It is not even necessary that the country which takes its goods, should supply it with any commodity whatever. Suppose that a country should be opened to our merchants, disposed to buy from us in abundance, but which can sell to us scarcely anything, as every commodity which it affords could be got cheaper by us from some other quarter. Nevertheless, our trade with this country will enable us to obtain from all other countries their commodities at a lower price. At the first opening of this commerce of mere exportation, we must have received in payment a large quantity of money; for which our customer will have been indemnified by other countries, in exchange for her commodities. Prices must consequently be lower in all other countries, and higher with us, than before the opening of the new branch of trade; and we therefore obtain the commodities of other countries at a less cost, both as we pay less money for them, and as that money is lower in value. 8. Another obvious application of the same principle will enable us to explain, and to bring within the dominion of strict science, the rivality of one exporting nation and another, or what is called, in the language of the mercantile system, _underselling_: a subject which political economists have taken little trouble to elucidate, from the habit before alluded to of disregarding almost entirely, in their purely scientific inquiries, those circumstances which affect the trade of a country by operating immediately upon the exports. Let us revert to our old example, and to our old figures. Suppose that the trade between England and Germany in cloth and linen is established, and that the rate of interchange is 10 yards of cloth for 17 of linen. Now suppose that there arises in another country, in Flanders, for example, a linen manufacture; and that the same causes, the working of which in England and Germany has made 10 yards exchange for 17, would in England and Flanders, putting Germany out of the question, have made the rate of interchange 10 for 18. It is evident that Germany also must give 18 yards of linen for 10 of cloth, and so carry on the trade with a diminished share of the advantage, or lose it altogether. If the play of demand in England and Flanders had made the rate of interchange not 10 for 18 but 10 for 21, (10 to 20 being in Germany the comparative cost of production,) it is evident that Germany could not have maintained the competition, and would have lost, not part of her share of the advantage, but all advantage, and the trade itself.