Page:Popular Science Monthly Volume 75.djvu/218

214 Beyond the plowed fields of the present, the arid and wet lands and the superfluous forests, are no inconsiderable reserves of food from lands deemed useless. We may consider potential gardens along more than two hundred thousand miles of railway, the fruit that might grow by millions of miles of highway, the steep and immature slopes that are more capable of terracing than those of Capri or Amalfi, or ancient Palestine, and finally those rugged areas of glacial hillside or mountain slope, where nut-bearing trees might produce no inconsiderable amount of highly nutritious food. The possible production of food substances in the laboratory is at present so far from the geographer's domain that it would be profitless to dwell upon it.

It is plain that the whole circle of conservation problems applies here, not only by directly increasing food, as in irrigation, but in cheapening the cost of transportation, in saving land by forest conservation and in utilizing power of every kind to the full, thus releasing time and energy for the free use of opportunity and the complete employment of all our resources. Thus a well ordered civilization would sustain the greatest number at good standards, as a well-managed household may maintain a large family on a lesser sum than is required by a neighboring small household.

Population capacity would afford a less baffling inquiry if food alone were needed. Mere questions of mouths, bushels and pounds might involve simple ratios, easily determined, but we must at once include clothing, of vegetable fibers, animal fibers, furs and skins, nearly all requiring land for their production. Man must have shelter and a long catalogue of objects of domestic utility, for the household and for the tillage of the soil. These things may become chiefly derivable from subterranean sources with the single exception of a minimum demand on the forest. Many rocks and mineral substances would far outrun any possible use of them, but it seems certain that we could not for many generations supply iron for as marry millions as we can feed. It may be doubtful whether our ultimate expansion will receive its first effective check above or below the surface of the earth.

We must include also a wide range of objects of public utility, such as roads and all appliances of transportation and manufacture, and public structures for education, worship, government, health and charity, adding instruments of knowledge and pleasure such as books, music, ornaments and all works of art.

Almost as fundamental as food is the requirement of power. Here, however, the supply seems ample and permamentpermament [sic]. Long before the stores of buried fuel are exhausted, other natural forces, particularly that of moving water, will meet the needs of any population which we can feed. The maximum of population therefore for the whole world hinges upon the supply of material substances derived from the atmosphere, the water, the soil and the rocks.