NOMOS. 9 



the way which appears to lead most directly to the 

 desired result. 



What, then, is electricity ? There are, we answer, 

 several kinds of electricity. There is ordinary elec- 

 tricity, or that which is obtained from the gearch after 

 common machine, from the atmosphere, the hidden 



. central law 



and from several other sources ; there is in the phe- 



, . , .. , i i i -i i nomena of 



voltaic electricity, or that which is yielded artificial 

 by the common pile or battery ; and be- 

 sides these, which are the principal kinds, there are 

 the electricities which are elicited from magnetism, 

 from heat, and from animals such as the torpedo. 

 All these several kinds, however, are allowed to be 

 essentially one and the same. This is allowed ; but 

 it is necessary for our purpose to state the evidence 

 upon which this identity is established, even though 

 this evidence be long and in some respects tedious. 

 At the same time we may assume the identity of the 

 electricities which are derived from magnetism, from 

 heat, and from animals such as the torpedo, and at 

 once proceed to show the identity of ordinary and 

 voltaic electricity. We may do this because the two 

 latter kinds of electricity are incomparably more im- 

 portant than the others, and because the identity of 

 the others with themselves and with these is proved 

 by a similar train of arguments. We pro- 

 ceed then, first, to consider the identity of 

 ordinary and voltaic electricity a ques- 

 tion of great interest and importance, and 

 one which affords the clue to almost all the questions 

 which remain in the background. 



