146 



foote: magnetic rotation 



nickel, invar, magnetite, and Heusler's alloy in the attempt to 

 establish the magnitude of these effects. 



The mirrors, small polished metal plates, were mounted upon 

 the pole face of a ring magnet capable of producing 25000 c.g.s. 

 induction. For the measurement of the rotation, a Lippich 

 half nicol was employed, and for the ellipticity, a Brace Elliptic 

 Halfshade analyzing system. The magnetic field was calibrated 

 by the rotation produced on double transmission thru a plate of 

 glass for which the Verdet constant had been previously obtained. 



Fig. 1. Ellipticity Dispersion Curves. 



The rotatory dispersion curves for the mirrors examined were 

 in reasonable agreement with the work of preceding investigators, 

 being negative thruout (contrary to the magnetizing current) 

 in the case of iron, cobalt, steel, nickel and invar, and in the case 

 of magnetite, negative in the violet, zero at 454/*/*, and positive 

 in the red. Heusler's alloy showed signs of an extremely small 

 negative rotation. 



