MACNETO-OPTIC ROTATION. 



Gases. 



Table 308. 



Du Bois discusses Kundt's results and gives additional experiments on nickel and cobalt. 

 He shows that in the case of substances like iron, nickel, and cobalt which have a variable mag- 

 netic susceptibility the expression in Verdet's equation, which is constant for substances of con- 

 stant susceptibility, recjuires to be divided by the susceptibility to obtain a constant. For this 

 expression he proposes the name "Kundt's constant." These experiments of Kundt and Du 

 Bois show that it is not the difference of magnetic potential between the two ends of the medium, 

 but the product of the length of the medium and the induction per unit area, which controls the 

 amount of rotation of the beam. 



Table 309. 



VERDET'S AND KUNDT'S CONSTANTS. 



The following short table is quoted from Du Bois' paper. The quantities are stated in c. g. s. measure, circular 

 measure (radians) being used in the expression of "Verdet's constant" and " Kundt's constant." 



Smithsonian Tables. 



291 



