By means of these three industries—cotton, wheat, and cattle—we are provided with food and clothing. But besides these necessaries, we must have fuel. We need it both for heat in our households and for running most of our engines in factories and on trains. Our chief fuel is coal.
To see coal-mining, western Pennsylvania is a good place for us to visit. Were you to go into a mine there you might easily imagine yourself in a different world. In descending the shaft you suddenly become aware that you are cut off from beautiful sunlight and fresh air. You find that to supply these every-day benefits, which you have come to accept as commonplace, there are ventilating machines working to bring down the fresh air from above, and portable lamps, which will not cause explosion, to supply light, and that, where there is water, provision has been made for drainage.
The walls of the mine, also, have to be strongly supported, in order that they may not fall and crush the workers or fill up the shaft. In deep-shaft mines, coal is carried to the surface by cages hoisted through the shaft. It is sorted and cleaned above ground.
One of the largest 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.
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.