172 On the Origin of the [Srer. 
Articre IT. 
On the Origin of the Carbureted Hydrogen Gas of Coal-Mines. 
By Mr. John 3B. Longmire. 
(To Dr. Thomson ) 
SIR, 
Tue carbureted hydrogen gas of coal-mines having lately at- 
tracted the attention of philosophers, as well on account of the 
ravages it commits, when ignited, on the mines and miners, as on 
its mode of formation, I have drawn out the following essay from 
a manuscript copy of observations made on this gas in different parts 
of England, Wales, and Scotland ; and if you think it so interesting 
as to ensure its insertion in your Annals ef Philosophy, it is very 
much at your service. 
Lam, Sir, your very humble servant, 
June 30, 1815. Joun B. Lonemire. / 
Many opinions have been entertained respecting the origin of the 
inflammable air of coal-mines. Some writers attribute its existence 
in these mines to the agency of iron pyrites : the pyrites, they say, 
decomposes the water, unites with its oxygen, and becomes sulphate 
of iron or green vitriol, while its hydrogen is set at liberty ina 
gaseous state. Other persons assert that the coal is undergoing a 
slow decomposition, and that the inflammable air and carbonic acid 
gas are given out by it in consequence. And other persons maintain 
the opinion that it exhales from the putrefying animal and vegetable 
matter in the stagnant water of coal-mines. But before we con- 
clude as to its origin, let us carefully examine its mode of entry into 
the mine. 
The carbureted hydrogen, gas proceeds from the body of the coal, 
and generally enters the mine from the pores, sometimes from the 
seams of distinct concretions, and occasionally from small rents of 
the coal. A miner extends a common working at the rate of two. 
or three yards every week ; and if he is, cutting through the gas- 
yielding parts of the coal, they generally discharge all their gas, or 
as the miner calls it, “‘ bleed off,” as fast as he advances; so that 
the greatest quantity of the gas always enters a working near its 
forehead. But, although the gas is exhausted in the most of these 
workings as fast as they are driven, there are many places where the 
coal continues to yield gas for several weeks, or months, after work- 
ings are driven past them. ‘This gas, besides entering the mine 
from the coal, sometimes proceeds from small rents in the incum- 
bent strata. In many of the coal formations these rents are small, 
not numerous, and generally only simply filled with gas; but in 
some they are large, numerous, and filled with gas, which appears 
to have been forced into them by a compressing power ; for on 
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