2 76 THE POPULAR SCIENCE MONTHLY
entirely too small for silver, while many statisticians are using the 2,000-lb. ton for both metals. A ton of gold would make a little cube measuring about 14^ inches along its edges, and of silver, one of 17^ inches. Measure these off on your desk ruler and it will become ap- parent into what small packages nature can pack her valuables if she has a mind to, for the golden cube will represent $603,861.22, while that of silver, at the price of 55 cents per ounce, will be worth $16,- 041.30. Now, in 1850, just before California and Australia began to produce the former metal in quantity, the world's annual crop of gold was about 60 tons, which could all be stacked away in a small bank vault, having a floor space four feet square and a height of six and one half feet — a mere closet. But in 1906 the crop amounted to 675 tons, more than ten times as much, and to accommodate it would require a vault of the same height, but with a floor space of twelve by fifteen feet — quite a good-sized room. As to silver, in the fifty-six years that have elapsed since 1850, the world's annual production has grown from about 975 to 6,360 tons. Carefully piled up in cubes this mass of the white metal would nearly fill up a room 100 feet long, 20 feet wide and 10 feet high.
In iron, the metal which is at the basis of the civilization of the day, the record is, if possible, even more remarkable. Reasonably ac- curate statistics of the world's production do not go back of the year 1865, when it amounted to 10,009,632 tons. In 1906 the output was 64,983,481 tons, showing an increase of nearly 650 per cent, in the forty years. Such figures are not easily grasped by the mind, but let us make the effort. Metallic iron weighs seven and a half times as much as an equal bulk of water. A cubic foot of water will weigh in round figures 62 pounds, and consequently one of iron will tip the beam at 465 pounds. This means that a ton of metal will contain a little more than four and a quarter cubic feet, and that a cube of it measuring about nineteen and a half inches along its edges will weigh a ton. Hence, the output of the year 1906, if put in the form of a solid cube, would contain 279,429,000 cubic feet, and would measure along its edges nearly 650 feet. A city block in New York measures, say, 250 by 500 feet, and its area is about 125,000 square feet, or roughly, three acres. Ten such blocks would be completely covered to the depth of 220 feet by the world's output of iron during the year 1906. This would be the equivalent in dimensions of an eighteen sk>ry building, completely covering a thirty-acre tract of land in the metropolis of America.
But to gain even a more striking impression of what the metal is to modern man, let us figure up the total production of the iron mines of the world during the last eventful forty years. In round numbers.