Chap. XIX. ANTIENT METAPHYSICS. 267 



any the leafl: thing. Now, the reafon of the motion of projediles 

 here on earth being produced by two powers operating differently, is, 

 that it was neceflary thofe two powers fhould cxift ; for the fyftem of 

 nature here below could not have been carried on without both gravi- 

 tation and projedion, whether by animal force, or by fome other ex- 

 ternal impulfe ; whereas, in the celefcial regions, there can be no 

 reafon affigned for a double force being applied for producing the 

 fimpleft ot all motions, by which fpace can be inclofed. This, as I 

 have ihown, would be contrary to a fundamental law of nature, ac- 

 knowledged by Sir liaac Newton. At the fame time, as the two mo- 

 tions are precifely of the fame kind, it is perfectly agreeable to the 

 wiidom of Nature, and that uniformity of defign that we fee in all 

 her works, that they Ihould be governed by the fame laws. Now, 

 that the motions are the fame, is admitted by all the philofophers of 

 this fchool, and, indeed, is the foundation of their fyftem : For tney 

 tell uf, that * the moon is a projedile; and that, if {he were brought 



* down to earth, and projected in the fame line, and with the fame 

 ' velocity as bodies here on earth, (he would move in the fame curve ; 



* and, if any body was carried from our earth, to the diRance of the 



* moon, and was projected in the fame diredion, and with the fame 

 ' velocity with which the moon is moved, it would proceed in the 



* fame orbit which the moon defcribes, with the fame velocity *.' And 

 they tell us, that every projedile, if the projection was of fufficient 

 force to overcome the refiftence of the medium, and the force of gra- 

 vitation towards the earth, would go round the earth as the moon 

 does ; and the fame conformity that is betwixt the motion of the 

 moon and projedilesupon earth, has been fhown to take place betwixt 

 the motions of other fatellites round their primary planets, and of the 

 primary planets themfelves round the fun. Now, it would be fome- 

 thing anomalous and incongruous in Nature, if two motions of the 



L 1 2 fame 



* See M'Laurin, ubifuprd. 



