SOLAR EADIATIOK ABBOT 



177 



surely not due to water vapor. I have seen quite recently some beau- 

 tiful absorption spectra by H. J. Unger, of the University of Oregon, 

 wliich prove that wi and a>2 are really caused by terrestrial carbonic 

 acid gas. 



TEMPERATURE 

 DEP/IRTURES . 





North America 

 20 Stations. ° 



Azores, l^iflDEiPAS, 

 Brjtish Isles, 



SW Europe, o 



N /iFFICfl. 



18 Stktions. 



NW.Ehfope. 

 15 stations. 



Central Europe. . 

 10 Stations. ° 



European 

 Russia 

 11 Station-; 



A:iftTic 



8 STATIONS 

 Hl&H RUTITUDES 



SW. Europe. 

 7 Stations. 



GFNERflLMEfiK 



North 

 Temperate 

 Zone, 

 89 Stations. 



Solar 

 RflDIHTION 



Outside the 

 Atmosphere . 





\ 



IT 



^■ 



V^. 



:^^~P 



IXK I 



-J— p= 



V^ 



r4 



Pv 



Jan Feb Mar Spl May Juno J^Uy ilug. Sept oH JJou Dec. J^n 



Figure 2. — Simultaneous lowering of the sun's radiation and of the temperature of 

 the earth's northern hemisphere as observed in March, 1903 



SOLAR-CONSTANT WORK BEGUN IN 1902 



Doctor Langley was deeply interested in the value of the solar 

 constant of radiation, which is the measure of the intensity of the 

 sun's rays as they are in free space at the earth's mean solar distance. 



