rs may be working. The places where the
men are taking out the ore are called "stopes," and to reach them
we have to crawl and creep through all sorts of winding passages,
now through a "manhole," and now down a long ladder which descends
into black depths.

From the stopes the ore, as it is blasted out, is shovelled into
chutes running down to some drift where there are men with cars.
Each car holds about a ton of ore, and after being filled it is
pushed along the drift and upon a cage which raises it to the surface.

[Illustration: FIG. 106.--HOMES OF MINERS, BISBEE, ARIZONA]

The mine is not wet, for there is so little rain in this region
that there are few underground streams. In places, however, it is
warm, for when the oxygen of the air reaches the fresh sulphide
it begins to oxidize the ore; that is, it begins to burn it, and
change it into a different compound, just as fire changes wood
or coal. Wherever oxidation is going on, heat is produced.

Fresh air is constantly needed in these workings far underground.
A supply is forced down in pipes, and then allowed to flow back
to the surface. In this way a thorough circulation is kept up.

Underground one loses all thought of the changes between night and
day, for it is always dark there. Consequently we are surprised
on coming up from the mine to find that night has settled over
the town. Lights are twinkling everywhere, and miners with their
pails of luncheon are coming for the night shift.

Another interesting experience now awaits us in the form of a visit
to the smelter. Here the bright copper is extracted from the
rough-looking ores. How different the two substances appear! They
look as if they had scarcely anything in common.

The interior of the smelter seems like a bit of the infernal regions
set upon the earth. While watching what goes on, we might imagine
that we were far down in the earth, where Vulcan, the fire god, was
at work. At night the scene is particularly weird and impressive,
for the shadows and general indistinctness make everything appear
strange. The glowing furnaces, the showers of sparks, the roar
of the blast furnaces, the suffocating fumes of sulphur, and the
half-naked figures of the Mexican workmen, passing to and fro with
cloths over their mouths, form all together a bewildering scene.

The ore is first pulverized, and then placed in large revolving
cylinders, where it is roasted. A fire is started in the cylinder
at first,