1 78 THE ART OF PROJECTING. 



energy of gases, free path motion, heat motion (5), 

 momentum, attraction and repulsion (6) as due to 

 motion, gravitative action (3), chemical action 

 (12), elasticity (5). It is not to be understood that 

 these phenomena are the same as those mentioned, 

 only that they are strikingly like them in some 

 respects. 



