lymington. 
 This lady was afterward Viscountess Lymington, 
 ind the estate of Kensington descended to the late 
 Earl of Portsmouth, by whom it was sold. Sir Isaac 
 was succeeded as master and warden in the mint by 
 his nephew, John Conduit, Esq., who wrote a trea- 
 tise on the gold and silver coin, and who died in 
 1737, leaving behind him his wife and daughter, the 
 former of whom died in 1739, in the 59th year of 
 her age, 
 
 * Turnor's Collections* &c. j>- 158- See APPENDIX, P 3J6.
 
 292 SIR ISAAC NEWTON 
 
 CHAPTER XIX. 
 
 Permanence of Newton's Reputation Character of his GeniusHi* 
 Met-hods of Investigation similar to that, used by Galileo Error in 
 ascribing his Discoveries to the Use of the Methods recommended by 
 Lord Bacon The Pretensions of the Baconian Philosophy examined 
 Sir Isaac Newton's social Character His great Modesty The 
 Simplicity of his Character His religious and moral Character 
 His Hospitality and Mode of Life His Generosity and Chanty 
 His Absence His personal 'Appearance Statues and Pictures of 
 him Memorials and Recollections of him. 
 
 SUCH were the last days of Sir Isaac Newton, and 
 such the last laurels which were shed over his grave. 
 A century of discoveries has since his day been 
 added to science ; but brilliant as these discoveries 
 are, they have not obliterated the . minutest of his 
 labours, and have served only to brighten the halo 
 which encircles his name. The achievements of 
 genius, like the source from which they spring, are 
 indestructible. Acts of legislation and deeds of war 
 may confer a high celebrity, but the reputation which 
 they bring is only local and transient; and while 
 they are hailed by the nation which they benefit, 
 they are reprobated by the people whom they ruin 
 or enslave. The labours of science, on the contrary, 
 bear along with them no counterpart of evil. They 
 are the liberal bequests of great minds to every 
 individual of their race, and wherever they are wel- 
 comed and honoured they become the solace of 
 private life, and the ornament and bulwark of the 
 commonwealth. 
 
 The importance of Sir Isaac Newton's discoveries 
 has been sufficiently exhibited in the preceding 
 chapters : the peculiar character of his genius, and 
 tne method which he pursued in his inquiries, can 
 be gathered only from the study of his works, and
 
 CHARACTER OF HIS GENIUS. ^3 
 
 from the history of his individual labours. Were 
 we to judge of the qualities of his mind from the 
 early age at which he made his principal discoveries, 
 and from the rapidity of their succession, we should 
 be led to ascribe to him that quickness of penetra- 
 tion, and that exuberance of invention, which is 
 more characteristic of poetical than of philosophical 
 genius. But we must recollect that Newton was 
 placed in the most favourable circumstances for the 
 development of his powers. The flower of his 
 youth and the vigour of his manhood were entirely 
 devoted to science. No injudicious guardian con- 
 trolled his ruling passion, and no ungenial studies or 
 professional toils interrupted the continuity of his 
 pursuits. His discoveries were, therefore, the fruit 
 of persevering and unbroken study ; and he himself 
 declared, that whatever service he had done to th 
 public was not owing to any extraordinary sagacity, 
 but solely to industry and patient thought. 
 
 Initiated early into the abstractions of geometry, 
 he was deeply imbued with her cautious spirit ; and 
 if his acquisitions were not made with the rapidity 
 of intuition, they were at least firmly secured ; and 
 the grasp which he took of his subject was propor- 
 tional to the mental labour which it had exhausted. 
 Overlooking what was trivial, and separating what 
 was extraneous, he bore down with instinctive 
 sagacity on the prominences of his subject, and 
 having thus grappled with its difficulties, he never 
 failed to intrench himself in its strongholds. 
 
 To the highest powers of invention Newton 
 added, what so seldom accompanies them, the talent 
 of simplifying and communicating his profoundest 
 speculations.* In the economy of her distributions, 
 nature is seldom thus lavish of her intellectual gifts 
 The inspired genius which creates is rarely con- 
 
 * Tills valuable faculty characterizes all his writings, whether theo. 
 logical, chymicttl, or mathematical ; but it is peculiarly displayed itt his 
 treatise on Universal Arithmetic, and in his Optical Lectures. 
 
 z
 
 294 SIR ISAAC NEWTON. 
 
 ferred along with the matured judgment which 
 combines, and yet without the exertion of both the 
 fabric of human wisdom could never have been 
 reared. Though a ray from heaven kindled the 
 vestal fire, yet an humble priesthood was required to 
 keep alive the flame. 
 
 The method of investigating truth by observation 
 and experiment, so successfully pursued in the Prin- 
 cipia, has been ascribed by some modern writers of 
 great celebrity to Lord Bacon ; and Sir Isaac New- 
 ton is represented as having owed all his discoveries 
 to the application of the principles of that distin- 
 guished writer. One of the greatest admirers of 
 Lord Bacon has gone so far as to characterize him 
 as a man who has had no rival in the times which 
 are past, and as likely to have none in those which 
 are to come. In a eulogy so overstrained as this, 
 we feel that the language of panegyric has passed 
 into that of idolatry ; and we are desirous of weigh- 
 ing the force of arguments which tend to depose 
 Newton from the high-priesthood of nature, and to 
 unsettle the proud destinies of Copernicus, Galileo, 
 and Kepler. 
 
 That Bacon was a man of powerful genius, and 
 endowed with varied and profound talent, the most 
 skilful logician, the most nervous and eloquent 
 writer of the age which he adorned, are points which 
 have been established by universal suffrage. The 
 study of ancient systems had early impressed him 
 with the conviction that experiment and observation 
 were the only sure guides in physical inquiries ; 
 and, ignorant though he was of the methods, the 
 principles, and the details of the mathematical 
 sciences, his ambition prompted him to aim at tfre 
 construction of an artificial system by which the 
 laws of nature might be investigated, and which 
 might direct the inquiries of philosophers in every 
 future age. The necessity of experimental research, 
 and of advancing gradually from the study of facts
 
 BACONIAN PHILOSOPHY. 295 
 
 to the determination of their cause, though the 
 groundwork of Bacon's method, is a doctrine which 
 was not only inculcated but successfully followed 
 by preceding philosophers. In a letter from Tycho 
 Brahe to Kepler, this industrious astronomer urges 
 his pupil " to lay a solid foundation for his views 
 by actual observation, and then by ascending from 
 these to strive to reach the causes of things ;" and 
 it was no doubt under the influence of this advice 
 that Kepler submitted his wildest ^ancies to the test 
 of observation, and was conducted to his most 
 splendid discoveries. The reasonings of Coperni- 
 cus, who preceded Bacon by more than a century, 
 were all founded upon the most legitimate induction. 
 Dr. Gilbert had exhibited in his treatise on the 
 magnet* the most perfect specimen of physical re- 
 search. Leonardo da Vinci had described in the 
 clearest manner the proper method of philosophical 
 investigation ;f and the whole scientific career of 
 Galileo was one continued example of the most 
 
 * De Magnete, p. 42, 52, 169, and Pref. p. 30. 
 
 t The following passages from Leonardo da Vinci are very striking : 
 
 ' Theory is the general, and practice the soldiers. 
 
 " Experiment is the interpreter of the artifices of nature. It never 
 deceives us ; it is our judgment itself which sometimes deceives us, be- 
 cause we expect from it effects which are contrary to experiment. We 
 must consult experiment by varying the circumstances till we have 
 deduced from it general laws ; for it is it which furnishes true laws. 
 * " In the study of the sciences which depend on mathematics, those 
 who do not consult nature, but authors, are not the children of nature ; 
 they are only her grandchildren. Nature alone is the master of true 
 genius. 
 
