it by the wires with the galvanometer, arranged as before described,
and bringing the permanent magnet, F, suddenly against the poles of
the magnet, as shown in Fig. 11, a current will be induced in the
coil, which, in passing through the galvanometer, causes the needle to
be deflected in one direction, and when the permanent magnet is
suddenly removed from the electro-magnet, a current will be set up in
the opposite direction, which will cause a deflection of the needle of
the galvanometer in the opposite direction.


INDUCTION COIL.

By placing both coils, A, upon the bundle of soft iron wires, G,
connecting one of them with the terminals of the battery, as shown in
Fig. 12, and holding the terminals of the other coil in the moistened
thumb and fingers of the two hands, when the battery circuit is opened
and closed by touching one of the wires to the battery, and removing
it, a slight shock will be felt from the coil which is disconnected
from the battery. By placing a coarse file in the circuit and drawing
one of the terminals along the file the circuit will be rapidly
interrupted. This shock is due to the current induced in the detached
coil by the magnetism of the bundle of wires.

[Illustration: FIG. 11.--MAGNETO-ELECTRIC INDUCTION.]


EXTRA CURRENT.

An experiment showing the extra or self-induced current consists in
arranging the motor as shown in Fig. 6, and connecting wire with each