Historical and Personal 9 



1778, when his experiments on the formation of nitric acid by the electric 

 spark from phlogisticated and dephlogisticated air (nitrogen and oxygen) 

 had been repeated without success by Van Marum with the great Teylerian 

 electrical machine, and by Lavoisier and Monge, and when Cavendish 

 "thought it right to take some measures to authenticate the truth of it." 

 For this purpose he requested Mr Gilpin, clerk to the Royal Society, to 

 repeat the experiment, and desired some of the gentlemen most conversant 

 with these subjects to be present at putting the materials together, and 

 at the examination of the produce*. 



The other occasion, with which alone we are now concerned, is the only 

 one in which the presence of visitors to Cavendish's laboratory is recorded. 

 There can be no doubt that Cavendish had completely satisfied not only 

 Mr Walsh, but what was more to the purpose, himself, that the electric 

 phenomena of the torpedo are such as might arise from the discharge of 

 a large quantity of electricity at a very feeble degree of electrification. 

 It must therefore have been to satisfy other persons on this point that he 

 took the trouble to construct an artificial torpedo of wood covered with 

 leather, a rude model of the figure given by Walsh, with electric organs of 

 pewter supplied with electricity from a battery of Leyden jars, by wires 

 protected by glass tubes. 



The accessories of this machine were equally unlike the kind of 

 apparatus which Cavendish made when working for himself. The torpedo 

 had a trough of salt water, the saltness of which was carefully adjusted, 

 so as to be equal to that of the sea. It had also a basket to lie in, and a 

 bed of sand to be buried in, and there were pieces of sole-leather, well 

 soaked in salt water, which Cavendish placed between the torpedo and 

 his hands, so that he might form some idea of what would happen if a 

 traveller with wet shoes were to tread on a live torpedo half buried in 

 wet sand. 



It was on Saturday, 27th May, 1775, that Cavendish tried the effect 

 of his Torpedo on a select company of men of science. We find in the 

 Journal (Art. 601), the names of John Hunter, the great anatomist, Dr 

 Joseph Priestley, chemist, electrician and expounder of human knowledge 

 in general, Mr Thomas Ronayne, from Cork, the disbeliever in the electrical 

 character of the torpedo, Mr Timothy Lane, apothecary and electrician, 

 and Mr Edward Nairne, the eminent maker of philosophical instruments. 



They got shocks from the torpedo to their complete satisfaction, and 

 probably learnt a good deal about electricity, but it was neither to satisfy 

 them nor to communicate to them his electrical discoveries, that Cavendish 

 admitted them into his laboratory on this memorable occasion, but simply 

 to obtain the testimony of these eminent men to the fact, that the shocks 

 of the artificial torpedo agreed in a sufficient manner with Walsh's de- 



* Phil. Trans. 1788. 



