onnecting with these are little
gravelike depressions two or three feet long and as close together as
can be. These are called "pigs." When the time has come, the workmen
gather about the furnace, and with a long bar they drill into the
hard-baked clay of the tapping hole. Suddenly it breaks, and with a
rush and a roar the crimson flood of molten iron gushes out. It flows
down the trench into the ditches, then into the pigs, till their whole
pattern is marked out in glowing iron. Now the blast begins to drive
great beautiful sparks through the tapping hole. This means that the
molten iron is exhausted. The blast is turned off, and the "mud-gun"
is brought into position and shoots balls of clay into the tapping
hole to close it for another melting, or "drive." The crimson pigs
become rose-red, darken, and turn gray. The men play streams of water
over them and the building is filled with vapor. As soon as the pigs
are cool enough, they are carted away and piled up outside the
building.

In some iron works moulds of pressed steel carried on an endless chain
are used instead of sand floors. The chain carries them past the mouth
of a trough full of melted iron. They are filled, borne under water
to be cooled, and then dropped upon cars. A first-class machine can
make twenty pigs a minute.

[Illustration: IN THE STEEL FOUNDRY

It is a dangerous business to visit a steel mill. Tremendous kettles
travel overhead on huge cranes, hot metal flows from unexpected
places, and there is a constant glow and steam and roar everywhere to
confuse the unwary.]

Most of the iron made in blast furnaces is turned into steel. Steel
has been made for centuries, but until a few years ago the process was
slow and costly. A workman's steel tools were treasures, and a good
jackknife was a valuable article. Railroads were using iron rails.
They soon wore out, but at the suggestion to use steel, the presidents
of the roads would have exclaimed, "Steel, indeed! We might as well
use silver!" Trains needed to be longer and heavier, but iron rails
and bridges could not stand the strain. Land in cities was becoming
more valuable; higher buildings were needed, but stone was too
expensive. Everywhere there was a call for a metal that should be
strong and cheap. Iron was plentiful, but steel was dear. A cheaper
method of making iron into steel was needed; and whenever there is
pressing need of an invention, it is almost sure to come. Before long,
what