REPORT OF THE SECRETARY. 105 



establishment of a first-rate " solar-constant " observing station at 

 the best site, but the appropriation failed. 



At this juncture Messrs. Abbot and Marvin held a long- discussion 

 by correspondence and verbally as to the reality of the supposed solar 

 variability, and its availability as a forecasting element, in view of 

 the use being made of the Smithsonian solar observations in Chile 

 by the Argentine and Brazilian weather bureaus. The discussion 

 brought out very clearly the urgency of obtaining corroborative 

 observations of the solar radiation daily in the United States. 



Fortunately the proposed new station obtained private financial 

 support in the lack of congressional action. Mr. John A. Roebling, 

 of Bernardsville, JS T . J., at Dr. Abbot's solicitation, made a grant of 

 $11,000 for promoting measurements of solar radiation. Mr. Roeb- 

 ling made the condition that so much of this sum as necessary should 

 be devoted to removing the Smithsonian station from the plain near 

 Calama, Chile, to a mountain site above the reach of dust and smoke. 

 Any balance remaining after this improvement of the Chilean station 

 could be used for the removal of the Mount Wilson equipment to the 

 Harqua Hala Mountain in Arizona, or for such other purpose as Dr. 

 Abbot might prefer for the advance of the study of solar radiation. 



A I a cost of between $1,000 and $5,000 the Calama station was re- 

 moved to a mountain about 10 miles south of Calama, where skies of 

 extraordinary purity have been experienced. The removal was com- 

 pleted and first observations made at the mountain shortly after the 

 close of the fiscal year. 



Dr. Abbot visited Wenden, Ariz., and the Harqua Hala Mountain 

 in the last week of June, 1920. Contracts were made for the erection 

 on the summit of a stone and adobe building of two stories, a lower, 

 partly underground, for observing, and an upper for quarters of ob- 

 servers. This is to be ready for occupancy by September 15, 1920, 

 when it is proposed to remove the " solar-constant " observing equip- 

 ment from Mount Wilson to Harqua Hala. 



The purpose of these improvements is to enable us to obtain nearly 

 every day in the year first-rate check observations of the " solar con- 

 stant " of radiation at two stations remote from one another in the 

 two hemispheres. On\j thus is it possible to lay a firm foundation 

 of solar observations extending over a considerable interval of time, 

 which will enable meteorologists to determine if the sun's variations 

 are really of value as a weather-forecasting element. In view of the 

 results published by Mr. H. H. Clayton, of the Argentine weather 

 service, there is sufficient evidence that this may be the case to war- 

 rant the expense and discomfort attending the continuous occupation 

 of two desert mountain observatories like Harqua Hala and the 

 Chilean station. 



