[A] Annales de Chimie, xxxviii. 5.

[B] Ibid. xxviii. 190.

[C] Ibid. xxxviii. 49.

78. I had occasion in the commencement of this paper (2.) to refer to an
experiment by Ampère, as one of those dependent upon the electrical
induction of currents made prior to the present investigation, and have
arrived at conclusions which seem to imply doubts of the accuracy of the
experiment (62. &c.); it is therefore due to M. Ampère that I should attend
to it more distinctly. When a disc of copper (says M. Ampère) was suspended
by a silk thread and surrounded by a helix or spiral, and when the charge
of a powerful voltaic battery was sent through the spiral, a strong magnet
at the same time being presented to the copper disc, the latter turned at
the moment to take a position of equilibrium, exactly as the spiral itself
would have turned had it been free to move. I have not been able to obtain
this effect, nor indeed any motion; but the cause of my failure in the
_latter_ point may be due to the momentary existence of the current not
allowing time for the inertia of the plate to be overcome (11. 12.). M.
Ampère has perhaps succeeded in obtaining motion from the superior delicacy
and power of his electro-magnetical apparatus, or he may have obtained only
the motion due to cessation of action. But all my results tend to invert
the sense of the proposition stated by M. Ampère, "that a current of
electricity tends to put the electricity of conductors near which it passes
in motion in the same direction," for they indicate an opposite direction
for the produced current (26. 53.); and they show that the effect is
momentary, and that it is also produced by magnetic induction, and that
certain other extraordinary effects follow thereupon.