270 
CAPTAIN W. DE W. ABNEY ON THE TRANSMISSION 
Diagram 2 shows this plotted. 
Diagram 2. 
Photographs were then taken through a clear-water cell, through 3'069-in. turbid 
water, and through 1'759-in. the same water, the light being admitted through 
varying apertures of the rotating disc. The results are as follows :— 
Clear Cell; 20 sec. exposure. 
Aperture. 
Density. 
Equivalent on 
above scale. 
J 
481 
301 
42 
42 
Therefore 1 = ‘865. 
384 
33 
Reduced to standard of 
284 
59 
25 
1 min. exposure, 1 = 
18| 
96 
17 
2-595. 
134 
117 
If-in. turbid : 1 min. exposure. 
Aperture. 
Density. 
Equivalent on 
above scale. 
17£ 
104 
14 
284 
584 
604 
29“ 
23 
45 
Therefore 1 = - 795. 
861 
181 
70 
191 
152 
