42a ANTIENT METAPHYSICS. BookV. 



by the other that Motion is dire(Sl:ed, being bent into a Cun^e in- 

 ftead of going on in a Straight Line. 



That the Motion of the Planets is not actually fo compofed, even 

 upon the fuppofition that the Motion of Projediles was fo compo- 

 fed, I think I have clearly proved ; and much lefs can it be 

 underftood to be fo compoled, if it be true, which I think I have 

 likewife proved, that even the Motion of Projedliles is fimple and 

 uncompounded. But it will be faid, that the phaenomena corre- 

 fpond with Sir Ifaac's Theory of the Compofition of the Motion 

 of the Planets, and therefore it muft be fuppofed to be true. And, 

 if thefe phaenomena could not be otherwife explained, except upon 

 the fuppofition of the actual compofition of their Motion, I think 

 there might be fome reafon for granting it. But I am perfuaded all 

 thefe phaenomena may be accounted for, without any fuch actual 

 compofition ; though, for the fake of teaching and of demonftration, 

 it may be laid down hypothetically, that the Motion is fo compo- 

 fed, in the fame manner as Sir Ifaac has for the fame reafon analyfed 

 the Circular or Elliptic Motion into a Polygon of an infinite number 

 of fides, though, I think, no body can believe that any Curvilineal 

 Motion is fo compofed. 



That the Motion of the Planets may, by the nature of things, be 

 a fimple Curvilineal Motion, I think I have clearly proved ; and not 

 only that it may be fo, but that it is in the higheft degree impro- 

 bable, if not impofTiblc, that it fliould be otherwife. Now, I would 

 alk thofe, who maintain the adtual compofition of the Motion, 

 Whether, upon the fuppofition that it was fimple, as I maintain it 

 to be, it would not have all the qualities which they afcribe to It, 

 fuch as the Defcent from the Tangent, — Its being carried on in an 

 Orbit of a certain curvature, — and with a Force or Velocity by which 

 it makes its revolution in a certain time? If this cannot be denied, 



though 



