This is the usual definition of wealth. Henry George (see “Progress and Poverty,” pp. 34-37) regards wealth as consisting “of natural products that have been secured, moved, combined, separated, or in other ways _modified by human exertion_, so as to fit them for the gratification of human desires.... Nothing which Nature supplies to man without his labor is wealth.... All things which have an exchange value are, therefore, not wealth. Only such things can be wealth the production of which increases and the destruction of which decreases the aggregate of wealth.... Increase in land values does not represent increase in the common wealth, for what land-owners gain by higher prices the tenants or purchasers who must pay them will lose.” Jevons (“Primer,” p. 13) defines wealth very properly as what is transferable, limited in supply, and useful. F. A. Walker defines wealth as comprising “all articles of value and nothing else” (“Political Economy,” p. 5). Levasseur’s definition (“Précis,” p. 15) is, “all material objects possessing utility” (i.e., the power to satisfy a want). (Cf. various definitions in Roscher’s “Political Economy,” section 9, note 3.) Perry (“Political Economy,” p. 99) rejects the term _wealth_ as a clog to progress in the science, and adopts _property_ in its stead, defining it as that “which can be bought or sold.” Cherbuliez (“Précis,” p. 70) defines wealth as the material product of nature appropriated by labor for the wants of man. Carey (“Social Science,” i, 186) asserts that wealth consists in the power to command Nature’s services, including in wealth such intangible things as mental qualities. BOOK I. PRODUCTION. Chapter I. Of The Requisites Of Production. § 1. The Requisites of Production are Two: Labor, and Appropriate Natural Objects. There is a third requisite of production, capital (see page 58). Since the limitation to only two requisites applies solely to a primitive condition of existence, so soon as the element of _time_ enters into production, then a store of capital becomes necessary; that is, so soon as production requires such a term that during the operation the laborer can not at the same time provide himself with subsistence, then capital is a requisite of production. This takes place also under any general division of labor in a community. When one man is making a pin-head, he must be supplied with food by some person until the pins are finished and exchanged. Labor is either bodily or mental; or, to express the distinction more comprehensively, either muscular or nervous; and it is necessary to include in the idea, not solely the exertion itself, but all feelings of a disagreeable kind, all bodily inconvenience or mental annoyance, connected with the employment of one’s thoughts, or muscles, or both, in a particular occupation.