464 Prof. D. B. Brace on the Resolution of Light into 



In conclusion, I desire to express my best thanks to 

 Prof. Thomson for many useful suggestions and valuable 

 criticisms. I also wish to thank Mr. Everett for the assistance 

 he has afforded in the construction of the very elaborate glass 

 apparatus required in these researches. 



Cavendish Laboratory, Cambridge, 

 November 1900. 



XLII. The Observation of the Resolution of Light into its 

 Circular Components in the Faraday " Effect." By D. B. 

 Brace, Ph.D., Professor of Physics, University of 

 Nebraska *. 



THE ingenious interpretation by Fresnel of the kinematical 

 principle that two opposite circular vibrations will 

 produce a linear vibration and vice versa, and his experimental 

 verification in the case of quartz, has led several to investigate 

 whether the same principle may not explain the important 

 discovery made by Faraday in 1846 of magnetic rotary 

 polarization. This rotation, however, even under the most 

 favourable conditions, is much less than that of quartz. This 

 may explain why the usual explanation of the Faraday 

 " effect " has remained so long without experimental veri- 

 fication. Indirect evidence by interference methods, for 

 example, has tended to confirm the above principle, without 

 however conclusivelv establishing it. 



The discovery of Zeeman f (anticipated by Fievez J) has 

 added new interest as well as significance to the problem, 

 and encouraged me to repeat experiments made a number of 

 years ago. After several failures I have finally succeeded, 

 by means of refraction, in resolving natural light into its 

 two opposite circular components, when propagated along 

 the lines of force. Various attempts had been made to obtain 

 an arrangement of sufficient sensibility to show the double 

 circular-refraction if it existed, and it w<as only through a 

 fortunate idea that I finally succeeded. 



In my earlier experiments §, interference methods were 

 first used. Two cylinders of Faraday glass were placed, one 

 between the poles of a Ruhmkorff magnet, and the other at 

 the further end of one of the solenoids, so that one of the two 

 interfering rays in a Jamin Interferometer passed through 

 each cylinder respectively. These rays could be either 



* Communicated by the Author : read before the American Phvsical 

 Society, Oct. 27, 1900. 



t Phil. Mag. [5] xliii. p. 226 (1897). 



t Bulletin de I Acad, des Sciences de Belgique, [3] ix. p. 381 (1885). 



§> Wied. Ann. xxvi. p. 576 (1885). 



