_Baumstark_ very correctly says: "Rent rises, not because new capital has been invested, but when the circumstances of trade make a new addition to capital possible." (Volkswirthschaftliche Erläuterungen über Ricardo's System, 1838, 567.) _Fuoco's_ Nuova Teoria della Rendita, Saggi economici, No. 1, is nothing but an Italian version of the doctrines of Malthus and Ricardo. The greater number of anti-Ricardo theories of rent have originated from the rapid and apparently unlimited growth of national husbandry in recent times. Thus it is a fundamental thought in _Rodbertus_, Sociale Briefe, 1851, No. 3, that an increase of the price of corn need not attend an increase of population, either uniformly or necessarily. According to _Carey_, The Past, the Present and the Future, ch. 1, 1848, the most fertile land is last brought under cultivation, because it is covered with swamps, forests, etc.; and because it offers greater resistance to the work of the agriculturist, by reason of its luxurious vegetation. The more elevated lands are first cultivated which present fewer obstacles to cultivation on account of their dryness, their thinner crust, etc. Carey generalizes this and thinks he has reversed the _Ricardo_ law of rent! He overlooks entirely that _Ricardo_ speaks only of the original powers of the soil. Now a swampy land which must be dried at the expense of a great deal of labor, possesses less of these original powers than a sandy soil which may be sown immediately. See _Carey_, Essay on the Rate of Wages, 232 ff., and the lengthy exposition of the same doctrine rank with inexact natural science and unhistorical history in the same author's Principles of Social Science, 1858, vol. I. There is this much truth, however, in Carey's error that, with increasing economic progress, the superiority not only of situation, relatively to the market, but also of natural fertility, may of itself go over to other lands. Thus, for instance, the ancient Slaves used clay soil everywhere as pasturage, and cultivated the sandy soil, because their pick-axes could overcome the resistance only of the latter. _Langethal_, Geschicte der deutschen Landw., II, 66; _Waitz_, Schlesw. Holstein, Gesch., I, 17. Similarly in Australia: _Hearne_, Plutology, 1864. Compare, _Roscher_, Nationalökonomik des Ackerbaues, § 34. The word fertility should not be taken too exclusively in its present agricultural sense. In a lower stage of civilization, the facility of military defense or the _ut fons, ut nemus placuit_--_Tacit._, Germ., 16--may have more weight.