 "In treating any particular subject, I wonld first of all make some 
 experiments, because my design is first to refer to experiment, and then 
 to demonstrate why bodies are constrained to act in such a manner. 
 This is the method which we ought to follow in investigating the phe- 
 nomena of nature. It is very true that nature begins by reasoning and 
 ends with experiment ; but it matters not, we must take the opposite 
 course ; as I have said, we must begin by experiment, and endeavour 
 by Us means to discover general principles " Thus, says Ventusi, spoke 
 Leonard a century before Bacon, and thus, we add, did Leonard tell phi- 
 losophers all that they required for the proper investigation of general 
 laws. See Essai sur las ozuvrages physico-mathematiques de Leonard 
 de Vinci, par J. B. Venturi. Paris, 1799, p. 32, 33, &c. See also Carlo 
 Amoretti's Memorie storiche su la vita gli studi e le Opere de Lionard* 
 ia Vinci. Milano, 1804.
 
 296 SIR ISAAC NEWTON. 
 
 sagacious application of observation and experiment 
 to the discovery of general laws. The names of 
 Paracelsus, Van Helmont, and Cardan have been 
 ranged in opposition to this constellation of great 
 names, and while it is admitted that even they had 
 thrown off the yoke of the schools, and had suc- 
 ceeded in experimental research, their credulity and 
 their pretensions have been adduced as a proof that 
 to the " bulk of philosophers" the method of induc- 
 tion was unknown. The fault of this argument con- 
 sists in the conclusion being infinitely more general 
 than the fact. The errors of these men were not 
 founded on their ignorance, but on their presump- 
 tion. They wanted the patience of philosophy and 
 not her methods. An excess of vanity, a wayward- 
 ness of fancy, and an insatiable appetite for that 
 species of passing fame which is derived from eccen- 
 tricity of opinion, moulded the reasonings and dis- 
 figured the writings of these ingenious men ; and it 
 can scarcely admit of a doubt, that, had they lived 
 in the present age, their philosophical character 
 would have received the same impress from the 
 peculiarity of their tempers and dispositions. This 
 is an experiment, however, which cannot now be 
 made ; but the history of modern science supplies 
 the defect, and the experience of every man fur- 
 nishes a proof that in the present age there are 
 many philosophers of elevated talents and inventive 
 genius who are as impatient of experimental re- 
 search as Paracelsus, as fanciful as Cardan, and as 
 presumptuous as Van Helmont. 
 
 Having thus shown that the distinguished philoso- 
 phers who nourished before Bacon were perfect 
 masters both of the principles and practice of in- 
 ductive research, it becomes interesting to inquire 
 whether or not the philosophers who succeeded 
 him acknowledged any obligation to his system, or 
 derived the slightest advantage from his "precepts. 
 If Bacon constructed a method to which modern
 
 BACONIAN PHILOSOPHY. 297 
 
 science owes its existence, we shall find its cultiva- 
 tors grateful for the gift, and offering the richest 
 incense at the shrine of a benefactor whose gene- 
 rous labours conducted them to immortality. No 
 such testimonies, however, are to be found. Nearly 
 two hundred years have gone by, teeming with 
 the richest fruits of human genius, and no grateful 
 disciple has appeared to vindicate the rights of the 
 alleged legislator of science. Even Newton, who 
 was born and educated after the publication of the 
 Novum Organon, never mentions the name of Bacon 
 or his system, and the amiable and indefatigable 
 Boyle treated him with the same disrespectful 
 silence. When we are told, therefore, that Newton 
 owed all his discoveries to the method of Bacon, 
 nothing more can be meant than that he proceeded 
 in that path of observation and experiment which 
 had been so warmly recommended in the Novum 
 Organon ; but it ought to have been added, that the 
 same method was practised by his predecessors, 
 that Newton possessed no secret that was not used 
 by Galileo and Copernicus, and that he would 
 have enriched science with the same splendid dis- 
 coveries if the name and the writings of Bacon had 
 never been heard of. 
 
 From this view of the subject we shall now pro- 
 ceed to examine the Baconian process itself, and 
 consider if it possesses any merit as an artificial 
 method of discovery, or if it is at all capable of being 
 employed, for this purpose, even in the humblest 
 walks of scientific inquiry. 
 
 The process of Lord Bacon was, we believe, never 
 tried by any philosopher but himself. As the sub- 
 ject of its application, he selected that of heat. With 
 his usual erudition, he collected all the facts which 
 science could supply, he arranged them in tables, 
 he cross-questioned them with all the subtlety of a 
 pleader, he combined them with all the sagacity 
 of a judge, and he conjured with them by all the
 
 298 SIR ISAAC NEWT**. 
 
 magic of liis exclusive processes. But, after all this 
 display of physical logic, nature thus interrogated 
 was still silent. The oracle which he had himself 
 established refused to give its responses, and the 
 ministering priest was driven with discomfiture from 
 his own shrine. This example, in short, of the ap- 
 plication of his system, will remain to future ages 
 as a memorable instance of the absurdity of attempt- 
 ing to fetter discovery by any artificial rules. 
 
 Nothing even in mathematical science can be 
 more certain than that a collection of scientific facts 
 are of themselves incapable of leading to discovery, 
 or to the determination of general laws, unless they 
 contain the predominating fact or relation in which 
 the discovery mainly resides. A vertical column of 
 arch-stones possesses more strength than the same 
 materials arranged in an arch without the key-stone. 
 However nicely they are adjusted, and however no- 
 bly the arch may spring, it never can possess either 
 equilibrium or stability. In this comparison all the 
 facts are supposed to be necessary to the final re- 
 sult ; but, in the inductive method, it is impossible 
 to ascertain the relative importance of any facts, or 
 even to determine if the facts have any value at all, 
 till the master-fact which constitutes the discovery 
 has crowned the zealous efforts of the aspiring phi- 
 losopher. The mind then returns to the dark and 
 barren waste over which it has been hovering ; and 
 by the guidance of this single torch it embraces, 
 under the comprehensive grasp of general princi- 
 ples, the multifarious and insulated phenomena which 
 had formerly neither value nor connexion. Hence 
 it must be obvious to the most superficial thinker, 
 that discovery consists either in the detection Of 
 some concealed relation some deep-seated affinity 
 which baffles ordinary research, or in the discovery 
 of some simple fact which is connected by slender 
 ramifications with the subject to be investigated; 
 but which, when once detected, carries us back by
 
 TRUE PROCESS OF INVESTIGATION. 299 
 
 its divergence to all the phenomena which it em- 
 braces arid explains. 
 
