Not
only that, but each shaft must have a complete outfit of winding
machinery coupled to separate engines, so that, in the event of an
accident happening to one shaft, the men below ground can be rescued
up the other."

"That sounds all right," said Anton, rather gloomily, "but suppose the
way to both shafts is blocked?"

"Not likely," Clem responded cheerfully, "if a mine has been properly
laid out. Take this one, there are half a dozen ways to get from the
face to the shaft."

"But Otto said--"

The other turned upon him sharply.

"I've had about enough of that Otto business! If you can't keep from
thinking about it, keep from talking about it, anyhow!"

To this rebuke Anton maintained a stubborn silence, and, without
another word said, the two walked on until they reached their
respective places of work.

In the gloomy world of below ground, where the dusty wall of sooty
black is the only landscape to be seen, one day is very much like
another. Reaching his room, Clem stood his tools in order along the
rib, hung his safety lamp on a nail which he drove into a prop
supporting the roof, and, reaching up so as to put one hand on the
roof, tapped it with the flat side of his pick to make sure that there
was no loose slate overhead. He then examined the coal face, as it had
been left by the hewer who had been working on the night shift, to
make sure that it had been properly spragged or timbered.

This done, Clem stripped naked to the waist, for it was hot in that
hole far below ground. Then, lying down flat on his side, his bare
shoulder resting on the gritty ground, he started to pick away the
coal at the level of the floor and just above it, making a
wedge-shaped hole extending under the seam for a distance in of three
feet.

Many mines, especially in America, use mechanical coal-cutters for
this back-breaking labor. These machines are especially useful in
mines where the coal-seams are less than 3-1/2 feet thick, and they
are well adapted to "long-wall" workings where the whole face of the
coal is removed in a single operation. Some are mounted with a toothed
bar which moves in and out, chipping the coal; other types are like
circular saws; several forms have the same action as a miner's pick,
the percussions being at the speed of two hundred strokes a minute,
the motive-power being compressed air.

In pillar-and-room workings, such as this Ohio mine, chain heading
machines were used. This American inv