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from a tree, led his thoughts upon the sub- told him that he thought Des Cartes's vor-
ject of gravity; and, reflecting on the tices might concur with the aetion of gra-
power of that principle, he began to consi- vity.
der, that, as this power is not found to be Nor did he resume this enquiry on bis
sensibly diminished at the remotest distance return to Cambridge, which was shortly
from the centre of the earth, to which we after. The truth is, his thonghts were now
can rise, neither at the tops of the loftiest engaged upon his newly projected reflecting
buildings, nor on the summits of the highest telescope, of which he made a small speci-
mountains, it appeared to him reasonable men with a metallic reflector spherically
to conclude, that this power mast extend concave. It was but a rude essay, chiefly
much further, than is usually thought.- defective by the want of a good polish for
“ Why not as bigh as the moon?” said he the metal. This instrument is now in the
to himself; “and if so, her motion must be possession of the Royal Society. In 1667,
influenced by it; perhaps she is retained in "he was chosen fellow of his college, and
her orbit by it; however, though the power took the degree of master of arts. And in
of gravity is not sensibly weakened in the 1669, Dr. Barrow resigned to him the ma-
little change of distance at which we can thematical chair at Cambridge, the business
place ourselves from the centre of the earth, of which appointment interrupted, for a
yet it is very possible that, at the heiglit of while, his attention to the telescope ; how-
the moon, this power may differ in strength ever, as his thoughts had been for some
much from what it is here.” To make an time chiefly employed upon optics, he made
estimate of what might be the degree of this his discoveries in that science the subject
diminution, he considered with himself, that of his lectures for the first three years after
if the moon be retained in her orbit by the he was appointed mathematical professor:
force of gravity, `no doubt the primary and having now brought his theory of light
planets are carried about the sun by the and colonrs, to a considerable degree of
like power; and by comparing the periods perfection, and having been elected a Fel-
of the several planets with their distances low of the Royal Society, in January 1672,
from the sun, he found, that if any power he communicated it to that body, to bave
like gravity held them in their courses, its their judgment upon it; and it was after-
strength must decrease in the duplicate wards published in their Transactions, riz,
proportion of the increase of distance. This “of February 19, 1672. This publication
he concluded, by supposing them to move occasioned a dispute upon the truth of it,
in perfect circles, concentric to the sun, which gave him so much uneasiness, that
from which the orbits of the greatest part he resolved not to publish any thing further
of them do not much differ. Supposing, for a while upon the subject; and in that
therefore, the force of gravity, when extend-resolution he laid by his optical lectures,
ed to the moon, to decrease in the same although he had prepared them for the press.
manner, he computed whether that force And the analysis by'infinite series, which
would be sufficient to keep the moon in her he had intended to subjoin to them, unhap-
orbit.

pily for the world, underwent the same
In this computation being absent from fate, and for the same reason.
books, he took the common estimate in use In this temper he resumed his telescope:
among the geographers and our seamen, and observing that there was no absolute
before Norwood had measured the earth, necessity for the parabolic figure of the
namely, that sixty miles make one degree of glasses, since, if metals could be ground
latitude; but as that is a very erroneous truly spherical, they wonld be able to bear
supposition, each degree containing about as great apertures as men could give a polish
sixty-nine and one-third of our English miles, to, he completed another instrument of the
his computation upon it did not make the same kind. This answering the purpose so
power of gravity, decreasing in a duplicate well, as, though only half a foot in length,
proportion to the distance, answerable to to show the planet Jupiter distinctly round,
the power which retained the moon in her with his four satellites, and also Venns
orbit; whence he concluded, that some horned, he sent it to the Royal Society, at
other cause must at least join with the ac- their request, together with a description of
tion of the power of gravity on the moon. it, with further particulars; which were
For this reason he laid aside for that time, published in the Philosophical Transactions
any further thoughts upon the matter. Mr. for March, 1672. Several attempts were
Whiston (in his Memoirs, p. 33.) says, he also made by that society to bring it to per-

