410 
MR. LOUIS VESSOT KING ON THE SCATTERING AND 
Table VII.— Total Solar and Shy Radiation Calculated at Mount JFilson Level from Mean 
A ttenuation Coefficients. 
In order to obtain the total solar intensity reaching the earth’s surface for different zenith distances of 
the sun, a table of the values of was drawn up for the various values of C, A, S, and ( given in 
Table VI. From these curves were drawn on a large scale, which, when integrated, gave the values of 
Jo Jo 
the units of intensity being those given for S in Table I., and the unit of wave-length being taken as Ip, 
and dX = - Ip. As a check on the calculations it is interesting to see ho\r far the total intensity can be 
represented by a formula of the type 
('"E(0dA = pSdA. 
Jo Jo 
The values of the “ apparent ” coefficient of attenuation C calculated from the integrated area of each of 
the curves of solar intensity ^corresponding to different values of ( are given below :— 
0°. 
20°. 
o 
o 
o 
0 
1 
o 
o 
o 
o 
GO 
Mean values C between 
0° and 60°. 
c 
•102.3 
•1140 
•1293 
•1079 
• 0953 
•0817 
C = -1134, = -893. 
The value of the apparent transmission of total radiation given for Mount Wilson* is e = '895, 
C = -111, in good agreement with the above values. It will be noticed that an exponential formula for 
the total intensity fails for greater zenith distances than 60°. 
From the intensities from zenith sky given in Table VI., and drawn in Diagrams II.-VII., the integrals 
I T (0, {■) dX were calculated for various values of (. From those the total sky radiation on a horizontal 
Jo 
plane, H ({■), was calculated from the approximate formula (68), and is plotted against values of ( in 
Diagram IX. It will be noticed that the value of the ratio 
|jH(0dA/|“E(0dA 
is very nearly constant for all zenith distances and has the mean value ‘0.50. This value is in fair 
agreement with the value •0.52 (August 18, 1905) but is considerably smaller than the value ‘077 
(September 8, 1906, October 19, 1906) determined at Mount Wilson, f It will be noticed under 
Table XII. that the attenuation coefficients for August 18, 1905, are in much better agreement with the 
mean values employed in these calculations than those for October 19, 1906. 
The entries in the last row of the present table give the ratio shyjsun for equal solid angles, the semi- 
diameter of the sun being taken as 16' of arc. These values are those most often measured in oliservations 
on sky radiation ; the results are shown graphically in Diagram XL 
* ‘Annals,’ vol. II., p. 9G. 
t ‘ Annals,’ vol. II., Table 3.5, p. 153. 
