PROCEEDINGS 



OP 



THE ROYAL SOCIETY. 



1845. No. 62. 



November 27, 1845. 



The MARQUIS OF NORTHAMPTON, President, in the Chair. 



" Experimental Researches in Electricity." By Michael Faraday, 

 Esq., D.C.L., F.R.S., &c. Nineteenth Series. Section 25 : On the 

 Magnetization of Light, and the Illumination of Magnetic Lines of 

 Force. 



For a long time past the author had felt a strong persuasion, de- 

 rived from philosophical considerations, that among the several 

 powers of nature which in their various forms of operation on mat- 

 ter produce different classes of effects, there exists an intimate rela- 

 tion ; that they are connected by a common origin, have a reciprocal 

 dependence on one another, and are capable, under certain condi- 

 tions, of being converted the one into the other. Already have elec- 

 tricity and magnetism afforded evidence of this mutual convertibility ; 

 and in extending his views to a wider sphere, the author became con- 

 vinced that these powers must have relations with light also. Until 

 lately his endeavours to detect these relations were unsuccessful ; 

 but at length, on instituting a more searching interrogation of na- 

 ture, he arrived at the discovery recorded in the present paper, 

 namely, that a ray of light may be electrified and magnetized ; and 

 that lines of magnetic force may be rendered luminous. 



The fundamental experiment revealing this new and important 

 fact, which establishes a link of connexion between two great de- 

 partments of nature, is the following. A ray of light issuing from 

 an Argand lamp is first polarized in the horizontal plane by reflexion 

 from a glass mirror, and then made to pass, for a certain space, 

 through glass composed of silicated borate of lead, on its emergence 

 from which it is viewed through a Nichols eye-piece, capable of re- 

 volving on a horizontal axis, so as to intercept the ray, or allow it 

 to be transmitted, alternately, in the different phases of its revolu- 

 tion. The glass through which the ray passes, and which the author 

 terms the diamagnetic, is placed between the two poles of a powerful 

 electro-magnet, arranged in such a position as that the line of mag- 

 netic forces resulting from their combined action shall coincide with, 



