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.

    17/612 (page 5)
    just described may be considered as the chief example: they will be referred to, as far as is necessary, hereafter. 2157. The same phasnomena were produced in the silicated . borate of lead (2151.) by the action of a good ordinary steel!] horse-shoe magnet, no electric current being now used. ^ The 1 results were feeble, but still sufficient to show the perfect iden- | tity of action between electro-magnets and common magnets in this their power over light. 2158. Two magnetic poles were employed end-ways, i. e. the cores of the electro-magnets were hollow iron cylinders, and the ray of polarized Hght passed along their axes and through the diamagnetic placed between them: the effect was the same. 2159. One magnetic pole only was used, that being one end of a powerful cylinder electro-magnet. When the heavy glass was beyond the magnet, being close to it but between the mag- net and the polarizing reflector, the rotation Avas in one direc- tion, dependent on the nature of the pole; when the diamag- netic was on the near side, being close to it but between it and the eye, the rotation for the same pole was in the contrary direction to what it was before; and when the magnetic pole was changed, both these directions were changed with it. When the heavy glass was placed in a corresponding position to the pole, but above or below it, so that the magnetic curves were no longer passing through the glass parallel to the ray of polarized light, but rather perpendicular to it, then no effect was pro- duced. These particularities may be understood by reference to fig. 1, where a and b represent the first positions of the diamagnetic, and c and d the latter positions, the course of the ray being marked by the dot- ft ted line. If also the glass were placed ^;?{p. directly at the end of the magnet, then no effect was produced on a ray ^^^^ passing in the direction here described, ^ though it is evident, from what has been already said (2155.), that a ray passing parallel to the magnetic lines through the glass so placed, would have been affected by it. 2160. Magnetic lines, then, in passing through sihcatcd borate of lead, and a great number of other substances (2173.),