192 ELECTRIC FISHES. LECT. X. 



tridty. The earliest observers soon perceived the identity 

 of the phenomenon presented by the torpedo with the elec- 

 trical discharge : they found that when the animal was in- 

 sulated, no shock was felt by touching it with sticks of 

 sealing-wax, glass rods, &c. : but it was immediately felt 

 when they employed, instead of resin or glass, water, wet 

 cloths, or better still, metallic bodies. Walsh went still 

 farther : he demonstrated by experiments, the accuracy of 

 which are generally admitted at the present day, that the 

 two opposite surfaces of the body of the torpedo are the 

 poles, at which the opposite electricities are found at the 

 moment of the discharge. It follows, therefore, that the 

 greatest possible shock is obtained by connecting the belly 

 and the back of the fish, by means of a conductor, which 

 may be the body of the observer. At one time it was 

 thought that, in order to obtain this shock, it was sufficient 

 to touch, with a conductor, any part whatever of the back 

 or the belly of the animal ; and, consequently, that it was 

 unnecessary to make the connexion, which we have spoken 

 of, between the two opposite surfaces of the fish. But it is 

 now clearly proved that this condition is indispensable, and 

 that if we succeed in getting a shock by touching the 

 animal, at a single point, with a metallic conductor held in 

 the hands, it must be in consequence of the torpedo not 

 being insulated, whereby the circuit is completed through 

 the ground and the body of the observer. If, however, the 

 torpedo be insulated by placing it, with one of its surfaces, 

 on a resinous plate, a slight shock is obtained when we 

 touch the other surface with the finger. This phenomenon 

 will be fully understood when we shall have explained to 

 you the laws of the distribution of electricity, on the body 

 of the animal, at the moment of its discharge. 



Phenomena of the Shock. The shock of the torpedo is 

 accompanied by all the phenomena proper to the electric 



