MISCELLANEOUS
The supplies of many of the materials used in buildings and bridges, such as stone, gravel, clay, cement and lime are so great that they appear inexhaustible, and need of care in their use is not so much to be considered as is their development to take the place of other resources.
In the past they have not been used freely because wooden buildings have been so much cheaper; but cement, concrete and brick are now manufactured much more cheaply, on account of improved methods, while the price of lumber has been increasing rapidly. Within the last ten years, the value of cement manufactures has increased nearly six times. In 1900 we used seventy pounds of cement for each person; in 1907, two hundred and twenty-eight pounds. The value of brick and other products made from clay has doubled in the same period and is now $160,000,000, while the value of building-stone quarries is three times as great as it was ten years ago. There are many reasons why these materials should take the place of wood; as they are stronger, more durable, do not require paint, and are so much less liable to loss by fire.
The waste of minerals used in building is due to improper and reckless methods of taking them from the ground and preparing them for market and in careless methods in manufacturing.
Of such minerals as quartz, grindstone, millstone, emery stone, mineral paints, talc and salt, there seems to be enough to meet the needs of the future as well as the present. Such supplies as sulphur, asphalt, magnesia, borax, and asbestos, as well as coal and iron, are not very plentiful. If used carelessly, they will be exhausted in a few years; if wisely, they may be expected to last beyond the limits of the present century.
Our supplies of quicksilver, antimony, graphite, mica, tin, nickel, platinum, and many minerals less well known, as well as our petroleum, natural gas, copper, gold, silver, lead, zinc, and phosphate rock will be almost exhausted well within the present century unless large new deposits are discovered.