When they employed a very powerful battery, it was ob served that considerable SII0d:b were given by it to an in dividual; but that in a chain of four or live persons, it was not felt in the centre ; and in the extremities of the chain, that part of the body received the greatest impression which was nearest to the apparatus. This fact is sup posed to prove, that the electric fluid cannot circulate through the whole circuit, according to the Franklineal) hypothesis. When the battery is pul into strong action, its chemical effect, i. e. its power of decomposing water, soon declines, or altogether ceases, while its electrical tension remains for some time longer unimpaired.
An interesting train of experiments is next detailed, in which mercury was interposed between the wires, and formed an amalgam with the substance which was intend ed to be decomposed : an arrangement which we have al ready pointed out as having been employed by Sir H. Da vy in his decomposition of the proper earths. They re: vented the experiments of this philosopher on ammonia, and they formed the amalgam with mercury, which he con ceived• was composed of this substance with the metallic basis of ammonia ; but they differ from him in their idea of its constitution, and suppose that there is no evidence of the existence of the metal of the volatile alkali, although the analogy of the fixed alkalies offers so powerful an ar gument in its favour.
While Sir H. Davy was pursuing, with so much success, his interesting researches into the clectro-chcmical action of bodies upon each other, AI. De Luc undertook to inves tigate the nature of the galvanic pile, and to examine the mode of its operation. After some animadversions upon the hypothesis of the inherent electric energies of bodies, which constitute the origin of the train of phenomena that are connected with the pile, he proceeds to dissect this in strument into three parts. He divides it into three sepa rate groups, corresponding to what he regards as the three elements of the pile. These elements are the two metals and a fluid. They were first placed with the fluid between the two metals ; then with the fluid in contact with one, and afterwards in contact with the other metal, the differ ent groups being kept distinct from each other by small wire stands, so as to confine the action to that part alone. When the piles were fitted up in these three different ways, a delicate electrometer was attached to each extremity, and they were also connected by the interrupted wire pass ing through water, (Plate CCLXIII. Figs. 14, 18, 19.)
His first set of experiments were made upon the pile in which the groups were arranged with the fluid between the two metals. By means of the electrometer, lie ob Eel ved which ends of the apparatus were in the positive and negative states respectively ; and he likewise made some new observations on the direction which the electric current takes in its passage across the water—in the in terrupted circuit—and in the body of the pik itself. His observations agreed with those originally made by Nichol son, thet the extremity of the pile which is connected with the wire emitting oxygen, is positive, and that the current is directeu from this to the wire which emits the hydrogen. He Informs us, however, that although electrometers plac ed at the extremities, when they are affected, indicate the electricity to be in the state mentioned above ; yet they are not Lys both of them affected, sometimes only the posi tive electricity is visible, sometimes only the negative, while at other times both of them are perceptible. He that, from causes, the electric fluid passes through the apparatus with different velocity at dif ferent times, or through its • different parts at the same time, so as to produce a partial accumulation or deficiency: It scents to be always retarded when it passes from the point wire into water. Ile observes, that the expres sions positive and negative, as applied to the ends of the pile, or to the wires in the interrupted circuit, can only be regarded as comparative terms, because the chemical ac• don of the pile goes on as usual in the decomposition of water, although the whole instrument be rendered po!itive or negative, by attaching it to the prime conductor, or to the rubber of the electrical machine. This experiment is adduced to prove, that the action of the pile is not neces sarily connected with the electric energy of the substances that enter into its composition. The pile, when dissected in the first way, with the fluid interposed between the two metals, acts in the same manner as if the parts were con tinuous, except that the effect is rather less powerful.