Chap. I. A N T I E N T METAPHYSICS. ^29 



In order to make a machine perfcd: and complete, two things are 

 nccefTarily required : i/?, Tliat the Moving Power fhould never 

 fail, fo that the machine may not flop for want of it ; 2^//, That 

 the machinery fhould iiot be difordered or deranged by the adtion, 

 or interference, of the fcveral parts with one another. And accor- 

 dingly, even a machine of human invention, if it be well contri- 

 ved, will not flop through either of thcfe defedts. And what hi- 

 therto has rendered a Perpetuiim Mobile impofhblc to be contri- 

 ved by human art, is the fridtion of the parts upon one another, and 

 the necefTary tear and wear thereby produced. This defedt of hu- 

 man machinery we cannot conceive the Celeflial Bodies liable to. 

 But we are to confider, whether the Heavenly Machine may not 

 have the two defedts above mentioned, from which even a machine 

 of human invention may be exempted. 



And, firjl, as to the Moving Power, which is two-fold ; either 

 Gravitation, or the Projedlile Force. As to Gravitation, if it were 

 the Operation of a Fluid, as Sir Ifaac fuppofed it might pofTibly be, 

 it is not eafy to fay whether it would ever ceafe or not, Sir Ifaac 

 never having fufhciently explained the nature of this fluid, which 

 he only fuppofed might exifl. On the other hand, if this Power be 

 Mind, as is no\v generally agreed by the Newtonians, it is evident 

 that it can never ceafe, except by the Will of the Great Author of 

 Nature, upon whom every thing muft depend for its prefervation 

 and continuance, as well as for its exiflence at firfl j but, as to the 

 other Moving Power, the Projedlile Force by which the Celeflial 

 Bodies are to be carried on forever, it is evident that it mufl be de- 

 creafmg every moment, and mufl at laft ceafe altogether. This, in- 

 deed, could not happen, according to Sir Ifaac's hypothefis of the 

 eternity of Motion once begun, if it were true, as he fuppofes, 

 that there was a perfedl vacuum in the celeflial regions. And, ac- 

 VoL. II. T t cordingly, 



