168 On the Production of Light by Chemical Action. 
on examination through the telescope, though all the colors had 
increased in brightness, the most remarkable effect took place 
among the extreme refrangible rays. Far out of the limits of the 
ordinary spectrum, a ray of great purity and force was developed, 
as represented in No. 5. Its color is violet. 
I have made similar experiments on many other flames beside 
those here mentioned. [t is not necessary to relate them in de- 
tail, for they give the same results. In every instance of com- 
bustion i in the air, when the flame is bright enough, all the colors 
are visible ; and when the combustion takes place i in oxygen, they 
are increased in intensity. With hydrogen gas and alcohol, the 
light is so feeble that the eye cannot catch the terminal rays, but 
as soon as the combustion is made in oxygen, the red and the vio- 
let both appear, the latter however predominating. Several of 
these spectra both in air and oxygen are represented in fig. 1. In 
o. 9 the letters mg and mb roe a maximum of green and 
of blue light in the form of bright line 
It does not require the use of a stn to satisfy one’s self of 
the change of tint that flames exhibit when the chemical action 
increases. In reality it is only necessary to contrast the color of 
the light emitted in air and in oxygen gas. In the latter case, 
rays of a higher refrangibility uniformly arise 
On the evidence furnished by the foreg going experiments, I re- 
gard all flames as consisting of a shell of ignited matter, in which 
combustion is going on with different degrees of rapidity at dif- 
ferent depths; being most rapid at the exterior, where there is a 
eombustion is incipient, ane from with’ ed light ISSUES ; a 
follow orange, yellow, green, blites indigo oi violet circles 
cession; the production of each of these tints being dependent 
on the rapidity with which chemical action is going forward, that 
is, on the amount of oxygen present, the tints gradually shading 
off into one another, and forming as I have already said a circular 
raiubow. An eye placed on the exterior of such a flame sees all 
the colors conjointly, and from their general mixture arises the 
predominant tin 
An examination of the flame of a candle vertically, contin 
this conclusion. For the red As hints on the top of the 
and the blue towards its botto 
From this, which may be peek” as the normal flame, the 
flame of cyanogen differs, It must consist of as many concen- 
tric strata as the prism separates it into regions of definite refran- 
gibility. ‘The interior part is therefore divided into four red lay- 
ers, followed by one of orange, one of yellow, seven of green; 
&c. are two great inactive spaces towards the outside of 
