REPORT OF THE SECRETARY ■ 107 



Arizona and Chile. Mount Harqua Hala continues under the direc- 

 tion of Mr. A. F. Moore, who was assisted until March 1, 1924, by 

 Mr. P. E, Greeley. After Mr. Greeley's resignation, Mr. A. H. Wor- 

 thing assisted from May 20 to June 30, but then resigned. At 

 Montezuma, Chile, the station continued in charge of Mr. L. B, 

 Aldrich, assisted by Mr. F. A. Greeley. 



Many comforts and observing improvements have been added at 

 both stations at small expense owing to the ingenuity and hard 

 manual labor of the obserAers. At both stations all possible days for 

 solar-constant work have been utilized, and with very high accuracy 

 of observation. About 75 per cent of all days were observed in 

 Arizona and above 80 per cent in Chile. The months of July, 

 August, and September, however, were very unfavorable at Harqua 

 Hala, because of unusual cloudiness which prevailed all over that 

 section of the United States. This abnormal state of the sky was 

 indeed made specially prominent by the almost complete failure 

 of all the California observations of the total solar eclii^se of Sep- 

 tember 10, 1923. Many observations of these months must be 

 rejected on account of unfavorable sky. 



Mr. W. H. Hoover assisted Mr. Moore for a few weeks in May, 

 1923. While Mr. and Mrs. Moore were away in Australia setting 

 up near Sydney a solar-radiation outfit ordered by Rev. E. F. 

 Pigot, of lliverview College, for a committee of interested Aus- 

 tralians, Mr. and Mrs. Hoover relieved them at Harqua Hala from 

 July until September. Mr. Hoover Avas thus prepared by actual 

 field experience to be director of the Argentine GoA^ernment's new 

 solar-radiation station at La Quiaca. 



The outfit for this station was prepared at the Smithsonian in- 

 stitution after designs of the Avriter, and the finer parts, such as 

 those of the bolometer and gah^anometer, were constructed by Mr. 

 Hoover. Shipment was made in January, 1924, and the station at 

 La Quiaca made ready for solar observing in June, 1924. Thus the 

 Argentine GoA'ernment is the first agency outside the Smithsonian 

 Institution to undertake regular determinations of the variation of 

 the sun. Their official Aveather service still receives daily telegraphic 

 reports from our station at Montezuma, Chile, and it will supple- 

 ment these by its own solar-radiation measurements at La Quiaca. 



Field work at Mount Wilson. — The director and Mrs. Abbot occu- 

 pied this station from Jvily to October, 1923. Three objects Avere in 

 view — First, to set up apparatus and begin observations on the varia- 

 tions of atmospheric ozone after the ingenious spectroscopic method 

 of Fabry and Buisson. M. Fabry Avas so kind as to supervise the 

 ordering in Paris of all the special quartz and fluorite optical parts 

 needed. Owing to the detached service of the Smithsonian instru- 



