344 



GALVANISM. 



acted powerfully. The conducting powers of these several metals were then 

 considered as nearly equa-L* 



In considering the various arrangements and combinations in which Voltaic 

 action had been manifested, Davy observed, as a common character, that, in 

 every case, one of the two metallic elements was oxydated, and the other not. 

 Did the production of the electric current, then, depend merely on the pres- 

 ence of two metallic surfaces, one undergoing oxydation, separated by a con- 

 ductor of electricity ] and, if so, might not a Voltaic arrangement be made by 

 one metal only, if its opposite surfaces were placed in contact with two differ- 

 ent liquids, one of which would oxydate it, and the other transmit electricity 

 without producing oxydation ? To reduce this to the test of experiment with 

 a. single metallic plate would have been easy ; but in constituting a series of 

 pile, the two liquids, the oxydating and the non-oxydating, must be in contact, 

 and subject to intermixture. To overcome this difficulty, different expedients 

 were resorted to, with more or less success ; but the most convenient and 

 effectual method of attaining the desired end was suggested to Davy by Count 

 Rumford. Let an oblong trough be formed, similar to that suggested by 

 Cruickshank, as a substitute for the pile ; and let grooves be made in it such 

 as to allow of the insertion of a number of plates, by which the trough may be 

 divided into a series of water-tight cells. Let plates of the metal of which 

 the apparatus is to be constructed be made to fit these grooves ; and let as 

 many plates of glass or other non-conducting material, of the same form and 

 magnitude, be provided. Let the metallic plates be inserted in alternate 

 grooves of the trough, and the glass plates in the intermediate grooves, so as 

 to divide the trough into a succession of separate cells, each cell having on 

 one side metal, and on the other glass. Let such an arrangement be repre- 

 sented in fig. 1, where the metallic plates are represented at M, the interme- 



Fig. i. 





d'iate plates being glass. Let the alternate cells be filled with the oxyda- 

 ting liquid, and the intermediate cells L with the liquid which conducts 

 without oxydating. Let slips of moistened cloth be hung over the edge of 

 each of the glass tubes, so that its ends shall dip into the liquids in the ad- 

 jacent cells. This cloth, or rather the liquid it imbibes, will conduct the elec- 

 tric current from cell to cell, without permitting the intermixture of the liquids. 



In the first arrangements made on this principle, the most oxydable metals, 

 such as zinc, tin, and some others, were tried. The oxydating liquid O was 

 dilute nitric acid, and the liquid L was water. In a combination consisting of 

 twenty plates of metal, sensible but weak effects were produced on the organs 

 of sense, and water was decomposed slowly by wires from the extremities. 

 The wire from the end toward which the oxydating surfaces were directed 

 evolved hydrogen, and the other oxygen. 



To determine whether the evolution of the electric current was dependant 

 on the production of oxydation, or would attend other chemical effects produci- 

 ble by the action of substances in solution upon metal, the oxydating liquid 

 was now replaced by solutious of the sulphurets, and metallic plates were se- 

 lected on which these solutions would exert a chemical action. Silver, copp'.-r, 

 and lead, were tried in this way. Solution 01 suiphuret of potash was used in 



The relative conducting power of the metals has not even yet been satisfactorily established. 



