38 HISTORY OF GALVANISM. 



he accomplished by coating two silver wires, the 

 ends of them only being left exposed. He then 

 connected these wires with the two conductors of 

 the electrical machine, and passed the spark, from 

 one to the other, through a solution of a salt of 

 copper ; the negative wire was found to be covered 

 with a metallic coating, as if it had been con- 

 nected with the copper or silver end of the pile.* 

 Remarks The experiments of Dr. Wollaston, and the 



on Wollas- 



ton's expe- reasoning which he employed concerning them, 

 must be considered as both affording a very im- 

 portant addition to our knowledge of galvanism, 

 and as giving a greater precision to our ideas on 

 the theory of its production, and on the nature of 

 the relation which it bears to common electricity. 

 In the experiment in which the plates of zinc 

 and silver are separately immersed in a diluted 

 acid, we find that the decomposition of the water 

 is effected solely by the zinc ; but that when the 

 metals are connected, the hydrogen is disengaged 

 from the silver. In this case it does not appear 

 that the silver in any way tends to promote the 

 decomposition of the water, but that it merely 

 influences the manner in which its constituent 

 parts are liberated, which, there is every reason to 

 suppose, depends essentially upon the electrical 

 condition of the different parts of the metallic 

 surface. Although Nicholson, by applying his 

 doubler to the two extremities of the pile, may be 



* Phil, Trans, for 1801, p. 4-27. 



