OF SUNLIGHT THROUGH THE EARTH’S ATMOSPHERE. 
15 
Using formula as before 
log 5‘06 
1-62136 
1-7 
•953. 
The optical measures of the clear and turbid cells— 
3 inches, clear water 59, turbid, 22'5, 
1-7 inch, ,, 59, ,, 34. 
Taking the light through the 3-inch length of the cell as lying on the curve and 
using the formula 
log 59 - log 22-5 1-77495 - -81093 -96402 
=-- - = - ^ - = 
= -321. 
Taking 1-7-inch breadth of the cell 
log 59 — log 34 
o o 
1-77495 - 1-22377 
1-7 
55118 
rr 
•324. 
Mean of these values = '3225. 
Mean of {j} = '950. 
= - X 105 
•950 
•3225 
= 309-3. 
X 105, 
From these three experiments we may derive a very good approximation to the 
true value of A^. The following are the values obtained for A,^"^— 
Therefore 
1st experiment. 306-6 
2nd „ ..... 309-1 
3rd „ 309-3 
Mean .... 308-3 
A = 4244 wave length. 
That is, the variation in the intensities of tbe spectrum, as photographed on platinum 
paper, is the same as would be observed if a ray of X 4244 were isolated and the 
variation in its intensity were observed optically or otherwise. 
