to form an electro-magnet, and then the other spiral
connected with the galvanometer (58.) approximated to it; the needle
vibrated, indicating a current in the galvanometer spiral the reverse of
that in the battery spiral (18. 26.). On withdrawing the latter spiral, the
needle passed in the opposite direction.

55. Single wires, approximated in certain directions towards the magnetic
pole, had currents induced in them. On their removal, the currents were
inverted. In such experiments the wires should not be removed in directions
different to those in which they were approximated; for then occasionally
complicated and irregular effects are produced, the causes of which will be
very evident in the fourth part of this paper.

56. All attempts to obtain chemical effects by the induced current of
electricity failed, though the precautions before described (22.), and all
others that could be thought of, were employed. Neither was any sensation
on the tongue, or any convulsive effect upon the limbs of a frog, produced.
Nor could charcoal or fine wire be ignited (133.). But upon repeating the
experiments more at leisure at the Royal Institution, with an armed
loadstone belonging to Professor Daniell and capable of lifting about
thirty pounds, a frog was very _powerfully convulsed_ each time magnetic
contact was made. At first the convulsions could not be obtained on
breaking magnetic contact; but conceiving the deficiency of effect was
because of the comparative slowness of separation, the latter act was
effected by a blow, and then the frog was convulsed strongly. The more
instantaneous the union or disunion is effected, the more powerful the
convulsion. I thought also I could perceive the _sensation_ upon the tongue
and the _flash_ before the eyes; but I could obtain no evidence of chemical
decomposition.

57. The various experiments of this section prove, I think, most completely
the production of electricity from ordinary magnetism. That its intensity
should be very feeble and quantity small, cannot be considered wonderful,
when it is remembered that like thermo-electricity it is evolved entirely
within the substance of metals retaining all their conducting power. But an
agent which is conducted along metallic wires in the manner described;
which whilst so passing possesses the peculiar magnetic actions and force
of a current of electricity; which can agitate and convulse the limbs of a
frog; and which, finally, can produ