 In order to give additional support to these views, 
 it would be interesting to ascertain the general char- 
 acter of the process by which a mind of acknow- 
 ledged power actually proceeds in the path Df suc- 
 cessful inquiry. The history of science does not 
 furnish us with much information on this head, and 
 if it is to be found at all, it must be gleaned from 
 the biographies of eminent men. Whatever this 
 process may be in its details, if it has any, there 
 cannot be the slightest doubt that in its generalities 
 at least it is the very reverse of the method of in- 
 duction. The impatience of genius spurns the re- 
 straints of- mechanical rules, and never will submit 
 to the plodding drudgery of inductive discipline. 
 The discovery of a new fact unfits even a patient 
 mind for deliberate inquiry. Conscious of having 
 added to science what had escaped the sagacity of 
 former ages, the ambitious spirit invests its new 
 acquisition with an importance which does not be- 
 long to it. He imagines a thousand consequences 
 to flow from his discovery : he forms innumerable 
 theories to explain it, and he exhausts his fancy in 
 trying all its possible relations to recognised diffi- 
 culties and unexplained facts. The reins, however, 
 thus freely given to his imagination, are speedily 
 drawn up. His wildest conceptions are all subjected 
 to the rigid test of experiment, and he has thus been 
 hurried by the excursions of his own fancy into new 
 and fertile paths, far removed from ordinary obser- 
 vation. Here the peculiar character of his own ge- 
 nius displays itself by the invention of methods of 
 trying his own speculations, and he is thus often led 
 to new discoveries far more important and general 
 than that by which he began his inquiry. For a 
 confirmation of these views, we may refei to the 
 History of Kepler's Discoveries ; and if we do not 
 recognise them to the same extent in the labours of
 
 300 SIR ISAAC NEWTON. 
 
 Newton, it is because he kept back his discoveries 
 till they were nearly perfected, and therefore with- 
 held the successive steps of his inquiries. 
 
 The social character of Sir Isaac Newton was 
 sucli as might have been expected from his intel- 
 lectual attainments. He was modest, candid, and 
 affable, and without any of the eccentricities of ge- 
 nius, suiting himself to every company, and speaking 
 of himself and others in such a manner that he was 
 never even suspected of vanity. " But this," says 
 Dr. Pemberton, " I immediately discovered in him, 
 which at once both surprised and charmed me. 
 Neither his extreme great age nor his universal re- 
 putation had rendered him stiff in opinion, or in any 
 degree elated. Of this I had occasion to have 
 almost daily experience. The remarks I continually 
 sent him by letters on the Principia were received 
 with the utmost goodness. These were so far from 
 being any ways displeasing to him, that on the con- 
 trary it occasioned him to speak many kind things 
 of me to my friends, and to honour me with a public 
 testimony of his good opinion." 
 
 The modesty of Sir Isaac Newton in reference to 
 his great discoveries was not founded on any indif- 
 ference to the fame which they conferred, or upon 
 any erroneous judgment of their importance to 
 science. The whole of his life proves, that he knew 
 his place as a philosopher, and was determined to 
 assert and vindicate his rights. His modesty arose 
 from the depth and extent of his knowledge, which 
 showed him \vhat a small portion of nature he had 
 been able to examine, and how much remained to 
 be explored in the same field in which he had him- 
 self laboured. In the magnitude of the comparison 
 he recognised his own littleness ; and a short time 
 before his death he uttered this memorable senti- 
 ment : " I do not know what I may appear to the 
 world ; but to myself I seem to have been only like 
 a boy playing on the seashore, and diverting myself
 
 SIMPLICITY OF CHARACTER. 301 
 
 in now and then finding a smoother pebble or a pret 
 tier shell than ordinary, while the great ocean of 
 truth lay all undiscovered before me." What a les- 
 son to the vanity and presumption of philosophers, 
 to those especially who have never even found the 
 smoother pebble or the prettier shell ! What a pre- 
 paration for the latest inquiries, and the last views 
 of the decaying spirit, for those inspired doctrines 
 which alone can throw a light over the dark ocean 
 of undiscovered truth ! 
 
 The native simplicity of Sir Isaac Newton's mind 
 is finely portrayed in the affecting letter in which 
 he acknowledges to Locke that he had thought and 
 spoken of him uncharitably; and the huminty and 
 candour in which he asks forgiveness could have 
 emanated only from a mind as noble as it was pure. 
 
 In the religious and moral character of our author 
 there is much to admire and to imitate. While he 
 exhibited in his life and writings an ardent regard 
 for the general interests of religion, he was at the 
 same time a firm believer in revelation. He was 
 too deeply versed in the Scriptures, and too much 
 imbued with their spirit, to judge harshly of other 
 men who took different views of them from himself. 
 He cherished the great principles of religious tole- 
 ration, and never scrupled to express his abhorrence 
 of persecution, even in its mildest form. Immo- 
 rality and impiety he never permitted to pass unre- 
 proved ; and when Dr. Halley* ventured to say any 
 thing disrespectful to religion, he invariably checked 
 him, and said, " I have studied these things, you 
 have not."f 
 
 After Sir Isaac Newton took up his residence in 
 London, he lived in a very handsome style, and kept 
 his carriage, with an establishment of three male 
 
 * Mr. Hearne, in a memorandum dated April 4th, 1726, states, that a 
 great quarrel happened between Sir Isaac Newton and Mr. Halley. If 
 this is true, the difference is likely to have originated in Halley's impiety. 
 
 * Professor Rigaud of Oxford heard this anecdote from Dr. Maskelyne
 
 302 siu ISAAC ISEWTON. 
 
 and three female servants. In his own house he 
 was hospitable and kind, and on proper occasions 
 he gave splendid entertainments, though without 
 ostentation or vanity. His own diet was frugal, and * 
 his dress was always simple ; but on one occasion, 
 when he opposed the Honourable Mr. Annesley ID 
 1705, as a candidate for the university, he is said to 
 have put on a suit of laced clothes. 
 
 His generosity and charity had no bounds, and he 
 used to remark, that they who gave away nothing 
 till they died never gave at all. Though his wealth 
 had become considerable by a prudent economy, yet 
 he had always a contempt for money, and he spent 
 a considerable part of his income in relieving the 
 poor, in assisting his relations, and in encouraging 
 ingenuity and learning. The sums which he gave 
 to his relations at different times were enormous ;* 
 and in 1724 he wrote a letter to the Lord Provost 
 of Edinburgh, offering to contribute 20/. per annum 
 to a provision for Mr. Maclaurin, provided he ac- 
 cepted the situation of assistant to Mr. James Greg- 
 ory, who was professor of mathematics in the uni- 
 versity. 
 
 The habits of deep meditation which Sir Isaac 
 Newton had acquired, though they did not show 
 themselves in his intercourse with society, exer- 
 cised their full influence over his mind when in the 
 midst of his own family. Absorbed in thought he 
 would often sit down on his bedside after he rose, 
 and remain there for hours without dressing himself, 
 occupied with some interesting investigation which 
 had fixed his attention. Owing to the same absence 
 of mind, he neglected to take the requisite quantity 
 
 * "He was very kind to all the Ayscoughs. To one he gave 8007., trf 
 another 200/., and to a third 100L, and many other sums ; and other en 
 gagements did he enter into also for them. He was the ready assistant 
 of all who were any way related to him, to their children and grandchil- 
 dren." Annual Register, 1776, vol. xix. p. 25. Sir Isaac gave some do- 
 nations to the chapel and parish of Colsterworth. Hearne says " that 
 he promised to become a benefactor to the Royal Society, but failed "
 
 PERSONAL APPEARANCE. 303 
 
 of nourishment, and it was therefore often necessary 
 to remind him of his meals.* 
 
 Sir Isaac Newton is supposed to have had little 
 knowledge of the world, and to have been very ig- 
 norant of the habits of society. This opinion has, 
 we think, been rashly deduced from a letter which 
 he wrote in the twenty-seventh year of his age to 
 his young friend, Francis Aston, Esq., who was about 
 to set out on his travels. This letter is a highly 
 interesting production ; and while it shows much 
 knowledge of the human heart, it throws a strong 
 light upon the character and opinions of its author. 
 
