10 
CAPTAIN W. DE W. ABNEY ON THE TRANSMISSION 
of cell, 1'7 inches. When light passed through length of cell to the sensitive paper a 
double sector with an opening of 12° rotated in front of the clear cell. When light 
passed through the breadth of the cell, the sector opening was 36°‘13. 
For the cells placed lengthways, the value obtained for the light after passing 
through the clear cell had to be multiplied 180/12 = 15. When the cells were placed 
breadthways, the value for the light passing through the clear cell had to be multi¬ 
plied by 180/36-13 = 4-982. 
1st exposure. 
2nd exposure. 
Cell. 
Mean r 
eading. 
Mean reading. 
Value 
Value 
from scale. 
' from scale. 
White = 45. 
White = 100. 
White = 45. White = 100.' 
3T5 in., clear water 
23 
51 
98 
1 
33 73-5 i 47 
3T5 in., turbid „ 
25 
55'5 
84 
35 78 1 40 
1 st Exposure 
action through clear water 
action through turbid water 
2 nd 
3 J 
53 
98 
84 
47 
40 
Mean = 
1T66 + 1-175 
o 
= 1-17. 
1-166. 
1-175. 
The photographic light passing through the clear water = 1-17 X 15 = 17-55 times 
that passing through the turbid water. 
U-sing the formula T = le 
log 17-55 = 2-86504 = 3-15/ri 
= -911 for each inch of turbid water. 
1st exposure. 
2nd exposure. 
1 
3rd exposure. 
Mean reading. 
Mean reading. 
Mean reading. 
Cell. 
Vidue. 
Value. 
Value. 
\Vhite 
White 
White 
White 
White 
White 
=45. 
= 100. 
= 45. 
= 100. 
= 45. 
11 
o 
p 
1 
1’7 in., clear water 
37 
72-5 
147 
32 
63 
172 
26-5 
52 
204 
1'7in.,turbid „ 
36 
70-5 
152 
30-5 
60 
181 
25 
49 
212 
