5o6 DISSERTATION ON 



of v/hich he compofes the orbits of the planets. Thefe fides of pofjr- 

 gons always incrcafing in number, and diminifliing in magnitude, 

 become at laft evanefcent, as he exprelTes it, and undiftinguifhable 

 from the curve. Inftead of thefe, which only his hypothefis of gra- 

 vitation, ading by repeated impulfes, made neceflary, we muft fup- 

 pofe Mind to be always carrying the planet, with a fteady tendency, 

 towards its center, of fuch a force, that, if the planet were let loofe 

 from its orbit, it will go to the center with a force accelerating as 

 the fquares of the diftances inverfely. 



But, how^ever great this improvement may be, I think it is evident, 

 that Sir Ifaac, when he wrote his Principia, had no idea of the celeftial 

 motions, or any part of them, being produced by the conftant agency 

 of Mind, as I fhall afterwards more clearly (how : But a farther cor- 

 redion, I think, will ftill be neceffary, in order to make Sir Ifaac's 

 philofophy ftand firm upon found metaphyfical principles. 



And here I know I fhall be laughed at by thofe who underftand no 

 fcience higher than mathematics, which they are pleafed to call Philo- 

 fophy, and have only examined the lines, and figures, and calculations, 

 of Sir Ifaac's fyftem : But, if 1 have any readers that have accompa- 

 nied me thus far, I hope they, at leaft, will be convinced, that the prin- 

 ciples of all fcience are to be found in this firft fcience ; and that, if 

 the principles of any inferior fcience cannot bear a ftrid metaphyfical 

 examination, that fcience does not ftand upon a found foundation.— 

 But to proceed : 



Even this amendment of Sir Ifaac's fyftem removes but one-half of 

 my objedion to it ; for ftill one part of ihe motion of the planets is 

 mechanical, I mean the projedile motion ; for, as I have faid, whatever 

 motion goes on of ilfelf, without the continual agency of Mind, is 



me- 



