1815.] Carlureted Hyarogen Gas of Coal-Mines. 173 
meeting with them, it issues into the mine with a considerable 
velocity. These gas-yielding rents are frequently met with in the 
coal-mines round Newcastle-on-the-Tyne; and the gas is often 
discharged into these mines in such streams, as to be compared, in 
force and quantity, with the air from powerful blast furnaces ; but 
the quantity of gas discharged, however great at first, continually 
decreases till the rents cease to yield it. 
» The gas-yielding parts of the coal differ considerably in dimen- 
sions ; they are situated at variable distances from one another; and 
the quantity of gas varies very much in different parts, as well as in 
different situations in any one part. Sometimes the gas-yielding 
parts have the characteristic appearance of the common coal, but 
occasionally they are softer, in small pieces, or dusty; in some 
parts iron pyrites is abundant; in others it is not found; water 
sometimes enters the mine along with the gas, but often the gas 
comes off alone ; but the coal has its characteristic appearance, or 
is soft, in small pieces, or dusty, in many parts which give out 
water, but not gas; so that the parts which produce this gas, appa- 
rently, are not essentially different to those which do not pro- 
duce it. 
When the carbureted hydrogen gas leaves the coal alone, it: 
comes off silently ; but when accompanied with water, it always 
makes a noise. When it enters the mine, along with water, from 
many pores, in small quantities, and at intervals, various sounds 
are produced, which have some resemblance to those expertly made 
on the musical glasses, but which are not so loud, though more 
agreeable. If the gas escape much quicker, the sounds are consi- 
derably lower, but not so various as in the first instance: this is a 
simmering noise, and would be well imitated by the noise from the 
pipes of a few tea-kettles when boiling gently. But if the gas 
escape more copiously than in the last instance, it makes a hissing 
noise, not unlike, but not so loud; as that made by the steam 
escaping quickly from the safety valve of a steam-engine. 
If the gas is set on fire as it enters a working, when the atmos- 
pheric current is traversing the mine, its inflammation is carried on, 
close to the sides of the coal wall, under different circumstances. 
Where the gas enters the mine sparingly, but from many pores and 
seams, to set it on fire, the candle must be moved in every direction 
along the sides or forehead of a working ; then it will inflame the 
gas issuing from one pore, after it has done so with that from’ 
another as it moves forwards ; and each inflammation will resemble 
in sound and appearance that which is produced by the firing of two 
or three grains of gunpowder. When it enters more abundantly 
‘after the gas from one pore is fired, the burning gas fires the gas 
from many other pores, during which.the flame flies from the first 
pore in avery varying direction, and in a very fantastic and enters 
taining manner; for sometimes it runs horizontally for a small dis- 
tance, then bends obliquely in different directions, then perhaps 
horizontally, and then obliquely again, till it ceases, During these 
