418 
MR. LOUIS VESSOT KING ON THE SCATTERING AND 
Table XL — Tofal Ski/ Badiation at Mount Wilson, October 19, 1906. 
Observations on the total intensity of sky-radiation are given for Mount MTlson* under the date 
October 19, 1906. Attenuation coefficients for this day are not given, so that the observations are 
compared with values calculated from the mean coefficients at Mount AVilson. If w is the solid angle 
subtended by the sun, the value of 
w T {(t>, 0 dX 
is calculated from the approximate formula (66), 
a. f“ T {4>, 0 dX = <0 sec </. r T (0, C) dX. 
Jo 1-1- COS'^ f jo 
Making use of the values of 
o .|“ t ( 0 , 0dxl\y.{0dx 
from Table VIL, and interpolating for intermediate values of (from the curves given in Diagram XL, the 
ratio 
was calculated. 
The angle 0 between sun and sky was calculated from the formula 
cos 6 = cos cj) cos ( + sin (f> sin ( cos ijy, 
the azimuth ip being measured from a vertical plane through the sun in the direction N.-E.-S.-AV. 
The comparison of the calculated ratios with those observed is fairly satisfactory; the greatest 
discrepancies occur when 9 is small and when (is large. The prol>al)le reasons for this lack of agreement 
are given at the end of Section 8. 
* ‘ Annals,’ vol. II., Table 32, p. 1.51. 
