MOUNT WILSON OBSERVATORY. 209 



scopic observations and has carried on investigations on stellar motions. Dr. 

 R. F. Sanford has investigated the orbits of spectroscopic binaries and has 

 continued his work on R-type stars. Dr. Edwin P. Hubble has been engaged 

 in studies of nebulae and nebulous stars and the nature of the radiation of 

 nebulae. Dr. Edison Pettit has carried on solar observations and radiation 

 measurements on stars. Mr. Milton L. Humason has made direct photo- 

 graphic observations and has begun spectroscopic investigations of the stars 

 in the Selected Areas. Mr. Wendell P. Hoge, night assistant with the 60-inch 

 telescope, has taken part in the stellar spectroscopic work. Mr. Edison Hoge, 

 who carried on solar observations and assisted in the photographic work, 

 resigned on June 1. Mr. Joseph 0. Hickox has been appointed to this posi- 

 tion. Mr. Sinclair Smith has acted as part-time assistant in the Pasadena 

 Laboratory throughout the year and has assisted Professor Michelson in his 

 investigations. 



In the Computing Division, Miss Mayberry has assisted the Director in 

 his investigations of the sun-spot spectrum. Miss Ware and Miss Miller 

 have been associated with the work of Dr. St. John. Miss Miller resigned 

 on April 1 and Mr. Edward F. Adams was appointed to her position. Miss 

 Burwell, Miss Brayton, Miss MacCreadie, Miss Poole, and Miss Shumway 

 have been engaged in stellar spectroscopic work, and Miss Joyner and Miss 

 Richmond in photometric investigations. Miss MacCreadie resigned on 

 June 1. Mrs. Marsh has continued to assist Dr. van Maanen in his measure- 

 ments of stellar parallaxes and the motions in spiral nebulae. Miss Keener 

 has given all of her time to the work of the Physical Laboratory. During 

 the temporary absence of Miss Poole and Miss Keener their positions were 

 filled by Miss Helen Davis and Miss Louise Ellerman. Mr. Theodore S. 

 Jacobson, of Stanford University, assisted in the measurement and reduction 

 of stellar spectrograms during the summer months. Miss Connor has con- 

 tinued in charge of the library and has assisted in the editorial work. 



Dr. John C. Duncan spent the summer months at the Observatory and 

 made direct photographs of nebulae in addition to stellar spectroscopic obser- 

 vations. Dr. Bertil Lindblad, volunteer assistant from the University of 

 Upsala, returned to Sweden in October 1921. Dr. Knut Lundmark, also 

 of the University of Upsala, joined the staff as volunteer assistant on June 1. 

 Dr. Lundmark is carrying on investigations on the effective wave-lengths of 

 nuclei of spiral nebulae and on related problems. Professor D. T. Wilson, of 

 the Case School of Applied Science, spent the winter months in Pasadena 

 and served as volunteer assistant during a portion of that time. Dr. C. H. 

 Gingrich, of the Carleton College Observatory, spent the greater part of the 

 year at the Observatory as volunteer assistant and took part in observations 

 of proper motion and trigonometric parallax. 



Professor A. A. Michelson, of the University of Chicago, Research Associate, 

 has continued on Mount Wilson his investigations on the velocity of light 

 and the relative motion of the earth and the ether. Professor Henry Norris 

 Russell, of Princeton University, Research Associate, spent two months during 

 the winter in Pasadena and carried on several studies bearing on ionization 

 phenomena and related subjects. 



