Cavallo's expe- 

 riments of elec- 

 tricity afforded 

 by the fall of 

 conducting bo- 

 dies upon a tin 

 plate. 



\QQ EXPERIMENTS dN ELECTRICITY 



the electricity of the tin plate was negative. Thefe refmW 

 were the lame, when the bifmuth was call into a fmooth flat 

 piece, inftead of being broken from a lump. When the iron 

 tongs were ufed with the bifmuth, the tin plate became nega- 

 tive, contrary to what it was when the hand was ufed. 



An infulatcd filver fpoonwas fubftituted in the place of the 

 tin plate, and in this zinc dropped from the hand produced 

 negative electricity, which was ftronger when the zinc was 

 heated. The kind of electricity was not changed when the- 

 fpoon was heated, and the zinC cold, but its degree was 

 much lefs. Mr. Cavallo coniiders it as a very extraordinary 

 fact, that the experiments varied as to the intenfity of the 

 electricity very much on different days, and is inclined to 

 afcribe this difference to the difpolition of the atmofphere. 



In order to difcover the fource of the electricity produced 

 in thefe experiments, he repeated them in a great variety of 

 ways, namely, inftead of the hand, he dropped the zinc from 

 a tin plate held with one hand into a fpoon, and from the lat- 

 ter back upon the former. He performed this operation with 

 both the tin plate and the filver fpoon infulated. He likewife 

 tied a li Ik thread to the zinc, and holding the other extremity 

 of the thread in one hand, ftruck the zinc repeatedly againft 

 the fpoon ; but in thofe cafes very felclom any electricity was* 

 manifefted, except when the weather, and every other circum- 

 ftance was very favourable, and then the electricity could with 

 difficulty be manifefted ; yet when the tin plate was held in 

 the hand, and the zinc thrown from it into an infulated fpoon, 

 fome electricity was more frequently produced than in the 

 other two cafes. 

 Whether animal After a careful review of his experiments, he doubts whe- 



electncity can fa er ^ phenomena of animal electricity can be attributed to 



be deduced from . r • 



the preceding the caule fuppofed to operate in them. For as he remarks, 



the action of metallic bodies produces the fame effects, with 



hardly any obfervable difference, upon prepared animal limbs ; 



whereas the effects in his experiments were fluctuating, and 



differed confiderably in zinc and bifmuth, which neverthelefs 



do not excite the animal electricity more powerfully than zinc 



and filver, or zinc and gold. He alio remarks, that he found 



by experiments with minute quantities of electricity applied to 



the prepared limbs, that they were not excited when thefe 



quantities were neverthelefs very much greater than what was 



produced 



fi&S? &c. 



