382 On the Heat in the Sun’s Rays. 
Ame. XXXI.— Circumstances sapecing sa Heat of the Sun’s Rays ; 
by Eunice Foor 
(Read before the American Association, August 23d, 1856.) 
My investigations have had for their object to determine the 
different circumstances that — the thermal action of the rays 
of light that proceed from the 
Several oe have been awe ed. 
action increases with the density of the air, and 
is dirashinhad as it becomes more rarifie 
The experiments were made with an air- pump and two cylin- 
drical receivers of the same size, about four inches in diame- 
ter and thirty in length. In each were placed two thermometers, 
and the air was exhausted from one and condensed in the other. 
After both had acquired the same temperature they were placed 
in the sun, side by side, and while the action of the sun’s rays 
rose to 110° in the condensed tube, it attained only 88° in the 
other. I had no means at hand of measuring the degree of con- 
densation or rarefactio 
he observations taken once in two or three minutes, were a8 
follows: 
Exhausted Tube H Condensed Tube. 
In shade. Tn sun. In shade. In sun. 
vis) 80 45 80 
46 82 48 95 
80 a 80 100 
83 36 82 : 105 
84 88 85 110 
This circumstance must affect the power of the sun’s rays in 
different places, and contribute to produce their feeble action on 
“Bascal. i on mountains, 
cond e action of the sun’ ter 
in moist aha; in dry air. ee 3 me ae 
In one of the receivers the air was saturated with moishtte-= 
in the other it was dried by the use of chlorid of calcium. 
ve were placed in the sun as before and the result was as 
follow: 
Dry Air Damp Air. 
Tn shade In sun In shade. ee 
75 15 
78 ¢ 78 
82 102 82 106 
82 104 82 110 
82 105 82 114 
88 108 92 120 
