"We hang before the portal to a long avenue excavated in a deeper-seated
bed of coal. In some of the dark and dusty chambers which open here the
miner's pick is heard, and now and then the muffled report of the
miner's blast comes echoing through the vaulted aisles.

"But this is not the station where we are intended to stop. Our car
moves on, and we plunge through two hundred feet more of the rocky rind
of the earth. Above us the mouth of the shaft seems narrowed into an
insignificant hole; before us opens a dark street, over which, on a
tramway, mules are hauling carloads of coal, which is starting on its
way to the surface. Miners with picks are moving to and fro; the sound
of hammers is heard, the signs of busy life are about us.

"In the seam of coal, passages are cut about eight feet wide and about
five feet high. These are shored up with timber or iron, to prevent them
giving way.

"A main gangway may be half a mile or a mile in length. From this, at
suitable intervals, passages are quarried out, running at right angles
with the main gangway.

"These chambers cross and recross one another, and make a network of
passages like the streets of a city.

"Along the principal passages tram-rails are laid to carry the coal to
the shaft. The trams are moved over the track by mules, which often
spend their lives underground. They are stalled and fed in side rooms
cut out of the coal.