cities would be compelled to scatter and build many smaller cities, or else live as scattered families, in order to be nearer the sources of supply. Even with our present means of transportation there are limits beyond which it does not seem to be advantageous to concentrate our population. Consequently we find many small cities and towns whose people live by the indoor industries. They are nearer sources of supplies of various kinds, besides having more room for their own industries.

Increasing floor space by erecting tall buildings. The necessity for room for the indoor industries can be supplied in part by tall buildings. Floor space can be increased by as many stories as can be built, subtracting, of course, the space necessary for elevators, stairways, airshafts, etc. But after a very moderate height is reached, the cost of construction increases more than in proportion to the added floor space. To add one more story on the top of a tall building requires stronger walls all the way down, and also a better foundation. Besides, it costs more to carry the building materials to the greater height; the cost of elevator service to the top floor is somewhat higher than for lower floors. A twenty-story building is of a very moderate height in some of our large cities, where land is very scarce; but even this height would be absolutely unprofitable in a town where there was plenty of room on the ground.

Streets. The traffic needs of a busy population also make demands upon land for streets. Much the same methods are used to economize land for street purposes as for building purposes. The building of subways, sub-subways, elevated roads, and viaducts is a familiar method. It used to be suggested in a jocular way that a road through the air would also economize land. Flying machines may eventually transform that joke into a real economy. Superior pavements for the support of larger and more powerful vehicles will also economize road space somewhat, by permitting more traffic to be carried on over a street of given width.

Economizing agricultural land. These methods of economizing land are suited to urban rather than to rural districts. Space is required in agriculture, as suggested above, for the utilization of solar energy, soil, and moisture in plant growth. "Two-story farming," as Professor J. Russell Smith calls it, consists in growing tree crops and ground crops underneath the trees. Some space can be saved in these ways, where there is plenty of sunlight, soil, and moisture, but not a great deal. It enables the plants to utilize sunlight a little more effectively, perhaps, because the low-growing plants can use that which filters through the foliage of the trees; but if the trees use too much (that is, if the low-growing plants are shaded too much), their development is retarded. There may be some economy of soil fertility also if the trees send their roots deeper than the smaller plants. In that case the two kinds of growth do not compete directly for soil fertility. Where an abundance of artificial fertilizer can be used and water for irrigation is plentiful, an adequate supply of plant food and moisture can be supplied to both kinds of vegetation. In this case the limiting factor is sunlight. This is a factor for which we have not yet found a good substitute. Therefore we must continue to spread our cultivation over wider areas if we are to support larger populations.

Intensive farming. "Two-story farming" is only one phase of intensive agriculture, which may be defined as the use of large quantities of labor and capital in the cultivation of relatively small areas of land in order to get large crops per unit of land; that is, large crops per acre. As pointed out in Chapter XV, extreme efforts to increase the productivity of land tend to decrease the productivity of labor; that is, to reduce the product per unit of labor. When a country becomes thickly populated, however, if its people are unwilling to migrate to countries where land is abundant, the problem of economizing land becomes one of great importance. So long as it can find markets for the products of indoor industries, it may

bring the products of the soil from less densely populated countries. When these outside markets cease to expand, and it is therefore compelled to live more and more from the products of its own soil, it must perforce get more and more out of its soil. Intensive agriculture is then forced upon it. Yet, as a matter of observed fact, intensive agriculture the world over is associated with the poverty of those who actually work on the soil, though it may be also associated with the riches of those who own the soil.

Intensive farming and poverty. This impoverishment of the worker on the soil where the soil is intensively cultivated is not absolutely necessary except where the intensive cultivation is carried to extremes. It is a necessary result, however, if the attempt is made to force a larger crop from the soil by the mere application of more and more labor to each acre of land. The yield is found not to increase in proportion as the labor is increased, which necessarily means a smaller product per man. But if more capital is used, as well as more labor, particularly if better methods of cultivation are adopted and carried out by means of the larger use of capital, increasing yields per acre may be secured for a time, and up to a certain point, without any diminution of yield per unit of labor. By using more power and larger tools in order to plow deeper and prepare a better seed bed, a given amount of labor may cultivate the same acreage of land as before and yet get a larger yield per acre. This would also give a larger yield per man. Again, by cultivating a slightly smaller acreage and cultivating it more thoroughly by means of better tools, the same product per man may be secured and a somewhat larger population may be supported without any diminution in average income. But experience shows that wherever even this process is carried too far, a smaller product per man, and consequent poverty, will be the result.

A seeming exception to this rule (but it is only a seeming exception) is found when a few cultivators turn from the growing

of staple crops to the growing of high-priced specialties. Only a few can do this, for the reason that the market is very limited. The mass of the farming population must grow the crops which feed and clothe the people. Those who do succeed in this field may manage to make good incomes from very small plots of land. This does not prove by any means that the growers of wheat or beef could do likewise. So long as consumers demand wheat bread and beef as parts of a steady diet, they must draw their subsistence from considerable areas, for these products can be most economically produced by what are commonly known as extensive methods of cultivation.

Turning to heavy-yielding crops. If people would change their habits of consumption, and consume products which could be economically produced under intensive methods, or products which are capable of yielding large quantities of food per acre, a great deal of land could be saved; in other words, a much larger population could be supported from a given area.

The following table shows the estimated power of an acre of land under good cultivation, but not the most intensive cultivation, to produce food of different kinds :

1 From Bulletin 28, United States Department of Agriculture, Office of

Experiment Stations. Government Printing Office, 1896.

Of course, there are elements of food value other than the heat-producing elements, but this table is enough to indicate that some economy of land could be effected by consuming other and more heavy-yielding crops than wheat and beef. Even these economies of land, however, might be gained by a less economical use of labor. While wheat and beef require considerable areas of land for their most economical production, they can be produced with comparatively small quantities of labor where the conditions are right. On our western wheat farms, for example, where powerful machinery can be used, a small number of men can grow and harvest a very large acreage of wheat. On our western cattle ranges also a small number of men can care for large numbers of cattle pasturing over very wide areas. If we did not have land enough for these purposes, and had to support a growing population from our own soil, potatoes, sweet potatoes, corn, beans, and milk, and milk products in the form of butter and cheese, would support many more people than could be supported on wheat and beef.

The banana and the date. Certain tropical countries have great advantages in the way of food production on small areas. Concerning the banana, Humboldt wrote: "I doubt if there exists another plant on the globe, which, on a small space of ground, can produce so considerable a mass of nourishment. . . . The product of bananas is to that of wheat as 133:1, to that of potatoes as 44:1." In Arabia and northern Africa the date is very prolific and in favorable locations produces large quantities of food.1

Turning to the indoor industries. It is not likely to be repeated too often that the favorite method of economizing land and supporting a large population is to give up trying to be physically self-supporting and try to become commercially self-supporting. By being physically self-supporting is meant producing from our own soil all or practically all that we need.

1 Cf. Buckle, History of Civilization in England, Chapter XI. London, 1857-1861.