Galvanism. 125 



water impregnated with a small quantity of mu- 

 riatic acid, the zinc will be immediately acted 

 upon by the diluted acid, and bubbles of gas will 

 be seen to proceed from it, but the silver wire EF 

 remains untouched. If then you bend the silver 

 wire FG so that its end may touch the zinc at C, 

 you will find not only that the fluid acts more 

 strongly upon the zinc at D, but that the silver 

 at F is also strongly acted upon, as appears by 

 the evolution of gas, &c. This is what is called 

 a galvanic circle, and this circle is completed, in 

 the technical language of this science, by bringing 

 the silver wire in contact with the zinc at C. 



The effects from simple galvanic circles, and 

 the analogy between the phaenomena of galvanism 

 with these of electricity, suggested the idea of 

 extending the combinations, and forming what 

 are now called galvanic batteries. The first and 

 simplest of these were formed of round pieces of 

 zinc and silver with pieces of cloth or leather 

 rather smaller, and moistened with water or diluted 

 acid, interposed in the manner of fig. 43, where 

 the silver, zinc, and wet cloth are marked by the 

 letters S, Z, W. This was at first called the gal- 

 vanic pile, from its form. 



The most convenient form for a galvanic bat- 

 tery, however, was soon afterwards found to be 

 that represented in fig. 44. It consists of an ob- 

 long vessel or trough of baked wood of different 

 sizes, according to the strength of the intended 

 battery. In the sides of the trough there are 



