The admission of cheaper food from a foreign country is equivalent to an agricultural invention by which food could be raised at a similarly diminished cost at home. It equally increases the productive power of labor. The return was before, so much food for so much labor employed in the growth of food: the return is now, a greater quantity of food for the same labor employed in producing cottons or hardware, or some other commodity to be given in exchange for food. The one improvement, like the other, throws back the decline of the productive power of labor by a certain distance: but in the one case, as in the other, it immediately resumes its course; the tide which has receded, instantly begins to readvance. It might seem, indeed, that, when a country draws its supply of food from so wide a surface as the whole habitable globe, so little impression can be produced on that great expanse by any increase of mouths in one small corner of it that the inhabitants of the country may double and treble their numbers without feeling the effect in any increased tension of the springs of production, or any enhancement of the price of food throughout the world. But in this calculation several things are overlooked. In the first place, the foreign regions from which corn can be imported do not comprise the whole globe, but those parts of it almost alone which are in the immediate neighborhood of coasts or navigable rivers; and of such there is not, in the productive regions of the earth, so great a multitude as to suffice during an indefinite time for a rapidly growing demand, without an increasing strain on the productive powers of the soil. In the next place, even if the supply were drawn from the whole instead of a small part of the surface of the exporting countries, the quantity of food would still be limited, which could be obtained from them without an increase of the proportional cost. The countries which export food may be divided into two classes: those in which the effective desire of accumulation is strong, and those in which it is weak. In Australia and the United States of America, the effective desire of accumulation is strong; capital increases fast, and the production of food might be very rapidly extended. But in such countries population also increases with extraordinary rapidity. Their agriculture has to provide for their own expanding numbers, as well as for those of the importing countries. They must, therefore, from the nature of the case, be rapidly driven, if not to less fertile, at least what is equivalent, to remoter and less accessible lands, and to modes of cultivation like those of old countries, less productive in proportion to the labor and expense.