382 GALVANISM. 



but Volta afterwards explained this effect, by ima- 

 gining that the moisture of the animal excited the 

 electrical agency of the metals, and that the organs 

 of animals served only as a delicate test of the pre- 

 sence of electricity. 



It has been found that the mere contact of two 

 metals is sufficient to produce electricity without 

 any intervening fluid j when separated, that which 

 has the strongest attraction for oxygen exhibits 

 signs of positive, the other of negative electricity. 



But when any fluid that acts chemically upon 

 the metals is also used, the developement of elec- 

 tricity is much more considerable. The fluids 

 commonly used are water, and acids very much 

 diluted with water : and the metals act best when 

 one is easily, and the other with difficulty, oxid- 

 able. 



The original source of the electricity is not yet 

 perfectly understood : there are two opinions re- 

 specting it ; one supposes that it depends merely 

 upon the contact of the metals, and that the che- 

 mical action is really the consequence of the evo- 

 lution of electricity : the other opinion is, that the 

 chemical action is the first in order of time, and 

 that it occasions the developement of the electric 

 fluid. 



The electricity excited by the contact of two 

 metals is perceived by the following easy experi- 

 ment. Place a piece of zinc upon the tongue, and 

 a piece of silver under the tongue, and let both 

 pieces project a little beyond the tip : then bring 

 the metals into contact, when a peculiar sensation 

 will be perceived resembling that of common elec- 

 tricity applied to the tongue. This is really owing 

 to the developement of a small quantity of elec- 

 tricitv, which is called Galvanic electricity. 