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fection; but for want of a proper composi- dozen propositions, relating to the motion tion of metal, and a good polish, nothing of the primary planets, round the sun, succeeded, and the invention lay dormant which were communicated to the Royal till Hadley made his Newtonian telescope Society in the latter end of 1683. This in 1723. At the request of Leibnitz, in coming to be known to Dr. Halley, that 1676, he explained his invention of Infinite gentleman, who had attempted the demonSeries, and took notice how far he had im- stration in vain, applied, in August, 1684, proved it by his method of Fluxions, which to Newton, who assured him that he had however he still concealed, and particularly absolutely completed the proof. This was on this occasion, by a transposition of the also registered in the books of the Royal letters that make up the two fundamental Society; at whose earnest solicitation Newpropositions of it, into an alphabetical ton finished the work, which was printed order; the letters concerning which are in under the care of Dr. Halley, and came serted in Collins's “ Commercium Episto. out about Midsummer, 1687, under the title licum," printed 1712. In the winter, be- of “ Philosophiæ Naturalis Principia Ma. tween the years 1676, and 1677, he found thematica,” containing, in the third book, out the grand proposition, that, by a cen- the cometic astronomy, which had been tripetal force acting reciprocally as the lately discovered by him, and now made its square of the distance, a planet must re- first appearance in the world : a work which volve in an ellipsis, about the centre of may be looked upon as the production of a force placed in its lower focus, and, by a celestial intelligence rather than of a man. radius drawn to that centre, describe areas This work, however, in which the great proportional to the times. In 1680 he made author has built a new system of natural several astronomical observations upon the philosophy, upon the most sublime geomecomet that then appeared; which, for some try, did not meet at first with all the apconsiderable time, he took not to be one plause it deserved, and was one day to reand the same, but two different comets; ceive. Two reasons concurred in producand upon this occasion several letters passed ing this effect: Des Cartes had then got between him and Mr. Flamsteed.

full possession of the world. His philoso. He was still under this mistake, when he phy was indeed the creature of a fine ima. received a letter from Dr. Hook, explain- gination, gaily dressed out : he had given ing the nature of the line described by a her likewise some of nature's fine features, falling body, supposed to be moved circu- and painted the rest to a seeming likeness larly by the diurnal motion of the earthi, of her. On the other hand, Newton had, and perpendicularly by the power of gra. with an unparalleled penetration and force vity. This letter put him upon enquiring of genius, pursued nature up to her most anew what was the real figure in which such secret abode, and was intent to demonstrate a body moved; and that enquiry convinc- her residence to others, rather than anxious ing him of another mistake which he had to describe particularly the way by which before fallen into concerning that figure, he arrived at it himself: he finished that put him upon resuming his former thoughts piece in that elegant conciseness, which with regard to the moon; and Picart hav- bad justly gained the ancients a universal ing not long before, riz. in 1679, measured esteem. In fact, the consequences flow a degree of the earth with sufficient accu- with such rapidity from the principles, that racy, by using his measures, that planet ap- the reader is often left to supply a long peared to be retained in her orbit by the chain of reasoning to connect them, so that sole power of gravity; and, consequently, it required some time before the world that this power decreases in the duplicate could understand it. The best mathema. ratio of the distance; as he had formerly ticians were obliged to study it with care, conjectured. Upon this principle he found before they could make themselves masters the line described by a falling body to be an of it; and those of a lower rank durst pot ellipsis, having one focus in the centre of venture upon it, till encouraged by the testhe earth. And finding by this means, that timonies of the more learned. But at last, the primary planets really moved in such when its value came to be sufficiently orbits as Kepler had supposed, he had the known, the approbation which had been so satisfaction to see that this enquiry, which slowly gained, became universal, and nohe had undertaken at first out of mere euri- thing was to be heard from all quarters, but osity, could be applied to the greatest pur. one general burst of admiration.“ Does poses. Hereupon he drew up about a Mr. Newton eat, drink, or sleep, like other men?" says the Marquis De l'Hospital, one primary constituent particles, which then of the greatest mathematicians of the age, admitted of no further separation, in the to the English who visited bim. “ I repre- discovery of the different refrangibilities of sent him to myself as a celestial genius en. these particles thus separated, and that tirely disengaged from matter.”

