8 CONTRIBUTIONS TO ELECTRICITY AND MAGNETISM. 



also depends, in a considerable degree, if not principally, on the adverse in- 

 fluence of the secondary current, induced in the primary conductor itself, as is 

 shown by the result of the following experiment. Helix No. 1 was placed on 

 a coil consisting of only three spires or turns of copper riband; with this, the 

 shock both at making and breaking the circuit with a single battery could be 

 felt in the hands. A compound coil was then formed of the copper ribands of 

 coils No. 3 and 4 rolled together so that the several spires of the two alternated 

 with each other, and when this was introduced into the circuit so as not to act 

 on the helix by its induction, and the battery current passed through, for 

 example, coil No. 3, the shock at making contact with the pole of the battery 

 was so much reduced as to be imperceptible in the hands, while the shock at 

 breaking the contact was about the same as before this addition was made to 

 the length of the circuit. The ends of coil No. 4 were now joined so as to pro- 

 duce a closed circuit, the induced current in which would neutralize the se- 

 condary current in the battery conductor itself; and now the shock at making 

 the contact was nearly as powerful as in the case where the short conductor 

 alone formed the circuit with the battery. Hence, the principal cause of the 

 feebleness of the effect at the beginning of the battery current is the adverse 

 action on the helix of the secondary current produced in the conductor of the 

 battery circuit itself The shock at the breaking of the circuit, in this experi- 

 ment, did not appear affected by joining or separating the ends of coil No. 4. 



20. Having investigated the conditions on which the inductive action at the 

 beginning of a battery current depends, experiments were next instituted to 

 determine the nature of the effects produced by this induction : and first the 

 coils were arranged in the manner described in my last paper, (HI. 79,) for 

 producing currents of the different orders. The result with this was similar 

 to that which I have described in reference to the ending induction, namely, 

 currents of the third, fourth, and fifth orders were readily obtained. 



21. Also, when an arrangement of apparatus was made similar to that de- 

 scribed in paragraph 87 of my last paper, it was found that a current of in- 

 tensity could be induced from one of quantity and the converse. 



22. Likewise, the same screening or rather neutralizing effect was produced, 

 when a plate of metal was interposed between two consecutive conductors of 

 the series of currents, as was described (HI. section IV.) in reference to the 

 ending induction. In short, the series of induced currents produced at the be- 



