186 CARNEGIE INSTITUTION OF WASHINGTON. 



star-cluster exists in the neighborhood of the sun, with its center 

 some 50 parsecs to the north of the central plane of the Galaxy. This 

 immediately suggests the hypothesis that the phenomena of star 

 streaming results in part from the apparent motion of this cluster 

 through a general field of stars widely scattered thi'ough space. 



The absorption of our physicists in war problems has greatly reduced 

 the year's output of the laboratory. Some instrumental improve- 

 ments have been effected, however, and investigations with the 

 electric furnace have been extended to new regions in the spectra of 

 manganese, iron, and titanium. The study of luminescence spectra, 

 produced by bombardment with cathode rays, has also gone forward 

 satisfactorily, and now includes iron, titanium, manganese, cadmium, 

 and calcium. 



The work of construction has naturally been greatly retarded by 

 war demands, which have absorbed most of the time of the instrument 

 and optical shops, and of the erecting force as well. Preliminary tests 

 on stars of the 100-inch reflector, made in November, were very 

 promising, but indicated the necessity of certain modifications in the 

 secondary mirror support, which was hardly stiff enough to define the 

 axis of the heavy Cassegrain mirror with sufficient exactness in all 

 positions of the telescope. This work, together with other minor 

 tasks needed to complete the dome and mounting, is not yet finished. 

 It is hoped, however, that the telescope may soon be placed in com- 

 mission, without delaying the war work with which the instrument 

 shop is chiefly occupied. 



The continually increasing importance of stellar observations in 

 our program of research indicates that the time has certainly come to 

 drop the designation "Solar" from the Observatory's name. While 

 the term is still appropriate because of the fact that our entire scheme 

 of operations is based upon intensive investigations of the sun as the 

 only star that can be studied in detail, it is misleading in view of the 

 practical completion of the 100-inch reflector, which will soon add 

 greatly to the range and number of night observations. Hereafter, there- 

 fore, the designation "Mount Wilson Observatory" will be employed. 



STAFF. 



As already stated, the Director has devoted most of his time to the 

 work of the National Research Council. He has also given such 

 attention as he could to solar investigations, continued in collaboration 

 with several members of the staff. As a part of this work he observed 

 the total eclipse of the sun on June 8 at Green River, Wyoming, as a 

 member of the Observatory expedition, which also included Messrs. 

 Adams, St. John, Anderson, Babcock, and EUerman. Dr. Walter S. 

 Adams, Assistant Director, who has had general charge of the Obser- 

 vatory during the Director's absence, has carried forward his investi- 



