SOLAR Tt.VDIATIOX ABBOT 



185 



150 miles east. Thus we were able to calibrate and test it, both 

 before and after the ascent, under the same conditions of temperature 

 and pressure which it encountered during the flight. Correcting 

 results to mean solar distance, this instrument recorded a solar in- 

 tensity of 1.84 calories at the elevation of 22,000 meters. The baro- 

 metric pressure there was 3 centimeters, so that twenty-four twenty- 



Bdrometer. 



Figure 8.- 



-Pyrheliometric measuri'mcnts of solar radiafioii from si'a level to 22,000 

 meters elevation 



fifths of the atmosiDhere had been left behind. Allowing for the 

 probable atmospheric absorption and scattering still remaining, the 

 result for the solar constant is 1.87 calories, which, within the error of 

 the determination, is certainly a good check on our adopted mean 

 value of the solar constant, 1.94 calories. 



DISTKTI'.UTION OF RADIATION OVER THE SOLAR DISK 



Mount Wilson observations seemed to confirm our impression that 

 the solar radiation is variable. Doctor Langley, therefore, suggested 

 that we make dailv observations of the distribution of brightness 



