2O2 Memoir on the Torpedo as imitated by electricity 



in air; for if I placed one hand on the upper, and the other on the lower 

 surface of the electric organs, and gave such a charge to the battery, that 

 the shock, when received in air, was as strong as, I believe, that of the 

 real torpedo commonly is; it was but just perceptible when received under 

 water. By increasing the charge, indeed, it became considerable; but then 

 this charge would have given a much greater shock out of water than the 

 torpedo commonly does. The water used in this experiment was of about 

 the same degree of saltness as that of the sea; that being the natural 

 element of the torpedo, and what Mr Walsh made his experiments with. 

 It was composed of one part of common salt dissolved in 30 of water, 

 which is the proportion of salt usually said to be contained in sea water. 

 It appeared also, on examination, to conduct electricity not sensibly better 

 or worse than some sea water procured from a mineral water warehouse. 

 It is remarkable, that if I used fresh water instead of salt, the shock seemed 

 very little weaker, when received under water than out; which not only 

 confirms what was before said, that salt water conducts much better than 

 fresh; but, I think, shews, that the human body is also a much better 

 conductor than fresh water : for otherwise the shock must have been much 

 weaker when received under fresh water than in air. 



416] As there appeared to be too great a disproportion between the 

 strength of the shock in water and in air, I made another torpedo*, exactly 

 like the former, except that the part ABCDE instead of wood was made of 

 several pieces of thick leather, such as is used for the soles of shoes, fastened 

 one over the other, and cut into the proper shape; the pieces of pewter 

 being fixed on the surface of this, as they were on the wood, and the whole 

 covered with sheep skin like the other. As the leather, when thoroughly 

 soaked with salt water, would suffer the electricity to pass through it very 

 freely, I was in hopes that I should find less difference between the strength 

 of the shock in water and out of it, with this than with the other. 



417] For suppose that in receiving the shock of the former torpedo 

 under water, the quantity of electricity which passed through the wood 

 and leather of the torpedo, through my body, and through the water, 

 were to each other as T, B, and Wf; the quantity of electricity which 

 would pass through my body, when the shock was received under water, 

 would be to that which would pass through it, when the shock was received 



r> J3 



out of water, as r> , T , w to ;g~T~T' as m tne nrst case > ^ e quantity 



D 



which would pass through my body would be the g -= , part of the 



D 



whole; and in the latter the part. Suppose now, that the latter 

 torpedo conducts N times better than the former; and consequently, that 



* [Arts. 599, 600.] f [Arts. 597, 598.] 



