Here are two flat spirals of silk-covered copper wire suspended
separately, spider-web fashion, in wooden frames marked respectively A
and B. The one marked A is so connected that reversals at any desired
speed per minute from a battery of one or more cells can be passed
through it. The one marked B is so connected to the galvanometer and a
reverser as to show the deflection caused by the induced currents, which
are momentary in duration, and in the galvanometer circuit all on the
same side of zero, for as the battery current on making contact produces
an induced current in the reverse direction to itself, but in the same
direction on breaking the contact, of course the one would neutralize
the other, and the galvanometer would not be affected; the galvanometer
connections are therefore reversed with each reversal of the battery
current, and by that means the induced currents are, as you perceive,
all in the same direction and produce a steady deflection. The
connections are as shown on the sheet before you marked 1, which I think
requires no further explanation.

Before proceeding, please to bear in mind the fact that the inductive
effects vary inversely as the square of the distance between the two
spirals, when parallel to each other; and that the induced current in
B is proportional to the number of reversals of the battery current
passing through spiral A, and also to the strength of the current so
passing. Faraday's fertile imagination would naturally suggest the
question, "Is this lateral action, which we call magnetism, extended to
a distance by the action of intermediate particles?" If so, then it is
reasonable to expect that all substances would not be affected in the
same way, and therefore different results would be obtained if different
media were interposed between the inductor and what I will merely call,
for distinction, the inductometer.