I 



en the Experiments of Volta, 303 



exerclfe, as has been fald, a reciprocal aftion on their re- 

 fpeiSlive elcAricities at the moment of conta6l. When the 

 metallic plate is held by its copper extremity, a part of its 

 eleftric fluid pallcs into the oppofite plate, which is of zinc; 

 but if this zinc is in immediate contact with the condenfer, 

 \vhich is alfo of copper, the latter tends to dilcharge itfelf of 

 its fluid with equal force, and the zinc cannot tranfmit any 

 toil: after the contat-t, therefore, it muft be found in its 

 iiaturnl thitc. On the otlier hand, if a piece of moid: paper 

 be placed between the zinc of the plate and the copper plate 

 of the condenfer, the moving power of the eletftricity, which 

 exifts only at the lime of coniacl:, is dellroyed between thefe 

 two metals : the water, which fecms to enjov this property 

 in a very weak degree in regard to metallic fubilances, checks 

 only a very little the tranimiilion of the fluid from the zinc 

 to the condenfer, and the latter mav be charged pofitively. 



In the lull |ilace, when the condenfer is touched w'wh the 

 extremity of the ])late which is of copper, the moifl: paper 

 jnterpofcd, the proper acHion of which is exceedingly weak, 

 does not prevent the metallic plate from conveying a part of 

 its metallic electricity into the plate of zinc : then, by de- 

 ftroying the contact, the condenfer is found charged nega- 

 tively. 



From this theory it is eafy to. explain the Voltaic pile. 

 To do it with more fimpliclly, we fliall fuppofe that it is 

 formed on an infulalur, and we fliall reprcfent by unity the 

 excefs of elei!"l;rieitv which a piece of zinc ought to have over 

 a piece of copper innnediatcly touched by it". 



If the pile is conipofed only of two pieces, a lower one of 

 copper and the fiiperior of zinc, the eletSlric llate of the 

 former will be reprefenled by — {, and that of the fecond 

 by + \. 



If a third piece be added, which mufl: be of copper, to 

 produce a difplaccment of the fluid, the lower piece of zinc 

 nmft be feparated by a piece of moilt pafleboard ; it muft 

 then acrpiire the fame eleclric fl:ate as the latter; at leafl:, it 

 will be lo if we nce;le6l the action proper to the water, which . 

 appears very fmall, and perhaps alfo the very weak refiitance 



• The quantities of cleft icity accumuhited in a body btvniul its natural 

 ftate arc, co'irris pcirilfus, proportional to the rtpiilfive forte with which the 

 mo!ecul« of tlic tluid tend to t'eparate from each other, or to repel a new 

 rnoiecula vvliicii one may aitcmj't to add to them. Tliis repulllvc foict-, 

 which in free bodies is baliiiced by thv refiitance of the ;i!r, confliiutis 

 wh'*, wc rail the loiji'jn of the fluid : a tenfion which is not proportioned 

 ro the diverpency of the ftraws in Volta's ele6tr«)mcter, nor to that of the 

 balls in Suuirure's, and which (.:innot be accurately mtaliircd l)y means of 

 the eiedtnc bviuucc. 



which 



