24 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 65 



quipa results confirm the variability of the sun, both from year to 

 year and from day to day, shown by investigations at Mount Wilson 

 and elsewhere. 



It seems probable that from observations similar to those at 

 Arequipa, if conducted at eight or ten favorable stations of high 

 level in various parts of the world, the variations of the sun could be 

 determined almost or quite as certainly as from two stations equipped 

 for complete spectro-bolometric determinations of the solar constant. 



The Arequipa results indicate that the volcanic dust which was 

 general in the atmosphere in the northern hemisphere for more than 

 a year after the volcanic eruption of Mt. Katmai, Alaska, in June, 

 1912, did not influence the transparency of the atmosphere in Peru. 





