THE ELECTRO-TONIC STATE. 
145 
seem explicable by the circumstances connected with the induction of elec- 
tricity from these two sources (25.). But as I have reserved this branch of 
the inquiry, that I might follow out the investigations contained in the present 
paper, I refrain (though much tempted) from offering further speculations. 
77* Marianini has discovered and described a peculiar affection of the sur- 
faces of metallic discs, when, being in contact with humid conductors, a cur- 
rent 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 *. 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 
in the same fluid, they themselves produce an electric current^. 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 cor- 
responding chemical effects 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. 
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 induc- 
tion 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 equilibri um, 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 ex- 
istence of the current not allowing time for the inertia of the plate to be over- 
come (11. 12.). M. Ampere has perhaps succeeded in obtaining motion 
* Annales de Chimie, XXXVIII. 5. t Ibid. XXVIII. 190. } Ibid. XXXVIII. 49. 
MDCCCXXXII. U 
