On Polarization of Light by Reflexion. 283 
DIAMOND. 
Inclination of Plane of Polarization 
iiamedes °° Helecuoed ite blane of Reflexion, Dterenee. 
90° 0” 249 [2 ao we oe Oe 0° 0’ 
85 0 24 6 34-30" Sa) BO +0 34 
80 0 23 48 PAs ae psi 2 +0 48 
7s Om 9s 19)’. 14 30 tar'6 ete oo 
00 Io 30) 4 30 3 54 - +0 36 
67 43 ee Ine. 0 O 0 O 0 0 
60 O 30 -A7 12 30 11 41 +0 49 
50 O 18 18 24 0 23 30 +0 30 
within the limits of the errors of observation. 
In all these experiments the value of x was 45°; but in order to 
determine the law of variation for 9, when x varies from 0° to 90°, 
I took a crystal of quartz with a fine natural surface parallel to its 
axis; and I found that at an angle of incidence of 75°, and when « 
was 45°, the inclination of the plane of polarization to the plane of 
reflexion was 26° 20’. 
results : 
Values of x. @ Observed. 
Ge. 0° 0’ 
10 4 54 
p20 <6 1000 
8 ae 15 50 
a5. 20 0 
Ae. 23 30 
Bi 26 20 
50 30 O 
55 35 30 
60 40 0O 
70 53 O 
80 q 70 O 
90 90 0O 
In these experiments the 
degree. 
Inclination of Plane of Polarization. 
® Calculated. 
aes O27 0! 
- ABO at oe 
SA at iO kG é 
op etn Oa G2 
rd hi ital Orpiiee 
at aei eee, es 
eh OIE 
30 40 
a PML ena 
- - 40 45 
- 53 49 
eo -29 
- 90 0 
° 
These differences, ence at an average amount to 464’, are also 
I then varied w, and obtained the following 
Difference. 
0° 0’ 
+0 25 
—0O 16 
—0O 12 
+0 48 
+0 50 
—0O 7 
—0O 40 
+0 7 
—0O 45 
—0O 49 
—0O 29 
0 O 
average error does not exceed half a 
The third column is computed by the formula tan p= 
(tan 26° 27’) tan z. 
From these experiments it appears that the formula expresses 
with great accuracy all the changes in the planes of polarization 
