6 Sir Humphry Davy on the fire-damp of coal mines , and on 
Different specimens of these gases were tried by the test 
of exposure to chlorine both in darkness and light: they 
exhibited no marks of the presence of olefiant gas or hydro- 
gene; and the residuum produced by detonation with chlorine 
showed them to be free from carbonic oxide. 
It is evident, then, that the opinion formed by other chemists 
respecting the fire damp is perfectly correct ; and that it is 
the same substance as the inflammable gas of marshes, the 
exact chemical nature of which was first demonstrated by Mr. 
Dalton; and that it consists, according to my view of definite 
proportions, of 4 proportions of hydrogene in weight 4, and 
1 proportion of charcoal in weight 11.5. 
I made several experiments on the combustibility and ex- 
plosive nature of the fire-damp. When 1 part of fire-damp 
was mixed with 1 of air, they burnt by the approach of a 
lighted taper, but did not explode ; 2 of air and 3 of air to 1 
of gas produced similar results. When 4 of air and 1 of gas 
were exposed to a lighted candle, the mixture being in the 
quantity of 6 or 7 cubical inches in a narrow necked bottle, 
a flame descended through the mixture, but there was no 
noise : 1 part of gas inflamed with 6 parts of air in a similar 
bottle, produced a slight whistling sound : 1 part of gas with 
8 parts of air, rather a louder sound : 1 part with 10, 11, 12, 
13 and 14 parts, still inflamed, but the violence of combustion 
diminished. In 1 part of gas and 15 parts of air, the candle 
burnt without explosion with a greatly enlarged flame ; and 
the effect of enlarging the flame, but in a gradually dimi- 
nishing ratio, was produced as far as 30 parts of air to 1 
of gas. 
The mixture which seemed to possess the greatest explo- 
