Whatever be the commodity--the supply in any market being given, there is some price at which the whole of the supply exactly will find purchasers, and no more. That, whatever it be, is the price at which, by the effect of competition, the commodity will be sold. If the price be higher, the whole of the supply will not be disposed of, and the sellers, by their competition, will bring down the price. If the price be lower, there will be found purchasers for a larger supply, and the competition of these purchasers will raise the price. This, then, is what we mean, when we say that price, or exchangeable value, depends on demand and supply. We should express the principle more accurately, if we were to say, the price so regulates itself that the demand shall be exactly sufficient to carry off the supply. Let us now apply the principle of demand and supply, thus understood, to the interchange of broadcloth and linen between England and Germany. As exchangeable value in this case, as in every other, is proverbially fluctuating, it does not matter what we suppose it to be when we begin; we shall soon see whether there be any fixed point about which it oscillates--which it has a tendency always to approach to, and to remain at. Let us suppose, then, that by the effect of what Adam Smith calls the higgling of the market, 10 yards of cloth, in both countries, exchange for 17 yards of linen. The demand for a commodity, that is, the quantity of it which can find a purchaser, varies, as we have before remarked, according to the price. In Germany, the price of 10 yards of cloth is now 17 yards of linen; or whatever quantity of money is equivalent in Germany to 17 yards of linen. Now, that being the price, there is some particular number of yards of cloth, which will be in demand, or will find purchasers, at that price. There is some given quantity of cloth, more than which could not be disposed of at that price,--less than which, at that price, would not fully satisfy the demand. Let us suppose this quantity to be, 1000 times 10 yards. Let us now turn our attention to England. There, the price of 17 yards of linen is 10 yards of cloth, or whatever quantity of money is equivalent in England to 10 yards of cloth. There is some particular number of yards of linen, which, at that price, will exactly satisfy the demand, and no more. Let us suppose that this number is 1000 times 17 yards. As 17 yards of linen are to 30 yards of cloth, so are 1000 times 17 yards to 1000 times 10 yards. At the existing exchangeable value, the linen which England requires, will exactly pay for the quantity of cloth which, on the same terms of interchange, Germany requires. The demand on each side is precisely sufficient to carry off the supply on the other. The conditions required by the principle of demand and supply are fulfilled, and the two commodities will continue to be interchanged, as we supposed them to be, in the ratio of 17 yards of linen for 10 yards of cloth.