Experimental researches in electricity. Vol. 3 / by Michael Faraday.

  • Faraday, Michael, 1791-1867.
Date:
[1855?]
Catalogue details

Licence: Public Domain Mark

Credit: Experimental researches in electricity. Vol. 3 / by Michael Faraday. Source: Wellcome Collection.

    589/612 (page 577)
    Feb. 1855.] Time of the electric wave. ^11 were avoided, Melloni says, '^t appears, fhen, that when the electric current possesses sufficient force to overcome the sum of the resistance offered by a given conductor, whatever its length may be, an augmentation of its intensity ten or twentyfold does not alter the velocity of its propagation. This fact is in open contradiction with the general meaning attributed to the deno- minations of quantity and intensity, since the first compares the mass of electricity to that of a fluid, and the second represents its elasticity or tendency to motion. The equal velocity of cur- rents of various tension offers, on the contrary, a fine argument in favour of the opinion of those who suppose the electric current to be analogous to the vibrations of air under the action of sono- rous bodies. As sounds, higher or lower in pitch, traverse m air the same space in the same time, whatever be the length or the intensity of the aerial wave formed by the vibration of the sonorous body; so the vibrations, more or less rapid or more or less vigorous, of the electric fluid excited by the action of bat- teries of a greater or smaller number of plates, are propagated in conductors with the same velocity. Every one will see how the hypotheses imagined by us to give a reason for natural phse- nomena, will serve to suggest certain experimental investigations, the results of which will test their validity or insufficiency.- Melloni then says that he shall shortly have occasion to pubhsh facts which clearly demonstrate the errors of certain conclusions admitted up to the present time respecting electro-static indue tion; and I am aware, from written communications with him, that he considered the results arrived at by Coulomb, Poissou, and others since their time, as not accordant with the truth of nature^. In the mean time he died, and whether his researches are svifficiently perfected for pubhcation or not, I do not know. » He says, I deceive myself much, or else the fundamental theorem of electrical induction, as we find it ordinarily announced, ought to be modi- fied so as not to confound two effects completely distinct—the electric state during induction, and after the contact and separation of the inducing body. We know perfectly what occurs in the latter case, but not in the former, &c. Again, In my last letter I raised doubts with regard to the con- sequences which have up to the present been deduced fi-om the exijenments serving as a base for the fundamental theorem of electro-static induction. These doubts have passed to a state of certitude in my mind, ...... aud behold me at this time thoroughly convinced that the enunciation of that theorem ought to be essentially modified. (July 1854.) VOL. III. , 2 P