Report on the Astrophysical Observatory 



Sir : I have the honor to submit the following report on the opera- 

 tions of the Astrophysical Observatory for the fiscal year ended 

 June 30, 1955 : 



The Astrophysical Observatory includes two research divisions : the 

 Division of Astrophysical Kesearch, for the study of solar radiation, 

 and the Division of Radiation and Organisms, for investigations 

 dealing with radiation as it bears directly or indirectly upon bio- 

 logical problems. Three shops, for metalwork, for woodwork, and 

 for optical and electronic work, are maintained in Washington to 

 prepare special equipment for both divisions. 



On November 20, 1954, 1 reached the mandatory age for retirement. 

 No successor having been chosen at that time, however, I was asked 

 to continue in office pending the installation of a new director. Dr. 

 Fred L. Wliipple, professor of astronomy at Harvard University, will 

 become Director of the Astrophysical Observatory effective July 1, 

 1955. At Dr. Whipple's request, A. G. Froiland, director of the 

 Table Mountain station, was transferred to Washington to act as 

 liaison officer. 



DIVISION OF ASTROPHYSICAL RESEARCH 



During the fiscal year 1955 the two high-altitude observing sta- 

 tions, Montezuma in northern Chile and Table Mountain in southern 

 California, remained in continuous operation. 



Work in Washington. — The cooperative work with the U. S. 

 Weather Bureau, mentioned in last year's report, was continued. This 

 concerned the calibration of Eppley pyrheliometers and the simplifi- 

 cation and automatic recording of silver-disk pyrheliometry. The 

 progress of this work is summarized in two papers by T. H. MacDonald 

 and Norman B. Foster, published in the Monthly Weather Review for 

 August 1954 and February 1955. 



The loss of William H. Hoover, whose sudden death in September 

 1953 was recorded in last year's report, has continued to delay not 

 only the preparation and testing of improved equipment but also the 

 statistical studies of field observations normally carried on in Wash- 

 ington. No one has been appointed to succeed Mr. Hoover since it 

 was felt that the new director should choose liis own staff. 



Orders were received during the year from interested institutions 

 and laboratories for three silver-disk pyrheliometers and five modi- 

 fied Angstrom pyrheliometers. Preparation and calibration of these 

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