 In his personal appearance, Sir Isaac Newton was 
 not above the middle size, and in the latter part of 
 his life was inclined to be corpulent. According to 
 Mr. Conduit " he had a very lively and piercing eye, 
 a comely and gracious aspect, with a fine head of 
 hair as white as silver, without any baldness, and 
 when his peruke was off was a venerable sight." 
 Bishop Atterbury asserts,! on the other hand, that 
 the lively and piercing eye did not belong to Sir 
 Isaac during the last twenty years of his life. " In- 
 deed," says he, " in the whole air of his face and 
 make there was nothing of that penetrating sagacity 
 which appears in his compositions. He had some- 
 thing rather languid in his look and manner which 
 did not raise any great expectation in those who did 
 not know him." This opinion of Bishop Atterbury 
 is confirmed by an observation of Mr. Thomas 
 
 * The following anecdote of Sir Isaac's absence has been published, 
 but I cannot vouch for its authenticity. His intimate friend Dr. Stukely, 
 who had been deputy to Dr. Hailey as secretary to the Royal Society, 
 was one day shown into Sir Isaac's dining-room, where his dinner had 
 been for some time served up. Dr. Stukely waited for a considerable 
 time, and getting impatient, he removed the cover from a chicken, which 
 he ate, replacing the bones under the cover. In a short time Sir Isaac 
 entered the room, and after the usual compliments sat down to his din- 
 ner, but on taking off the cover, and seeing nothing but bones, he re- 
 marked, " How absent we philosophers are. I really thought that I b*4 
 not dined." 
 
 t Epistolary Correspondence, vcl i.p. 180, sec. 71
 
 304 SIR ISAAC NEWTOX. 
 
 Hearne,* who says " that Sir Isaac was a man of no 
 very promising aspect. He was a short, well-set 
 man. He was full of thought, and spoke very little in 
 company, so that his conversation was not agreeable. 
 When he rode in his coach, one arm would be out 
 of his coach on one side and the other on the other." 
 Sir Isaac never wore spectacles, and never " los* 
 more than one tooth to the clay of his death." 
 
 Besides the statue of S : r Isaac Newton executed 
 by Roubiliac, there is a bust of him by the same 
 artist in the library of Trinity College, Cambridge. 
 Several good paintings of him are extant. Two 
 of these are in the hall of the Royal Society of 
 London, and have, we believe, been often engraved. 
 Another, by Vanderbank, is in the apartments of 
 the Master's lodge in Trinity College, and has been 
 engraved by Vertue. Another, by Valentine Ritts, 
 is in the landing-place near the entrance to Trinity 
 College library ; but the best, from which our en- 
 graving is copied, was painted by Sir Godfrey Knel- 
 ler, and is in the possession of Lord Egremont at 
 Petworth. In the university library there is pre- 
 served a cast taken from his face after death. 
 
 Every memorial of so great a man as Sir Isaac 
 Newton has been preserved and cherished with pecu- 
 liar veneration. His house at Woolsthorpe, of which 
 we have given an engraving, has been religiously 
 protected by Mr. Turner of Stoke Rocheford, the 
 proprietor. Dr. Stukeley, who visited it in Sir 
 Isaac's lifetime, on the 13th October, 1721, gives the 
 following description of it in his letter to Dr. Mead, 
 written in 1727 : " 'Tis built of stone as is the way 
 of the country hereabouts, and a reasonable good 
 one. They led me up stairs and showed me Sir 
 Isaac's study, where I suppose he studied when in 
 the country in his younger days, or perhaps when 
 he visited his mother from the university. I ob- 
 served the shelves were of his own making, being 
 pieces of deal boxes which probably he sent his 
 
 * MS. Memoranda in the Bodleian Library.
 
 MEMORIALS AND RECOLLECTIONS. 305 
 
 books and clothes down in on those occasions. 
 There were some years ago two or three hundred 
 books in it of his father-in-law, Mr. Smith, which 
 Sir Isaac gave to Dr. Newton of our town."* 
 
 When the house was repaired in 1798, a tablet of 
 white marble was put up by Mr. Turnor in the room 
 where Sir Isaac was born, with the following in- 
 scription : 
 
 " Sir Isaac Newton, son of John Newton, Lord 
 of the manor of Woolsthorpe, was born in this room 
 on the 25th December, 1642." 
 
 Nature and Nature's laws lay hid in nign.., 
 God said, " Let Newton be," and all was light. 
 
 The following lines have been written upon the 
 liouse: 
 
 Here Newton dawned, here lofty wisdom woke, 
 
 And to a wondering world divinely spoke. 
 
 If Tully glowed, when Phaedrus' steps he trode, 
 
 Or fancy formed Philosophy a god ; 
 
 If sages still for Homer's birth contend 
 
 The Sons of Science at this dome must bend. 
 
 All hail the shrine ! All hail the natal day, 
 
 Cam boasts his noon, This Cot his morning ray. 
 
 The house is now occupied by a person of the 
 name of John Wollerton. It still contains the two 
 dials made by Newton, but the styles of both are 
 wanting. The celebrated apple-tree, the fall of one 
 of the apples of which is said to have turned the 
 attention of Newton to the subject of gravity, was 
 destroyed by wind about four years ago ; but Mr. 
 Turnor has preserved it in the form of a chair.f 
 
 The chambers which Sir Isaac inhabited at Cam- 
 bridge are known by tradition. They are the apart- 
 ments next to the great gate of Trinity College, and 
 it is believed that they then communicated by a 
 staircase with the observatory in the Great Tower, 
 
 * Tumor's Collections, p. 176. 
 
 t The anecdote of the fall ing apple is mentioned neither by Dr. Stake! y 
 nor by Mr. Conduit, and as I have not been able to find any authority for 
 it whatever, I did not feel myself at liberty to use it.
 
 306 SIR ISAAC NEWTON. 
 
 an ooservatory which was furnished by the contri 
 butions of Newton, Cotes, and others. His telescope, 
 represented in Jig. 1, page 41, is preserved in the 
 library of the Royal Society of London, and his globe, 
 his universal ring-dial, quadrant, compass, and a re- 
 flecting telescope said to have belonged to him, in 
 the library of Trinity College. There is also in the 
 same collection a long and curled lock of his siher 
 white hair. The door of his bookcase is in the Mu- 
 seum of the Royal Society of Edinburgh. 
 
 The manuscripts, letters, and other papers of New- 
 ton have been preserved in different collections. His 
 correspondence with Cotes relative to the second 
 edition of the Principia, and amounting to between 
 sixty and a hundred letters, a considerable portion 
 of the manuscript of that work, and two or three 
 letters to Dr. Keill on the Leibnitzian controversy, 
 are preserved in the library of Trinity College, Cam- 
 bridge. Newton's letters to Flamstead, about thirty- 
 four in number, are deposited in the library of Corpus 
 Christi College, Oxford.* Several letters of New- 
 ton, and, we believe, the original specimen which he 
 drew up of the Principia, exist among the papers of 
 Mr. William Jones (the father of Sir William Jones), 
 which are preserved at Shirburn Castle, in the library 
 of Lord Macclesfield. But the great mass of New- 
 ton's papers came into the possession of the Ports- 
 mouth family through his niece, Lady Lymington, 
 and have been safely preserved by that noble family. 
 There is reason to believe that they contain nothing 
 which could be peculiarly interesting to science ; but 
 as the correspondence of Newton with contempo- 
 rary philosophers must throw considerable light on 
 his personal history, we trust that it will ere long be 
 given to the public. 
 
 * In the Monthly Review for August, 1829, p. 593, it is stated, that the 
 correspondence between Newton and Flamstead, from 1680 to 1698. exists 
 in the Sloane collection of Manuscripts in the British Museum. Pro- 
 fessor Rigaud, however, has had the kindness to inquire into the accuracy 
 of this statement, and he has ascertained that these letters are merely 
 fonies, which Dr. Birch had made from the originals at Oxford-
 
 i 307 
 
 APPENDIX. 
 
