250 INDUCTION OF 



resistance of the wall is no property of the matter 

 of which it is composed ; if the cohesion of the 

 particles forming it be destroyed, it no longer resists 

 or converts the motion. In the same matter, friction 

 produces heat or electricity, according to most incon- 

 siderable diversities of structure. Light is partially 

 resisted and converted into heat, if the surface of 

 glass be roughened. All non-conductors or resisting 

 bodies are such by virtue of their structure : not the 

 elements, but the mode in which they are arranged 

 determines their resisting power. A gaseous mix- 

 ture of oxygen, hydrogen, nitrogen, and carbonic 

 acid, resists the electric current, but the same 

 elements united into a muscle conduct it readily. 



The resistance to chemical action, which causes 

 it to become vital action, might be termed organic 

 cohesion. 



A comparison of organic cohesion with the co- 

 hesion of inorganic bodies, which, by resistance, 

 changes one form of force into another, elicits many 

 points of resemblance. 



For example, the change of the force depends 

 upon a certain relation between the force and the 



