160 WRITINGS OF JOSEPH HENRY. [1840 



shock was felt in the hands at the moment of closing the cir- 

 cuit, but the effect at opening the same was scarcely percep- 

 tible through the tongue. An attempt was also made to get 

 indications of induction by placing the helix within a circle 

 of dilute acid, connected with a battery instead of a coil, but 

 the effect if any was very feeble. 



29. I have shown, in the second number of my Contribu- 

 tions, that if the body be introduced into a circuit with a 

 battery of one hundred and twenty elements, without 

 a coil, a thrilling sensation will be felt during the con- 

 tinuance of the current, and a shock will be experienced at 

 the moment of interrupting the current by breaking the cir- 

 cuit at any point. This result is evidently due to the in- 

 duction of a secondary current in the battery itself, and on 

 this principle the remarkable physiological effects produced 

 by Dr. Ure, on the body of a malefactor, may be explained. 

 The body, in these experiments, was made to form a part of 

 the circuit, with a compound galvanic apparatus in which 

 a series of interruptions was rapidly made by drawing the 

 end of a conductor over the edges of the plates of the bat- 

 tery. By this operation a series of induced currents must 

 have been produced in the battery itself, the intensity of 

 which was greater than that of the primary current. 



30. In this connection I may mention that the idea has 

 occurred to me that the intense shocks given by the elec- 

 trical fish may possibly be from a secondary current, and 

 that the great amount of nervous organization found in 

 these animals may serve the purpose of a long conductor.* 

 It appears to me, that in the present state of knowledge, this 

 is the only way in which we can conceive of electricity so 

 intense being produced in organs imperfectly insulated and 

 immersed in a conducting medium. But we have seen that 

 an original current of feeble intensity can induce, in a long 

 wire, a secondary current capable of giving intense shocks, 

 although the several strands of the wire are separated from 

 each other only by a covering of cotton thread. Whatever 



*Since writing the above, I have found that M. Masson has suggested the 

 same idea, in an interesting thesis lately published. 



