Page:Popular Science Monthly Volume 74.djvu/278

274 of no practicable use, even if they had desirable properties, have only to be searched for, to be found in sufficient quantity for our needs.

Returning to the eleven well-known true metals, viz., aluminum, copper, gold, iron, lead, mercury, nickel, platinum, silver, tin and zinc, wonderful progress has been made during recent years in the matter of their production. Few of us appreciate the extent to which we are absolutely dependent on some of these substances which, a generation ago, were so rare. It is quite impossible now to conceive of a metal-less civilization, or one in which they were so costly as to be practically unavailable for the ordinary affairs and circumstances of life. In the home, the office, the factory and the club they confront us everywhere. Upon the person of a day laborer ordinarily clothed, half of the list will usually be found, while in the home of the average well-to-do citizen every one, except perhaps platinum, will exist in more or less abundance. It will be both interesting and instructive to note just what amounts of these metals have been taken from the crust of the globe during recent years, for the benefit of our modern civilization.

This metal began to appear on the market as a costly curiosity, in 1888, just twenty years ago, commanding a price of $5 per pound, and the total world's output for that year did not exceed 50 tons. By the end of the century, however, the annual production had increased to nearly 5,000 tons, while the price had fallen to $1.50 per pound. Since then there has been a steady increase of output until during 1906 it amounted to about 20,000 tons, while the price had fallen to 35 cents, causing the metal to be available in so many ways and forms that the civilized world would now find very great difficulty in getting along without it. But, remarkable as has been this growth, it is as nothing to what may be expected in the near future. For aluminum is the most abundant of all the metals, existing in such enormous quantity in the crust of the earth, and in deposits so accessible and so easily mined, that it is certain to become, before another century has passed, and as soon as its metallurgy has been perfected, the rival and supplanter of iron. Every clay bank and slate quarry is a high-grade mine of the metal, only we have not yet learned how to extract it cheaply from these ores. Innumerable other rocks and formations contain it in various quantities. A well-known geologist has recently calculated that 8.13 per cent, of the earth's crust is aluminum, against 4.71 per cent, for iron, and less than one tenth of one per cent, for copper. Bulk for bulk, aluminum has one third the weight of iron. In tensile strength it is almost the equivalent of cast iron, though far inferior in that respect to steel. Yet the metallurgists are rapidly learning how to increase its strength by alloying