But the natural scientists--the foresters, the physiographers, the geologists--have within a very few years been making themselves heard in warning. They have said that "the mountains of France, of Spain, and China have been denuded of their forests in large measure so that the supply of wood is inadequate to meet the needs of the people," [Footnote: C. R. Van Hise, "Conservation of Natural Resources in the United States," p. 3.] that "in Spain and Italy, though warm countries, the people suffer more from the cold than in America because of insufficient fuel," [Footnote: Van Hise, p. 2.] that "one-half of the people of the world go to bed hungry," [Footnote: Van Hise, p. 3.] or at any rate insufficiently nourished for the next day's work. But few listened to them except in the hills and in the valleys of abandoned farms. France, Italy, Spain, China were remote. The optimism fostered of new teeming acres and newly discovered mines was heedless of the warning. It tore down barns and built bigger, and it gave even more generously to the need of the hour and the day. But the scientists came even nearer home in their studies and statistics. These are some of the ominous and disturbing facts that are getting to the ears of the people out of their laboratories and experiment stations: The coal-fields of the United States (which lie almost exclusively in and upon the eastern and western edges of the Mississippi Valley) were, at the rate at which coal was used a few decades ago, practically inexhaustible. But the per-capita consumption has increased from about a ton in 1870 to 5.6 tons in 1907. [Footnote: Van Hise, p. 23.] Up to 1908, 7,240,000,000 [Footnote: Van Hise, p. 25.] tons had been mined, but over ten million tons were wasted in the mining of seven billions. You may recall the prophecy which I quoted earlier, that if the mining and wasting go on at the same rate of increase as in the past few decades the supposed illimitable fields will be exhausted in one hundred and fifty years--that is by the year 2050. [Footnote: Van Hise, p. 25.] This is one of the statistics of those watchmen on the walls who, instead of standing in high places with telescopes, sit at microscopes or over tables of figures. That seems a long period of time, one hundred and fifty years, but it was only a little longer ago that a French explorer saw the first signs of coal in that valley along the Illinois, and, as the scientist has intimated, there is no reason why we should not expect a future of thousands of years for the coal that has been thousands or millions of years in the making.