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 contained in the bowels of the earth, the precious metals, and the precious stones.

Food is, in this manner, not only the original source of rent, but every other part of the produce of land which afterward affords rent derives that part of its value from the improvement of the powers of labor in producing food by means of the improvement and cultivation of land.

Those other parts of the produce of land, however, which afterward afford rent, do not afford it always. Even in improved and cultivated countries the demand for them is not always such as to afford a greater price than what is sufficient to pay the labor, and replace, together with its ordinary profits, the stock which must be employed in bringing them to market. Whether it is or is not such, depends upon different circumstances.

Whether a coal mine, for example, can afford any rent, depends partly upon its fertility, and partly upon its situation.

A mine of any kind may be said to be either fertile or barren, according as the quantity of mineral which can be brought from it by a certain quantity of labor is greater or less than what can be brought by an equal quantity from the greater part of other mines of the same kind.

Some coal mines, advantageously situated, cannot be wrought on account of their barrenness. The produce does not pay the expense. They can afford neither profit nor rent.

There are some of which the produce is barely sufficient to pay the labor, and replace, together with its ordinary profits, the stock employed in working them. They afford some profit to the undertaker of the work, but no rent to the landlord. They can be wrought advantageously by