REPORT OF THE SECRETARY 117 
solar constant values as heretofore published in Volume LV of the 
Annals give the dotted curve. 
Both curves agree very harmoniously except in 1914, when they 
differ by about 1 per cent. They unite to indicate a range of solar 
variation in July, 1910, to 1920, of over 2 per cent. Along with 
them is plotted in a double line the variation of sun-spot numbers. 
Kven in details the agreement is quite remarkable. 
T’rom another arrangement of the same data, Doctor Abbot found 
that those individual days on which the sun’s rays appeared to the 
pyrheliometer more intense (when observed through unchangingly 
transparent atmospheres), appeared to yield on the average higher 
solar constant values, as heretofore published. Similarly low days 
for the pyrheliometer were low for the solar constant. Thus is con- 
firmed by this new test the reality of both long and short interval 
solar variations. The test is not, however, as satisfactory in the 
latter as in the former application. As the new method has other 
valuable applications, it is being used also with all Montezuma and 
Harqua Hala observations since 1920. 
Personnel.—The present personnel of the Astrophysical Observa- 
tory is as follows: 
Director, Dr. C. G. ABBOT. Field director, Mr. H. B. FrReemMan. 
Research assistani, Mr. F. H. Fowre. Assistant, Mr. KF. A. GREELEY. 
Research assistant, Mr... B. AtpRicH. Assistant, Mr. BH. E. Smiru. 
Field director, Mr. A. F. Moore. Instrument maker, Mr. A. KRAMER. 
Computer, Mrs. A. M. Bonn. 
Summary.—tin three promising directions the work of the ob- 
servatory, aimed to secure accurate determinations of solar varia- 
bility, has been promoted. 1. The National Geographic Society has 
undertaken to equip and support for several years a cooperating 
solar radiation station at the best location available in the Eastern 
Hemisphere. This project is rapidly going forward, and observa- 
tions may begin at Mount Brukkaros, South West Africa, by October, 
1926. 2. By Mr. J. A. Roebling’s generosity, the station at Mount 
Harqua Hala has been removed and reestablished on Table Moun- 
tain, Calif., 2,000 feet higher, and much more favorable for obsery- 
ing as well as much less isolated than Mount Harqua Hala. Improved 
apparatus and methods were introduced there from the beginning 
of observations, in October, 1925. 3. A complete revision of all 
Montezuma observations is well advanced. New methods of meas- 
urement and reduction are employed identical with those introduced 
at Table Mountain. The results thus far reached show greatly 
superior accuracy. 
By a new and simple test, the reality of solar variation is confirmed. 
At the recommendation of the National Academy of Sciences and 
20837—27——_9 
