Hackett — The Ionic Theories of Magneto-optic Rotation. 5 



•we get 



2w^- _D -1,1 



(4) 



and from these transformed equations (2) and (3) of Drude, we have 

 the following equation, which is the basis of the present paper : — 



(5) 



Drude tested this formula (4) for carbon disulphide and creosote, 

 and found very satisfactory agreement with experiment, both in the 

 case of the index of refraction and the magnetic rotation. To save 

 the trouble of reference, the tables he gives have been reproduced 

 below : — 





BisuJphid 



e of Carbon. 





K = 



0-212/x 





0-0450 



A = 



2-516 





0-0433 



a' = 



- 0-0136 



b' = 



+ 0-1530 



Spectr. Line. 



n calc. 



n obs. 



5 calc. 



5 obs. 



A 



1-6115 



1-6118 







B 



1-6179 



1-6181 







G 



1-6210 



1-6214 



0-592 



0-592 



D 



1-6307 



1-6308 



0-762 



0-760 



E 



1-6439 



1-6438 



0-999 



1-000 



F 



1-6560 



1-6555 



1-232 



1-234 



G 



1-6805 



1-6800 



1-704 



1-704 



H 



1-7033 



1-7032 







Creosote. 



1845/x 



2-2948 



01799 



V = 0-0340, 

 JB^ = 0-0227, 

 b' = + 0-3140. 



