y inactive conductor, the lines of
force of some already existing magnetic field must be caused to pass
through the conductor, and that the strength of the current so produced
is proportional to the number of lines of magnetic force cut in a given
time, say, per second; or, in other words, is directly proportional to
the strength of the magnetic field, and to the velocity and length of
the moving conductor.

Or, briefly recapitulating: Oersted showed that an electric current,
passed through a conducting circuit, sets up concentric circular whirls
around its axis; that is, an electric current invariably produces
magnetism; Faraday showed, that if the lines of magnetic force, or
magnetism, be caused to cut or pass through an inactive conductor,
concentric circular whirls will be set up around the conductor; that is,
lines of magnetic force passed across a conductor invariably set up an
electric current in that conductor.

The wonderful completeness of Faraday's researches into the production
of electricity from magnetism may be inferred from the fact that all
the forms of magneto-electric induction known to-day--namely,
self-induction, or the induction of an active circuit on itself; mutual
induction, or the induction of an active circuit on a neighboring
circuit; and electro-magnetic induction, and magneto-electric induction,
or the induction produced in conductors through which the magnetic flux
from electro and permanent magnets respectively is caused to pass--were
discovered and investigated by him. Nor were these investigations
carried on in the haphazard, blundering, groping manner that
unfortunately too often characterizes the explorer in a strange country;
on the contrary, they were singularly clear and direct, showing how
complete the mastery the great investigator had over the subject he was
studying. It is true that repeated failures frequently met him, but
despite discouragements and disappointments he continued until he had
entirely traversed the length and breadth of the unknown region he was
the first to explore.

Let us now briefly examine Faraday's many remaining discoveries and
inventions. Though none of these were equal to his great discovery, yet
many were exceedingly valuable. Some were almost immediately utilized;
some waited many years for utilization; and some have never yet been
utilized. We must avoid, however, falling into the common mistake of
holding in little esteem those parts of Faraday'