REPORT OF THE SECRETARY 31 
The daily solar constant values have been cabled to Washington 
from the Montezuma station as heretofore, and since January 1, 1926, 
the solar constant data have been published on the daily weather map 
at the request of the Chief of the Weather Bureau. On that date, 
the Institution made public announcement that it would furnish 
“through the United States Weather Bureau, through either of the 
telegraph companies, or through the Associated Press, or Science 
Service, if any or all of these organizations shall request it for the 
use of their clients, daily or 10-day mean values of the solar constant 
of radiation as early and as frequently as results are available from 
its field stations in Chile and California.” 
The staff of the observatory at Washington have been largely oc- 
cupied during the year with a complete revision of all of the Mount 
Montezuma data. As a result of this extensive work, the newly 
derived solar constant values show a new and higher order of ac- 
curacy than ever reached before. 
A new proof of solar variability was devised by Doctor Abbot, on 
the basis that if the atmosphere had uniform temperature, trans- 
parency, and humidity, and if the pyrheliometer observations were 
made always at the same altitude above the horizon, the readings of 
the pyrheliometer would be directly proportional to the intensity of 
the solar rays. Testing this idea on all observations made in the 
months of July at Mount Wilson, from 1910 to 1920, excluding the 
years 1912 and 1913 as well as many individual days of unusual 
atmospheric conditions, Doctor Abbot plotted a full curve from the 
remaining observations. Then using the identical days, the mean 
solar constant values as heretofore published were plotted as a dotted 
curve. Both curves agree very closely except in 1914, when they 
differ by about 1 per cent. Both curves indicate a range of solar 
variation in July of 1910 to 1920 of over 2 per cent. With them was 
plotted in a double line the variation of sun-spot numbers. Even in 
details the agreement is quite remarkable. 
INTERNATIONAL CATALOGUE OF SCIENTIFIC 
LITERATURE 
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to enable the organization to resume publication. The United States 
is the only country sufficiently prosperous to furnish this support, 
and no bibliographic enterprise more worthy of assistance could be 
found than this great international cooperative undertaking which 
for so many years was the only complete bibliographic aid to students 
and investigators in all branches of science. More than ever before, 
commercial enterprises depend on scientific work, and as it is through 
the literature of science that all such work is announced and re- 
