On the Heat in the Sun’s Rays. 379 
some in amount from the different degrees of brightness in the 
sun. The change in the temperature of the air was still to 
added, and the conclusion seemed to be irresistible, that the sun’s 
trays in passing into the heated room acquired a temperature that 
the ad not derive from the sun. ; 
he experiment was next repeated with different temperatures 
of the room, and it was found that the intensity of the rays de- 
pended upon the heat of the room. Indeed in the coldest 
weather in winter I could impart to them a power which belonged 
a summer’s sun 
ameter and twenty-two in height. A copper base was adap 
to it with a groove around the outer edge into which the receiver 
fi ashes the point was 
purpose of simultaneous comparison. he air within it was 
Cooled by inserting a tin canister filled with frigorific mixtures. 
The thermometers were supported within the receivers, and thus 
atthe same time the same rays could be tested in the opposite 
extremes of temperatures. 
_ I subjoin, as an example, the following table (p. 380) contain- 
Ing the results of an experiment made in February last, at eight 
O'clock in the morning. It was a clear day an shone 
through a window into the room where the instruments were 
* 
