POWER AND RESISTANCE. 27? 



employs, and the arrangement in which the 

 assertion is conveyed, show most clearly, that 

 he refers to the power possessed by elastic bo- 

 dies of reacting, and of returning from their 

 forced to their natural state. Had it been 

 otherwise, he would have inverted the order 

 and the arrangement in his terms ; instead of 

 saying, that reaction was equal to action, he 

 would have said that action was equal to re- 

 action ; in either case, however, he would have 

 been incorrect He would have been incorrect, 

 because it is necessary in that case, to suppose 

 what is not, for the purpose of proving what is. 

 It is absolutely necessary to pre-suppose, not 

 only that the medium through which bodies act 

 upon one another, opposes no resistance what- 

 ever to them, but that space should exist without 

 matter to fill it, and a vacuum be the natural 

 condition of the greatest part of space. 



The illustrious author of this conjecture, it 

 appears to me, not only made it without proof, 

 but contrary to every principle in nature. A 

 condition of things such as that which has been 

 hypothetically supposed, I maintain is falsified 

 by every fact of which we are in possession ; 

 the plenitude of matter is the cause why a finite 

 power can never produce an infinite effect, and 

 why motion excited, perpetually diminishes, 

 and is ultimately lost ; it is the case with the 



