134 THEORY OF GALVANISM. 



PLATE ii. If a number of metallic wires are placed in a line, 

 with their extremities immersed in a fluid, and the 

 whole connected with the pile, each wire will 

 evolve oxygen at one end, and hydrogen at the 

 other. Now, he conceives it impossible that every 

 wire can have an opposite electricity at its two ex- 

 tremities, when it is surrounded by a conducting 

 fluid ; for no metallic body can be made polar, i . e. 

 one end positive and the other negauve, but by the 

 temporary disturbance of the equilibrium of its na- 

 tural electricity ; an event which can only hapjren 

 when they are separated by a non-conducting s lib- 

 stance. But he observes, " No one can maintain, 

 that water, or any saline fluid or acid mixture, is a 

 non-conductor, either of the chemical or electrical 

 effects of the voltaic apparatus; yet the usual che- 

 mical changes produced by voltaic electricity occur 

 at every interruption of the metallic circuit in such 

 fluids."* 



Chemical As I am disposed to think that the electric hy- 

 p thesis, under any of its modifications, is inade- 

 quate to explain the action of the pile, we must 

 substitute in its place the chemical hypothesis, 

 which supposes that the first step of the process 

 consists in the action of the fluid upon one of the 

 metals, and that the electrical, or rather the galva- 

 nic phenomena, depend upon this action. This ac- 

 tion essentially consists in the oxidation of the sur- 

 face of one of the metals, while the opposite sur- 



* Elements, p. 376. 



