286 ATMOSPHERIC ELECTRICITY. 



vapour is the basis of lightning, their radical 

 identity must follow as a necessary consequence, 

 notwithstanding the widely different properties 

 which they exhibit. The truth is, that diversity 

 of form and external appearance, is no evidence 

 of a difference in the nature and fundamental 

 constitution of things ; for it has been demon- 

 strated experimentally by numerous philoso- 

 phers, that all the varieties of electricity are 

 essentially the same. What can be more diffe- 

 rent than ice, water, and steam ? Yet they are 

 composed of the same elements, combined with 

 different proportions of caloric. What more op- 

 posite in all their properties than nitric acid 

 and the gases of which it is formed ? and so of 

 a thousand other bodies. 



It was long imagined, that when Franklin 

 verified the identity of lightning and common 

 electricity, he had laid the foundation of its true 

 theory. But it is now evident that many of his 

 opinions in regard to its origin and nature, were 

 partial and erroneous. At one time he supposed 

 that it was generated in the ocean by the friction 

 of salt and water that oceanic vapour was held 

 in a state of expansion by electricity and heat 

 united, while evaporation from the land was 

 caused by heat alone. He also maintained that 

 the fusion of metals by the electric fluid was a 

 cold fusion ; whereas it is now well known that 

 lightning heats, melts, ignites, and volatilizes all 



