PROGRESS OF ELECTRICAL THEORY. 43 



Thus our conclusion with regard to this subject 

 is, that if we wish to form a stable physical theory 

 of electricity, we must take into account, not only 

 the laws of statical electricity, which we have been 

 chiefly considering, but the laws of other kinds of 

 agency, different from the electric, yet connected 

 with it. For the electricity of which we have 

 hitherto spoken, and which is commonly excited 

 by friction, is identical with galvanic action, which 

 is a result of chemical combinations, and belongs 

 to chemical philosophy. The connexion of these 

 different kinds of electricity with one another leads 

 us into a new domain ; but we must, in the first 

 place, consider their mechanical laws. We now 

 proceed to another branch of the same subject, 

 Magnetism. 



Reports of the British Association for 1835. I may seem there 

 to have spoken more favourably of the Theory as a Physical 

 Theory than I have done here. This difference is principally 

 due to a consideration of the present aspect of the Theory of 

 Heat. 



