Nov. 184-5.] Rotation of a Ray of Light by Magnetism, 295 



tion *. In modern times the proofs of their convertibility have 

 been accumulated to a very considerable extent, and a com- 

 mencement made of the determination of their equivalent 

 forces. Imml 



214-7. This strong persuasion extended to the powers of 

 light, and led, on a former occasion, to many exertions, ha- 

 ving for their object the discovery of the direct relation of 

 light and electricity, and their mutual action in bodies subject 

 jointly to their power f; but the results were negative and 

 were afterwards confirmed, in that respect, by WartmannJ. 



2148. These ineffectual exertions, and many others which 

 were never published, could not remove my strong persuasion 

 derived from philosophical considerations; and, therefore, I 

 recently resumed the inquiry by experiment in a most strict 

 and searching manner, and have at last succeeded in magne- 

 tizing and electrifying a ray of 'light '; and in illuminating a 

 magnetic line of force. These results, without entering into 

 the detail of many unproductive experiments, I will describe 

 as briefly and clearly as I can. 



2149. But before I proceed to them, I will define the mean- 

 ing I connect with certain terms which I shall have occasion to 

 use : — thus, by line of magnetic force, or magnetic line of force, 

 or magnetic curve, I mean that exercise of magnetic force which 

 is exerted in the lines usually called magnetic curves, and 

 which equally exist as passing from or to magnetic poles, or 

 forming concentric circles round an electric current. By line 

 of electric force, I mean the force exerted in the lines joining 

 two bodies, acting on each other according to the principles 

 of static electric induction (1161, &c), which may also be 

 either in curved or straight lines. By a diamagnetic, I mean 

 a body through which lines of magnetic force are passing, and 

 which does not by their action assume the usual magnetic 

 state of iron or loadstone. 



2150. A ray of light issuing from an Argand lamp, was po- 

 larized in a horizontal plane by reflexion from a surface of 

 glass, and the polarized ray passed through a Nichol's eye- 

 piece revolving on a horizontal axis, so as to be easily exa- 

 mined by the latter. Between the polarizing mirror and the 

 eye-piece, two powerful electro-magnetic poles were arranged, 

 being either the poles of a horse-shoe magnet, or the contrary 

 poles of two cylinder magnets ; they were separated from each 

 other about two inches in the direction of the line of the ray, 



* Experimental Researches, 57, 366, 376, 877, 961, 2071. 

 f Philosophical Transactions, 1834. Experimental Researches, 951- 

 955. 



\ Archives de FElectricite, ii. pp. 596-600. 



