[Footnote 149-1: According to _von Thünen_, Der isolirte Staat. in Beziehung auf Landwirthschaft und Nat. Oek, 1850, I, 14: "what remains of the revenue of an estate after deducting the interest on all the objects of value which may be separated from the soil." According to _Whately_, it is surplus profit. The expression "regular product" supposes, among other things, an average skillfulness of the economic individual. Thus, for instance, the farm-rent of a piece of land generally includes besides the real rent of the land, interest on much capital which is more or less firmly fixed in the soil. The importance of the latter may be approximately determined from the fact that in the electorate of Hesse, for instance, the value of all meadow lands, woods, and agricultural lands is estimated at from 205 to 206 millions of thalers, and the value of all the houses at 100 millions. (_Hildebrand_, Statist. Mittheil. über die volkswirthschaftlichen Zustände Kurhessens, 1852, 37.) In the English income tax of 1843, the annual value of all lands in Great Britain was estimated at over 45 millions sterling, that of all houses at over 38 millions. However the farm-rent of a piece of land does not by any means always embrace the entire rent. A part of the rent is paid to the state in the form of taxes, and another portion to the payment of tithes. Short leasehold terms, frequent land sales, the comparatively great difficulty of disengaging capital invested in the cultivation of land, the union of landed proprietor, capitalist and laborer in one person easily obscure the law of rent.] [Footnote 149-2: The stores of immediate plant food in a piece of land, of minerals in a mine, of salt in a salt mine, etc., are subject to the law of rent only in so far as they may be considered inexhaustible; that is, they are not, strictly speaking, subject to it. Our definition applies all the more to the capacity for cultivation, and of support or bearing capacity mentioned in § 35; and hence it is easier to follow the law of rent in the case of land used for building purposes than for agriculture. When _v. Mangoldt_ claims that the exhaustibility or inexhaustibility of the soil has nothing to do with rent so long as it flows evenly (_so lange sie eben fliesst_) he is in harmony with his own general conception of rarity-premiums (_Seltenheitsprämien_).] SECTION CL. THEORY OF RENT. (CONTINUED.)