industry, multiply at will the instruments of production of the same degree of productivity—that is to say, the soils of the same degree of fertility. Then, in proportion as population grows, it is necessary to exploit soils of inferior quality, or to expend on the same soil additional capital proportionately less productive than the first. In either case a larger quantity of labor is expended in order to obtain a product proportionally smaller. The needs of the population having rendered this increase of labor necessary, 'the product of the soil more costly to cultivate has its sale forced as well as that of the more cheaply cultivated soil. Competition levels the market price, and the product of the better soil will fetch as high a price as that of the inferior soil. It is the excess of the price of the products of the superior soil over their cost of production which constitutes rent. If there were always at disposal soils of the same degree of fertility, if, as in manufacturing industry, recourse could always be had to the less costly and more productive machinery, or if the second expenditure of capital produced as much as the first, then the price of agricultural products would be determined by the price of the commodities produced by the better instruments of production, as we have seen in the price of manufactured articles. But also, from this moment, rent would have disappeared.
For the theory of Ricardo to be generally true, it is further necessary that capital could be freely applied to the different branches of industry; that a strongly developed competition between the capitalists should have reduced profits to an equal rate; that the farmer should be no more than an industrial capitalist who asks for the employment of his capital upon the land, a profit equal to that which he would draw from his capital applied to any manufacture; that agricultural exploita-
