ON ELECTRO-DYNAMIC INDUCTION. 313 



dary conductors, exerted the same amount of inductive force, and that 

 in one case this was expended (to use the language of theory) in giving 

 a great velocity to a small quantity of the fluid, and in the other in 

 producing a slower motion in a larger current; but in the two cases, 

 were it not for the increased resistance to conduction in the longer 

 wire, the quantity multiplied by the velocity would be the same. This, 

 however, is as yet a hypothesis, but it enables us to conceive how in- 

 tensity and quantity may both be produced from the same induction. 



43. From some of the foregoing experiments we may conclude, that 

 the quantity of electricity in motion in the helix is really less than in 

 the coil, of the same weight of metal ; but this may possibly be owing 

 simply to the greater resistance offered by the longer wire. It would 

 also appear, if the above reasoning be correct, that to produce the most 

 energetic physiological effects, only a small quantity of electricity, 

 moving with great velocity, is necessary. 



44. In this and the preceding section, I have attempted to give 

 only the general conditions which influence the galvanic induction. 

 To establish the law would require a great number of more refined 

 experiments, and the consideration of several circumstances which 

 would affect the results, such as the conduction of the wires, the con- 

 stant state of the battery, the method of breaking the circuit with per- 

 fect regularity, and also more perfect means than we now possess of 

 measuring the amount of the inductive action; all these circumstances 

 render the problem very complex. 



SECTION III. 



On the Indudion of Secondary Currents at a distance. 



45. In the experiments given in the two preceding Sections, the 

 conductor which received the induction, was separated from that which 

 transmitted the primary current by the thickness only of a pane of 

 glass; but the action from this arrangement was so energetic, that I 

 was naturally led to try the effect at a greater distance. 



46. For this purpose coil No. 1 was formed into a ring of about two 



