ON ELECTRO-DYNAMIC INDUCTION. 319 



68. First a flat coil (No. 3) was interposed instead of the plates. 

 When the two ends of this were separated, the shocks were received 

 as if the coil were not present ; but when the ends were joined, so as 

 to form a perfect metallic circuit, no shocks could be obtained. The 

 neutralization with the coil in this experiment was even more perfect 

 than with the plate. 



69. Again, coil No. 2, in the form of a ring, was placed not between 

 the conductors, but around the helix. With this disposition of the 

 apparatus, and the ends of the coil joined, the shocks were scarcely per- 

 ceptible, but when the ends were separated, the presence of the coil has 

 no effect. 



70. Also when helix No. 1 and 2 were together submitted to the in- 

 fluence of coil No. 1, the ends of the one being joined, the other gave 

 no shock. 



71. The experiments were further varied by placing helix No. 2 

 within a hollow cylinder of sheet brass, and this again within coil No. 

 2 in a manner similar to that shown in Fig. 12, which is intended to 

 illustrate another experiment. In this arrangement the neutralizing 

 action was exhibited, as in the case of the plate. 



72. A hollow cylinder of iron was next substituted for the one of 

 brass, and with this also no shocks could be obtained. 



73. From these experiments it is evident that the neutralization 

 takes place with currents in the interposed or adjoining conductors of 

 all lengths and intensities, and therefore cannot, as it appears to me, be 

 referred to the interference of two systems of vibrations. 



74. This part of the investigation was, for a time, given up almost in 

 despair, and it was not until new light had been obtained from another 

 part of the inquiry, that any further advances could be made towards 

 a solution of the mystery. 



75. Before proceeding to the next Section,! may here state that the 

 phenomenon mentioned, paragraph 54, in reference to helix No. 4, is 

 connected with the neutralizing action. The electrical discharge 

 having destroyed the insulation at some point, a part of the spires would 

 thus form a shut circuit, and the induction in this would counteract 

 the action in the other part of the helix ; or, in other words, the helix 



VI. — 4 E 



