118 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1950 



was published in'^December 1949 (Smithsonian Misc. Coll., vol. Ill, 

 No. 14). This paper gives the constants and the present locations 

 of more than 90 pyrheliometers that have been constructed and 

 calibrated by the Smithsonian Institution and are now in use in 

 widely scattered parts of the world. 



Five progress reports were submitted during the year, summarizing 

 observations and exposures of textiles made under contract with the 

 Office of the Quartermaster General, as mentioned in last year's 

 report. This work was carried on mainly at Montezuma, Chile. 



Both Dr. C. G. Abbot, research associate of the Observatory, and 

 Dr. H. Arctowski continued their special studies referred to in last 

 year's report. 



Work in the field. — At the two continuously operating field stations 

 (Montezuma, Chile, since 1920, and Table Mountain, Calif., since 

 1925) observations for the determination of the solar constant were 

 made on all days having sufficiently clear skies. In addition to this 

 work, at Montezuma considerable time and effort were spent to main- 

 tain the necessary radiation measurements in the work being done 

 for the Quartermaster, mentioned above. These measurements were 

 hampered by a lack of sufficient electric power. It is hoped soon to 

 install new batteries and an improved generator. Since March 1, 

 1950, the Montezuma station has also exposed certain textiles and 

 other materials at the request of the National Bureau of Standards. 



With the cooperation of General Motors Corp. and under the 

 sponsorship of the Office of the Quartermaster General, Department 

 of the Army, as mentioned in our reports for 1947 and 1948, the 

 Observatory established at Miami, Fla., in November 1947, a tem- 

 porary observing station, where exposures to the sun and sky were 

 made, both direct and through ffiters, of certain tent materials. 

 Measurements of radiation received were made, as had been done 

 previously at Camp Lee, Va. In addition, studies were made of the 

 water-vapor absorption and spectral-energy distribution of sunlight 

 at this moist, sea-level location. The equipment of the former field 

 station at Tyrone, N. Mex., was used in these studies. By July 1949 

 the work at Miami was nearly completed. Early in August 1949, 

 Mr. Hoover supervised the dismantling of this temporary Miami 

 station, and the equipment was transported in two trucks to the 

 Table Mountain, Calif., field station. Here, with the aid of funds 

 generously given by John A. Roebling, a second observing tunnel was 

 prepared, similar to, but somewhat larger than, the regular tunnel 

 in use at this station. The new tunnel is about 100 feet to the west 

 of the old one. 



It is now possible, for the first time since the solar-constant program 

 was inaugurated nearly 50 years ago, to make simultaneous, duplicate, 



