the destructive force of nature is greater in warmer than in colder countries. (§ 209.)(204) Section XXXIII. External Nature.—Gifts Of Nature With Value In Exchange. B. Those gifts of external nature which may become objects of private property, and at the same time possess sufficient relative scarcity to give them value in exchange, are either movable, and exhaustible in a given place, or firmly connected with the land. The first category embraces, for instance, such wild animals and plants as serve some useful purpose, minerals, above all, fossil combustible matter(205)—the “black diamonds,” coal, of which, with its canals, Franklin said that it had made England what it is. The economical effect of their moveable character is best seen, when the use made of an ordinary stratum of coal is compared with that of a protracted subterranean fire in a coal mine.(206) The latter can be directly useful only to those in its immediate vicinity. Every lower layer of the burning coal would be less useful. An increase of its actual power by accumulation in time or place is scarcely possible. In all these respects, the movable coal is incomparably better adapted to the satisfaction of man’s wants. It may be said that the capacity of heat for drying, distilling, melting and hardening purposes, of imparting rapid motion to heavy objects by the production of confined steam, is, at least, a thousand times as great when a thousand bushels of coal are consumed as when one is consumed. In most cases even the concentration of a large quantity of coal will increase, the result not only absolutely, but relatively.(207)(208) Section XXXIV. External Nature. (Continued.)