20 Proceedings of the Royal Irkh Academy, 



Note A. 



Transformation of Drude's Expressions for Magnetic Rotation.^ 



I. 



Driide writes for the rotation on the hypothesis of rotating ions 



where 



1 + 2 



cv' = 



' s 



.2' 



Ts = period of ion in circuit 



= number of ions per unit volume, 

 27rT = period of light-vibration, 

 27rT, = period of ionic vibration, 

 c = velocity of light, 

 e' = dielectric constant. 

 Transformation 



Write X = wave-length of light-vibration. 

 X, = wave-length of ionic vibration, 

 n = index of refraction, 



^2 ^2 



These substitutions give 



6 = — cvnz, 



[p. 428.] 

 [p. 425.] 



[p. 425.] 

 [p. 424.] 



^ Drude's " Theory of Optics " — Longmans. 



