314 Prof. A. Kundt on the Electromagnetic Rotation 

 Cobalt mirror No. 4. 



o / 



Rotation due to glass and platinum . . +1 3 

 „ „ glass, platinum, and cobalt +3 1 



Rotation due to cobalt +158 



Nickel. 

 I give observations with two good homogeneous mirrors : — 



No. 1. 



Rotation due to glass and platinum . . +1 26 

 „ „ glass, platinum, and nickel + 2 5 



Rotation due to nickel +0 39 



No. 2. 

 Rotation due to glass and platinum . . + 1 35 

 „ „ glass, platinum, and nickel + 2 24 



Rotation due to nickel -f 49 



The question may now arise whether the rotations obtained 

 for iron, cobalt, and nickel are actually produced by these 

 substances, or whether the observations admit of being ex- 

 plained in any other way. Since in these experiments por- 

 tions of glass coated with magnetic metal and coated only 

 with platinum are successively brought between the conical 

 magnetic poles, it might be thought that the intensity of the 

 magnetic field between the poles might be different in the 

 two cases, and that the difference in rotation might be thus 

 brought about. I have convinced myself by numerous and 

 varied experiments that even when large masses of iron are 

 brought into the field, neither the rotation of the iron mirror 

 nor that of a piece of glass is perceptibly altered. 



It might further be supposed that the thin, strongly mag- 

 netic film of iron which clings close to the glass might have 

 some special unknown influence upon the power of rotation 

 possessed by the glass, and the difference observed in rotation 

 between the glass covered with iron and without this cover- 

 ing should be attributed to this effect. In order to decide 

 this point, I placed between the poles a narrow vessel with 

 plane glass sides filled with carbon sulphide, and placed in 

 this a portion of the platinized glass not coated with iron, and 

 determined the rotation produced by the whole system ; then 

 a portion of the platinized glass coated with iron was put in 

 the fluid, and the rotation again determined. 



