The owners, however, of those portions of the produce enjoy a privilege; they obtain a value which yields them more than the ordinary profit. The advantage depends on the possession of a natural agent of peculiar quality, as, for instance, of more fertile land than that which determines the general value of the commodity; and when this natural agent is not owned by themselves, the person who does own it is able to exact from them, in the form of rent, the whole extra gain derived from its use. We are thus brought by another road to the Law of Rent, investigated in the concluding chapter of the Second Book. Rent, we again see, is the difference between the unequal returns to different parts of the capital employed on the soil. Whatever surplus any portion of agricultural capital produces, beyond what is produced by the same amount of capital on the worst soil, or under the most expensive mode of cultivation, which the existing demands of society compel a recourse to, that surplus will naturally be paid as rent from that capital, to the owner of the land on which it is employed. The discussion of rent is here followed wholly from the point of view of value, while before (Book II, Chap. VI) the law of rent was reached through a limitation of the quantity of land due to the influence of population. In the former case the rent and produce were stated in bushels. By introducing price now (as the convenient symbol of value), instead of the separate increased demands of population in our illustration than used (p. 240), it will be seen how the same operation, looking at it solely in respect to value, brings us to the same law: Price A B C D per Bushel. 24 18 12 6 bushels bushels bushels bushels Total Rent. Total Rent. Total Rent. Total value of value of value of value of product. product. product. product. $1.00 $24.00 $0.00 .... .... .... .... .... $1.33 $32.00 $8.00 $24.00 $0.00 .... .... .... $2.00 $48.00 $24.00 $36.00 $12.00 $24.00 $0.00 .... $4.00 $96.00 $72.00 $72.00 $48.00 $48.00 $24.00 $24.00