Chap. I. A P P E; N D I X. 



J05 



I therefore hold it to be certain, that, upon my hypothefis, of the 

 planets being moved in their orbits in the mofl: fimple and dired 

 manner, the Motion will have all the properties that we know it 

 has : The revolution will be in the fame time ; the fall from the tan- 

 gent, and the velocity in its orbit, will be the fame ; and the fpaces 

 defcribed by the planet^ in its Motion, will be as the times. 



What, therefore, the Newtonians have only left for the eftablifh- 

 ment of th^ir fyftem, is to prove the third propofition. That all the 

 Bodies in our fyftem have a tendency to one another, or attradion^ 

 as it is commonly called ; and,particularly, that the planets are carried- 

 by a centripetal force towards the fun, which makes it of abfolute 

 neceffity that their Motion Ihould be compounded, and that this 

 centripetal force ihould be counterbalanced by another movino- Power 

 carrying them on in a ftraight line. This reafoning I have examined 

 in the Second Volume *, and have fhown that it is founded upon a 

 very imperfed analogy. They fay that, becaufe Bodies move towards 

 one another on this earth, therefore all Bodies, through the regions 

 of infinite fpace, have a Motion towards one another at the greateft 

 diftances. The conclufion would be far from being demonftrable 

 fuppofing it were true that all Bodies on this earth move towards 

 one another, and at all diftances, as far as we know : For, though it 

 were fo upon our earth, v/e could not from thence conclude, with 

 any degree of certainty, that it was fo over all the univerfe, compa- 

 red with whicli our earth is but a fpeck ; it would only be an argu- 

 ment from analogy, and an analogy carried much too far, and un- 

 fupported by any argument to prove, that becaufe it is fo on our 

 earth. It muft be fo every where. But, how miferably does the argu- 

 ment fail, when it is confidered,firft, That all Bodies are not moved 

 towards one another upon this earth, but fome of them the contrary 



Vol. hi. Q^q way, 



* Page 400. 



