110 
MR. J. G. LEATHEM ON THE THEORY OF THE 
His result as regards phase compares with theory as follows :— 
Polar Peflection from Iron. Yellow Light, yg = + ^50 C.G.S. 
Angle of incidence. 
Calculated value of 
d;, - .T -h 180°. 
Zeeman’s observed 
value of 
m - 180°. 
1 
S^p + m — X. 
, 51° 22' 
1 
245° 30' 
49° 55' 
295° 25' 
The theory will agree accurately with the experiment if the value of x be 
.'T = 64° 35'. 
The values of m given by Zeeman for yellow light are 
(1.) Derived from “ rotations to zero ” 
m, = 48° 58' + 180° = 50° 53' + 180°. 
(2.) Derived from “ minimum rotations ” 
m, = 45° + 180° = 44° 53' + 180°. 
In determining the phase the method of “ rotations to zero ” is preferable to that 
of “ minimum rotations,” and so in the above table I have used the mean of the 
values got by the former method. 
24. Another test of the present theory is afforded by observations of the amplitude 
of the “magneto-optic component.” This is denoted by or according as the 
incident light is polarised in or perpendicularly to the plane of incidence. In the 
former case the magneto-optic component is represented by — A/cos i, and the 
incident ray by — ; in the latter case the incident ray is represented by — Aq/cos i, 
and the magneto-optic component by — Bq. Hence 
Pi = mod ( - 
\i>, 
A 
yl>Q cos '2 '/Aq = 0 
p/) 
= mod 
' B cos i 
A 
\ -“^0 /Bo = 0 
. . (44). 
Thus, for equatorial reflection, we readily derive from (36) 
2cA sill i cos i 
and therefore 
p, mod -t- cos i) 
fXp= the same, 
1^: = P^ = p (say), 
which agrees with SissiNGii’s result. 
