This is why, during all this century of invention and progress, agriculture has only improved from time to time on very limited areas. Happily there have always been small oases, neglected for some time by the vulture; and here we learn what intensive agriculture can produce for mankind. Let us mention a few examples. In the American prairies (which, however, only yield meagre spring wheat crops, from 7 to 15 bushels acre, and even these are often marred by periodical droughts), 500 men, working only during eight months, produce the annual food of 50,000 people. With all the improvements of the last three years, one man's yearly labour (300 days) yields, delivered in Chicago as flour, the yearly food of 250 men. Here the result is obtained by a great economy in manual labour: on those vast plains, ploughing, harvesting, thrashing, are organized in almost military fashion. There is no useless running to and fro, no loss of time--all is done with parade-like precision. This is agriculture on a large scale--extensive agriculture, which takes the soil from nature without seeking to improve it. When the earth has yielded all it can, they leave it; they seek elsewhere for a virgin soil, to be exhausted in its turn. But here is also "intensive" agriculture, which is already worked, and will be more and more so, by machinery. Its object is to cultivate a limited space well, to manure, to improve, to concentrate work, and to obtain the largest crop possible. This kind of culture spreads every year, and whereas agriculturists in the south of France and on the fertile plains of western America are content with an average crop of 11 to 15 bushels per acre by extensive culture, they reap regularly 39, even 55, and sometimes 60 bushels per acre in the north of France. The annual consumption of a man is thus obtained from less than a quarter of an acre. And the more intense the culture is, the less work is expended to obtain a bushel of wheat. Machinery replaces man at the preliminary work and for the improvements needed by the land--such as draining, clearing of stones--which will double the crops in future, once and for ever. Sometimes nothing but keeping the soil free of weeds, without manuring, allows an average soil to yield excellent crops from year to year. It has been done for forty years in succession at Rothamstead, in Hertfordshire. However, let us not write an agricultural romance, but be satisfied with a crop of 44 bushels per acre. That needs no exceptional soil, but merely a rational culture; and let us see what it means.