Magneto-optic Phenomenon. 



305 



it was always observed, on rotating the polarizer or analyser 

 in order to again obtain a minimum intensity of light in the 

 centre of the field of the analyser (that is, the centre of the 

 image of the slit), after magnetizing the mirror, that the 

 greatest minimum was not in the centre of the field but 

 somewhat above or below this position. This minimum ren- 

 dered an exact adjustment, so that the intensity of light was 

 least in the centre of the field, almost impossible ; and there- 

 fore by means of the cross slit only the centre of the colli- 

 mator-slit was left. 



The minimum rotations <f>f and 0™ were determined for the 

 two positions in which the polarizer was parallel and perpen- 

 dicular respectively to the plane of incidence ; and for each 

 position of the polarizer the analyser was read in two positions 

 180° apart. 



The following series of observations is given in order to 

 show what degree of accuracy is obtained ; then follow the 

 means from several series of observations : — 



Polarizer perpendicular 

 Mirror demagnetized. 



Polarizer 



perpendicular 



to Plane of 



Incideuce. 



385*5 

 385-5 

 386-0 

 386-0 

 385-8 

 385*5 

 385-7 

 385-5 



385-7 



Analyser 



parallel 



to Plane of 



Incidence. 



281*7 

 282-1 



282-4 

 283-2 

 283-3 

 2S2S 

 282-7 

 282-6 



282-6 



to the Plane of Incidence. 



Mirror again demagnetized. 



Polarizer 

 erpendicular 

 to Plane of 



Analyser 



parallel 



to Plane of 



Incidence. 



Incidence. 



385*6 



283*0 



386*2 



283*1 



386*8 



283-5 



386-4 



283-7 



386-6 



284-2 



385-7 



282-7 



386*7 



283*7 



385-7 



283-0 



386-2 



283-3 



Mean of these Observations. 

 Polarizer perpendicular to Plane of Incidence, 385-9. 

 Analyser parallel to Plane of Incidence, 28r3'0. 

 Polarizer perpendicular to 

 Plane of Incidence. 

 Minimum positions of the Analyser 

 for Magnetization 

 + 

 278*0 28S'2 



277-6 288-1 



278*8 288*8 



278-1 289*2 



278-1 



288-6 



Analyser parallel to 



Plane of Incidence. 



Minimum positions of the Polarizer 



for Magnetization 



382-4 



389*6 



381-8 



389*4 



381-9 



390*4 



382-0 



390*1 



382-0 



389-9 



