NO. 2 



SMITHSONIAN EXPLORATIONS, I918 



29 



measurements being made at Calama, Chile, under the direction 

 of Mr. A. F. Moore, assisted by Mr. L. H. Abbot. The outfit there 

 is the same that was used by them during the previous year at Hump 

 Mountain, in North Carohna. The present station was chosen as 

 the most cloudless one to be found upon the earth, and they have been 

 able to observe about 75 per cent of the days since the 27th of July, 



Fig. 28. — The Coelostal, Pvrheliometers, and Theodolite. 



Fig. 29. — Part of the Spectro-Bolometer. 



when the measurements began. For long periods of time, as, for 

 example, the period from the middle of November to the middle of 

 December, tliere was not a single day lost, although this required 

 that the sky should l)e j^erfectly cloudless for about three hours, 

 either in the early morning or the late afternoon. Notwithstanding 

 the great number of favorable davs for the observations, the records 



