The next great use of iron is for buildings and bridges. The greatly increasing use of cement and concrete is reducing this and will reduce it still further. Cement is made from slag, or the refuse of iron ore—the clays and shales—and the cost of this valuable product is little more than the former cost of piling it away. By making the useless slag into cement the cost of iron production is lowered and at the same time the drain on the iron is lessened.
A large use of steel of the highest quality is for battleships, cannon, and war supplies. If the great nations of the world would agree to reduce their armament, one of the great drains on the world's iron, coal, and wood supply would cease, and these materials be put to improving the world.
The worst feature of it is that these war supplies are continually changing. They must be of the latest pattern, or they are of small value for fighting purposes. The construction of battleships differs greatly year by year, and the older ships are discarded to make place for newer and larger ones. It is said that our newest battleship alone could with a few shots destroy all of Admiral Dewey's fleet. The following is from a recent magazine article:
"It is admitted by naval officers that the ships of ten years ago are of obsolete type and would be useless against the new vessels. It is admitted that within ten years or less the new types will in turn become obsolete, and will be useless against the type of vessel certain to be evolved. That is, as soon as a vessel costing millions of dollars leaves the docks, she enters into active competition for a place on the junk pile."
The greatest improvement that can be imagined in the iron situation will be in the discovery and use of alloys or mixtures of iron with other materials. Steel, the strongest of all forms of iron, is an alloy of iron and carbon, and for various purposes these are further mixed with nickel and silicas. Many other alloys have been discovered within the last few years, and each makes possible new uses for iron requiring greater strength. One of the best of these is a mixture of iron and silicon, called ferro-silicon. Silica is one of the cheapest and most abundant materials of all the earth's products, so its combination with iron will greatly lengthen the life of the iron supply; and it is probable that in the future combinations of other materials will yield better and cheaper metals than any thus far produced.
The amount of metal which can be reworked is constantly increasing. Most of the iron factories remelt large quantities of old iron, to be used with the new, and this will lessen each year the demand on the ores. It is also possible that new deposits of iron ore will be found and these will greatly increase the supply. But from the whole iron situation we may draw the following conclusions:
First, the amount of iron remaining in the ground is very uncertain. It may be more, or it may be less, than the present estimate.
Second, if the estimates are nearly correct, and if the present rate of increase continues, all the high-grade ores will be exhausted by the time the small boys of to-day are the business men of the nation.
Third, the best methods of reducing the drain on the supply are, (a) The use of old iron as a mixture; (b) Carrying a part of the freight by water to reduce the amount of iron required by the railroads; (c) The larger use of concrete and cement to take the place of steel in buildings; (d) Lessening the amount used for war; (e) The use of alloys. This opens a large and promising field for invention. (f) More care in preserving articles made of iron. This is a practical thing for every person in our country to do. Every farm implement, or tool, that stands out in the rain or is left without shelter during the winter, every article carelessly lost or broken, has its part in making conditions worse. All that are well cared for help to make the iron supply last a little longer.