286 M. De la Rive's Researches 



conducting body which connects its poles. The only means 

 of attaining this object is to separate the two metals of a pair 

 by other pairs as similar to the first as possible ; these inter- 

 mediate pairs, the number of which should correspond to the 

 more or less imperfect conductibility of the bodies interposed, 

 will each produce as much electricity as the extreme pair, but 

 these electricities do not pass through the conductor ; they 

 only compel the electricities of the extreme pair to pass through 

 it almost in totality. We shall now endeavour to show how 

 this effect is produced. We shall take a pile in activity ; and 

 suppose that all the pairs of which it is composed are so ex- 

 actly similar to each other, in every respect, that the free elec- 

 tricity upon each of them has the same intensity. Let b be a 

 pair in the pile, taken at hazard, and disposed in such a man- 

 ner that its zinc is immersed in the same liquid as the copper 

 of the pair a which precedes it, and its copper in the same li- 

 quid as the zinc of the pair c which follows it. The chemical 

 action of the liquid upon the zinc of the pair b develops in it 

 a certain quantity of electricity ; the portion of this electricity 

 which does not undergo immediate recomposition remains free, 

 and the same for all the pairs, they being similar and symmetric- 

 ally disposed with relation to each other. According to this 

 the positive electricity of b, developed by chemical action, in the 

 liquid in which the copper of a is immersed, neutralizes the 

 negative electricity of this latter pair, which is equal to it. In 

 the same manner the negative electricity of b, which by che- 

 mical action is carried to the zinc, and thence to the copper 

 in contact with the zinc, neutralizes the positive electricity of 

 c, which also is perfectly equal to it. There remains then an 

 excess of free positive electricity in the liquid in which the 

 zinc of a is immersed, and an excess of free negative electri- 

 city perfectly equal upon the copper of c. But these free ex- 

 cesses are neutralized by the equal and opposite electricities 

 of the following pairs, with regard to which we may reason in 

 the same manner as for the pairs a, b 9 and c. Thence there 

 results an excess of free positive electricity at the extremity of 

 the pile at the side of a, and an exactly equal excess of nega- 

 tive electricity at the extremity situated at the side of 6. Such 

 is found to be the fact if a communication be established be- 

 tween each of the extremities and an electroscope; and if they 

 be united by a conductor, the two excesses of free electricity 

 are collected together and form the current. The intensity 

 of this current, as experiment has proved, ought to be per- 

 fectly equal to that of the current which is established in the 

 pile itself, between all the pairs. 



It most frequently happens that the quantity of freeelectri- 



