65G PROCEEDINGS OF THE AMERICAN ACADEMY. 



Transmission of Solak Eadiation in the Visible Spectrum. 



Calories received from Visible Portion 



tlie Whole Spectrum. trausmitted. 



Outside the atmosphere . . . . 3.127 1.000 



Camp Whitney 1.896 . .664 



Lone Pine 1.533 .482 



Sea-Level 1.180 .210 



The relative loss in the regions I, X = 0.393 |U to A = 0.76 /u, and II, 

 X = 0.76 |U. to X = 1.2 /u, between the several stations is as foUows: 



L n. 



Outside to Camp Whitney . . 0.105 0.029 



Camp Whitney to Lone Pine . . 0.055 0.010 



Lone Pine to Sea-Level . . . 0.086 0.027 



Light received from the Day Sky. 



To these transmissions must be added that part of the solar radia- 

 tion which is lost by reflection and diifraction in the atmosphere before 

 reaching the ground, but is reflected again upon it, causing the bright- 

 ness of the day sky. This amount is sufficient to obliterate the stars. 

 Compared with direct sunlight, its ratio as determined by Langley ^ is 



Sun. Sky. 



Illumination .... 80 19 



or 24 per cent of the sun's light. 



We must therefore increase the energy transmitted by 24 per cent 

 of itself. This gives finally : 



Transmission. Portions reflected into Space. 



Outside 1.000 1000 



Sea-Level 21 26 74 



Albedo of the Earth. 



Now the fraction of the incident energy in the visible spectrum is that 

 by which we see the body and is called its albedo. The albedo of our 

 air, then, comes out .74. To get the whole albedo of the earth we 

 must add to it the albedo of the surface. 



3 Professional Papers of tlie Signal Service, Vol. 15. 



