Table 183. 



SOLAR ENERGY AND ITS ABSORPTION BY THE EARTH ATMOSPHERE. 



This table gives some of the results of Langley's researches on the atmospheric absorption of solar energy.* The 

 first column gives the wave-length A, in microns, of the spectrum line, wliilc the second and third columns give 

 the corresponding absorption, according to an arbitrary scale, for high and low solar attitudes. The fourth column, 

 E, gives the relative values of the energy for the different wave-lengths which would be observed were tlicre no 

 terrestrial atmosphere. 



Table 184. 



THE SOLAR CONSTANT. 



The " solar constant " is the amount of heat per unit of area of normally exposed surface which, at the earth's mean 

 distance, would be received from the sun's radiation if there were no terrestrial atmosphere. The following table 

 is taken from Langley's researches on the energy of solar radiation.! The first column gives the wave-length in 

 microns. The second and third columns give relatively on an arbitrary scale an upper and a lower limit to the 

 possible value of spectrum energy. 



The areas of the energy curves are respectively 

 The solar constants deduced from these areas are 



149,060 and 95,933 

 3.505 and 2.630 



Langley concludes that "in view of the large limit of error we can adopt three calories as the most probable value 

 of the solar constant," or that " at the earth's mean distance, in the absence of its absorbing atmosphere, the solar 

 rays would raise one gramme of water three degrees per minute, for each normally exposed square centunetre of its 

 stirface." 



* "Am. Jour, of Sci." vols, xxv., xxvii., and xxxii. 



t "Professional Papers of U. S. Signal Service," No. 15, 1884. 



Smithsonian Tables. 



177 



