§ 10. #Exports and exhaustion of the soil#. It has been ingeniously argued that a tariff may keep some of the natural agricultural resources of a new country from becoming quickly exhausted. The export of food takes out of the soil and out of the country fertile qualities never to be returned. The shipment of several hundred million dollars of food products year after year represented a tremendous drain from the soil of the United States, but this has now largely ceased. The assumption, however, that the use of the food in this country preserves the fertility of our own fields is in the main mistaken. The fertile material in the food for human consumption hauled to a town five miles away from the field is almost as entirely lost as if it were shipped to Europe. Engineering skill has as yet succeeded in returning economically to the fields from which it comes hardly a fraction as much fertile organic matter as that which flows into the sewers, that is dumped into river and ocean, and that is buried in heaps at the borders of our own cities. Artificial fertilizers are increasingly used, to be sure, but they are obtained in other ways. On the other hand, the increased use of iron, coal, and timber, as a result of encouraging manufacturers, has very effectually hastened the exhaustion of the natural resources of the country. § 11. #Protection as a monopoly measure#. It has rightly been observed that a new country has a limited potential monopoly in certain kinds of products and that a tariff may make it effective. The rapid opening up of America with its rich natural resources greatly benefited the average consumer in Western Europe, altho it caused a loss to a special class of landowners.[10] Whether the citizens of the older or of the newer country shall reap the greater benefit in the trade depends on the reciprocal demand for the two classes of goods, as was seen in discussing the equation of international demand. A wide margin of advantage may go to one party and a narrow margin to the citizen of the more favored land. To put it concretely: America, having great natural resources for agriculture, might continue to trade food for manufactured goods even tho England reaped most of the benefits of the trade. An American tariff on manufactures from England would, under such conditions, check the demand for English products and compel some Americans to leave farming. This reduction of the American supply of wheat or corn and of the American demand for English manufactures compels a new ratio of trade (expressed in prices). It is conceivable that trading fewer goods with a larger gain on each trade would give a larger total of gain to the favored nation. Thus, foreigners may conceivably be compelled to pay a part of the tariff duties to enjoy the favored market. This is but a special case of the monopoly principle; the government by law artificially limits the supply of goods offered by its citizens.