one bushel of oats; that is, oats will have a larger exchange value. If, on the other hand, A cares less for oats than B does for spades, then the exchange will result in an increased value of spades relatively to oats. When two commodities exchange against each other, their exchange values will depend entirely upon the relative intensity of the demand [pg 394] on each side for the other commodity. And this simple form of the statement of reciprocal demand and supply is also the law of international values.
If instead of spades and oats we substitute iron and corn, and let the trade be between England and the United States, the quantity of corn required to buy a given quantity of iron will depend upon the relative demands of England for corn and of the United States for iron. Something may cut off England's demand for our breadstuffs, and they will then have a less exchange value relatively to iron (if we keep up our demand), and their prices will fall. But if, on the other hand, England has poor harvests, and consequently a great demand for corn, and if our demand for iron is not excessive at the same time, then our breadstuffs will rise in value. And this was precisely what happened from 1877 to 1879. Now, in the above illustration of corn and iron, how can we know whether or not x bushels of corn (the produce of 100 days' labor in the United States) will exchange for exactly y tons of English iron? That, again, will depend upon the reciprocal demands of the two countries for corn and iron respectively. Moreover, it will have been already observed that the ratio of exchange is not capable of being ascertained exactly, since it varies with changing conditions, namely, the desires of the people of the two countries, together with their means of purchase.
But yet these variations are capable of ascertainment as regards their extreme limits. The reciprocal demand