 - 
 
 No. I. 
 
 OBSERVATIONS ON THE FAMILY OF SIR ISAAC NEWTON - 
 
 IN the year 1705, Sir Isaac gave into the Herald's 
 Office an elaborate pedigree, stating upon oath that 
 he had reason to believe that John Newton of Westby, 
 in the county of Lincoln, was his great-grandfather's 
 father, and that this was the same John Newton who 
 was buried in Basingthorpe church, on the 22d De- 
 cember, 1563. This John Newton had four sons, 
 John, Thomas, Richard, and William Newton of 
 Gunnerly, the last of whom was great-grandfather 
 to Sir John Newton, Bart., of Hather. Sir Isaac 
 considered himself as descended from the eldest of 
 these, he having, by tradition from his kindred ever 
 since he can remember, reckoned himself next of kin 
 (among the Newtons) to Sir John Newton's family. 
 
 The pedigree, founded upon these and other con- 
 siderations, was accompanied by a certificate from 
 Sir John Newton, of Thorpe, Bart., who states that 
 he had heard his father speak of Sir Isaac Newton 
 as of his relation and kinsman, and that he himself 
 believed that Sir Isaac was descended from John New- 
 ton, son to John Newton of Westby, but knoweth not in 
 what particular manner. 
 
 The pedigree of Sir Isaac, as entered at the Her 
 aid's Office, does not seem to have been satisfactory 
 either to himself or to his successors, as it could not
 
 308 APPENDIX. 
 
 be traced with certainty beyond his grandfather ; and 
 it will be seen from the folio wing" interesting corres- 
 pondence, that upon making further researches, he 
 had found some reason to believe that he was of 
 Scotch extraction. 
 
 Extract of a Letter from the Reverend Dr. Reid of 
 Glasgow to Dr. Gregory of Edinburgh, dated \th 
 March, 1784. 
 
 " I send you on the other page an anecdote re 
 specting Sir Isaac Newton, which I do not remem- 
 ber whether I ever happened to mention to you in 
 conversation. If his descent be not clearly ascer- 
 tained (as T think it is not in the books I have seen), 
 might it not be worth while to inquire if evidence 
 can be found to confirm the account which he is said 
 to have given of himself. Sheriff Cross was very 
 zealous about it when death put a stop to his in- 
 quiries. 
 
 "When I lived in old Aberdeen above twenty 
 years ago, I happened to be conversing over a pipe 
 of tobacco with a gentleman of that country, who 
 had been lately at Edinburgh. He told me that he 
 had been often in company with Mr. Hepburn of 
 Keith, with whom I had the honour of some ac- 
 quaintance. He said that, speaking of Sir Isaac 
 Newton, Mr. Hepburn mentioned an anecdote, which 
 he had from Mr. James Gregory, professor of mathe- 
 matics at Edinburgh, which was to this purpose : 
 
 " Mr. Gregory, being at London for some time 
 after he resigned the mathematical chair, was often 
 with Sir Isaac Newton. One day Sir Isaac said to 
 him, * Gregory, I believe you don't know that I am 
 connected with Scotland.' * Pray how, Sir Isaac V 
 said Gregory. Sir Isaac said he was told that his 
 grandfather was a gentleman of East Lothian ; that 
 he came to London with King James at his acces- 
 sion to the crown of England, and there spent his
 
 APPENDIX. 309 
 
 fortune, as many more did at that time, by which his 
 son (Sir Isaac's father) was reduced to mean cir- 
 cumstances. To this Gregory bluntly replied, 
 4 Newton a gentleman of East Lothian, I never 
 heard of a gentleman of East Lothian of that name.' 
 Upon this Sir Isaac said, * that being very young 
 when his father died, he had it only by tradition, 
 and it might be a mistake ;' and immediately turned 
 the conversation to another subject. 
 
 " I confess I suspected that the gentleman who 
 was my author had given some colouring to this 
 story, and therefore I never mentioned it for a good 
 many years. 
 
 " After I removed to Glasgow, I came to be very 
 intimately acquainted with Mr. Cross, then sheriff 
 of Lanark, and one day at his own house mentioned 
 this story, without naming my author, of whom I 
 expressed some diffidence. 
 
 " The sheriff immediately took it up as a matter 
 worth being inquired into. He said he was well 
 acquainted with Mr. Hepburn of Keith (who was 
 then alive), and that he would write him to know 
 whether he ever heard Mr. Gregory say that he had 
 such a conversation with Sir Isaac Newton. He 
 said he knew that Mr. Keith, the ambassador, was 
 also intimate with Mr. Gregory, and that he would 
 write him to the same purpose. 
 
 " Some time after, Mr. Cross told me that he had 
 answers from both the gentlemen above mentioned, 
 and that both remembered to have heard Mr. Greg- 
 ory mention the conversation between him and Sir 
 Isaac Newton, to the purpose above narrated, and 
 at the same time acknowledged that they had made 
 no further inquiry about the matter. 
 
 " Mr. Cross, however, continued the inquiry, and 
 a short time before his death told me that all he 
 had learned was, that there is, or was lately, a baro^- 
 net's family of the name of Newton in West Lothian 
 <?r Mid Lothian (I have forgot which) : that there is 
 A A
 
 310 APPENDIX. 
 
 a tradition in that family that Sir Isaac Newton 
 wrote a letter to the old knight that then was (I 
 think Sir John Newton of Newton was his name), 
 desiring to know what children, and particularly 
 what sons he had, their age, and what professions 
 they intended : that the old baronet never deigned 
 to return an answer to this letter, which his family 
 was sorry for, as they thought Sir Isaac might have 
 intended to do something for them." 
 
 Several years after this letter was written, a Mr. 
 Barren, a relation of Sir Isaac Newton, seems to 
 have been making inquiries respecting the family 
 of his ancestor, and in consequence of this the late 
 Professor Robison applied to Dr. Reid, to obtain 
 from him a more particular account of the remark- 
 able conversation between Sir Isaac and Mr. James 
 Gregory referred to in the preceding letter. In 
 answer to this request, Dr. Reid wrote the following 
 letter, for which I was indebted to John Robison, 
 Esq. Sec. R. S. E., who found it among his father's 
 manuscripts. 
 
 Letter from .Dr. Reid to Professor Robison respecting 
 the Family of Sir Isaac Newton. 
 
 " DEAR SIR, 
 
 ** I am very glad to learn by yours of April 4, that 
 a Mr. Barron, a near relation of Sir Isaac Newton, 
 is anxious to inquire into the descent of that great 
 man, as the family cannot trace it farther, with any 
 certainty, than his grandfather. I therefore, as you 
 desire, send you a precise account of all I know ; 
 and am glad to have this opportunity, before I die, 
 of putting this information in hands that will make 
 the proper use of it, if it shall be found of any use. 
 
 " Several years before I left Aberdeen (which I 
 did in 1764), Mr. Douglas of Feckel, the father of 
 Sylvester Douglas, now a barrister at London, told
 
 APPENDIX. 311 
 
 me, that having been lately at Edinburgh, he was 
 often in company with Mr. Hepburn of Keith, a 
 gentleman of whom I had some acquaintance, by 
 his lodging a night at my house at New Machar, 
 when he was in the rebel army in 1745. That Mr. 
 Hepburn told him that he had heard Mr. James 
 Gregory, professor of mathematics, Edinburgh, say, 
 that being one day in familiar conversation with 
 Sir Isaac Newton at London, Sir Isaac said, * Greg- 
 ory, I believe you don't know that I am a Scotch- 
 man.' * Pray, how is that ?' said Gregory. Sir 
 Isaac said he was informed that his grandfather (or 
 great-grandfather) was a gentleman of East (or 
 West) Lothian : that he went to London with King 
 James the I. at his accession to the crown of Eng- 
 land : and that he attended the court in expectation, 
 as many others did, until he spent his fortune, by 
 which means his family was reduced to low circum- 
 stances. At the time this was told me Mr. Gregory 
 was dead, otherwise I should have had his own tes- 
 timony, for he was my mother's brother. I likewise 
 thought at that time that it had been certainly known 
 that Sir Isaac had been descended from an old English 
 family, as I think is said in his eloge before the 
 Academy of Sciences at Paris, and therefore I never 
 mentioned what I had heard for many years, be- 
 lieving that there must be some mistake in it. 
 
