sgS APPENDIX. Chap. L 



producing another, and twt) Motions fympathyfing or correfpond- 

 ing one with another, which I have exempHficd in a manner that 

 muft make it obvious to the moil common underftanding * 



I have been the longer upon this 'uis infita^ that Sir Ifaac's whole 

 fyftem, as it has been hitherto taught, appears to me to hang upon 

 it, and particularly the compofition of the Planetary Motion ; for, if 

 there be no 'vis inftta^ by which, according to Sir Ifaac's firft law of 

 Motion, a Body proje<ilcd is carried on for ever in a flraight line, 

 unlefs by fome obftrudion it be flopped, or turned put of its 

 courfe, there can be neither 'v'ls ccntr'ipcta nor 'v'n centr'ifuga in the 

 Planetary Motion, nor any compofition of that Motion, but it muft 

 be fimple and diredl, as I fuppofe it ; at leaft, it has hitherto been 

 underftood only to be compofed in that way. But, I think, I have 

 fhown, that, upon the hypothefis of the Planetary Motion being be- 

 gun diredly in the elliptical line without projedion, which, I think, 

 muft be the hypothefis of every theift, it is neccflary that the New- 

 tonians, if they ftill maintain the compofition of Motion, muft ac- 

 count for it in fome other way. 



And this leads me to inquire in how many different ways the Pla- 

 netary Motion may be compounded. And, firft, it is evident that 

 there muft be the adion of two powers upon the Body, otherwife 

 the Motion would be quite fimple and uncom.pounded f- Now, thefe 

 Powers muft be either two Bodies or two Minds, or one Body and 

 one Mind ; and, befides thefe, there can be nothing elle. 



When Sir Ifaac wrote his Principiciy I think, it is evident that he 

 underftood the Planetary Motion to be immediately produced by the 



adion 



•* Vol. 11. p- 40^' 



f Of the nature of fimple and compounded Motion, and the diftlndlion betwixt the 



tvvo, fee Vol. ii. p- 389. 



W 



