NO. 2 



SMITHSONIAN EXPLORATIONS, I924 



31 



will soon prevail again. We had hitherto noted an association of 

 higher solar radiation with greater sun-spot activity. (See tig. 38.) 

 As we have now passed the minimum of sun-spots, and greater solar 

 activity is' to be expected in the next years, the rising tendency of the 

 solar radiation is not surprising. 



During the past year, the Institution has received each morning tele- 

 grams from Arizona and Chile giving the solar results of the preceding 



1.9S 



132} 



o 20 A-o ^6 §0 70S Jzo 'i^ Te^J /So zoo 220 



Fig. 38. — Increased solar activity brings higher solar-constant values. 



day, and has forwarded the combined result by telegraph to Mr. H. H. 

 Clayton in Massachusetts. Mr. Clayton has returned to the Institution 

 on the same afternoon a letter giving forecasts for the temperature 

 of New York City several days in advance. Mathematical methods, 

 independent of personal bias, show that these forecasts indicate some 

 degree of real prevision, based on the solar observations, even to 

 5 days in advance. These investigations are supported by Mr. John A. 

 Roebling. A continuation of them is intended. 



Interesting results were secured in quite a different field. Dr. Abbot 

 employed a Nichols radiometer in connection with the 100-inch reflect- 