these constituent rays had each its own In the midst of these profound mathema- peculiar colour inherent in it; that rays tical researches, just before his Principia falling in the same angle of incidence have went to the press in 1686, the privileges of alternate fits of reflection and refraction; the University being attacked by James that bodies are rendered transparent by the the Second, Newton appeared among its minuteness of their pores, and become most strenuous defenders, and was on that opaque by having them large; and that the occasion appointed one of their delegates most transparent body, by having a great to the High-commission Court; and they thinness, will become less pervions to the made snch a defence, that James thought light; in all these, which make up his new proper to drop the affair. Our author was theory of light and colours, he was absolutely also chosen one of their members for the and entirely the first starter; and as the subConvention Parliament, in 1688, in which ject is of the most subtile and delicate nature, be sat till it was dissolved.

he though it necessary to be himself the last Newton's merit was well known to Mr. finisher of it. Montague, then Chanceller of the Exche- In fact, the affair that chiefly employed quer, and afterwards Earl of Halifax, who his researches for so many years was far had been bred at the same college with from being confined to the subject of light him; and when he undertook the great alone. On the contrary, all that we know work of recoining the money, he fixed his of natural bodies seemed to be compreeye upon Newton, for an assistant in it; hended in it; he had found out that there and accordingly, in 1696, he was appointed was a natural action, at a distance, between Warden of the Mint, in which employment light and other bodies, by which both the he' rendered very signal service to the na. reflections and refractions, as well as inflection. And three years after he was promot- tions, of the former, were constantly proed to be Master of the Mint, a place worth duced. To ascertain the force and extent 12 or 15001. per annum, which he held till of this principle of action was what had all his death. Upon this promotion he appoint. along engaged his thoughts, and what, after ed Mr. Whiston his deputy in the mathe. all, by its extreme subtlety, escaped his matical professorship at Cambridge, giving most penetrating spirit. However, though him the full profits of the place, which ap. he has not made so full a discogery of this pointment itself be also procured for him in principle, wlich directs the course of light, 1703. The same year our author was cho. as he has in regard to the power by which sen President of the Royal Society, in the planets are kept in their courses ; yet which chair hé sat for 25 years, namely, till he gave the best directions possible for such the time of his death; and he had been as should be disposed to carry on the work, chosen a member of the Royal Academy of and furnished matter abundantly sufficient Sciences at Paris, in 1699, as soon as the to animate them to the pursuit. He has, new regulation was made for admitting indeed, hereby opened a way of passing foreigners into that society.

from optics to an entire system of physics; Ever since the first discovery of the hete- and, if we look upon his queries as containrogeneous mixture of light, and the producing the history of a great man's first tion of colours thence arising, he had em. thoughts, even in that view they must be ployed a good part of his time in bringing always at least entertaining and curious. the experintent upon which the theory is This same year, and in the same book founded, to a degree of exactness that with his Optics, he published, for the first might satisfy himself. The truth is, this time, his Method of Fluxions. It has been seems to bave been his favourite invention; already observed, that these two inventions thirty years he had spent in this arduous were intended for the public so long before task, before he published it in 1704. In infi- as 1672; but were laid by then, in order to pite series and fuxions, and in the power prevent his being engaged on that account and rule of gravity, in preserving the solar in a dispute abont them. And it is not a system, there had been some, though dis. little remarkable that, even now, this last tant hints, given by others before him; piece proved the occasion of another diswhereas in dissecting a ray of light into its pute, which continued for many years.

