commerce, and that it applies only within certain limited territories and does not materially affect the problem if we consider the world at large. Because several million people happen to make a living on Manhattan Island by substituting capital for land, it does not follow that the whole world could do the same, nor would it follow even if two hundred million people could make a living in a similar way within the present boundaries of the United States. Our country would not then be truly self-supporting, in any large and complete sense, any more than the Island of Manhattan, or the Island of Great Britain, or Belgium now is. All urbanized populations bring in the products of the soil from regions where soil is abundant, work them over in industries which require much labor and little land, and send them out again to exchange for raw materials, living all the while on the profits of this class of transactions. As these urbanized populations grow, it is necessary to send farther and farther, to wider and wider fields for the products of the soil. Why is this necessary? Why should not England get all her agricultural products from her own area? Merely because of the law of diminishing returns. To double the produce of the English farms would not double, but treble or quadruple, the cost of cultivation. That is what the law of diminishing returns means, and it never meant anything else. Because of this law England finds it cheaper to send to distant countries for her wheat and beef, paying the cost of transportation, than to cultivate her own farms with a sufficiently high degree of intensity to enable her to live off her own soil.
To be sure, the available waste land of the world is not all in use yet, and our increasing urban populations will be able, for many years to come, to thrust their transportation systems out farther and farther in order to secure these products which require land—space—superficial area for their efficient production. Therefore we need not worry about the food supply for a long time to come. It may, however, surprise some of our urban economists to learn how little modern science has enabled us to economize land, our inventions and machines having in the main, increased the product per unit of labor rather than the product per unit of land. So little has it increased the latter that, taking into account the rise in the standard of living, it is probable that it takes as much land to support the average family in any part of the civilized world to-day as it did when Malthus wrote his epoch-making work on population. By support I mean support in a complete economic sense. I mean that it probably takes as much land to supply all the things actually consumed by the average family to-day as it did then.
We could, to be sure, if we chose to do so, consume more of those crops which respond to intensive culture, such as corn, potatoes, bananas, etc., and less of those which yield their best results under ex-
