

CHAPTER XIV. 



ON THE RELATION WHICH EXISTS BETWEEN 

 THE EXPANSIBLE POWER OF GASEOUS BODIES, 

 AND THE RESISTANCE THEY ARE ABLE TO 

 OVERCOME. 



IN the investigation of action in general, whe- 

 ther original or derived, it is absolutely neces- 

 sary to ascertain the nature of the means rather 

 than of the end, of the cause more than of the 

 effect ; when the resistance is equal or greater 

 than the power of the body acting, the resisting 

 body continues passive and at rest ; when the 

 power is greater than the resistance, the body 

 moves ; the degree of motion produced, is the 

 proof or test which subsists, of the power in 

 the one, of overcoming the resistance of the 

 other;* so far, however, from action requiring 



* Professor Gravesande ridicules the idea that action is pos- 

 sible to exist without resistance : for who, says he, can con- 

 ceive the possibility of action without an obstacle ; soon after, 

 however, he allows resistance to be an impediment to action. 

 From these palpable contradictions the following corollary is 

 deduced, that the force and resistance are equal to one another. 



