REPORT OF THE SECRETARY. 9o 



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 ^Slount "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, 1919, Mr. Albion M. Bond, but remained in the 

 service of the Observatory. 



su:m:\iary. 



The year has been marked b}- the practical completion for publi- 

 cation of "\'olume I^^ 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 observations 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 employ's 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. Roebling. of 

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

 mountain above the dust and smoke of its former plateau location, and 

 also to erect a building on the Harqua Hala Mountain, in Arizona, 

 to which the ^Nlount "Wilson solar-constant work will be removed in 

 September. 1920. 



Eespectfully submitted. 



C. G. Abbot, Director. 



Dr. C. D. Walcott, 



Secretary^ Smithsonian Institution, 



