into the Cause of Voltaic Electricity. 279 



by chemical action ; and the particular nature of this action, 

 which, according to the bodies between which it is exerted, 

 gives rise to electric effects more or less intense. 



When there is chemical action between two bodies, one 

 takes possession of the positive electricity, (these are in gene- 

 ral oxygen, oxides, &c.) the other of the negative electricity, 

 (these are in general the bases, metals, oxides, &c). Each of 

 these bodies is in a state of electric tension, and it may be ren- 

 dered sensible by putting one of them in communication with 

 an electroscope, and the other with the earth. There is an 

 electric current when the two bodies are united exteriorly at 

 the points at which the chemical action takes place, and it may 

 be rendered sensible by employing the metallic wire of a 

 galvanometer to effect this union. Thus when a communi- 

 cation is established between the condenser of an electroscope 

 and an oxidable metal, and it is touched with the finger or 

 any other humid conductor, the metal takes the positive elec- 

 tricity, which it transmits to the condenser, and the humid con- 

 ductor the negative, which passes into the earth. In the 

 particular case in which the condenser is formed of one plate 

 of zinc and one of copper, the negative electricity which the 

 zinc acquires by the chemical action exerted upon its surface 

 by the air or some other gas, passes in part into the copper 

 with which the zinc communicates metallically ; the positive 

 electricity with which the layer of air adhering to the sur- 

 face of the zinc is charged passes into that metal, or, after 

 having neutralized what remains of the negative, charges it 

 positively; by means of condensation a sufficient quantity of 

 positive electricity is accumulated upon the surface of the zinc 

 and of negative upon the copper to admit of their presence 

 being easily perceived by the electroscope ; it may also be 

 seen, as experiment has constantly proved, why the electric 

 tension of each of the plates is the moiety of what it would be 

 if one of them were put in communication with the earth and 

 the other with the electroscope. In the same manner when two 

 metals communicating with each other metallically are im- 

 mersed in a liquid which exerts a chemical action upon one of 

 them, and not upon the other, the positive electricity with 

 which the liquid becomes charged, and the negative which is 

 taken by the attacked metal, unite by the intervention of the 

 metal not attacked, and the conductor which unites the two 

 metals, constituting the electric current which it is said leaves 

 the metal attacked in a state which is called positive in rela- 

 tion to the other. It is not necessary that the second metal 

 should not be attacked ; it is sufficient that it be attacked in a 

 less degree than the other in order to the establishment of the 



