196 8S. P. Langley—Selective Absorption of Solar Energy. 
infra-red energy at sea-level may be roughly taken, as thus de- 
fined, at three-fifths the whole. At the same time the ratio of 
luminous to obscure energy without our atmosphere is, we 
repeat, far greater than within it. 
We conclude (among other consequences of our observations) 
that since the heat in the shorter wave-lengths (corresponding 
in a general sense to high solar temperature) was thus relatively 
greater before absorption, we are obliged to increase our usu 
estimates, not only of the amount of heat the sun sends us, but 
{and very greatly) of the effective temperature of the solar surface. 
he relatively small amount of energy, corresponding to 
e not so much to 
The discussion of these and other points is reserved for ® 
subsequent memoir. Among these will be the fuller considera- 
tion of the place of the principal absorption of water vapor, @ 
consideration which it will be advantageous to present 10 
another connection. It is to be remembered that all the values 
Allegheny Observatory, Allegheny, Penn., Dec. 30, 1882. 
