MOUNT WILSON OBSERVATORY. 



George E. Hale, Director. 



INTRODUCTORY SKETCH OF THE YEAR'S WORK. 



In times like these, when the fundamental principles of civiHzation, 

 for which the man of science must always contend, are seriously 

 imperiled by the savage attack of the Central Powers, the duty of 

 a research mstitution is plainly evident : it must utilize every available 

 resource in aiding to overcome the enemy. For this reason the Mount 

 Wilson Observatory, in harmony with the policy which has guided 

 the Carnegie Institution since the entrance of the United States into 

 the war, has endeavored to be of service to the Government. The 

 Director's work in this field began in April 1916, when he was called 

 upon by the National Academy of Sciences to assist in the organization 

 of the National Research Council. Since that date his duties in 

 connection with the Council have kept him in or near Washington 

 during the greater part of the time. During these periods of absence 

 Dr. Adams has conducted the Observatory as Acting Director. Most 

 of the work described in the present report was thus done under his 

 general direction. 



Many other members of the Observatory staff have also devoted 

 themselves to war service. In view of the confidential nature of 

 much of the work thus undertaken, the various war activities of the 

 Observatory have been made the subject of a separate report to the 

 President of the Carnegie Institution. It may be stated, however, 

 that most of the facilities of the instrument and optical shops, and 

 many of those of the physical laboratory, have been utihzed for 

 Government purposes. A specially equipped laboratory has also been 

 built (in cooperation with Throop College of Technology) for experi- 

 mental researches for the Navy, and a large optical shop, in which one 

 hundred opticians will be trained for work of precision, has been 

 erected at the request of the Ordnance Department of the Army. 

 Those members of the staff who have not yet been called into war ser- 

 vice have continued their investigations with great \agor and success. 



Many of the efforts initially directed to war service may also con- 

 tribute in a permanent way to the promotion of research. Thus the 

 organization and development of the National Research Council 

 have been effected with both of these objects in view. The losses 

 which science has sustained because of the war must be made good, 

 and advantage should therefore be taken of the present unique oppor- 

 tunity to demonstrate the national importance of research and the 

 advantages to be derived from cooperation among investigators. The 

 pohcy of the National Research Council is based upon this principle. 

 In the organization of the Research Information Service, for example, 



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