52 NOMOS. 



molecule of chloride of silver must be changed, and 

 pari passu with this wasting and change must be the 

 growth of the positive electrode. Nor is the appa- 

 rent absence of any change in the fused chloride of 

 silver between the electrodes any objection to this 

 view, for there was the same absence of apparent 

 change when soda was made to pass through acid in 

 the last experiment, and yet the existence of this 

 change was demonstrated when it was attempted to 

 pass baryta. The latter experiment, indeed, not only 

 demonstrates the existence of hidden change, but it 

 shews that this change is chemical in its character; 

 and hence it is scarcely possible to doubt that there 

 are similar hidden changes in the fused chloride of 

 silver, and that the silver is carried from one electrode 

 to the other by these changes. Certainly this expla- 

 nation is sufficient ; and, as certainly, none other has 

 been offered. 



It is more difficult to account for the transfer of 

 matter by the current through aeriform media, but 

 still no new explanation appears to be necessary. 

 This transfer is exhibited in various ways. It is 

 seen in the colour of the spark when metallic elec- 

 trodes are used, for this colour is the same as that of 

 the flame of the same metal in common combustion. 

 Thus, iron gives a sparkling red flame, silver a green, 

 and zinc a blue. Here, then, we have evidence both 

 of transfer of matter and of the means of transfer, 

 for combustion is a known chemical process. But 

 there are other kinds of transfer which are not so, 

 easily understood. When a voltaic current is dis- 

 charged between charcoal electrodes, the charcoal is 



