became one of the staple industries of the island; and of course the more was produced the more easy it was to obtain it; that is to say, those who did not grow it for themselves could obtain it in exchange for a much smaller quantity of labour or commodities of their own manufacture than was possible after the first harvest had been gathered in. If the people on the island had carried on their exchanges by the means of money, we should say that the price of wheat went down very rapidly when a greater quantity was grown and when improved methods of cultivation were adopted. As, however, they did not use money, but exchanged commodities for commodities, we cannot speak of price declining; for price means the value of anything measured in money. But we can say that the value of the wheat went down; for value is measured by the rate at which commodities exchange for each other. Exchange without the use of money is called barter; and every schoolboy is familiar with its practice, which he calls "chopping." When we say, therefore, that the
