On Ellectro-Dynamic Induction. 225 
tion, can neutralize each other? I was at first disposed to con- 
sider the phenomenon as a case of real electrical interference, in 
which the impulses succeed each other by some regular interval. 
But if this were true, the effect should depend on the length and 
other conditions of the current in the interposed conductor. In 
order to investigate this, several modifications of the experiments 
Were instituted, 
68. First a flat coil (No. 3) was interposed instead of the plates. 
When the two ends of this were separated, the shocks were re- 
ceived as if the coil were not present; but when the ends were 
joined, so as to forma perfect metallic circuit, no shocks could be 
obtained. The neutralization with the coil in this experiment 
was even more perfect than with the plate. ae 
69. Again, coil No. 2, in the form of a ring, was placed not 
between the conductors, but around the helix. With this dispo- 
Sition of the apparatus, and the ends of the coil joined, the shocks 
Were scarcely perceptible, but when the ends were separated, the 
presence of the coil has no effect. . 
70. Also when helices No. 1 and 2 were together submitted to 
the influence 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 neutraliza- 
tion takes place with currents in the interposed or adjoining con- 
ductors of all lengths and intensities, and therefore cannot, as it 
appears to me, be refetred 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 ob- 
tained 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, I may here state, 
that the phenomenon mentioned, paragraph 54, in reference to 
helix No. 4, is connected with the neutralizing action. The 
Vol. xxxvi1, No, 2.—Jan.—March, 1840. 29 
