AND TRANSMITTED BY CERTAIN KINDS OP GLASS. 
271 
Section IV.—Amount of Light Reflected at Various Incidences hettveen 0° and 90° hy 
the Crown Glass before and after Repolishing. 
In the experiments already described the liglit incident on the glass consisted of a 
divergent beam, or rather of a complex of rays, the mean incidence of which, if such 
a term may be used, was as nearly normal as the construction of the apparatus 
permitted. 
Measurements were also made with the crown glass both before and after it was 
repolished, when the light was incident upon its surface at various angles, the angle 
between the axis of the beam of light and the normal to the surface being considered 
as the angle of incidence. Table XII. gives these results. 
Table XII.—Crown Glass. 
Before repolishing. 
After repolishing. 
Anffle of 
incidence. 
Per cent. 
Per cent. 
xi. 
^2* 
(x — To). 
of light 
Ti. 
(t-Ti). 
Tj. 
(T-T 2 ). 
of light 
reflected. 
reflected. 
0 
O 
156-5 
94-6 
61-4 
189-7 
3-83 
155-5 
95-4 
63-1 
187-8 
4-25 
156-7 
94-4 
61-5 
189-6 
3-82 
150-0 
95-9 
63-1 
187-6 
4-36 
156-8 
94-3 
61-2 
189-9 
3-76 
154-4 
96-5 
63-5 
187-4 
4-48 
i 
154-0 
96-9 
63-6 
187-3 
4-56 
Mean 
3-80 
Mean 
4-41 
20° B. 
157-2 
93-9 
61-1 
190-0 
3-69 
154-9 
96-0 
66-1 
184-8 
4-91 
156-2 
94-9 
609 
190-2 
3-78 
154-7 
96-2 
65-3 
185-6 
4-79 
155-9 
95-2 
60-7 
190-4 
3-79 
154-7 
96-2 
65-1 
185-8 
4-75 
155-7 
95-4 
60-7 
190-4 
3-81 
154-4 
96-5 
65-2 
185-7 
4 81 
Mean 
3-77 
Mean 
4-81 
30° A. 
171-8 
85-0 
73-8 
183-0 
3-9B 
170-4 
86-4 
74-1 
182-7 
4-23 
170-6 
86-2 
73-1 
183-7 
4-04 
170-6 
86-2 
73-1 
183-7 
4-04 
B. 
155-0 
96-1 
59-3 
191-8 
3-67 
15.3-6 
97-3 
63-0 
187-9 
4-51 
1 
154-4 
96-7 
59-9 
191-2 
3-86 
152-9 
98-0 
62-8 
188-1 
4-58 
1 
153-8 
97-3 
59-7 
191-4 
3-89 
153-0 
97-9 
62-9 
188-0 
4-58 
1 
154-2 
96-9 
58-7 
192-7 
3-68 
152-8 
98-1 
62-5 
188-4 
4-53 
Mean 
3-92 
Mean 
4-55 
40° B. 
156-4 
94-7 
64-7 
186-4 
4-42 
158-3 
92-6 
72-0 
178-9 
5-54 
156-5 
94-6 
65-6 
I 85-5 
4-57 
158-1 
92-8 
71-3 
179-6 
5-43 
156-3 
94-8 
65-8 
185-3 
4-64 
158-2 
92-7 
70-4 
180-5 
5-22 
155-7 
95-4 
64'4 
186-7 
4-47 
157-4 
93-5 
69-3 
181-6 
5-14 
i 
156-6 
94-3 
68-9 
182-0 
5-19 
]\Iean 
4-52 
Mean 
5-30 
