ections, but stronger. When
the helix was put at right angles to the magnetic direction or dip, then
the introduction or removal of the soft iron cylinder produced no effect at
the needle. Any inclination to the dip gave results of the same kind as
those already described, but increasing in strength as the helix
approximated to the direction of the dip.

147. A cylinder magnet, although it has great power of affecting the
galvanometer when moving into or out of the helix, has no power of
continuing the deflection (39.); and therefore, though left in, still the
magnetic needle comes to its usual place of rest. But upon repeating (with
the magnet) the experiment of inversion in the direction of the dip (141),
the needle was affected as powerfully as before; the disturbance of the
magnetism in the steel magnet, by the earth's inductive force upon it,
being thus shown to be nearly, if not quite, equal in amount and rapidity
to that occurring in soft iron. It is probable that in this way
magneto-electrical arrangements may become very useful in indicating the
disturbance of magnetic forces, where other means will not apply; for it is
not the whole magnetic power which produces the visible effect, but only
the difference due to the disturbing causes.

148. These favourable results led me to hope that the direct
magneto-electric induction of the earth might be rendered sensible; and I
ultimately succeeded in obtaining the effect in several ways. When the
helix just referred to (141. 6.) was placed in the magnetic dip, but
without any cylinder of iron or steel, and was then inverted, a feeble
action at the needle was observed. Inverting the helix ten or twelve times,
and at such periods that the deflecting forces exerted by the currents of
electricity produced in it should be added to the momentum of the needle
(39.), the latter was soon made to vibrate through an arc of 80 deg. or 90 deg..
Here, therefore, currents of electricity were produced by the direct
inductive power of the earth's magnetism, without the use of any
ferruginous matter, and upon a metal not capable of exhibiting any of the
ordinary magnetic phenomena. The experiment in everything represents the
effects produced by bringing the same helix to one or both poles of any
powerful magnet (50.).

149. Guided by the law already expressed (114.), I expected that all the
electric phenomena of the revolving metal plate could now be produced
without any other magnet