450 Additional Notes. 



is first proper to ascertain the action which takes place Tit 

 the zinc end of the wire. This appears to be the disengage- 

 ment of oxygen in a concentrated state, by which the wire 

 itself, when oxydable, is corroded, but wnich, when the 

 wire is formed of a perfect metal, is disengaged in the form 

 of oxygen gas. This oxygen appears to be derived from the 

 decomposition of the water in which the wire terminates, in 

 consequence of the attraction which the electric fluid pos- 

 sesses for hydrogen, and its incapacity of passing through 

 water without being united to this substance, according ro 

 the second and third postidates. The electric fluid, thus united 

 to hydrogen, is carried to the other point of the wire, where, 

 upon entering the oxydable conductor, it is disengaged in the 

 form of hydrogen gas, if water be the medium of communi- 

 cation. If a solution of metallic oxyd be employed, it unites 

 with the oxyd, and reduces it. The decomposition of water 

 is, theref::)fe, effected at the zinc point alone, thoi-gii the 

 different gases which compose it are dii^engaged at each of 

 the points; and the process will continue even when the 

 points terminate in two ditferent portions of water, as was 

 discovered by Mr. Davy, provided that the glasses are unit- 

 ed by a conductor which is not oxydable. 



To explain the operation carried on in the body of the pile 

 itself. Dr. Bostock says — 



In the construction of the pile there are two points which 

 are essential to its action; viz. 1. That the electric fluid be 

 disengaged; and, 2. That it be confined and carried forward 

 in one direction, so as to be concentrated in the end of the 

 apparatus. The first object is evidently attained by the oxy- 

 dation of the zinc, or other oxydable body employed. If 

 both sides of the zinc were oxydated, the electric fluid would, 

 indeed, be liberated, but it would be immediately dispersed, 

 and its effects could not be observed. As soon, however, 

 as the electric matter is evolved, it is immediately attracted by 

 the hydrogen, which is, at the same time, necessarily gene- 

 rated in tile fluid which oxydates the metal; and it is by this 

 means conveyed across the water to the silver plate, when 

 two metals are used, or, in other cases, simply to the oppo- 

 site surface of the oxydating substance. The electric fluid 

 then enters the silver plate, and, instantly passing on to the 

 contiguous zinc plate, arrives at a second oxydating surface. 

 11ie same series of events that have been described is here re- 

 peated, except that die electric fluid being in some degree ac- 

 cumulated in the metallic plate, is disengaged by the second 



