On Electro- Dynamic Induction. 125 



ced as to be imperceptible in the hands, while the shock at break- 

 ing 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 circuit, the induced current 

 in which would neutralize the secondary 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 cur- 

 rent produced in the conductor of the battery circuit itself. The 

 shock at the breaking of the circuit, in this experiment, 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 pro- 

 duced by this induction ; and first, the coils were arranged in the 

 manner described in my last paper, (HI, 79,) for producing cur- 

 rents of the different orders. The result with this arrangement 

 was similar to that which 1 have described in reference to the end- 

 ing 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 de- 

 scribed (HI, section 4,) in reference to the ending induction. In 

 short, the series of induced currents produced at the beginning 

 of the primary current appeared to possess all the properties be- 

 longing to those of the induction at the ending of the same current. 



23. I may mention in this place, that I have found, in the 

 course of these experiments, that the neutrahzing power of a 

 plate of metal depends, in some measure, on its superficial extent. 

 Thus a broad plate which extends, in every direction, beyond 

 the helix and coil, produces a more perfect screening than one of 

 the same metal and of the same thickness, but of a diameter 

 only a little greater than that of the coil. 



