122 ANNTJAL REPORT SMITHSONIAN rNSTmJTION, 1953 



8. Summary of 13 years of solar-constant determinations. This, 

 added to 17 years published in volume 6 of the Annals, forms 

 as nearly as possible a homogeneous record covering 30 years, 

 based upon the scale of the original Mount Wilson work. 



Work in Washington. — William H. Hoover, chief of the division, 

 in April 1953 completed a study of the silver-disk pyrheliometer 

 under carefully controlled conditions of temperature, timing, shutter 

 operation, and source of energy. This important work, together with 

 a report of new calibrations against the standard water-flow pyrheli- 

 ometer which Mr. Hoover and Mr. Froiland made in September 1952 

 on Table Mountain, is described in a paper to be published in the 

 Smithsonian Miscellaneous Collections. 



Preliminary to certain laboratory tests of new equipment, the ob- 

 servatory siderostat was completely overhauled by Mr. Talbert and 

 Mr. Harrison. This excellent instrument, built by Grubb of Dublin 

 over 60 years ago, is now fitted with a synchronous motor instead of 

 clock drive, new bearings have been installed, and the instrument 

 carefully adjusted. A new sliding house of aluminum protects it from 

 the weather. Inside the laboratory a light-tight housing has been 

 built around the spectrometer to reduce stray light. 



Last year's report referred to cooperative work with the United 

 States Weather Bureau in an effort to improve the method of cali- 

 brating the Eppley pyrheliometers in use by the Bureau. This co- 

 operation has continued and the results will shortly be published un- 

 der the auspices of the Weather Bureau. 



Tlie Smithsonian standard scale of radiation, established in 1913 

 and widely adopted, has been further disseminated during the year 

 by the sale, at cost, of two silver-disk pyrheliometers, built and cali- 

 brated at the Institution, as follows : 



S. 1. 91 to the Observatory, India Meteorological Department, New Delhi, 



India. 

 S. 1. 92 to the University of Wisconsin, Madison, Wis. 



All the galley proof of the Ninth Revised Edition of the Smith- 

 sonian Physical Tables has been received from the printer. 



An important paper by Dr. C. G. Abbot, research associate, sum- 

 marizing all his findings concerning the effect of solar-radiation 

 changes upon weather, was in press at the close of the year. 



Andrew Kramer, instrument maker of the Observatory for nearly 

 61 years, retired on June 30, at the age of 84. His record is unique. 

 Not only was his work outstanding, but his kindliness and cooperative 

 spirit endeared him to many Smithsonian employees. 



Work in the -field. — At Montezuma, Chile, the series of tape ex- 

 posures made under contract with the Office of the Quartermaster 

 General was continued during the year. Daily measurements are 

 made of the total sun and sky radiation as received upon a horizontal 



