GALVANISM. 



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The investigations of which the pile became the instrument now began to 

 ') assume an importance which rendered it necessary to give it considerably aug- 



> mented power, either by increasing its height or enlarging its component plates. 

 ; In either case, inconveniences were encountered which imposed a practical 

 ? limit on the increase of its power. When the number or magnitude of the 

 ) metallic disks was considerable, the incumbent pressure discharged the liquid 

 / from the intermediate disks of cloth or card. The trouble of refilling it when- 

 ever its use was required, and of wetting the cloth or card, was very great. 

 Mr. Cruickshank, adopting the principle of Volta's couronne des lasses, pro- 

 posed, as a more convenient form for the apparatus, an arrangement consisting 

 of a trough of baked wood, which is a non-conductor of electricity, divided by 

 parallel partitions into a series of cells. Into these cells the liquid to be in- 

 terposed between the successive pairs of metallic plates was poured. A se- 

 ries of rectangular plates of metal, alternately zinc and copper, were arranged 

 so as to be parallel to each other, and at such a distance as to allow the pnrti- 



> tions of the trough to pass between each pair of plates. This modification 

 ' rendered the Voltaic apparatus capable of having its power increased without 



practical limit. 



While these investigations were proceeding, Ritter, afterward so distin- 

 guished for his experimental researches, but then young and unknown, made 

 various experiments at Jena on the effects of the pile ; and, apparently with- 

 out knowing what had been done in England, discovered this property of de- 

 composing water and saline compounds, and of collecting oxygen and the acids 

 at the positive, and hydrogen and the bases at the negative pole. He also 

 showed that the decomposing power in the case of water could be transmitted 

 through sulphuric acid, the oxygen being evolved from a portion of water on 

 one side of the acid, while the hydrogen was produced from another separate 

 portion of water on the other side of it.* 



When the chemical powers of the pile became known in England, Sir 

 Humphry (then Mr.) Davy was commencing those labors in chemical science 

 which subsequently surrounded his name with so much lustre, and left traces 

 of his genius in the history of scientific discovery which must remain as long 

 as the knowledge of the laws of nature is valued by mankind. The circum- 

 stance attending the decompositions effected between the poles of the pile 

 which caused the greatest surprise, was the production of one element of the 

 compound at one pole, and the other element at the other pole, without any 

 discoverable transfer of either of the disengaged elements between the wires. 

 If the decomposition was conceived to take place at the positive wire, the con- 

 stituent appearing at the negative wire must be presumed to travel through the 

 fluid in the separated state from the positive to the negative point ; and if it 

 was conceived to take place at the negative wire, a similar transfer must be 

 imagined in the opposite direction. Thus, if water be decomposed, and the 

 decomposition be conceived to proceed at the positive wire where the oxygen 

 is visibly evolved, the hydrogen from which that oxygen is separated must be 

 supposed to travel through the water to the negative wire, and only to become 

 visible when it meets the point of that wire ; and if, on the other hand, the de- 

 composition be imagined to take place at the negative wire where the hydro- 

 gen is visibly evolved, the oxygen must be supposed to pass invisibly through 

 the water to the point of the positive wire, and there become visible. But 

 what appeared still more unaccountable was, that in the experiment of Ritter 

 ; ; ; would seem that one or other of the elements of the water must have passed 

 through the intervening sulphuric acid. So impossible did such an invisible 



* Nicholson's Journal, vol. iv., p- 511. 



