No sooner was the discovery of the galvanic pile an nounced, than the English experimentalists began their operations with it, and almost at the first trial of its effects made some important and interesting observations. Sir Joseph Banks, on the receipt of the letters, having com municated the information to his scientific friends, a pile was formed by Messrs Nicholson and Carlisle, with which they began to repeat the experiments of Volta. They ar ranged the substances in the order of silver, zinc, fluid ; silver, zinc, an arrangement which it is neces sary to attend to, in speaking of what have been called the silver and zinc ends of the apparatus. Volta, it appears, had satisfied himself that the action of the pile was electri cal, because it produced the shock ; but Messrs Nicholson and Carlisle applied to it the instrument called the re volving doubler, (See ELECTRICITY), and by this means decidedly proved it to be the case : They found, that the silver end was in the minus, and the zinc end in the plus state of electricity.
In the course of the experiments, a part of the circuit between the upper and lower ends of the pile was formed by water ; and it was observed, that there was a disengage ment of gas, at the part where the wire came in contact with the fluid. This gas was thought to have the odour of hydrogen; and it led them to notice, with more atten tion, the effect produced by causing the electricity to pass through a tube of water, into the two ends of which wires were inserted, which communicated with the extremities of the pile. We shall relate this very important experi ment in Mr Nicholson's own words. " On the 2d of May we inserted a brass-wire through each of two cocks, insert ed in a glass tube of half an inch internal diameter. The tube was filled with new river water, and the distance be tween the points of Ole wires in the water was one inch and three quarters. This compound discharger was appli ed, so that the external ends of its wire were in contact with the two extreme plates of a pile of 36 half-crowns, with the correspondent pieces of zinc and pasteboard. A fine stream of minute bubbles immediately began to flow from the point of the lower wire in the tube, which com municated with the silver, and the opposite point of the up per wire became tarnished, first deep orange, and then black. On reversing the tube, the gas came from the odicr point, which was now lowest, while the upper, in its turn, became tarnished and black."—" The product of gas, dur ing two hours an4 a hall; was two-thirtieths of a cubic inch. It was then mixed with an equal quantity of com mon air, and exploded by the application of a lighted wax ed thread." They observed, that the same process of the decomposi tion of water is carried on in the body of the pile, as be tween the two ends of the wire in the interrupted circuit ; the side of the zinc next to the fluid being covered with ox ide in two or three days, and the apparatus then ceasing to act. Mr Nicholson found, that, by using metallic plates of considerably more extensive surface, no greater effect was produced in the decomposition of water, or in the violence of the shock ; so that he concludes, " the repetition of the series is of more consequence to this action than the en largement of the surface." It was now clearly ascertained,
that the electricity of the silver or minus end was nega tive, that of the zinc or plus end positive. Although it ap peared evident that there had been a decomposition of water effected by the copper wire, yet Mr Nicholson determined to render the operation more decisive, by employing a me tal which was not oxidable. Platina was therefore substi tuted for the copper, and now gas was disengaged from both sides, and neither of the wires were tarnished. In a subsequent experiment, the wires were so managed, that the gases extricated from each side were kept distinct, and it was found that they consisted, the one of oxygen, and the other of hydrogen, and that in the proportion necessary to produce water. (Plate CCLXII1. Fig. 6.) In some or these experiments the spark was visible (Nicholson's Jour nal, 4to, iv. 179.) Our readers will at once perceive the important views that were disclosed by the experiments re lated in this paper, in connexion with those performed by Mr Cruickshanks of Woolwich, of which we shall next give an account. They must be regarded as leading directly to the wonderful discoveries that have been made by means of the galvanic apparatus, as well as the theoretical deduc tions to which it has given rise, and which have produced almost a complete revolution in our ideas of the action of bodies upon each other.
Mr Cruickshanks confirmed the obserVations of Messrs Nicholson and Carlisc, respecting the actual appearance of sparks and the decomposition of water. This last process he varied in different ways. By employing the interrupt ed circuit with silver wires, and passing the influence' through water tinged with litmus, he found, that the wire connected with the zinc end of the pile communicated a red tinge to the fluid contiguous to it ; and afterwards, by em ploying water tinged with Brazil wood, he found that the wire connected with the silver end of the- pile produced a deeper shade of colour in the surrounding fluid. Hence it appeared, that an acid was formed in the former, and an alkali in the latter case. The galvanic influence was pass ed through the interrupted circuit, in which the tube was filled With the solution of acetate of lead, when it was ob served that the le:id was separated in the metallic state, and deposited at the end of the silver wire, or the wire connect ed with the silver end of the pile, in the form of fine needles. Experiments were afterwards made upon the solutions or sulphate of copper and nitrate of silver : in this last case, he observes, " the metal shot into fine needles, like crystals articulated or jointed to each other, as in the Arbor Diane." He also succeeded in decomposing some of the neutral salts. See Nicholson's Journal, 4to, iv. 187.