l8 SiVIITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 72 



Janeiro. Both the Argentine and Brazihan Weather Bureaus employ 

 them with approval for forecasting purposes. 



Dr. Abbot, vv^ith the advice and assistance of the U. S. Weather 

 Bureau, which carried on special observations in several localities for 

 the purpose, selected a site on Mount Harqua Hala, near Wenden, 

 Arizona, as the best place to relocate the Mount Wilson outfit. A 

 building, partly underground, was erected there in July and August 

 by local contractors. Messrs. Abbot and Aldrich occupied the Mount 

 Wilson Station as usual from July i to September 15, when the outfit 



Fig. 24. — Coelostat and pyrheliometer, Alt. Harqua Hala. 



was removed to Mount Harqua Hala, where observations were begun 

 on October 2, 1920. Dr. Abbot took charge and continued observing 

 until January 25, 1921, assisted by Mr. Fred A. Greeley. Mr. Aldrich 

 then relieved Dr. Abbot, and it is expected will himself be succeeded 

 about May i, 1921, by Mr. A. F. Moore, formerly at Calama. 



Thus the Institution has now in charge two first-class solar radia- 

 tion observatories, which are to be operated continuously hereafter 

 imtil the question of the value of the solar variation as a meteoro- 

 logical datum is definitely settled. Heretofore the measurements have 



