I shall endeavour to show hereafter, does not fluctuate from year to year with the money price of corn, but seems to be everywhere accommodated, not to the temporary or occasional, but to the average or ordinary price of that necessary of life. The average or ordinary price of corn again is regulated, as I shall likewise endeavour to show hereafter, by the value of silver, by the richness or barrenness of the mines which supply the market with that metal, or by the quantity of labour which must be employed, and consequently of corn which must be consumed, in order to bring any particular quantity of silver from the mine to the market. But the value of silver, though it sometimes varies greatly from century to century, seldom varies much from year to year, but frequently continues the same, or very nearly the same, for half a century or a century together. The ordinary or average money price of corn, therefore, may, during so long a period, continue the same or very nearly the same too, and along with it the money price of labour, provided, at least, the society continues, in other respects, in the same or nearly in the same condition. In the meantime the temporary and occasional price of corn may frequently be double, one year, of what it had been the year before, or fluctuate, for example, from five and twenty to fifty shillings the quarter. But when corn is at the latter price, not only the nominal, but the real value of a corn rent will be double of what it is when at the former, or will command double the quantity either of labour or of the greater part of other commodities; the money price of labour, and along with it that of most other things, continuing the same during all these fluctuations.

Labour, therefore, it appears evidently, is the only universal, as well as the only accurate measure of value, or the only standard by which we can compare the values of different commodities at all times, and at all places. We cannot estimate, it is allowed, the real value of different commodities from century to century by the quantities of silver which were given for them. We cannot estimate it from year to year by the quantities of corn. By the quantities of labour we can, with the greatest accuracy, estimate it both from century to century and from year to year. From century to century, corn is a better measure than silver, because, from century to century, equal quantities of corn will command the same quantity of labour more nearly than equal quantities of silver. From year to year, on the contrary, silver is a better measure than corn, because equal quantities of it will more nearly command the same quantity of labour.

But though in establishing perpetual rents, or even in letting very long leases, it may be of use to distinguish between real and nominal price; it is of none in buying and selling, the more common and ordinary transactions of human life.

At the same time and place the real and the nominal price of all commodities are exactly in proportion to one another. The more or less money you get for any commodity, in the London market for example, the more or less labour it will at that time and place enable you to purchase or command. At the same time and place, therefore, money is the exact measure of the real exchangeable value of all commodities. It is so, however, at the same time and place only.

Though at distant places, there is no regular proportion between the real and the money price of commodities, yet the merchant who carries goods from the one to the other has nothing to consider but their money price, or the difference between the quantity of silver for which he buys them, and that for which he is likely to sell them. Half an ounce of silver at Canton in China may command a greater quantity both of labour and of the necessaries and conveniences of life than an ounce at London. A commodity, therefore, which sells for half an ounce of silver at Canton may there be really dearer, of more real importance to the man who possesses it there, than a commodity which sells for an ounce at London is to the man who possesses it at London. If a London merchant, however, can buy at Canton for half an ounce of silver, a commodity which he can afterwards sell at London for an ounce, he gains a hundred per cent by the bargain, just as much as if an ounce of silver was at London exactly of the same value as at Canton. It is of no importance to him that half an ounce of silver at Canton would have given him the command of more labour and of a greater quantity of the necessaries and conveniences of life than an ounce can do at London. An ounce at London will always give him the command of double the quantity of all these which half an ounce could have done there, and this is precisely what he wants.