102 Proceedings of Learned Societies. 
A 
air to enter your cylinder; a portion of this moisture is condensed as a | 
liquid film upon the interior surface of your tube; its reflective power 
is thereby diminished; less heat therefore reaches the pile, and you — 
incorrectly ascribe to the absorption of aqueous vapor an effect which 
is really due to diminished reflection of the interior surface o' 70 ' 
cylinder. 
five inches produce their proportionate absorption. The driest day, om 
the driest portion of the earth’s surface, would make no ap roach to 
proportional to the quantity of vapor present. It is next toa phy 
impossibility that this could be the case if the effect were due to co 
densation. But lest a doubt should linger in the mind, not only bee a 
the plates of rocksalt abolished, but the cylinder itself was dispensed with. 
Humid air was displaced by dry, and dry air by humid in the free atmo 
ere ; the absorption of the aqueous vapor was here manifest, as in all 
; 
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a 
No pets therefore, can exist of the extraordinary opacity of this 
substance to the rays of obscure heat; and particularly — — as are 
emitted by the earth after it has been wavhe rmed by the sun perfectly — 
nope that more than ten per cent of the terrestrial aan from : 
; 
/ 
say scovered peoerty of sen vapors must exert on the pheno- . 
mena = seo ogy. : 
fast. in the iron grip of frost. The aqueous vapor pana a - 
local dam, by which the temperature at the ori surface is dee pice 
the dam, _— finally overflows, and we give to space all that we 
receive from the sun. 
by their levity, —. have penetrated the vapor screen, which lies close 
to the earth’s surface, what must occur? : 
of aqueous vapor is 16,000 times that of air. Now | we 
fo abnor aud the power trad are perfectly reciprocal and pro- 
_ portion The atom of aqueous’ vapor will st radiate W 
0 times the energy of a an atom of air. Imagine then this 
