THEORY OF GALVANISM. 



their contact forms the foundation of the theory ; 

 it is supposed that all bodies have specific affinities, 

 which are transferable under certain circumstances, 

 and that this interchange depends upon the nature 

 of affinity itself, and is entirely unconnected with 

 any electrical action. He brings forward many 

 experiments to prove that electricity is not in any 

 case the agent which produces the phenomena of 

 galvanism, but that they may all be referred to 

 the principle of transfer. 



A number of experiments are detailed on vari- 

 ous combinations of metals, to prove that the same 

 effect which takes place with respect to zinc and 

 copper may be observed in all similar cases, and 

 hence is deduced the conclusion, that " the princi- 

 ple of transferred electricity is general ; and what- 

 ever may be the attraction of any metal to oxy- 

 gen, that it is always either diminished or increased 

 by the contact of another metal ; the more oxyda- 

 ble metal acquiring the increase, and the less 

 oxydable suffering the diminution." * This hy- 

 pothesis is then applied to all the operations which 

 are usually styled galvanic, such as metallic arbori- 

 zations, the chemical effects of the pile, the effect 

 upon the muscle and nervous fibre, and other phe- 

 nomena which are more related to common elec- 

 Remarks tricity. It must, I think, be admitted that there is 

 Tan's hy " much ingenuity in many parts of Mr. Donovan's 

 reasoning, an d that he has adduced many valuable 



* Essay on Galvanism, p. 285. 



