MOUNT WILSON SOLAR OBSERVATORY.* 



George E. Hale, Director. 



The progress of the year, in spite of unusually cloudy weather in the 

 winter and spring, has been satisfactory in all departments of the 

 Observatory's work. The reconstructed 60-foot tower telescope, for 

 which a spectroheliograph of 13 feet focal length has been built, has 

 proved of great service in the enlarged scheme of solar observations. 

 The 60-inch reflector still remains our only instrument for work on 

 stars and nebulae, but the 10-inch portrait-lens telescope is now nearly 

 ready for use, and the completion of the larger parts of the 100-inch 

 reflector mounting makes it probable that this instrument will be in 

 working order by the end of 1916. As the laboratory equipment has 

 also been increased, by the addition of apparatus for the study of the 

 Stark effect, the entire general plan of research, which has been grad- 

 ually taking form since the inception of the Observatory, will soon be 

 completed and in operation. A series of investigations on nebulae, 

 which will form a part of this plan, has recently been outlined with the 

 valued counsel of Professor ChamberUn. 



STAFF. 



The Du'ector has continued his investigations of solar phenomena 

 and has conducted a series of vortex experiments with the assistance 

 of Mr. Luckey. Dr. Walter S. Adams has carried on his work as 

 Assistant Director and head of the department of stellar spectroscopy, 

 together with a variety of researches on stellar and solar spectra. 

 Professor Frederick H. Scares, superintendent of the Computing Divi- 

 sion and editor of the Observatory publications, has continued his 

 investigations in stellar photometry and his work on the position of the 

 magnetic axis of the sun. Dr. Arthur S. King, superintendent of the 

 Physical Laboratory, has been engaged mainly in the study of furnace 

 and spark spectra. Professor G. W. Ritchey, who discontinued his 

 astronomical observations in 1911 in order to have time for private 

 business as an optician, has returned to the photography of nebulae, 

 besides continuing his work on the 100-inch mirror. Dr. Charles E. 

 St. John has carried forward his solar investigations and his studies 

 of the electric arc. Mr. Harold D. Babcock has studied the pole 

 effect in the arc jointly with Dr. St. John, continued his work on the 

 Zeeman effect, and experimented with the interferometer for the 

 investigation of nebulae. Mr. Ferdinand Ellerman has performed his 

 usual duties as Observatory photographer and continued his work with 

 the Snow and tower telescopes. Mr. Francis G. Pease has gone on 



♦Situated on Mount Wilson, California. Address, Pasadena, California. 



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