OF SUNLIGHT THROUGH THE EARTH’S ATMOSPHERE. 
21 
The following coefficients were obtained from observations made on days which were 
classed as ordinarily bright. 
Barometer. 
Observed. 
Calculated. 
21-,5 
Faulliom. 
•261 
•261 
2.3-4 
Above Grin del wald 
•290 
•306 
25-6 
Jlontanvert. 
•384 
•370 
26-6 
Grindelwald. 
•400 
•400 
29-7 
Derby. 
•514 
•497 
It will be seen that on such days the same order of change in the coefficients is to 
be found. 
Other coefficients were obtained on moderately bright days, which are higher than 
the above for the varying heights of the barometer. These observations are given to 
show the great variations which may occur owing to atmospheric conditions. 
It thus appears that the light acting on platinum paper at any altitude up to those 
observed can be expressed by 
I' — Jg-|a,;i2jc/30 
where h is the height of the barometer and is the coefficient of absorption. 
In the case of the most transparent atmosphere = ’453 at a barometer of 
30 inches in height. 
Therefore 
J' _ Jg —•0005033/i2 
The coefficient for the visual absorption is ■341ja'. 
-0001716*2 
where A and A' are the original and transmitted lights. 
We thus arrive at the following results :— 
Barometer. 
/ 
M- 
a' 
a 
a 
30 
•453 
•639 
•154 
•853 
29 
•423 
•654 
•144 
•866 
28 
•344 
•671 
•134 
•875 
27 
•367 
•689 
•124 
•884 
26 
•340 
•708 
•115 
•891 
25 
•314 
•7.30 
•107 
•899 
24 
•289 
•746 
•098 
•908 
23 
•266 
•763 
•090 
•915 
22 
•244 
•787 
•083 
•922 
21 
•222 
•800 
•075 
•928 
20 
•201 
•819 
•068 
•934 
19 
•182 
•833 
•062 
•940 
