16 SIR HUMPHRY DAVY'S ACCOUNT OP 



Mola di Gaeta, with an apparatus in which the smallest possible surface of 

 silver was exposed, and in which good conductors, such as solutions of potassa 

 and sulphuric acid, were made to connect the circuit ; but with the same 

 negative results. 



Having obtained a larger Torpedo at Rimini in June in the same year, I re- 

 peated the experiments, using all the "precautions I could imagine, with like 

 results; and at the same time I passed the shock through a very small circuit, 

 which was completed by a quarter of an inch of extremely fine silver wire, 

 drawn by the late Mr. Cavendish for using in a micrometer, and which was 

 less than the TuVodth of an inch in diameter ; but no ignition of the wire took 

 place. It appeared to me after these experiments, that the comparison of the 

 organ of the Torpedo to an electrical batteiy weakly charged, and of which 

 the charged surfaces were imperfect conductors, such as water, was more cor- 

 rect than that of the comparison to the pile : but on mentioning my researches 

 to Signor Volta, with whom I passed some time at Milan that summer, he 

 showed me another form of his instrument, which appeared to him to fulfill the 

 conditions of the oi'gans of the torpedo ; a pile, of which the fluid substance 

 was a very imperfect conductor, such as honey or a strong saccharine extract, 

 which required a certain time to become charged, and which did not decom- 

 pose water, though when charged it communicated weak shocks. 



The discovery of Oersted of the effects of Voltaic electricity on the magnetic 

 needle, made me desirous to ascertain if the electricity of living animals pos- 

 sessed this power ; and after several vain attempts to procure living torpedos 

 sufiiciently strong and vigorous to give powerful shocks, I succeeded in Oc- 

 tober of this year, tlu'ough the kind assistance of George During, Esq., His 

 Majesty's Consul at Trieste, in obtaining two lively and recently caught Tor- 

 pedos, one a foot long, the other smaller. I passed the shocks from the largest 

 of these animals a number of times through the circuit of an extremely delicate 

 magnetic electrometer, (of the same kind, but more sensible, than that I have 

 described in my last paper on the electro-chemical phaenomena, which the 

 Royal Society has honoured with a place in their Transactions for 1826,) but 

 without perceiving the slightest deviation of or effect on the needle; and I con- 

 vinced myself that the circuit was perfect, by making my body several times a 

 part of it, holding the silver spoon, by which the shock was taken, in one hand, 



