106 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1920. 



Great appreciation is due Mr. John A. Eoebling for his generous 

 aid in stepping into the breach at this time when it proved impossi- 

 ble to obtain public support for the urgent need. Only the most 

 primitive equipment has, it is true, been possible on the Harqua Hala 

 Mountain with the means available. Unfortunately, too, it means a 

 considerable restriction of other interesting investigations under way 

 or proposed, owing to the partial dismantling of the Mount Wilson 

 station. This is greatly to be regretted. It is recommended that 

 Congress be urged to appropriate the money needed to complete the 

 independent equipment of Harqua Hala, so as to permit needed 

 apparatus to return to Mount Wilson. The Harqua Hala station 

 should also be relieved of its limitations of water, of accessibility, and 

 of communication, and the buildings made more commodious. Other- 

 wise it will be only at such personal sacrifice of comfort as few can 

 be found willing to make that its work can go on. 



PERSONNEL. 



Miss Inez Ensign resigned as computer on September 22, 1919. 

 Miss F. A. Graves returned as computer from leave for overseas work 

 in France on September 4, 1919. Miss Gladys Thurlby, computer, 

 married, on May 8, 1920, Mr. Albion M. Bond, but remained in the 

 service of the Observatory. 



SUMMARY. 



The year has been marked by the practical completion for publi- 

 cation of Volume IV of the Annals, but no appropriation is yet 

 available for its publication. Close agreement in solar variation was 

 found for 1918 and 1919 between results of Mount Wilson, Calif., 

 and Calama, Chile, 4,000 miles apart. A further remarkable con- 

 firmation of the solar variation comes from a comparison of Smith- 

 sonian observations in Chile with photo-electric observation of the 

 brightness of Saturn by Dr. Guthnick, of the Berlin-Babelsberg Ob- 

 servatory. This comparison indicates that the nature of the rapid 

 solar variation consists in the rotation with the sun of rays of unequal 

 brightness which strike the different planets successively in the order 

 of their longitudes and fall one after the other upon the earth as 

 the sun by rotation brings them into line with us. A new nocturnal 

 radiation instrument, provisionally called the " honeycomb pyrano- 

 meter" on account of its cellular structure, and which employs the 

 well-known hollow-chamber principle of the " absolutely black " 

 body, but without loss of sensitiveness, has been successfully con- 

 structed and tried. By the generosity of Mr. John A. Eoebling, of 

 New Jersey, it has been possible to remove the Chile station to a 



