64 ANNUAL REPOET SMITHSONIAN INSTITUTION, 19 3 2 



This instrument, called water-flow pyrheliometer No. 5, was fin- 

 ished in May, 1932. Immediately afterwards Messrs. Aldrich and 

 Kramer constructed a doubly dispersing spectroscope designed to 

 observe the extreme infra-red solar spectrum between wave lengths 

 10 and 30 microns. This is the spectral region wherein the earth 

 emits radiation most strongly. As the sun rays come through the 

 atmosphere much as the earth rays pass out through it, the instru- 

 ment was intended to measure accurately the transmission of the 

 atmosphere to earth rays, a subject fundamental to meteorology. 



A large diffraction grating of 25 lines per millimeter was very 

 kindly ruled for this instrument by Dr. H. D. Babcock, of the Mount 

 Wilson Observatory, b}^ cooperation of Director W. S. Adams. A 

 potassium-iodide prism for the second dispersion was kindly loaned 

 by the University of Michigan. The instrument was completed 

 about June 1, 1932, and shipped to Mount Wilson, Calif. 



Mrs. A. M. Bond and Doctor Abbot did a great deal of work on 

 the investigation of periodicities in solar and terrestrial phenomena 

 by the aid of the periodometer, referred to in last year's report. 

 Several papers descriptive of this work will be found in Smith- 

 sonian Miscellaneous Collections, volume 85, No. 1, and volume 87, 

 Nos. 4 and 9. 



FIELD WORK AT MOUNT WILSON 



Messrs. Abbot and Aldrich left Washington about June 4, 1932, to 

 conduct experiments on Mount Wilson. They obtained excellent 

 comparisons between water-flow pyrheliometer No. 5 and silver-disk 

 pyrheliometer S. I. 5bis during June. These results, it is believed, 

 fix the standard scale of sol:ir radiation to within 0.2 per cent. The 

 expedition was continued through the summer. Its results will be 

 described in next year's report. 



FIELD WORK AT MONTEZUMA, CHILE, AND TABLE ]MOUNTAIN, CALIF. 



Daily observations of the solar constant of radiation were con- 

 tinued at the two permanent field stations. Unfortunately a great 

 volcanic eruption in southern Chile rendered the atmosphere at 

 Montezuma very hazy. This has prevented obtaining satisfactory 

 measurements of the solar constant since April, 1932, and the daily 

 reports to the United States Weather Bureau and to Science Service 

 were therefore discontinued. 



A. F. MOORe's EXPEDITION 



As stated in last year's report, Mr. and Mrs. A. F. Moore have 

 been engaged in testing the availability of certain high mountains 

 in Africa as solar-constant stations. Their observations at Fogo in 

 the Cape Verde Islands and on some half dozen peaks in Southwest 