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Ever since 1684, Leibnitz had been artfully tice to the Elector of Hanover, so when working the world into an opinion, that he that prince was raised to the British throne, first invented this method. Newton saw Newton came more under the notice of the his design from the beginning, and had suf- court; and it was for the immediate satisficiently obviated it in the first edition of faction of George the First, that he was the “Principia,” in 1687, (riz, in the Scho prevailed on to put the last hand to the dislium to the 2nd lempa of the 2nd book): pute about the invention of Auxions. In and with the same view, when he now pub- this court, Caroline, Princess of Wales, lished that method, he took occasion to ac- afterwards Queen consort to George the quaint the world that he invented it in the Second, happened to have a curiosity for years 1665 and 1666. In the “ Acta Eru. philosophical inquiries; no sooner, thereditorum” of Leipsic, where an account is fore, was she informed of onr author's atgiven of this book, the author of that account tachment to the House of Hanover, than ascribed the invention to Leibnitz, intimat. she engaged his conversation, which soon ing that Newton borrowed it from him. endeared him to lier. Here she found, in Dr. Keill, astronomical professor at Oxford, every difficulty, that full satisfaction which undertook Newton's defence; and after she had in vain songht for elsewhore ; and several answers on both sides, Leibnitz she was often beard to declare, publicly, complaining to the Royal Society, this body that she thought herself happy in coming appointed a committee of their members to into the world at a juncture of time which examine the merits of the case. These, put it in her power to converse with him. after considering all the papers and letters It was at this Princess's solicitations that relating to the point in controversy, decided he drew up an abstract of his Chronology, in favour of Newton and Keill; as is related a copy of which was at her request comat large in the life of the last-mentioned municated about 1718, to Signior Conti, a gentleman; and these papers themselves Venetian nobleman, then in England, upon were published in 1712, under the title of a promise to keep it secret. But, notwith“ Commercium Epistolicum Johannis Col. standing this promise, the abbé, who while lins," 8vo.

here had also affected to shew a particular In 1705, the honour of knighthood was friendship for Newton, though privately beconferred upou our author by Queen Anne, traying him, as much as lay in his power, to in consideration of his great merit. And in Leibnitz, was no sooner goi across the 1714, he was applied to by the House of water, into France, than he dispersed copies Commons, for his opinion upon a new me- of it, and procured an antiquary to transthod of discovering the longitude at sea by late it into French, as well as to write a signals, which had been laid before them by confutation of it. This, being printed at Ditton and Whiston, in order to procure Paris, in 1725, was delivered as a present, their encouragement; but the petition was from the bookseller that printed it, to our thrown aside upon reading Newton's paper author, that he might obtain, as was said, delivered to the committee.

his consent to the publication ; but though The following year, 1715, Leibnitz, with he expressly refused such consent, yet the the view of bringing the world more easily whole was published the same year. Here. into the belief that Newton had taken the upon Newton found it necessary to publish Method of Fluxions from his Differential a defence of himself, which was inserted in Method, attempted to foil his mathematical the Philos. Trans. Thus, he who had so skill by the famous problem of the trajec- much all his life long been studious to avoid tories, which he, therefore, proposed to the disputes, was upavoidably all his lifetime, Euglish by way of challenge ; but the solu- in a manner, involved in them; nor did this tion of this, though the most difficult propo- last dispute even finish at his death, .which sition he was able to devise, and what might happened the year following. Newton's pass for an arduous affair to any other, paper was republished in 1726, at Paris, in yet was hardly any more than an amuse. French, with a letter of the Abbé Conti, in ment to Newton's penetrating genius : he answer to it; and the same year some disreceived the problem at 4 o'clock in the sertations were printed there by Father afternoon, as he was returning from the Souciet, against Newton's Chronological Mint; and, thougla extremely fatigued with Index; an answer to which was inserted, by business, yet he finished the solution before Halley, in the Philos. Trans. No. 397. be went to bed.

Some time before this business, in his As Leibnitz was Privy-Councellor of Jus. S0th year, our anthor was seized with an

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