money, and afterwards exchanges that money for bread and for beer. The
quantity of money which he gets for them regulates, too, the quantity of
bread and beer which he can afterwards purchase. It is more natural and
obvious to him, therefore, to estimate their value by the quantity of money,
the commodity for which he immediately exchanges them, than by that of
bread and beer, the commodities for which he can exchange them only by the
intervention of another commodity ; and rather to say that his butcher's
meat is worth three-pence or fourpence a-pound, than that it is worth three
or four pounds of bread, or three or four quarts of small beer. Hence it
comes to pass, that the exchangeable value of every commodity is more
frequently estimated by the quantity of money, than by the quantity either
of labour or of any other commodity which can be had in exchange for it.

Gold and silver, however, like every other commodity, vary in their value;
are sometimes cheaper and sometimes dearer, sometimes of easier and
sometimes of more difficult purchase. The quantity of labour which any
particular quantity of them can purchase or command, or the quantity of
other goods which it will exchange for, depends always upon the fertility or
barrenness of the mines which happen to be known about the time when such
exchanges are made. The discovery of the abundant mines of America, reduced,
in the sixteenth century, the value of gold and silver in Europe to about a
third of what it had been before. As it cost less labour to bring those
metals from the mine to the market, so, when they were brought thither, they
could purchase or command less labour; and this revolution in their value,
though perhaps the greatest, is by no means the only one of which history
gives some account. But as a measure of quantity, such as the natural foot,
fathom, or handful, which is continually varying in its own quantity, can
never be an accurate measure of the quantity of other things ; so a
commodity which is itself continually varying in its own value, can never be
an accurate measure of the value of other commodities. Equal quantities of