IN INCREASING THE INTENSITY OF ELECTRICITY. . 545 
15. The spiral conductor produces, however, little or no increase of 
effect when introduced into a galvanic circuit of considerable intensity, 
Thus when the large spiral used in experiment seventh, eighth, &c. was 
made to connect the poles of two Cruikshank’s troughs, each containing 
fifty-six four-inch plates, no greater effect was perceived than with a 
short thick wire: in both cases in making the contact a feeble spark 
was given, attended with a slight deflagration of the mercury. The 
batteries at the same time were in sufficiently intense action to give a 
disagreeable shock. It is probable, however, that if the length of the 
coil were increased in some proportion to the increase of intensity, an 
increased effect would still be produced. 
In operating with the apparatus described in the last experiment, a 
phenomenon was observed in reference to the action of the battery 
itself, which I do not recollect to have seen mentioned, although it is 
intimately connected with the facts of magneto-electricity, as well as 
with the subject of these investigations, viz. When the body is made to 
form a part of a galvanic circuit composed of a number of elements, a 
shock is, of course, felt at the moment of completing the circuit. If 
the battery be not very large, little or no effect will be perceived during 
the uninterrupted circulation of the galvanic current; but if the circuit 
be interrupted by breaking the contact at any point, a shock will be felt 
at the moment, nearly as intense as that given when the contact was 
first formed. The secondary shock is rendered more evident, when 
the battery is in feeble action, by placing in the mouth the end of one 
of the wires connected with the poles; a shock and flash of light will 
be perceived when the circuit is completed, and also the same when 
the contact is broken at any point; but nothing of the kind will be per- 
ceived in the intermediate time, although the circuit may continue un- 
interrupted for some minutes. This I consider an important fact in 
reference to the action of the voltaic current. 
The phzenomena described in this paper appear to be intimately con- 
nected with those of magneto-electricity, and this opinion I advanced 
with the announcement of the first fact of these researches in the Ame- 
rican Journal of Science. They may, I conceive, be all referred to that 
species of dynamical Induction discovered by Mr. Faraday, which pro- 
duces the following phenomenon, namely: when two wires, A and B, 
are placed side by side, but not in contact, and a voltaic current is 
passed through A, there is a current produced in B, but in'an opposite 
direction. The current in B exists only for an instant, although the 
current in A may be indefinitely continued ; but if the current in A be 
stopped, there is produced in B a second current, in an opposite direc- 
tion however to the first current. 
The above fundamental fact in magneto-electricity appears to me to be 
a direct consequence of the statical principles of “Electrical Induction” 
