158 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1920. 



mining company were very kind and helpful to the Smithsonian ex- 

 pedition under the charge of Mr. Moore, assisted by Mr. Abbot, and 

 placed at their disposal a building at Chorillos, near Calama, along 

 with furniture and other equipment which materially aided in the 

 establishment of the station. 



Observations were begun at Calama on July 27, 1918, and continued 

 there for exactly two years. The station proved to be not quite so 

 favorable as had been hoped, owing to the dust and smoke coming 

 from the city and from the mine which occasionally interfered with 

 the purity of the atmosphere. Nevertheless remarkably accordant 

 and satisfactory results were obtained there. 



In May, 1919, the writer, with Mrs. Abbot, visited the observers at 

 Calama, and with Mr. Moore went on to La Paz, Bolivia, where 

 they observed the total eclipse of the sun of May 28, 1919, under 

 extraordinary conditions. The sun rose partly eclipsed over a range 

 of snow-covered mountains over 20,000 feet high and was observed 

 under beautifully favorable conditions from the temporary station at 

 an altitude of nearly 13,000 feet, at El Alto, so-called, on the rim of 

 the tremendous canyon above the city of La Paz. Excellent photo- 

 graphs were secured, and also measurements with the pyranometer of 

 the brightness of the sky before and during the eclipse. 



On the return to Calama, Mr. Moore and the writer visited the 

 Argentine Weather Bureau station at La Quiaca, Argentina, where 

 they met Mr. Wiggin, chief of the Argentine Weather Service, and 

 Mr. Clayton, chief forecaster, and discussed with them the applica- 

 tion of solar radiation measurements to forecasting of weather. 

 Great progress had been made by Mr. Clayton and his colleagues in 

 the computation of the correlations between variations of the sun 

 and variations of temperature, rainfall, etc. So much so, that Mr. 

 Clayton and his chief had become fully convinced of the value of 

 solar variation work as a forecasting element. Already in Decem- 

 ber, 1919, the Argentine Weather Service had arranged with Mr. 

 Moore, director of the Smithsonian observatory at Calama, for a 

 daily telegraphic report of the " solar constant " value obtained at 

 Calama. In order to furnish this daily report, Messrs. Moore and 

 Abbot had been obliged to work with the greatest rapidity, accuracy, 

 and devotion in the computations. Observations for determining the 

 "solar constant" required several hours of observing, the develop- 

 ment and washing of a photographic plate, the reading of six bolo- 

 graphic curves at nearly 40 different places corresponding to 40 

 different wave lengths of radiation, and a great mass of computa- 

 tions such as formerly used to require nearly three days altogether. 

 Owing, however, to the introduction of a special slide-rule graphical 

 reduction machine, the work had been greatly shortened, and further 

 improvement was made by the use of the theodolite to determine the 



