MAGNETO-OPTIC PHENOMENA OF IRON, NICKEL, AND COBALT. 109 
various angles of incidence, and the theoretical values of the phase for the same 
angles of incidence, calculated from the present theory. 
It is to be observed that the calculation involves only the ordinary optic constants 
of the metal, and that it is from the comparison with experiment that we derive 
information as to the value of x in the magneto-optic constant Cge-h There is thus 
no question of being able to adjust two coefficients, Cg and x, so as to satisfy the 
observations, as might be supposed ; only one coefficient x is involved, and the test 
is accordingly a severe one. 
Equatorial Reflection from Iron. Yellow Light, a^ — — 1400 C.G.S. 
Angle of 
incidence. 
Calculated value of 
S-x + l80\ 
Sissingh’s observed 
value of m —180°. 
9 + m—a’. 
86 ° 0' 
267° 25' 
29° 26' 
296° 51' 
82° 30' 
274° 41' 
24° 22' ' 
299° 3' 
76° 30' 
283° 29° 
14° 49' 
298° 18' 
7L° 25' 
288° 47' 
10° 3' 
298° 50' 
61° ,30' 
295° 42' 
1° 49' 
297° 31' 
51° 22' 
300° 12' 
- 1° 0' 
299° 12' ' 
.36° 10' 
304° 33' 
- 5° 51' 
298° 42' 
24° 16' 
’ a • 
doubtful 
12 ° 0' 
• • 
doubtful 
6 ° 0' 
a a 
doubtful 
r 
The constancy of the angles in the last column is remarkably good ; and the theory 
accounts for the phenomena with great accuracy if the value assigned to x be the 
mean of the amounts by which these angles respectively fall short of 360°, namely 
a: = Gl°39'. 
23, When the reflection is polar, we see from (41) that 
2CA.Co7ot ■ c‘- 
9^ _ vector angle of + cos 7)' 
Taking positive as the standard case, and remembering that is negative, we 
find that 
.9^, = X — 90° — 2a — the sum of the vector 
angles of 
— cos ^) and (,^UftR -{- cos ^) 
. . . (43). 
Experiments as to the amplitude and phase of the magneto-optic component of 
light reflected from an iron mirror, magnetised normally to the reflecting surface, 
have been made by Zeeman. He gives an account of these in the ‘ Archives 
Neerlandaises,' vol. 27 ; he confines himself to one angle of incidence, viz., 7 = 51° 22'. 
