SMITHSONIAN MISCELLANEOUS COLLECTIONS 

 VOLUME 111, NUMBER 14 



^obsfeins Jfunb 



THE ABBOT SILVER-DISK 

 PYRHELIOMETER 



(With One Plate) 



BY 

 L. B. ALDRICH 



Director, Astrophysical Observatory 



M§^ 



m: 



(Publication 3991) 



CITY OF WASHINGTON 



PUBLISHED BY THE SMITHSONIAN INSTITUTION 



DECEMBER 8, 1949 



