273 
on the Production of Light and Heat. 
the air suffering any chemical change whatever, is not the 
light emitted identical with the heat received? This identity 
appears to be confirmed by the following observation : that 
if the solar ra} 7 s be made to converge upon one end of a 
blackened cylinder of metal, the other parts will become red 
hot, and emit light ; or, if the rays be converged upon the 
tube blackened, and air passed through it, the gold placed in 
the dark current will yield a constant light. 
The simultaneous absorption and emission of light, in a red 
hot body, is a subject of very difficult and abstruse investiga- 
tion, as it involves the nature of the constituent parts of mat- 
ter, and of their relative actions and arrangements. I shall 
not attempt to offer any hypothesis for explaining the various 
phenomena, as I have not been able to form one at all satis- 
factory to myself ; but shall proceed to state a few miscella- 
neous experiments and observations, which, though apparently 
unconnected, may yet be of some assistance to the speculation 
of some abler theorist. 
EXPERIMENT III. 
A quart of oil was poured into a bright tin vessel, which 
had a Fahrenheit's thermometer fixed in its neck. The mer- 
cury standing at 45 0 , the vessel was plunged into boiling water, 
and the time which elapsed before the mercury rose to 180° 
was exactly noted. I then blackened the exterior surface of 
the tin vessel, and, repeating the experiment, found the ther- 
mometer to require exactly the same time as before, to rise to 
the same degree. 
From the foregoing experiment it appears, that black matter 
