REPORT OF THE SECRETARY. 65 
Computations from the Mount Whitney results confirm Yntema’s conclusion 
that the great increase of brightness toward the horizon can not be due to any 
arrangement of starlight, but must be caused by some terrestrial source of 
light, perhaps a continuous faint aurora. 
Bolometric measuremeuts were made on Mount Whitney to determine the 
relative radiation of the sky by day in all directions, as compared with the 
sens Han 
Eee = 
E qgeOks: at 
Oo 
9 i 
feeeeect | 
+) a 6 nea 
fod 
fou 
oe a 4 Ee 
ae 
NAAN 
Lh Th I 
—_ 
ey 
ee 
(Gece! 
eee 
Kees 
ae 
een 
(amald 
Belge Set 
Leta 
eae 
1906 
ae 
jyury | Aus. 
Peo 
(nl omnes 
isl fe 
fi 
Se 
Fig. 1.—Solar-constant values. 
SEPT. 
ieee a 
ri bee Ce Sie 
reece ee 
OCT. 
eat as thy 
CAL UAE 
Baio 
PSS Rae es 
2) 
U 
ce 
BIN 
Hite 
— 
Pare TER 
ibomee eee aa 
re nlublniscetaecceeees 
sun. These measurements were numerous and seem to have been successful, 
but are not yet reduced. 
The sun’s energy spectrum.—A summary has been prepared showing the mean 
result of determinations of the distribution of the sun’s energy in the spectrum, 
as it would be found outside the atmosphere. The measurements on which it 
is based include Washington, Mount Wilson, and Mount Whitney work of 1903 
38734°-—sm 1911——5 
I 
nich 
HY A 
Baal 
45 elt a 
wim 
UNE 
TM NG : 
ee 
be 
ee 
Pee 
eel eae ae! 
Negi eae Se (alee a 
aca 
