MOUNT WILSON OBSERVATORY. 227 



van Maanen has carried forward his determinations of stellar paral- 

 laxes and proper-motions, and has continued the measurement of 

 spectra to fix the position of the sun's magnetic axis. Professor Alfred 

 Joy has continued his stellar spectroscopic investigations. Dr. Paul 

 Merrill, who joined the staff of the Observatory in January, has 

 divided his time between laboratory investigations and stellar spec- 

 troscopy. Dr. Gustaf Stromberg has given special attention to 

 investigations on the relation of mean stellar parallaxes to mean 

 proper-motion and on systematic corrections to the absolute magni- 

 tudes of stars as determined spectroscopically. Dr. R. F. Sanford has 

 continued his investigations in stellar spectroscopy and on the spectra 

 of nebulae and star-clusters. Mr. Frederick Brackett joined the staff 

 on June 1 as assistant in the solar observations. Messrs. Hugo Benioff , 

 Clarence Henshaw, and Sinclair Smith have served as assistants dur- 

 ing a part of the year. 



Professor J. C. Kapteyn, Research Associate of the Carnegie Institu- 

 tion, has continued in Groningen his investigations in cooperation 

 with the Observatory. Professor A. A. Michelson, recently appointed 

 Research Associate of the Carnegie Institution, is preparing apparatus 

 for use on Mount Wilson in measuring the diameter of stars by inter- 

 ference methods. 



The members of the Computing Division have assisted in the work 

 of the various departments as follows: Miss Ware and Miss Miller 

 have been engaged in solar and laboratory investigations under the 

 direction of Mr. St. John, Miss Ware devoting her time mainly to the 

 rotation of the sun. Miss Burwell has divided her time between the 

 classification of stellar spectra and the spectroscopic determination of 

 stellar parallaxes, together with the measurement and reduction of 

 stellar spectrograms for radial velocity. Miss Brayton and Miss 

 Shumway have been engaged wholly with determinations of radial 

 velocity. Miss Margherita Burns has given her entire time to the 

 measurement and reduction of spectra secured in the physical labora- 

 tory for the determination of standards of wave-length. Miss Davis, 

 and later Miss Ritchie, have been occupied with various investigations 

 relating to star-clusters. Miss Joyner and Miss Richmond have 

 devoted most of their time to stellar photometry. Miss Joyner has 

 also assisted in the hbrary, and Miss Richmond has made numerous 

 miscellaneous measures and reductions of stellar positions. Miss 

 Wolfe has been engaged in computations of parallax and proper- 

 motion and in reductions connected with the general magnetic field 

 of the sun. She has also made photographic reproductions of many 

 of the solar negatives. Miss Connor has continued as librarian, and 

 has assisted with the editorial work. 



Miss Davis resigned in September 1918, and Miss Burns in July 

 1919. Miss Mary Ritchie was appointed in April 1919. 



