HISTORY OF GALVANISM. 73 



decomposed, the acid is transferred to the zinc, 

 and the alkali to the copper surface. This tends to 

 restore the equilibrium which is destroyed by the 

 contact of the metallic elements of the pile ; but 

 the solution of the zinc, which then takes place, 

 again alters the electrical condition of the bodies, 

 and maintains the energy of the apparatus. Upon Primary 

 the whole, although it may be supposed that the 6 



chemical changes are an essential part of the pro- 

 cess, they are considered by the author as only of 

 secondary importance; the first step in the pro- 

 cess, and that which immediately gives rise to all 

 the rest, being an electrical effect arising from 

 the action of bodies placed in contact.* 



The uncommon merit of this paper will be a importance 

 sufficient reason for this copious abstract of its pe r thls pa ~ 

 contents. It may be regarded, not only as giving 

 rise to some of the most important experiments 

 and discoveries that have occurred in the history 

 of modern science ; but as leading to the establish- 

 ment of a new train of reasoning, and to a new 

 theory, respecting the action of bodies upon each 

 other, and the connexion which subsists between 

 the different branches of natural philosophy. The 

 general principle being clearly established, the con- 

 sequences were comparatively obvious, and the skill 

 and ingenuity which Sir H. Davy afterwards 

 manifested in the contrivance and execution of 

 the experiments, which are next to be related, 



* Phil. Trans, for 1807, p. I. 