 " Some years after I came to Glasgow, I men- 
 tioned (I believe for the first time) what I had heard 
 to have been said by Mr. Hepburn to Mr. Cross, late 
 sheriff of this county, whom you will remember. 
 Mr. Cross was moved by this account, and imme- 
 diately said, ' I know Mr. Hepburn very well, and I 
 know he was intimate with Mr. Gregory: I shall 
 write him this same night, to know whether he 
 heard Mr. Gregory say so or not.' After some re- 
 flection, he added, I know that Mr. Keith, the am- 
 bassador, was also an intimate acquaintance of Mr. 
 Gregory, and as he is at present in Edinburgh, I 
 shall likewise write to him this night.'
 
 " The next time I waited on Mr. Cross he told 
 me that he had wrote both to Mr. Hepburn and Mr. 
 Keith, and had an answer from both, and that both of 
 them testified that they had several times heard Mr. 
 James Gregory say, that Sir Isaac Newton told him 
 what is above expressed, but that neither they nor 
 Mr. Gregory, as far as they knew, ever made any 
 further inquiry into the matter. This appeared very 
 strange both to Mr. Cross and me, and he said he 
 would reproach them for their indifference, and 
 would make inquiry as soon as he was able. 
 
 " He lived but a short time after this, and in the 
 last conversation I had with him upon the subject, 
 he said, that all he had yet learned was, that there 
 was a Sir John Newton of Newton in one of the 
 counties of Lothian (but I have forgot which), some 
 of whose chLdren were yet alive : that they reported 
 that their father, Sir John, had a letter from Sir 
 Isaac Newton, desiring to know the state of his 
 family, what children he had, particularly what sons, 
 and in what way they were. The old knight never 
 returned an answer to this letter, thinking probably 
 that Sir Isaac was some upstart, who wanted to 
 claim a relation to his worshipful house. This omis- 
 sion the children regretted, conceiving that Sir Isaac 
 might have had a view of doing something for their 
 benefit. 
 
 " After this I mentioned occasionally in conver- 
 sation what I knew, hoping that these facts might 
 lead to some more certain discovery, but I found 
 more coldness about the matter than I thought it 
 deserved. I wrote an account of it to Dr. Gregory, 
 your colleague, that he might impart it to any mem- 
 ber of the Antiquarian Society who he judged 
 might have the curiosity to trace the matter further. 
 
 "In the year 1787, my colleague, Mr. Patrick 
 Wilson, professor of astronomy, having been in 
 London, told me on his return that he had met ac- 
 cidentally with a James Hutton, Esq. of Pimlico,
 
 APPENDIX. 313 
 
 Westminster, a near relation of Sir Isaac Newton,* 
 to whom he mentioned what he had heard from me 
 with respect to Sir Isaac's descent, and that I wished 
 much to know something more decisive on that sub- 
 ject. Mr. Hutton said, if I pleased to write to him 
 he would give me all the information he could give. 
 I wrote him accordingly, and had a very polite 
 answer, dated at Bath, 25th December, 1787, which is 
 now before me. He says, ' I shall be glad when I 
 return to London, if I can find in some old notes of 
 my mother any thing that may fix the certainty of 
 Sir Isaac's descent. If he spoke so to Mr. James 
 Gregory, it is most certain he spoke truth. But Sir 
 Isaac's grandfather, not his great-grandfather, must 
 be the person who came from Scotland with King 
 James I. If I find any thing to the purpose, I will 
 take care it shall reach you.' 
 
 " In consequence of this letter I expected another 
 from Mr. Hutton when he should return to London, 
 but have never had any. Mr. Wilson told me he 
 was a very old man, and whether he be dead or alive 
 I know not. 
 
 " This is all I know of the matter, and for the 
 facts above mentioned I pledge my veracity. I 
 am much obliged to you, dear sir, for the kind ex- 
 pressions of your affection and esteem, which, I 
 assure you, are mutual on my part, and I sincerely 
 sympathize with you on your afflicting state of 
 health, which makes you consider yourself as out 
 of the world, and despair of seeing me any more. 
 
 " I have been long out of the world by deafness 
 and extreme old age. I hope, however, if we should 
 not meet again in this world, that we shall meet and 
 renew our acquaintance in another. In the mean 
 time, I am with great esteem, dear sir, yours affec- 
 tionately, " THO. REID. 
 
 " Glasgow College, 
 
 " 12th April, 1792." 
 
 * See page 288, note.
 
 314 APPENDIX. 
 
 This curious letter I published in the Ed. Phil 
 Journal for Octoberl, 1820. It excited the particular 
 attention of the late George Chalmers, Esq., who 
 sent me an elaborate letter upon the subject ; but as 
 I was at that time in the expectation of obtaining 
 some important information through other channels, 
 this letter was not published. This hope, however, 
 has been disappointed. A careful search has been 
 made through the charter-chest of the Newtons 
 of Newton in East Lothian, by Mr. Richard Hay 
 Newton, the representative of that family, but no 
 document whatever has been found that can throw 
 the least light upon the matter. It deserves to be 
 remarked, however, that Sir Richard Newton, the 
 alleged correspondent of Sir Isaac, appears to have 
 destroyed his correspondence ; for though the char- 
 ter-chest contains the letters of his predecessors for 
 some generations, yet there is not a single epistolary 
 document either of his own or of his lady's. 
 
 Hitherto the evidence of Sir Isaac's Scottish de- 
 scent has been derived chiefly from his conversation 
 with Mr. James Gregory ; but I am enabled, by the 
 kindness of Mr. Robison, to corroborate this evi- 
 dence by the following information, derived, as will 
 be.seen, from the family of the Newtons of Newton. 
 Among various memoranda in the handwriting of 
 Professor Robison, who at one time proposed to 
 write the life of Sir Isaac, are the following : 
 
 " 1st, Lord Henderland informed me in a letter 
 dated March, 1794, that he had heard from his infancy 
 that Sir Isaac considered himself as descended from 
 the family of Newton of Newton. This he heard 
 from his uncle Richard Newton of Newton (who 
 was third son of Lord William Hay of Newhall) :" 
 " He said that Sir Isaac wrote to Scotland to learn 
 whether any descendants of that family remained, 
 and this (it was thought) with the view to leave 
 some of his fortune to the family possessing the 
 estate with the title of baronet. Mr. Newton, not
 
 
 having this honour, and being a shy man, did not 
 encourage the correspondence, because he did not 
 considei himself as of kin to Sir Isaac, &c." 
 
 " 2d, Information communicated to me by Hay 
 Newton, Esq., of that ilk, 18th August, 1800." 
 
