REPORT OF THE SECRETARY. 103 



sites in California, Arizona, and Nevada. From the middle of Sep- 

 tember, when Messrs. Abbot and Aldrich arrived in the vicinity, until 

 some time in February the conditions were found to be superior to 

 what had been expected. About 70 per cent of the days during that 

 interval were fit for observation. The months of March, April, and 

 May proved to be less satisfactory than was anticipated, owing to a 

 thick haziness and much cirrus cloud. This defect, however, seems 

 to be attending the generally unusual character of the weather in 

 large areas of the globe. During the first four months of the year 

 1921, for instance, hardly more than half of the usual number of 

 observations were made at the station in Chile, and other facts might 

 be cited which would tend to show that the earlier part of the year 

 1921 was of very unusual character from a weather standpoint. 



The station on Mount Harqua Hala, being 15 miles from Wenden, 

 the railroad station, and 5 miles from a wagon road, is very isolated. 

 The effect of such isolation on the morale of observers was very 

 thoughtfully considered by Mr. John A. Roebling, and he added con- 

 siderably to his first gift in order to provide a great many things for 

 the comfort and recreation of the observers, both in Arizona and 

 South America. Not all of these arrangements had been completed 

 at the close of the fiscal year, so that mention of them may be de- 

 ferred more properly to next year's report. 



PERSONNEL. 



Miss F. A. Graves resigned as computer on August 10, 1920. 



SUMMARY. 



The year has been marked by the transfer of the solar radiation 

 measurements from Mount Wilson, Calif., to Mount Harqua Hala, 

 Ariz., to secure more perfect weather conditions. It is intended to 

 continue solar constant observations there daily when possible 

 throughout the entire year for several years. Similar duplicate 

 observations are to be carried on at Montezuma, Chile, at the private 

 station of the Smithsonian. Thus it is hoped to provide an excellent 

 basis of solar radiation measurements to compare with weather 

 phenomena. This may lead to advance in methods of weather fore- 

 casting. Volume IV of the annals, covering the years 1912 to 1920, 

 is practically ready for the press. 



Eespectfully submitted. 



C. G. Abbot, 



Director. 

 Dr. C. D. Walcott, 



Secretary, Smithsonian Institution. 



