SUN S HEAT ABBOT. 



153 



3. Several simultaneous determinations of the solar constant of 

 radiation had been made at Washington, Mount Wilson, and Mount 

 Whitney. No difference in the result, depending upon the elevation 

 of the station, had been revealed, and the mean value for the solar 



Fig. 1. — Abbot silver disk pyrheliometer. 



constant of radiation of about 1.95 calories per square centimeter 

 per minute had been obtained. This in itself was a great step for- 

 ward, for now a reference point had been established which in future 

 times would be available to determine the question of possible secu- 

 lar variation in the radiant energy of the sun. 



4. The results had strongly indicated the short period variability 

 of the solar radiation. This discovery, if confirmed, bade fair to 

 have important consequences for meteorology. 



