ELECTRICITY AND GALVANISM. 65 



Voltaic Electricity, and the term Galvanism is confined to 

 that part of the subject which relates to animal motion. 



A Voltaic pile, capable of giving a pretty smart shock, 

 may be made as follows : Procure 30 or 40 pieces of 

 copper of the size of a penny piece, a penny piece will 

 do, (copper has been found to answer the purpose nearly 

 as well as silver), as many pieces of zinc of the same 

 size, and as many pieces of cloth or leather, rather less 

 in diameter than the metallic plates. Having soaked the 

 cloth or leather in a sohition of sal ammoniac, and 

 squeezed them out, erect the pile in the following order : 

 first, a piece of zinc, on this a piece of copper, and again 

 on this a piece of the moistened cloth ; continue to do 

 this until the pile is completed, and then by touching 

 the top and bottom of the pile with moistened fingers, 

 a shock will be perceived, and will be repeated as often 

 as the fingers are applied. By connecting several of 

 these piles by wires, taking care that each pile com- 

 mences with the contrary metal to that with which the 

 other is terminated, the effect will be proportionately 

 increased ; water may be decomposed, and other che- 

 mical truths developed. 



An improvement in the Voltaic pile was made by an 

 Englishman named Cniickshanks, \vho soldered together 

 the zinc and copper plates, and cemented them into 

 grooves in a mahogany trough. The cells between the 

 metals he filled with a mixture of some mineral acid and 

 water.* This arrangement was found not only much 

 more convenient, but it also increased the intensity of 

 the shock. A combination of these troughs, called a 

 Galvanic battery, has been found to produce the most 

 astonishing effects, burning and reducing to vapour the 

 firmest and most compact bodies in nature. The cause 

 of this action is attributed to the metals being of differ- 

 ent electricities ; thus zinc is said to possess a positite 

 electricity, and silver and copper a negative electricity. 



There are various experiments in order to produce a 

 Galvanic excitement of the human body ; for instance, 



* A weak mixture of nitric and sulphuric acid and water is now 

 generally used for this purpose. 



