Magneto-Optic Phenomena of Iron, Nickel, and Cobalt. 489 



Equatorial Reflection from Iron. 





Observed, value or in. 



Calculated value ot m. 



86° 0' 



209° 26' 



272° 35' - X 



82° 30' 



204° 22' 



265° 19' - x 



76° 30' 



194° 49' 



256° 31' - x 



71° 25' 



190° 3' 



251° 13' - x 



61° 30' 



181° 49' 



244° 18' - x 



51° 22' 



179° 0' 



239° 48' - X 



36° 10' 



174° 9' 



235° 27' - X 



If we suppose that the value of x is about 62°, the agreement 

 shewn is remarkably good. Experiments on polar reflection from 

 iron point to almost exactly the same value for x. 



If we suppose the value of C to be given by 



-Co = 7-283 x 10- u , 



the ratios of the calculated to the observed values of jx for the above 

 angles of incidence are found to be respectively 1*13, 0'96, 0"99, 0'97, 

 l'Ol, 1*03, and 97 ; so that in the case of the amplitudes also there 

 is good agreement. 



6. For nickel the agreement of theory with experiment, though 

 not so exact as in the case of iron, is still very good. The values 

 indicated for the constants are 



x = 76° to 80°, -C = 9-225 x 10" 12 . 



The agreement is better for cobalt, being specially good in the 

 amplitude experiments. For polar reflection at incidences of 45°, 

 60°, and 73°, the ratios of the calculated to the observed values of /t 

 are found to be 0'98, 97, and 107 respectively. The values indi- 

 cated for the constants are 



oj=64°, -Co = 1-227 xlO" 10 . 



7. The theory gives a satisfactory account of a phenomenon which 

 has only recently been discovered, namely an effect of the com- 

 ponent of magnetisation perpendicular to the plane of incidence. 

 The change of phase which measures this effect has been observed by 

 Zeeman, who, in a particular case, found it to be 0'003 X 90°, with a 

 mean error of 001 x 90°. The value indicated by the theory is 

 0-00243 x 90°. 



8. Two of the many available experiments on transmission through 

 magnetised metallic films are used to test the theory. In one of 

 these the rotation observed by Lobach is 1*62°, while the value indi- 

 cated by the theory is 0*961°. In the other the rotation observed by 



