184 APPENDIX TO MEMOIR OF PELTIER. 



physicist, tlie origin of the electricity of the pile of Volta is the chemical action 

 wliich takes place between the acidulated liquid and the zinc. The negative 

 electricity diffuses itself over the metal attacked, the positive electricity dilFusea 

 itself in the acidulated liquid. These electricities are afterwards neutralized, 

 each on its side, with the opposite electricities of the adjacent pairs, and the 

 same fact reappears as far as the two extremities of the pile, which alone are in 

 possession of free electricity. In a well-constructed pile, according to M. de la 

 Rive, there is a neutralization of all the intermediate electricities ; all the nega- 

 tive portions are neutralized by equal positive portions, proceeding from the 

 pairs in juxtaposition ; there are none free but the electricities of the two extreme 

 elements, and these polar electricities have, in order to become neutralized, only 

 the arc interposed between them or a return by the pile. 



From this it is evident that the quantity of electricity found at the poles of a 

 battery is independent of the number of pairs, and that the number of pairs 

 must only augment the difficulty of recomposition backwards ; that is to say, 

 must augment the tendency of the electricity to combine forwards. But in phys- 

 ics it is not enough to advance a theory more or less satisfactory : it is necessary to 

 demonstrate it ; it is necessary to prove the reality by numerous and positive experi- 

 ments which can leave no doubt or uncertainty ; it is necessary, in a word, to antici- 

 pate all objections and answer them in advance. This is what Peltier has done.* 

 Swumary of Peltier'' s researches on the Voltaic pile. — According to Peltier, in 

 a current there are two very different things to be distinguished : the quantity 

 and the intensity. The quantity is the number of electric perturbations which 

 traverse a conductor in a unit of time. The intensity is the power which a cur- 

 rent possesses of overcoming the resistance of the conductors presented to it. 



Peltier, to whom we are indebted for having clearly established this distinc- 

 tion, has demonstrated by multiplied experiments that in a battery the quantity 

 of electricity produced is in a ratio with the number of molecules pertaining to 

 one and the same surface, and undergoing a change in their equilibrium ; but 

 that, in the estimate of the quantity of electricity which passes by the conduct- 

 ors in the state of a current, it is necessary to regard the resistance of these 

 conductors, because these resistances almost always cause a portion of the quan- 

 tity of electricity produced to be in return neutralized. He has shown that 

 wlien the resistance of the conductors is null, the quantity of electricity which 

 passes by the closed circuit is proportional to the quantity of molecules attacked 

 on the same surface. 



He has proved that when a batter}^ is well constructed and the circuit without 

 resistance, the entire pile gives no more electricity than a single one of its pairs ; 

 consequently that when it is desirable to have a current of quantity, it is neces- 

 sary to use a battery with pairs of large dimensions. 



It was generally thought that in a battery, when one pair was smaller than 

 the others, this small pair decided the quantity of the whole cmi-ent. Peltier 

 proved that this opinion was not wholly exact. No doubt this small pair dimin- 

 ishes the quantity of the current. In consequence of its resistance, which is greater 

 by reason of its very littleness, it forces a portion of the electricity which reaches 

 it to recombine behind it, but it gives passage as a simple conductor to the rest. 

 By means of positive experiments, I'eltier has demonstrated that the intensity 

 of a current, that is to say, the power it possesses of overcoming obstacles, is 

 only due to the greater obstacles situated behind to prevent retrogradation of 

 the two polar electricities by the battery. Now, these obstacles may be of two 

 sorts : they may proceed from the reduplication in a battery of the same pairs, 

 or else from a more profound alteration in the state of equilibrium of the mole- 

 cules. In the first case, the intensity is proportional to the number of pairs; in 

 the second, it depends on the power of action of the disturbing substance. 



* See Annates de Cliimie et de Physique, 1836, t. 03, p. 245: the note of Peltier entitled 

 "Definition of the words electric quantity and intensity, drawn from direct experiments." 



