100 Prof. Majocchi on the Origin of the Voltaic Current. 



with the polarization of the platinum electrode, which weakens 

 or entirely annuls the effect of the first. For if the liquid is 

 placed together with the two platinum electrodes, by which the 

 voltaic circuit is completed, under the receiver of the air-pump 

 where a vacuum is effected, the hydrogen gas is forced to dif- 

 fuse itself by its expansibility in the same receiver, whereby 

 the negative electrode is not polarized, and the electric cur- 

 rent continues its course, until the gas can in such manner se- 

 parate itself from the surface of the platinum, and diffuse itself 

 in the vacuum of the air-pump. 



With a view to ascertain whether this mode of explaining 

 the phaenomenon of the current in the battery has any pro- 

 bability and contains the cause of the same, it occurred to me 

 to form an entirely metallic circuit, without any intermediate 

 electrolyte, to examine if the simple chemical action was able 

 of itself to generate a current. I shall first observe, that an 

 homogeneous metallic wire, forming a continuous circuit and 

 returning into itself, and perfectly identical throughout its whole 

 extension, if heated in any part, gives rise to no electrical 

 current ; because the propagation of the caloric, proceeding 

 uniformly from the two sides of the portion heated, gives rise 

 to two electrical currents in an opposite direction, which be- 

 come perfectly equal, and thence counteract one another, and 

 obstruct the continuous circulation of the fluid itself. And if 

 any obstacle, as a knot or a defect of homogeneity in the wire, 

 renders the propagation of the caloric more difiicult in one 

 direction than in another, then one of the electrical currents 

 which arise prevails over the other, and one results of in- 

 tensity equal to the difference of the two unequal elements, 

 which shows itself precisely on the galvanometer. In the 

 same way, if the homogeneous metallic wire, forming the 

 closed and re-entering circuit, is afterwards touched by a cold 

 body in a point near the heated part, an electrical current is 

 generated, which is indicated by the galvanometer. It seems 

 then that the cooling produced on one side of the heated part 

 weakens the cause from which the electric current springs, and 

 thence gives room to the other to circulate in the wire and 

 make its effects perceptible on the galvanometer. This case 

 is very different from that in which the thermo-electric circuit 

 is composed of two metals ; the one positively electric and the 

 other negatively electric ; since then there are two forces 

 from which the electric current springs in a given direction. 



Following this principle, applied to the development of 

 electricity by chemical action, 1 reasoned thus : — If the che- 

 mical action were able of itself to generate a current without 

 the aid of another force, it is clear that, on forming a wholly 



