t>AVY. 455 



and the different component parts of bodies submitted 

 to the action of the fluid. Nothing could be more 

 singular and unexpected than the laws which he now 

 found to regulate this operation, nor anything which 

 promised more clearly a rich harvest of new discoveries. 

 The effect of the current, whether of common or gal- 

 vanic electricity, in decomposing substances through 

 which it passed, had been before known. Thus water 

 had been resolved into its two elements by the passing 

 of the fluid througli wires whose points were opposite 

 to each other at a small distance. Nicholson had first 

 made this happy application of the voltaic pile ; but 

 he and others had been much disturbed by finding 

 other substances produced as well as oxygen and hy- 

 drogen gases. This perplexing circumstance was care- 

 fully investigated by Davy ; and he showed by a mas- 

 terly course of experiments, that these substances owed 

 their origin entirely to impurities in the water. 

 When it was quite pure, they wholly disappeared. 

 But he now proceeded farther, and found that when 

 the electric current is thus passed, there is always a 

 separation operated differently at the negative and at 

 the positive part of the current. The oxygen of the 

 water, for example, was accumulated round the positive 

 wire ; its hydrogen round the negative. So when a 

 neutral salt was subjected to the process, its acid was 

 evolved round the positive ; its alkaline base round the 

 negative wire. The same thing happened when a me- 

 tallic oxide was operated upon ; its oxygen went to the 

 positive, its metallic base to the negative side. The 

 oxygen, or the acid with the oxygen, went to the for- 

 mer ; the particles of the base were transferred to the 



