138. The remark which has already been made respecting iron (66.), and the
independence of the ordinary magnetical phenomena of that substance and the
phenomena now described of magneto-electric induction in that and other
metals, was fully confirmed by many results of the kind detailed in this
section. When an iron plate similar to the copper one formerly described
(101.) was passed between the magnetic poles, it gave a current of
electricity like the copper plate, but decidedly of less power; and in the
experiments upon the induction of electric currents (9.), no difference in
the kind of action between iron and other metals could be perceived. The
power therefore of an iron plate to drag a magnet after it, or to intercept
magnetic action, should be carefully distinguished from the similar power
of such metals as silver, copper, &c. &c., inasmuch as in the iron by far
the greater part of the effect is due to what may be called ordinary
magnetic action. There can be no doubt that the cause assigned by Messrs.
Babbage and Herschel in explication of Arago's phenomena is the true one,
when iron is the metal used.

139. The very feeble powers which were found by those philosophers to
belong to bismuth and antimony, when moving, of affecting the suspended
magnet, and which has been confirmed by Mr. Harris, seem at first
disproportionate to their conducting powers; whether it be so or not must
be decided by future experiment (73.)[A]. These metals are highly
crystalline, and probably conduct electricity with different degrees of
facility in different directions; and it is not unlikely that where a mass
is made up of a number of crystals heterogeneously associated, an effect
approaching to that of actual division may occur (127.); or the currents of
electricity may become more suddenly deflected at the confines of similar
crystalline arrangements, and so be more readily and completely discharged
within the mass.