 " The late Sir Richard Newton of Newton, Bart. 
 chief of that name, having no male children, settled 
 the estate and barony of Newton in East Lothian 
 county upon his relation Richard Hay Newton, Esq., 
 son of Lord William Hay."* " It cannot be dis- 
 covered how long the family of Newton have been 
 in possession of the barony, there being no tradition 
 concerning that circumstance further than that they 
 came originally from England at a very distant 
 period, and settled on these lands." "The celebrated 
 Sir Isaac Newton was a distant relation of the 
 family, and corresponded with the last baronet, the 
 above-mentioned Sir Richard Newton." 
 
 The preceding documents furnish the most com- 
 plete evidence that the conversation respecting Sir 
 Isaac Newton's family took place between him and 
 Mr. Gregory; and the testimony of Lord Henderland 
 proves that his own uncle, Richard Newton of New- 
 ton, the immediate successor of Sir Richard Newton, 
 with whom Sir Isaac corresponded, was perfectly 
 confident that such a correspondence took place. 
 
 All these circumstances prove that Sir Isaac New- 
 ton could not trace his pedigree with any certainty 
 beyond his grandfather, and that there were two dif- 
 ferent traditions in his family, one which referred 
 his descent to John Newton of Westby, and the 
 other to a gentleman of East Lothian who accom- 
 panied King James VI. to England. In the first of 
 these traditions he seems to have placed most confi- 
 dence in 1705, when he drew out his traditionary 
 pedigree; but as the conversation with Professor 
 James Gregory respecting his Scotch extraction 
 
 * This entail was executed in 1724, a year or two before Sir Richard's 
 death. D. B.
 
 316 APPENDIX. 
 
 toofc place twenty years afterward, namely, between 
 1725 and 1727, it is probable that he had discovered 
 the incorrectness of his first opinions, or at least 
 -aras disposed to attach more importance to the other 
 tradition respecting his descent from a Scotch family. 
 In the letter addressed to me by the learned George 
 Chalmers, Esq. I find the following observations 
 respecting the immediate relations of Sir Isaac. 
 " The Newtons of Woolsthorpe," says he, " who 
 were merely yeomen farmers, were not by any 
 means opulent. The son of Sir Isaac's father's 
 brother was a carpenter called John. He was after- 
 ward appointed gamekeeper to Sir Isaac, as lord 
 of the manor, and died at the age of sixty in 1725. 
 This John had a son, Robert, (John?) who was 
 Sir Isaac's second cousin, and who became possessed 
 of the whole land estates at and near Woolsthorpe, 
 which belonged to the great Newton, as his heir-at-- 
 law.* Robert (John ?) became a worthless and disso- 
 lute person, who very soon wasted this ancient patri- 
 mony, and falling down with a tobacco-pipe in his 
 mouth when he was drunk, it broke in his throat, 
 and put an end to his life at the age of thirty years, 
 in 1737." 
 
 No. II. 
 
 LETTER FROM SIR ISAAC NEWTON TO FRANCIS ASTO1C, 
 ESQ., A YOUNG FRIEND WHO WAS ON THE EVE OF SET- 
 TING OUT UPON HIS TRAVELS. 
 
 MR. ASTON was elected a Fellow of the Royal 
 Society in 1678. He held the office of Secretary 
 between 1681 and 1685 ; and he was the author of 
 some observations on certain unknown ancient char 
 acters, which were published in the Philosophical 
 Transactions for 1693. 
 
 * See p. 291.
 
 APPENDIX. 317 
 
 Tliis letter has been referred to in pages 270 and 
 303, and was written when Newton was only twen- 
 ty-six years of age. It is in every respect an inter- 
 esting document. 
 
 " Trinity College,Cam1>ridge, f 
 " SIR, May 18, 1669. 
 
 " Since in your letter you give mee so much 
 liberty of spending my judgement about what may 
 be to your advantage in travelling, I shall do it 
 more freely than perhaps otherwise would have 
 been decent. First, then, I will lay down some 
 general rules, most of which, I believe, you have 
 considered already ; but if any of them be new to 
 you, they may excuse the rest ; if none at all, yet 
 is my punishment more in writing than yours in 
 reading. 
 
 "When you come into any fresh company, 1. 
 Observe their humours. 2. Suit your own carriage 
 thereto, by which insinuation you will make their 
 converse more free and open. 3. Let your dis- 
 cours be more in querys and doubtings than peremp- 
 tory assertions or disputings, it being the designe 
 of travellers to learne, not to teach. Besides, it will 
 persuade your acquaintance that you have the greater 
 esteem of them, and soe make them more ready 
 to communicate what they know to you ; whereas 
 nothing sooner occasions disrespect and quarrels 
 than peremtorinesse. You will find little or no 
 advantage in seeming wiser or much more ignorant 
 than your company. 4. Seldom discommend any 
 thing though never so bad, or doe it but moderately, 
 lest you bee unexpectedly forced to an unhansom 
 retraction. It is safer to commend any thing more 
 than it deserves, than to discommend a thing soe 
 much as it deserves ; for commendations meet no 
 soe often with oppositions, or, at least, are no^ 
 usually soe ill resented by men that think otherwise, 
 as discommendations ; and you will insinuate into
 
 3 1 8 APPENDIX. 
 
 men's favour by nothing sooner than seeming to 
 approve and commend what they like ; but beware 
 of doing it by a comparison. 5. If you bee affronted, 
 it is better, in a forraine country, to pass it by hi 
 silence, and with a jest, though with some dishonour, 
 than to endeavour revenge ; for, in the first case, 
 your credit's ne'er the worse when you return into 
 England, or come into other company that have not 
 heard of the quarrell. But, in the second case, you 
 may beare the marks of the quarrell while you live, 
 if you outlive it at all. But, if you find yourself un- 
 avoidably engaged, 'tis best, I think, if you can com- 
 mand your passion and language, to keep them 
 pretty evenly at some certain moderate pitch, not 
 much hightning them to exasperate your adversary, 
 or provoke his friends, nor letting them grow over- 
 much dejected to make him insult. In a word, if 
 you can keep reason above passion, that and watch- 
 fullnesse will be your best defendants. To which 
 purpose you may consider, that, though such excuses 
 as this, He provok't mee so much I could not for- 
 bear, may pass among friends, yet amongst stran- 
 gers they are insignificant, and only argue a travel- 
 ler's weaknesse. 
 
 " To these I may add some general heads for in- 
 quirys or observations, such as at present I can 
 think on. As, 1. To observe the policys, wealth, 
 and state-affairs of nations, so far as a solitary 
 traveller may conveniently doe. 2. Their imposi- 
 tions upon all sorts of people, trades, or commoditys, 
 that are remarkable. 3. Their laws and customs, 
 how far they differ from ours. 4. Their trades and 
 arts wherein they excell or come short of us in 
 England. 5. Such fortifications as you shall meet 
 with, their fashion, strength, and advantages for de- 
 fence, and other such military affairs as are consider- 
 able. 6. The power and respect belonging to their 
 degrees of nobility or magistracy. 7. It will not be 
 time mispent to make a catalogue of the names and
 
 APPENDIX. 319 
 
 excellencys of those men that are most wise, learned, 
 or esteemed in any nation. 8. Observe the mecha- 
 msme and manner of guiding ships. 9. Observe the 
 products of nature in several places, especially in 
 mines, with the circumstances of mining and of ex- 
 tracting metals or minerals out of their oare, and of 
 refining theni ; and if you meet with any transmuta- 
 tions out of their own species into another (as out 
 of iron into copper, out of any metall into quicksilver, 
 out of one salt into another, or into an insipid body, 
 &c.), those, above all, will be worth your noting, 
 being the most luciferous, and many times lucrife- 
 rous experiments too, in philosophy. 10. The prices 
 of diet and other things. 11. And the staple com- 
 moditys of places. 
 
