Luckily aluminum is contained in common clay and in a great number of rocks, so that the supply is practically unlimited. The chief drawback is that to extract it from the ores strong electric currents are required. Therefore the great aluminum plants are located where the ore occurs near powerful waterfalls such as those of Schaffhausen, Switzerland, and Niagara Falls. Savoy in France and the mountainous portions of Germany and Italy are also the seat of aluminum factories. If power could be obtained cheaply enough, aluminum would soon be used more than any metal except iron. The towns where it is made are apt to be located in pleasant parts of the country, for that is where the water-power is found. They do not have a large body of low-grade laborers working under ground, for the ore is taken from open quarries requiring relatively little labor. Moreover, the amount of machinery and of skilled work required in the production of aluminum is unusually large. Alto gether aluminum has a large number of favorable characteristics in its effects on man.
Why We Need to Conserve our Mineral Deposits.—Minerals far
more than forests need to be carefully conserved. Forests will grow again, but when minerals have once been destroyed they can never be replaced. Among the metals discussed in this chapter gold and silver are conserved with great care, for everyone is careful not to lose the smallest bit of either. Yet they need to be conserved far less than the other metals, for they play little part in the world's work. Iron plays so great a part that our supplies of that metal are our most important mineral resource. As yet, however, they have not been seriously diminished, for there are vast quantities of low-grade ores. Aluminum is fortunately far more abundant than iron, and the supplies have as yet scarcely been touched. With copper the case is far more pressing. Its use is constantly growing, while the supplies are rapidly being exhausted. The same is true of many minor min erals, such as zinc, lead, phosphates, and tin. If they are once exhausted many of our industries will suffer seriously, and future generations will wonder how we could have been so careless.