The Mining Industry
3
VALUE oF CHIEF MINE AND QUARRY PRODUCTS IN THE UNIT
(AVERAGE OF 1926 anp 1927)
L
STATES
NETALS
Iron (pig iron) . .
Copper
Lead .
Zinc .
Gold .
Silver .
Coal:
Bituminous
Anthracite
Petroleum
Natural gas
Cement
Stone
Sand
B
698,000,200
232,000,000
96,000,000
83,000,000
47,000,000
37.000.000
FUELS
,106,000,000
“18.000.000
1,554,000,000
1.310,000,000
309,000,000
281,000,000
193,000,000
.12.000.000
Stony ProbucTs
What a typical mine is like. In mining for metals and also for coal,
vertical shafts are usually sunk. In some mines they extend a mile
below the surface; practically always great elevators are needed
to carry the workmen and the cars containing the ores up and
down. From the shaft, nearly horizontal tunnels or gal-
leries are dug at various levels to follow the veins that contain
the mineral. In the great mines there are many shafts, and the gal-
leries form a complicated network. Occasionally rooms or chambers
are formed where large masses of ore have been mined. In galleries
and chambers the roofs must be supported by strong beams to pre-
vent the overlying rock from falling. The galleries contain railway
tracks for the speedy transportation of both the ore and the miners.
Often electricity is used in lighting the galleries, in hauling the
trains of cars, and in driving the drills. In many mines mules do
the hauling; they thrive in their strange homes so long as they are
well cared for, and many of them spend their lives under the ground.
Most mines must be drained and ventilated. Water is contin-
ually seeping out of the surrounding rock, and it would soon flood
the mine if powerful pumps were not employed. The presence of
large numbers of men and perhaps animals causes the air in the mine
to become foul, and the smoke from the lamps in the miners’ caps
and the gases that are given off by the explosions when the rock is
blasted make it still worse. The air, especially in coal mines, may
also be contaminated by gases that come from the rocks themselves.
