MOUNT WILSON OBSERVATORY. 221 



has made photographic and stellar spectroscopic observations with the 

 10-inch telescope. Mr. Edison Hoge, who joined the staff in December 

 as successor to Mr. Clarence Henshaw, has taken part in the solar ob- 

 servations and served as assistant photographer. Mr. Hugo Benioff 

 has assisted during the summer in the solar observations and experi- 

 mented with the thalofide cell. Mr. Sinclair Smith has been part-time 

 assistant in the Pasadena laboratory throughout the year. 



Professor J. C. Kapteyn, Research Associate of the Observatory, has 

 continued his work in Groningen. Professor A. A. Michelson, who was 

 appointed Research Associate last year, has conducted investigations 

 at Mount Wilson on the application of interference methods in astron- 

 omy and on the velocity of light. Professor W. H. Wright, of the Lick 

 Observatory, spent 10 daj^s on Mount Wilson in June, photographing 

 the spectra of gaseous nebulae with his quartz spectrogi-aph, attached 

 to the 100-inch telescope. 



Of the staff of the Computing Division, Miss Ware and Miss Mil- 

 ler have continued to assist Dr. St. John. IMiss Biu-well, Miss Bray- 

 ton, Miss Hubbard (resigned August 1), and Miss Shumway have 

 been engaged with the investigations in stellar spectroscopy. Miss 

 Richmond, Miss Joyner, jMiss Ritchie (resigned April 1), and Miss 

 Mayberry have assisted Mr. Scares and Mr. Shapley. Miss Wolfe 

 (resigned August 1) continued with the work on the sun's general mag- 

 netic field and on trigonometric parallaxes, in which she has been suc- 

 ceeded temporarily by Mrs. Magnusen, while Miss Keener has given 

 her time to measures and reductions connected with the work of the 

 Physical Laboratory. Miss Connor has remained in charge of the 

 library and has assisted with the editorial work. 



Mrs. Harlow Shapley, volunteer assistant, has collaborated with Dr. 

 Shapley in his stellar investigations. ]Miss Edna Carter, professor of 

 physics at Vassar College, served as volunteer assistant in the Physical 

 Laboratory during the summer, where she investigated the spectrum of 

 the electric discharge in high vacuum (''hot spark"). 



Dr. Charles G. Abbot and Mr. L. B. Aldrich continued the work of 

 the Smithsonian Astrophysical Observatory on Mount Wilson during 

 the summer. 



INVESTIGATIONS IN PROGRESS. 



SOLAR RESEARCH. 



INSTRUMENTS. 



The adaptation of the interferometer to the Snow telescope and 

 spectrographic equipment has been completed. Recent tests have 

 shown that the interferometer with quartz plates and invar etalons, 

 surrounded by a water-jacket, can be successfully used with the full 

 aperture (2 feet) of the Snow telescope. A definite portion of the beam 

 is filtered through a 4-inch column of water, and the transmitted area 



