1840] 



WRITINGS OF JOSEPH HENRY. 157 



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 produce a closed cir- 

 cuit, the induced current in which would neutralize the sec- 

 ondary current in the battery conductor itself; and now 

 the shock at making the contact was nearly as power- 

 ful 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 ex- 

 periment did not appear affected by joining or separating 

 the ends of coil No. 4. 



20. Having investigated the conditions on which the in- 

 ductive 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, 

 (No. in, 79,) for producing currents of the different orders. 

 The result with this arrangement 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 described in paragraph 87 of my last paper, 

 it was found that a current of intensity 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 (No. HI section iv) in reference to the ending 



