166 On the Production of Light by Chemical Action. 
tint. This agrees with what has been observed as to anthracite 
and charcoal, for with carbonic oxyd a very limited supply of ox- 
ygen can bring about the maximum chemical action, and there- 
fore liberate in abundance rays of maximum. refrangibility. 
Pigs i: 
ABC d E ce 
l | i } I Solar spectrum. 
itis 
‘ 4 ~ Spirit lamp. 
: Se ee Carbonic oxyd. 
i : 
i | ae ene eee Seen 7 j 
; Cyanogen 1n air. 
I ao i | 
+ DONO DE00UI0 LI] Y eaee 
i 
6} Feces Oi] Jamp in air. 
7i: ' ; Oil lamp in 
i i i oxygen. 
8 i. § Hydrogen in 
( Ramin elena ere Ra oxygen. 
+ (IO0000 vn oe a 
10 |] [| [] {] [] Blowpipe cone. 
b 
Spectra of various flames.—The dotted line db, is Brewster’s yellow ray. 
This condition of things is inverted in the case of cyanogen 
It is the nature of its flame to be enveloped as it were in a 
sheet of nitrogen arising from its own burning; and this neces- 
sarily impedes the access of air, and checks the intensity of the 
chemical change; a check which is at once betokened by the 
emission of a predominant number of rays of low refrangibility, 
or of a red color. 
But there is a striking difference in the conditions under which 
earbonic oxyd and cyanogen burn. In the case of the former the 
whole gas is combustible, in the latter the carbon alone, and we 
have in reality introduced an incombustible element into 
flame ; for as the carbon burns, the incombustible nitrogen is set 
free. It occurred to me, in selecting this gas for experiment, that 
this condition should impress a physical characteristic on the 
flame. I thought it was not impossible that dark lines in its spec- 
trum might be the result; because there must be a peculiar ar- 
rangement of the burning strata, which together make up the 
shell of the flame, every two atoms of carbon setting free one of 
nitrogen. I did not know until subsequently that this flame had 
been examined by Mr. Faraday. Having therefore confined some 
cyanogen, made from the cyanid of mercury, in a glass gas-hold- 
er, which was filled with a saturated solution of common salt, I 
from the jet pipe, and found that what I had surmised 
