Not only the men, but the women and children as well, are affected by these food values, because it is from the extra money left over after the actual cost of living is taken out that the clothing, the house-furnishings, books, pictures, music, travel and all the pleasures of life must come. Great as are our harvests, we are not raising much more than enough for our present needs. Each year we are using more of our food at home, and have less to export to other countries. In a few years more the public lands will all be taken, and there will be comparatively little more land than we now cultivate to supply a population that will be many times as great as at present. Men who watch the great movements of the world tell us that the time is coming before many years when there will not be food enough to supply all our people, when we shall be buying food from other countries instead of selling to them, when we shall have famine instead of plenty unless we realize the danger and at once set about to make the most of every acre of our land. James J. Hill, the great railroad builder of the Northwest, and one of the best informed men of the country on food production and the increase of population, is doing a great work in pointing out these dangers to the people on every possible occasion. Watching the great food-producing region of the country, he has noted that each year the yield per acre is growing less, and the population steadily more. He tells us that when our first census was taken only four per cent. of the people lived in cities, that fifty years ago one-third of the people lived in cities, and two-thirds in the country, that is, two-thirds of the people were furnishing food to the remainder. Now conditions are almost exactly reversed. Only one-third remain in the country, and must supply the food, not only for themselves, but for all the two-thirds who are not food producers, so that the food supply is lagging far behind the demand. The price of corn has advanced from twenty-five cents to sixty-five cents a bushel in ten years, and this in turn raises the price of live stock. And so all along the line. Prices are growing higher all the time because not enough food is being produced to supply the demand. So we can see that it is absolutely necessary that the soil be properly cared for if we are to continue to increase and prosper, for as Secretary Wilson has said, "Upon the fertility of the soil depends the whole business of agriculture." The soil is exhausted in two ways: (1) By erosion, or the carrying away of the entire soil itself. (2) By so using the soil that one or more of its principal elements are worn out. We shall consider this form of soil exhaustion first, because it more directly concerns the work of every farmer.