uses of coal is found in the factories where numerous
articles of iron and steel are made. The world of industry depends so much
upon iron that it is called the metal of civilization.

[Illustration: Iron Smelters.]

The iron and coal industries are closely related, for coal is used to make
iron into steel. If you stay in Pennsylvania you may catch a glimpse of
the process by which iron is made usable.

As it comes from the mine it is not pure, but is mixed with ore from which
it must be separated. In the regions of iron-mines you will see towering
aloft here and there huge chimneys, or blast-furnaces, at times sending
forth great clouds of black smoke and at times lighting the sky with the
lurid glow of flames. In these big blast-furnaces, the iron ore and coal
are piled in layers. Then a very hot fire is made, so hot that the iron
melts and runs down into moulds of sand, where it is collected. This
process is called smelting.

The iron thus obtained, though pure, is not hard enough for most purposes.
It must be made into steel. Steel, you understand, is iron which has again
been melted and combined with a small amount of carbon to harden it.

At first this was an expensive process, but during the last century ways
of making steel were discovered which greatly lowered its cost. As a
result, steel took the place of iron in many ways, the most important
being in the manufacture of rails for our railroad systems. Since steel
rails are stronger than iron, they make it possible to use larger
locomotives and heavier trains, and permit a much higher rate of speed and
more bulky traffic. All this means, as you can easily see, cheaper and
more rapid transportation, which is so important in all our industrial
life.

Steel has an extensive use, also, in the structure of bridges, of large
buildings, of steamships and war vessels, as well as in the making of
heating equipment, tools, household utensils, and hundreds of other
articles which we are constantly using in our daily life. If you should
write down all the uses for this metal which you can think of, you would
be surprised at the length of your list.

These four great industries give us a little idea of how men make use of
the products of the farm, the mine, and the factory in supplying human
needs. Each fulfils its place, and we are dependent upon all. That means
that we are all dependent upon one another. There would be little in life
for any one if he were to do w