COAL MINING. 361 
the miner’s lamp will burn with clearness in a deadly mixture of this 
gas. When 3 per cent: of sulphureted hydrogen is found in the air of 
mines, human life cannot exist except with suffering. It produces faint- 
ing fits, giddiness and asphyxia. 
These gases are generated in mines from a variety of causes. FT ire- 
damp escapes from the fissures and minute pores of the coal and its as- 
sociate strata. It is seldom met with in very alarming quantities in 
drift or level-free mines, or in shafts of moderate depth. The most . 
fiery mines are those between 600 and 1200 feet in depth; below this 
zone fiery beds of coal are met, but it is the exception rather than the 
rule. Fire-damp exists in mines in a highly compressed state, being 
pent up in the interstices and fissures of the coal by the counterpoising 
pressure of the atmosphere. When the barometer falls, indicating a 
lightening of atmospheric pressure, the pent up gas escapes in great 
volumes. Many fatal mining explosions are due to this cause. The 
gas also frequently escapes in the form of blowers, which produce a 
hissing noice, and which, when ignited, burn like a long blow-pipe. 
The fire-damp of coal mines is one of the most fatal and dangerous 
elements ever encountered in human enterprise. 
Black damp, like fire-damp, is liberated from the coal and its asso- 
ciate rocks; it is also generated by the burning of lights in the mine, 
by the exhalations of men and animals, by decaying woodwork, and by 
decomposing strata. The gases formed by blasting also aid in the 
formation of black damp. This gas is perhaps a more deadly, as it is a 
more subtle enemy of the miner than even fire-damp ; the effects of fire- 
damp are instantaneous, while those of black damp are slow in opera- 
tion, gradually but surely undermining the constitution, and killing its 
victims by inches. 
White damp is formed largely from the products of exploded gun- 
powder; it is also generated freely in waste and abandoned parts of 
mines, particularly where breeding fires are liable to break out. Both 
sulphureted hydrogen and carbonic oxide are formed by breeding fires. 
The presence of these gases in mines makes ventilation a para- 
mount consideration in working coal or other minerals. Above ground 
vitiated air immediately flies upward into space, but the air of {mines 
has to circulate from one working-place to another, frequently traveling 
from 10 to 12 miles, and supplying 300 men and many horses before it 
reaches the upcast shaft, and is delivered to day. As it moves along the 
