Section XXXI The Factors of Production — External Nature189
The division of natural forces which formerly obtained, into organic, chemical and mechanical, is of no great importance in Political Economy. The tendency is more and more to resolve organic forces partly into chemical and partly into mechanical. Between mechanical and chemical forces, again, the boundary is not fixed, heat being always capable of producing motion, and motion always of producing heat. Hence, it is all the more important for us to find a division of the economic gifts (matter, forces190 and relations) of external nature, into such as are capable of acquiring exchange value, and such as are not. (See § 5.)
A. Those gifts of nature which, because they cannot be appropriated by any one, or which at least are inexhaustible as compared with the wants of man, and therefore never have a direct value in exchange, belong either to the class of free goods, in the fullest sense of the word, as, for instance, sunlight and the atmosphere (supra, § 5);191 or they constitute, by reason of their peculiar and intransmissible connection with the whole country, an essential element of the national resources.