Chap. I. APPENDIX. 



o'3 



fame hypotlief.s that I make with refpect to the Planetary Motion ; 

 for I fuppofe that Motion to be produced by two powers, when, in 

 fa(fl, it is produced only by one. But there is another hypothefis 

 made by Sir Ifaac, that is not fo well known, but which he has 

 made the foundation of his whole fyftem. It is the hypothefis of 

 Motion in a ftraight line, which he lays down as an axiom in his 

 Firfl: Law of Motion ; and yet it is mere hypothefis j for it is cer- 

 tain that, by means of the conftant rotation of the earth upon its 

 axis, there is no fuch thing on earth, nor, for any thing we know, 

 any where elfe, as Motion in a ftraight line : For even Bodies do not 

 fall in a right hne ; fo that it is not true, what is commonly faid, 

 that gravitation ads in a ftraight line ; yet, as there is nothing im- 

 poiTible, by the nature of things, in the hypothefis, Sir Ifaac, I think, 

 was at liberty to make it j nor do I, on that account, find fault with 

 his Firft Law of Motion. 



But there is ftill another hypothefis made by Sir Ifaac, much more 

 extraordinary, becaufe itisimpoihble. Yet, upon this hypothefis, he has 

 demonftrated that capital proportion in his Principia, That the fpaces, 

 which a planet defcribesin its revolution round the fun, areas the times ; 

 a propofition, upon which he founds his demonftrations of the laws 

 of the Planetary Motion. The hypothefis I mean is, That a circle is not 

 truly a figure comprehended under one line, as Euclid has defined 

 it, but a polygon of an infinite number of fides. Now, this is as 

 impoffible, as that one line flaould be many lines. For though, by 

 multiplying more and more the fides of a polygon, you may bring 

 it ftill nearer and nearer to a circle or cllipfis, it is impoffible, by 

 the nature of things, that a redilineal figure, of how many fides 

 foever, fhould ever be a circle ; and yet no Newtonian will difpute 

 the truth of the propofition Sir Ifaac has demonftrated upon this hy- 

 pothefis *. 



Vol. in. R r As 



* Vol. ii. p. 425. Sec v;hat I have further faid upon this fubjeft, Vol. i. p. 525. 



