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\ 
. 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. 
he 
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a 
_ 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 
B Age described in my last paper, (III, 79,) for producing cur-, ~ 
_ Tents o 
f the different orders. The result with this arrangement 
Was similar to that which 1 have described in reference to the end-» 
¥ 
a 
+ 
ing induction, namely, currents of the third, fourth, and fifth orders 
were readily obtained. Dee 
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. . A ” ad 
' 22. Likewise, the same screening or rather neutralizing effect 
ae biotincallterlien a plate of metal was interposed. between 
two consecutive conductors of the series of currents, as was de- 
 Scribed (ILI, 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 neutralizing 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 
guy a little greater than that of the coil. icrh 3 
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