 " These generals (such as at present I could 
 think of), if they will serve for nothing else, yet they 
 may assist you in drawing up a modell to regulate 
 your travells by. As for particulars, these that fol- 
 low are all that I can now think of, viz. Whether 
 at Schemnitium, in Hungary (where there are mines 
 of gold, copper, iron, vitrioll, antimony, &c.), they 
 change iron into copper by dissolving it in a vitriolate 
 water, which they find in cavitys of rocks in the 
 mines, and then melting the slimy solution in a 
 strong fire, which in the cooling proves copper. The 
 like is said to be done in other places, which I can- 
 not now remember ; perhaps, too, it may be done in 
 Italy. For about twenty or thirty years agone there 
 was a certain vitrioll came from thence (called 
 Roman vitrioll), but of a nobler virtue than that 
 which is now called by that name ; which vitrioll is 
 not now to be gotten, because, perhaps, they make 
 a greater gain by some such trick as turning iron into 
 copper with it than by selling it. 2. Whether, in 
 Hungary, Sclavonia, Bohemia, near the town Eila, 
 or at the mountains of Bohemia near Silesia, there 
 be rivers whose waters are impregnated with gold ; 
 pernaps, the gold being dissolved by some corrosive
 
 320 APPENDIX. 
 
 waters like aqua regis, and the solution carried 
 along with the streame, that runs through the mines. 
 And whether the practice of laying mercury in the 
 rivers, till it be tinged with gold, and then straining 
 the mercury through leather, that the gold may stay 
 behind, be a secret yet, or openly practised. 3. 
 There is newly contrived, in Holland, a mill to grind 
 glasses plane withall, and I think polishing them 
 too ; perhaps it will be worth the while to see it. 
 
 4. There is in Holland one Bony, who some 
 
 years since was imprisoned by the Pope, to have 
 extorted from him secrets (as I am told) of great 
 worth, both as to medicine and profit, but he escaped 
 into Holland, where they have granted him a guard. 
 I think he usually goes clothed in green. Pray in- 
 quire what you can of him, and whether his ingenuity 
 be any profit to the Dutch. You may inform your- 
 self whether the Dutch have any tricks to keep their 
 ships from being all worm-eaten in their voyages to 
 the Indies. Whether pendulum clocks do any ser- 
 vice in finding out the longitude, &c. 
 
 " I am very weary, and shall not stay to part with 
 a long compliment, only I wish you a good journey, 
 and God be with you. 
 
 "Is. NEWTON. 
 
 " Pray let us hear from you in your travells. 1 
 have given your two books to Dr. Arrowsmith " 
 
 No. III. 
 
 ** A REMARKABLE AND CURIOUS CONVERSATION BETWEEN 
 SIR ISAAC NEWTON AND MR. CONDUIT." 
 
 " I WAS on Sunday night, the 7th of March, 1724-5, 
 at Kensington with Sir Isaa*, Xewton, in his lodgings, 
 just after he was come out of a fit of the gout, 
 which he had had in both his feet, for the first time.
 
 APPENDIX. 321 
 
 in the eighty-third year of his age. He was better 
 after it, and his head clearer, and memory stronger 
 than I had known them for some time. He then 
 repeated to me, by way of discourse, very distinctly; 
 though rather in answer to my queries than in one 
 continued narration, what he had often hinted to 
 me before, viz. that it was his conjecture (he would 
 affirm nothing) that there was a sort of revolution 
 in the heavenly bodies ; that the vapours and light 
 emitted by the sun, which had their sediment as 
 water and other matter, had gathered themselves 
 by degrees into a body, and attracted more matter 
 from the planets, and at last made a secondary 
 planet (viz. one of those that go round another 
 planet and then by gathering to them, and attract- 
 ing more matter, became a primary planet ; and 
 then by increasing still became a comet, which after 
 certain revolutions, by coming nearer and nearer to 
 the sun, had all its volatile parts condensed, and 
 became a matter fit to recruit and replenish the sun 
 (which must waste by the constant heat and light 
 it emitted) as a fagot would this fire if put into it 
 (we were sitting by a wood fire), and that that 
 would probably be the effect of the comet of 1680, 
 sooner or later, for, by the observations made upon 
 it, it appeared, before it came near the sun, with 
 a tail only two or three degrees long ; but by the 
 heat it contracted in going so near the sun, it 
 seemed to have a tail of thirty or forty degrees 
 when it went from it ; that he could not say when 
 this comet would drop into the sun ; it might perhaps 
 have five or six revolutions more first, but whenever 
 it did it would so much increase the heat of the sun 
 that this earth would be .burnt, and no animals in it 
 could live. That he took the three phenomena seen 
 by Hipparchus, Tycho Brahe, and Kepler's disciples 
 to have been of this kind, for he could not otherwise 
 account for an extraordinary light as those were, 
 appearing all at once among the fixed stars (all
 
 322 APPENDIX. 
 
 which he took to be suns enlightening other planets 
 as our sun does ours) as big as Mercury or Venus 
 seems to us, and gradually diminishing for sixteen 
 months, and then sinking into nothing. He seemed 
 to doubt whether there were not intelligent beings 
 superior to us who superintended these revolutions 
 of the heavenly bodies by the direction of the 
 Supreme Being. He appeared also to be very 
 clearly of opinion that the inhabitants of this world 
 were of a short date, and alleged as one reason for 
 that opinion, that all arts, as letters, ships, printing, 
 needle, &c., were discovered within the memory of 
 history, which could not have happened if the world 
 had been eternal ; and that there were visible marks 
 of ruin upon it which could not be effected by a 
 flood only. When I asked him how this earth could 
 have been repeopled if ever it had undergone the 
 same fate it was threatened with hereafter by the 
 comet of 1680, he answered, that required the power 
 of a Creator. He said he took all the planets to be 
 composed of the same matter with this earth, viz. 
 earth, water, stones, &c., but variously concocted. 
 I asked him why he would not publish his conjec- 
 tures as conjectures, and instanced that Kepler had 
 communicated his ; and though he had not gone 
 near so far as Kepler, yet Kepler's guesses were so 
 just and happy that they had been proved and 
 demonstrated by him. His answer was, * I do not 
 deal in conjectures.' But upon my talking to him 
 about the four observations that had been made of 
 the comet of 1680, at 574 years' distance, and asking 
 him the particular times, he opened his Principle, 
 which laid on the table, and showed me there the 
 particular periods, viz. 1st, the Julium Sidus, in the 
 time of Justinian, hi 1106, in 1680. 
 
 And I, observing that he said there of that comet, 
 ' incidet in corpus sob's,' and in the next paragraph 
 adds, * stellae fixae refici possunt,' told him I thought 
 he owned there what we had been talking about, viz.
 
 APPENDIX. 3^3 
 
 that the comet would drop into the sun, and that fixed 
 stars were recruited and replenished by comets 
 when they dropped into them ; and, consequently, 
 that the sun would be recruited too ; and asked him 
 why he would not own as freely what he thought of 
 the sun as well as what he thought of the fixed stars. 
 He said, ' that concerned us more ;' and, laughing, 
 added, ' that he had said enough for people to know 
 his meaning.' " 
 
 The preceding paper, with the title prefixed to it, 
 was first published by Mr. Turnor in his Collections, 
 $c. p. 172. It was found among the Portsmouth 
 aanuscripts, in the handwriting of Mr. Conduit.
 
 University of California 
 
 SOUTHERN REGIONAL LIBRARY FACILITY 
 
 405 Hilgard Avenue, Los Angeles, CA 90024-1388 
 
 Return this material to the library 
 
 from which it was borrowed.
 
 UC SOUTHERN REGIONAL LIBRARY FACILITY