en, being in contact with humid conductors, a
current of electricity is passed through them; they are then capable of
producing a reverse current of electricity, and Marianini has well applied
the effect in explanation of the phenomena of Ritter's piles[A]. M.A. de la
Rive has described a peculiar property acquired by metallic conductors,
when being immersed in a liquid as poles, they have completed, for some
time, the voltaic circuit, in consequence of which, when separated from the
battery and plunged into the same fluid, they by themselves produce an
electric current[B]. M.A. Van Beek has detailed cases in which the
electrical relation of one metal in contact with another has been preserved
after separation, and accompanied by its corresponding chemical effects[C].
These states and results appear to differ from the electro-tonic state and
its phenomena; but the true relation of the former to the latter can only
be decided when our knowledge of all these phenomena has been enlarged.

[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 Ampere, 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. Ampere that I should attend
to it more distinctly. When a disc of copper (says M. Ampere) 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.
Ampere 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. Ampere, "that a current of
electricity tends to put the electricity of conduc