138 THEORY OF GALVANISM. 



the action of the apparatus ; it explains the rea- 

 son why the metals must differ in their degree of 

 oxidability, and why the fluid must be one that 

 will act differently upon the two metals. The 

 Nature of facts that have been noticed respecting the dif- 

 ferent effects of the interposed fluids may be ex- 

 plained by referring to three circumstances, which 

 all coincide with the chemical hypothesis, but 

 which seem to have no relation to any electrical 

 action : 1. That the fluid acts only upon one of 

 the metals : 2. That the surface of one of the me- 

 tals is oxidated with a certain degree of rapidity : 

 3. That the oxide is removed so as to present a 

 fresh surface to the fluid. If acids be employed, 

 those are the best that dissolve the oxide ; or if 

 neutral salts, those which form triple compounds 

 size of the with the oxide which is produced. The chemical 

 hypothesis affords a plausible method of accounting 

 for the different effects of the apparatus, whether 

 we use large or small plates ; for it is not unreason- 

 able to suppose that the electricity will become 

 more intense or concentrated at every successive 

 transmission through a new oxidating surface, 

 while its absolute quantity will depend upon the 

 amount of oxide that is formed. 



Nature of With respect to the experiments of Bennet, and 

 STiieri-' 8 ^ ers f a s i mu<ar kind, which have been adduced 

 meats. m favour of the electrical hypothesis, it is proba- 

 ble that Volta has been mistaken in his application 

 of them, and of the principle to which they should 

 be referred. Instead of supposing, as he does, that 



