On the Production of Light by Chemical Action. 163 
being red, and that ash gray in the position of the yellow, which 
I have described in my former memoir.* 
In the form of experiment here made, the combustion is of 
course merely superficial, and the rays come from the charcoal 
not as an incandescent but as a burning body. 
Ill. Of the constitution of flames; proving that they consist 
of a series of concentric and differently colored shells. 
I regard the foregoing experiments as affording the means of 
explanation of the much more complicated phenomena of flames ; 
and proceed to inquire whether the principle I have just brought 
forward, of the codrdinate increase of refrangibility an chemi- 
eal action, will hold good for them: premising the experiments 
now to be detailed with the following considerations. 
| common flames, as is well known, consist of a thin shell 
of ignited matter, the interior being dark ; the combustion taking 
effect on those points only which are in contact with the air. 
From the circumstances under which the air is usually supplied, 
this ignited shell cannot be a mere mathematical superficies, but 
must have a sensible thickness. If we imagine it to consist of 
a series of strata, it is obvious that the phenomena of combustion 
are different for each. The outer stratum is in absolute contact 
with the air, and there the combustion is most perfect. But by 
we analyze the light that 
ies of a flame, we in eflect 
Srcorn Srntes, Vol. V, No. 14.—March, 1848. 22 
