184 Whither Galvanifm be caufed by 



feveral Individuals have affirmed, that they faw what others could not perceive, and that 

 the aftion in all was a convulfive fenfation, or delufive appearance, like the light which is 

 feen when the eye is prefled with the finger, or when a blow is given in the vicinity of 

 that organ. It appears, therefore, that the fenfation of tafte, and the emanation of light, 

 are in this cafe the refults of a chemical operation. But thofe who have been defirous of 

 attributing the whole to electricity, have not been in want of plaufible obfervations to juf- 

 tify their hypothefis. It has been remarked, for example, that the fenfation here defcrlbed, 

 is felt even when the communication is made by a chain, or a long metallic condu£l:or. 

 But it is known, that eleftricity is propagated by this means to an indefinite diftance ; 

 and I have obferved, that fix or feven metres are the extreme limit to which the mani- 

 feftation of the metallic action on the tongue or the eye can be extended. It is certainly 

 at the precife point of conta£l of the two metals, that their mutual adtion is the ftrongeft, 

 and it is natural to think, that the particles which are the mod: affected, muft communicate 

 from the one to the other in their vicinity, to a certain point, the difpofing force which they 

 have received, It muft propagate itfelf with diminiflied force, like the circles imprefled in 

 ftagnant water by the fall of a body ; and the limit of its aftion is nearly that which I have 

 pointed out. 



By varying my experiments in feveral manners, I obferved, that if I covered the water 

 in which the two metals in contadl were placed, with a thin coat of oil, the oxidation was 

 very flight, and flopped at a certain point. But this afluredly did not fo happen, becaufe 

 the intervention of a non-condu£ting fluid had oppofed the completion of an ele£tric phe- 

 nomenon, as it may appear at firft fight ; for I attempted to keep up the communication 

 of the water and the metals with the, common flock, by plunging a metallic conductor be- 

 neath the oil, and the combuftion was not continued more than before. The fame inter- 

 ruption or limitation obtains, if the free contafl: of the atmofphere be excluded, by means 

 of a fmall bell glafs reverfed over mercury, which does not oppofe the paiTage of eleflri- 

 city. Befides which, the Galvanifts believe, that their phenomena do not depend on uni- 

 verfal ele£tricity, but on the fpecific eleflricity, as it is called, of the different metals. If 

 this were the cafe, it would be difficuh to conceal, why the efFecl fhould not be produced 

 at the very inftant of contadt, in the fame manner as it happens when two charged bottles 

 of oppofite eleflricities are brought into contact. And again, nothing would prevent 

 the continuation of the phenomenon when the two metals came into contaft, v/hatever 

 might be the circumftances. I am well aware, however, that if it may here perhaps be 

 objected to me, that if the two metals acquire the faculty of decompofing water by their 

 fimple. contact, and the mere difpofition of tJieir attradlion, or mutual affinity, a flight 

 coat of oil, or inverted glafs, ought not to oppofe the continuation of their complete 

 oxidation, while they continue furrounded by that element. I have remarked, that the 

 free contaiSt of the atmofphere is necelfary to this phenomenon ; becaufe it is necefl'ary 

 that the water (hould contain that portion of oxigen gas, which it always holds after having 

 •Remained for a certain time in conta£t with the air. It is necelfary in my apprehenfion, 



that 



