The use of iron was then abandoned, and the same effects were obtained by merely thrusting a permanent steel magnet into a coil of wire.

A rush of electricity through the coil accompanied the insertion of the magnet; an equal rush in the opposite direction accompanied its withdrawal.

The precision with which Faraday describes these results, and the completeness with which he defines the boundaries of his facts, are wonderful.

The magnet, for example, must not be passed quite through the coil, but only half through; for if passed wholly through, the needle is stopped as by a blow, and then he shows how this blow results from a reversal of the electric wave in the helix.

He next operated with the powerful permanent magnet of the Royal Society, and obtained with it, in an exalted degree, all the foregoing phenomena.
And now he turned the light of these discoveries upon the darkest physical phenomenon of that day.