THEORY OF GALVANISM. Ill 



it. It is usually developed by the mechanical aid 

 of friction ; and the same apparatus may continue 

 to be employed for an indefinite length of time. 

 Friction, on the contrary, has no effect in the pro- 

 duction of galvanic electricity ; it requires a che- 

 mical change in some part of the apparatus ; and 

 the individual parts which have been employed in 

 generating it acquire new properties, and are^ in- 

 capable of any farther galvanic action. In the 

 above remarks I have proceeded upon the hypo- 

 thesis which is the most generally received in this 

 country, and which I am disposed to consider as 

 the most plausible, that the two electricities differ 

 from each other merely in the relation of quantity. 

 But if the contrary opinion be adopted, which is 

 more current in France, and which has been so 

 elaborately detailed by Biot in his late' treatise, 

 and we regard them as differing in their nature, 

 still it will not essentially affect the reasoning that 

 I have employed, although it may require to be 

 expressed in somewhat different terms. According 

 to this view of the subject, when we employ the 

 common electrical machine, we forcibly alter the 

 proportion in which the vitreous and the resinous 

 electricities naturally exist in the different parts of 

 the apparatus, which have a constant tendency to 

 resume their former condition. In the action of 

 the pile, on the contrary, we alter the capacity of 

 some part of the instrument for one or other of the 

 electricities, and produce a state in which their ba- 

 lance is permanently changed. 



