114 THEORY OF GALVANISM. 



its powers in this respect, which had so completely 

 escaped the notice of Volta, and they were con- 

 sequently led to form a different idea of the mode 

 of its operation. Dr. Wollaston seems to have 

 been the first who decidedly adopted the opinion, 

 that the chemical action of the pile is the primary 

 origin of all the changes which it experiences, and 

 is the cause of the electrical effects ; and the same 

 idea was embraced by Sir H. Davy, although he has 

 since abandoned it for the hypothesis of electric 

 energies. 



An account I must now proceed to examine the two lead- 

 trie hyp 1 "" ing theories of the galvanic action, as exhibited in 



fhe S piie f ^ pile, with more minuteness ; and I shall ^ 

 gin with that of Volta, or the one which sup- 

 poses a change in the electrical condition of the 

 metals to be the primary cause of its operation. 

 This philosopher has given a statement of his opi- 

 nions on the subject, in several letters which he 

 wrote to his friends, and which have been pub- 

 lished in different scientific journals. His first 

 communication was in a letter to Cavallo ; the se- 

 cond toGren;* both written before his discovery of 

 the pile. His original account of this apparatus 

 is contained in a letter to Sir Joseph Banks, in 

 which he explains his ideas respecting its action ; 

 and he afterwards farther developed them in let- 

 ters to Delametherie and to Van Marum.f In 



* Phil. Trans, for 1793 ; Ann. de Chim. xxiii. 276. 

 f Phil. Trans, for 1800; Nicholson's Journal, Svo.i. 135; 

 Ann. fe Chim. 40, 225. 



