EXAMINATION OF VOLTa's EXPERIMENTS, &C« 287 



monly ufed for the galvanic experiments either upon the zinc 

 or the copper, and pufii them under the point ot'n again. Prefs 

 the point down upon them, that it may be perfectly in contact; 

 after they have remained the time before-mentioned, draw the 

 metals away, and feparate or turn back the large condenfer 

 plate, and alfo the fmall one, after feparating it from the pin of 

 the large one, and immediately the gold leaf will diverge. If 

 the zinc was the uppermoft, then the gold leaf will diverge 

 with pofitive electricity ; but if it was underneath, the gold leaf 

 will diverge with negative electricity. It makes no difference 

 in the general effect, upon which metal the wet cloth was laid ; 

 or whether two pieces of cloth were ufed, one under the metals 

 and the other above ; or only one either above the metals or 

 under them. But if the cloth be only laid upon the copper and 

 not upon the zinc, the electric fluid brought into action will be 

 fo weak, that the combined inftrument can hardly fhew it; if 

 laid upon zinc, the divergency will be about ■— of an inch ; 

 fometimes more and fometimes lefs *. 



By reflecting on this phenomenon I found the following ex- 

 planation, without having recourfe to any new hypothesis. 



Explanation of the Aclion of the EkSiric Fluid in the Galvanic 

 When flat pieces of zinc and copper are laid in contact, the Explanation of 

 zinc becomes pofitive and the copper negative at the moment zinAnc^co^ 

 of the touch ; and while they remain in contact, the electric in contact arrive 

 fluid contained in them both is perfectly in equilibrio. The at r an , e «H»J>rium 



• • , , • i ■ ■ i r i • of electricity ; 



copper has given and the zinc has received luch a quantity of the zinc + and 

 electric fluid as their mutual action upon each other required ; the C0 Pper — • 

 and in confequence of this property, they prefent a mutual re-, 

 fiftance to any further change being produced upon them. If Chemical action 

 then any menftruum be added to the oppofite fide of the metals, tr ical propertyof 

 capable of producing a change in their metallic property (fuch that part of the 

 as the fluid contained in the wet cloth), a change in their elec- ta ^ Q% 'pi^ 

 trical property mufl of courfe follow. But as this change in 

 the metallic property is only fuperficial, it will only be there 

 that its electric property is changed. The other parts of the 

 two metals in contact will remain unaltered, and maintain their 

 property of refinance. The change produced by the action of 



* When the atmofphere is in a favourable ftate. In this as well as 

 all other experiments where fo fmall quantities are to be made evi- 

 dent, the atmofphere has great influence, 



the 



