MAGNETIZATION OF' LIGHT. 147 



Dr. Faraday has been enabled to detect and exhibit 

 effects of a most startling character. He has proved 

 magnetism to have the power o influencing a ray of 

 light in its passage through transparent bodies. A 

 polarized ray is passed through a piece of glass or a 

 crystal, or along the length of a tube filled with some 

 transparent fluid, and the line of its path carefully 

 observed ; if, when this is done, the solid or fluid body 

 is brought under powerful magnetic influence, such as 

 we have at command by making a very energetic voltaic 

 current circulate around a bar of soft iron, it will be 

 found that the polarized light is disturbed; that, indeed, it 

 does not permeate the medium along the same line.* 

 This effect is most strikingly shown in bodies of the 

 greatest density, and diminished in fluids, the particles 

 of which are easily moveable over each other, and has 

 not hitherto been observed in any gaseous medium. 



* On the Magnetization of Light, and the Illumination of Magnetic 

 Lines of Force: by Michael Faraday, D.C.L., F.R.S. Philosophical 

 Transactions, vol. cxxxvii. The following remarks are to the 

 point of doubt referred to in the text. " The magnetic forces do 

 not act on the ray of light directly and without the intervention of 

 matter, but through the mediation of the substance in which they 

 and the ray have a simultaneous existence; the substances and 

 the forces giving to and receiving from each other the power of 

 acting on the light. This is shown by the non-action of a vacuum, 

 of air or gases, and it is also further shown by the special degree 

 in which different matters possess the property. That magnetic 

 force acts upon the ray of light always with the same character of 

 manner, and in the same direction, independent of the different 

 varieties of substance, or their states of solid or liquid, or their 

 specific rotative force, shows that the magnetic force and the light 

 have a direct relation; but that substances are necessary, and that 

 these act in different degrees, shows that the magnetism and the 

 light act on each other through the intervention of the matter. 

 Recognising or perceiving matter only by its powers, and knowing 

 nothing of any imaginary nucleus abstract from the idea of these 

 powers, the phenomena described must strengthen my inclination 

 to trust in the views I have advanced in reference to its nature." 

 Phil. Masr. vol. xxiv. 



