alone was cultivated, and mankind cou'd only be his pupil, not his enemy.

ONE very fingular difference in the lives of these two great men is, that Sir Ifaac, during the long courfe of years he enjoy'd, was never fenfible to any paffion, was not fubject to the common frailties of mankind, nor ever had any commerce with women; a circumftance which was affur'd me by the phyfician and furgeon who attended him in his laft moments.

WE may admire Sir Ifaac Newton on this occafion, but then we must not cenfure Des Cartes.

THE opinion that generally prevails in England with regard to these two philofophers is, that the latter was a dreamer, and the former a fage.

VERY few people in England read Des Cartes, whofe works indeed are now ufelefs. On the other fide, but a small number peruse those of Sir Ifaac, because to do this the ftudent must be deeply skill'd in the mathematicks, otherwise those works will be unintelligible to him. But notwithstanding this, these great men are the subject of every one's discourse. Sir Ifaac Newton is allowed every advantage, whilft Des Cartes is not indulg'd a fingle one. According to fome, it is to the former that we owe the difcovery of a Vacuum, that the air is a heavy body, and the in

vention

vention of telescopes. In a word, Sir Ifaac Newton is here as the Hercules of fabulous ftory, to whom the ignorant afcrib'd all the feats of ancient heroes.

In a critique that was made in London on Mr. de Fontenelle's difcourfe, the writer prefum'd to affert that Des Cartes was not a great geometrician. Those who make fuch a declaration may juftly be reproached with flying in their mafter's face. Des Cartes extended the limits of geometry as far beyond the place where he found them, as Sir Ifaac did after him. The former firft taught the method of expreffing curves by equations. This geometry, which, thanks to him for it, is now grown common, was fo abftrufe in his time, that not fo much as one profeffor would undertake to explain it; and Schotten in Holland, and Format in France, were the only men who understood it.

He applied this geomètrical and inventive genius to dioptricks, which, when treated of by him, became a new art. And if he was mistaken in fome things, the reafon of that is, a man who discovers a new tract of land cannot at once know all the properties of the foil. Those who come after him, and make thefe lands fruitful, are at least oblig'd to him for the difcovery. I will not deny but there are

in

innumerable errors in the rest of Des Cartes works.

GEOMETRY was a guide he himself had in fome measure fashion'd, which would have conducted him fafely thro' the feveral paths of natural philofophy. Neverthelefs he at laft abandoned this guide, and gave entirely into the humour of forming hypothefes; and then philofophy was no more than an ingenious romance, fit only to amufe the ignorant. He was mistaken in the nature of the Soul, in the proofs of the existence of a God, in matter, in the laws of motion, and in the nature of light. He admitted innate ideas, he invented new elements, he created a world; he made man according to his own fancy; and it is justly faid, that the man of Des Cartes is in fact that of Des Cartes only, very different from the real one.

HE pufh'd his metaphyfical errors fo far, as to declare that two and two make four, for no other reason but because God would have it fo. However, it will not be making him too great a compliment if we affirm that he was valuable even in his mistakes. He deceiv'd himself, but then it was at least in a methodical way. He destroy'd all the abfurd chimera's with which youth had been infatuated for two thousand years. He taught his contempoFaries how to reason, and enabled them to

employ his own weapons against himself. If Des Cartes did not pay in good money, he however did great fervice in crying down that of a base alloy.

I INDEED believe, that very few will prefume to compare his philofophy in any respect with that of Sir Ifaac Newton. The former is an effay, the latter a masterpiece: But then the man who first brought us to the path of truth, was perhaps as great a genius as he who afterwards conducted us through it.

DES CARTES gave fight to the blind. These faw the errors of antiquity and of the fciences. The path he ftruck out is fince become boundlefs. Robault's little work was, during fome years, a complete fyftem of phyficks; but now all the tranfactions of the feveral academies in Europe put together do not form fo much as the beginning of a fyftem. In fathoming this abyss no bottom has been found. now to examine what discoveries Sir Ifaac Newton has made in it.

We are

LE T

LETTER XV.

Ο Ν

ATTRACTION.

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HE difcoveries, which gain'd Sir Ifaac Newton fo univerfal a reputation, relate to the fyftem of the world, to light, to geometrical infinites, and laftly to chronology, with which he used to amufe himself after the fatigue of his feverer studies.

I WILL now acquaint you (without prolixity if poffible) with the few things I -have been able to comprehend of all these fublime ideas. With regard to the fyftem of our world, difputes were a long time maintain'd, on the cause that turns the planets, and keeps them in their orbits; and on those caufes which make all Bodies here below defcend towards the furface of the earth.

THE fyftem of Des Cartes, explain'd and improv'd fince his time, feemed to give a plausible reafon for all thofe phanomena; and this reason seem'd more just, as it is fimple, and intelligible to all capacities. But in philosophy a student ought to doubt of the things he fancies he underF 2 ftands