1835] WRITINGS OF JOSEPH HENRY. 99 



Cavendish, Poisson, and others. AVhen the two wires A and 

 B are in their natural state, an equihbrium is sustained by 

 the attractions and repulsions of the two fluids in each wire; 

 or, according to the theory of Franklin and Cavendish, by 

 the attractions and repulsions of the one fluid, and the matter 

 of the two wires. If a current of free electricity be passed 

 through A, the natural equilibrium of B will be disturbed 

 for an instant, in a similar manner to the disturbance of the 

 equilibrium in an insulated conductor, by the sudden addi- 

 tion of fluid to a contiguous conductor. On account of the 

 repulsive action of the fluid, the current in B will have an 

 opposite direction to that in A; and if the intensity of action 

 remains constant, a new state of equilibrium will be assumed. 

 The second state of B however may perhaps be regarded as 

 one of tension, and as soon as the extra action ceases in it, 

 the fluid in B will resume its natural state of distribution, 

 and thus a returning current for an instant be produced. 



The action of the spiral conductor in producing sparks, is 

 but another case of the same action; for since action and 

 reaction are equal and in contrary directions, if a current 

 established in A produces a current in an opposite direction 

 in B, then a current transmitted through B should accelerate 

 or increase the intensity of a current already existing in the 

 same direction in A. In this way the current in the several 

 successive spires of the coil may be conceived to accelerate, 

 or to tend to accelerate each other; and when the contact is 

 broken, the fluid of the first spire is projected from it with 

 intensity by the repulsive action of the fluid in all the suc- 

 ceeding spires. 



In the case of the double spiral conductor, in experiment 

 six, the fluid is passing in an opposite direction; and ac- 

 cording to the same views, a retardation or decrease of in- 

 tensity should take place. 



The phenomenon of the secondary shock with the battery, 

 appears to me to be a consequence of the law of Mr. Faraday. 

 The parts of the human body contiguous to those through 

 which the principal current is passing, may be considered as 

 in the state of the second wire B; when the principal current 



