APPENDIX 7 



REPORT ON THE ASTROPHYSICAL OBSERVATORY 



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

 ties of the Astrophysical Observatory for the fiscal year ended June 

 30, 1930: 



PLANT AND OBJECTS 



This observatory operates regularly the central 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, South West Africa, which was established by 

 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 11 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 princi- 

 pal 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 



Continuous series of solar observations having been made as 

 hitherto at several field stations on desert mountains in distant lands, 

 these observations have been critically studied and prepared for pub- 

 lication at Washington. Several new investigations based on these 

 obwrvations hnvo hpon ninde dui'infr thn year. 



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