APPENDIX 7 



EEPORT ON THE ASTROPHYSICAL OBSERVATORY 



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

 ties of the xVstrophysical Observatory for the fiscal year ended June 

 30, 1931 : 



PLANT AND (, EJECTS 



This observatory operates regularly the centrni station at Wash- 

 ington and two field stations for observing solar radiation on Table 

 Mountain, Calif., and Mount Montezuma, Chile. The station at 

 Mount Brukkaros, Southwest Africa, which was establislied b}'- the 

 National Geographic Society, is being continued for the present in 

 cooperation with the Astrophysical Observatory with funds donated 

 by a friend of the Institution. In addition the observatory controls 

 a station on Mount Wilson, Calif., where occasional expeditions are 

 sent for special investigations. 



The principal aim of the observatory is the exact measurement of 

 the intensity of the radiation of the sun as it is at mean solar distance 

 outside the earth's atmosphere. This is ordinarily called the solar 

 constant of radiation, but the observations of past years by this ob- 

 servatory have proved it variable. As all life, as well as the weather, 

 depends on solar radiation, the observatory has undertaken the con- 

 tinued measurement of solar variation on all available days. These 

 measurements have now continued all the year round for 12 years. 

 As will appear in this report, recent studies indicate that the perma- 

 nent continuation of these daily solar-radiation measurements may 

 have great value for weather forecasting. In addition to this prin- 

 cipal object the observatory undertakes spectroscopic researches on 

 radiation and absorption of atmospheric constituents, radiation of 

 special substances, such as water vapor, ozone, carbonic-acid gas, 

 liquid water, and others, and the radiation of the other stars as well 

 as of the sun. 



WORK AT WASHINGTON 



Funds having been appropriated by the Congress to print Volume 

 V of the Annals of the Astrophysical Observatory, the year was spent 

 principally in preparing text, tables, and illustrations expressing the 

 results of observations made since August, 1920, at the several 

 stations. 



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