138 «N THE GALVANIC PHENOMENA. 



efedridty equal of negative electricity (el. — ), accordingly, as.fuch a con. 

 Wr'coitafts- denfer : con denfes from 120 to 180 times. This proves that 

 the elcclric teniion of the above-mentioned plate c was about, 

 a fixtieth of a degree, or nearly equal to that which the two 

 plates of copper and of zinc acquired in the preceding expe- 

 riments, when applied to each other by the whole extent of 

 their flat furfaces. 

 which 1$ re- When we reverfe the experiment, that is to fay, when we 



ing with the " call ^ e * nc plate z of zinc to communicate with the condenfer, 

 other metal. we likewife obtain from two to three degrees, but of pofitive 



electricity (el. -{-.) 

 If the zinc piece However, if the difc of the condenfer be copper, and the 

 touch a copper pj ate z louc jj ft immediately without any intervening fub- 



condenfer while l ,. , . • ? 



the other piece nance, we obtain nothing, becaufe the zinc being then in 

 (of copper) is contact, at the two oppofite ends, with copper and copper, 

 no effect follows- tw0 equal forces act in oppofite directions, and by that means 



deftroy or counterbalance each other, 

 unlefs molfture It is therefore neceflary that the communication of the plate 

 be interpofed. f z j nc z w ith tne CO pp C r difc of the condenfer mould be ef- 

 fected by the interpofition of a conductor, which mould be a 

 fimple conductor nearly, an humid conductor, fuch as a piece 

 of wet card or cloth. 

 But it is aflrted, As to the reft, the action which excites and gives motion 

 that the humi- tQ the e \ Q ^ lQ fl^rf fi oes not exert frfetf ag has been errone . 

 dity acts merely 



as a condu&ori oufly thought, at the contact of the wet fubftance with the 



to prevent the m etal, where it exerts (o very fmall an action, that it may be 

 oppofite metallic _ . • , , , . i t , ,, 



contacts in the unregarded in companion with that which takes place, as all 



P ile « my experiments prove, at the place of contact of different 



metals with each other. Consequently the true element of 

 my electromotive apparatus, of the pile, of cups, and others 

 that may be conftructed according to the fame principles, is 

 the fimple metallic couple, or pair, compofed of two different 

 metals, and not a moid fubftance applied to a metallic one, or 

 inclofed between two different metals, as moft philofophers 

 have pretended. The humid ftrata employed in thefe com- 

 plicated apparatus are applied therefore for no other purpofe 

 than to effect a mutual communication between all the metal-* 

 lie pairs, each to each, ranged in fuch a manner as to impel 

 the electric fluid in one direction, or in order to make them 

 communicate, fo that there may be no action in a direction 

 contrary to the others. 



After. 



