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340 



GALVANISM. 



drop of water was used to make good the contact of the conducting wire with 

 a plate to which the electricity was to he transmitted ; Carlisle observed a dis- 

 engagement of gas in this water, and Nicholson recognised the odor ot' hydro- 

 gen proceeding from it. In order to observe this effect with more advantage, 

 a small glass tube, open at both ends, was stopped at one end by a cork, and 

 being then filled with water was similarly slopped at the other end. Through 

 both corks pieces of brass wire were inserted, the points of which were ad- 

 justed at a distance of an inch and three quarters asunder in the water. When 

 these wires were put in communication with the opposite ends of the pile, 

 bubbles of gas were evolved from the point of the negative wire, and the end 

 of the positive wire became tarnished. The gas evolved appeared on examina- 

 tion to be hydrogen, and the tarnish was found to proceed from the oxydalion 

 of the positive wire. It was inferred that the process in which these effects 

 were produced was the decomposition of water. This took place on the 2d 

 of May, shortly after the receipt of the first portion of Volta's letter. 



To ascertain whether the oxydation of the positive wire was an effect inci- 

 dental to the experiment, or had an influence in producing the decomposition, 

 Nicholson determined to try the effect of wires formed of metal more difficult 

 of oxydation. Wires of platinum were accordingly inserted through the corks, 

 and the experiment repeated. Bubbles of gas were now evolved from both 

 wires. Two platinum wires were next inserted at the closed ends of two 

 separate tubes, which, being open at the other ends and filled with water, -vere 

 inserted in the same vessel of water. Being placed side by side close together, 

 and the wires being continued to the lower ends of the tubes, so that the dis- 

 tance between their points was not more than two inches, their upper extremi- 

 ties were put in connexion with the ends of the pile. Gas was evolved from 

 the points of both wires, and, ascending through the water, was collected sep- 

 arately in the two tubes. These gases being examined, proved to be hydrogen 

 from the negative, and oxygen from the positive wire, nearly in the proportion 

 known to constitute water.* 



Thus was the decomposing power of the pile established within a few weeks 

 after the first intimation of the invention of that instrument had been received 

 in England, and before any description of it had been published. It seemed 

 proper to give these details here, not only on account of the great importance 

 of the discovery, but because it has been sought to depreciate the merit of it 

 by ascribing it altogether to chance. It is probably impossible to exclude 

 chance altogether from such investigations, but in this there Avas as little as is 

 generally found. 



When these experiments became known, Mr. W. Cruickshank, of Woohvich, 

 repeated them, and obtained similar results ; but observed that when the dis- 

 tilled water was tinged with litmus, the effects of an acid Avere produced at the 

 positive, and those of an alkali at the negative wire. Led by this indication, 

 he tried the effects of the wires on solutions of acetate of lead, sulphate of 

 copper, and nitrate of silver. In each case he found the metallic base depos- 

 ited at the negative pole, and the acid manifested at the positive pole. Muri- 

 ate of ammonia and nitrate of magnesia Avere next decomposed, the acid as be- 

 fore going to the positive, and the alkali to the negative pole. These experi- 

 ments of Mr. Cruickshank Avere made as early as June, ISOO.f 



In the September following, Mr. Cruickshank published the continuation of 

 his researches,^ in Avhich he corroborated the results of his former experiments, 

 showing more generally the tendency of oxygen and the acids in Voltaic de- 

 composition to collect round the positive wire, and hydrogen, metals, alkalies. 

 &c., round the negative pole. 



* Nicholson's Journal, vol. iv., p. 179. 1800. t Ibid., p. 137. t Ibid., p. 251. 



