gulate their
exchangeable value, every increase of the quantity of labour must
augment the value of that commodity on which it is exercised, as every
diminution must lower it.

Adam Smith, who so accurately defined the original source of
exchangeable value, and who was bound in consistency to maintain, that
all things became more or less valuable in proportion as more or less
labour was bestowed on their production, has himself erected another
standard measure of value, and speaks of things being more or less
valuable, in proportion as they will exchange for more or less of this
standard measure. Sometimes he speaks of corn, at other times of labour,
as a standard measure; not the quantity of labour bestowed on the
production of any object, but the quantity which it can command in the
market: as if these were two equivalent expressions, and as if because a
man's labour had become doubly efficient, and he could therefore produce
twice the quantity of a commodity, he would necessarily receive twice
the former quantity in exchange for it.

If this indeed were true, if the reward of the labourer were always in
proportion to what he produced, the quantity of labour bestowed on a
commodity, and the quantity of labour which that commodity would
purchase, would be equal, and either might accurately measure the
variations of other things: but they are not equal; the first is under
many circumstances an invariable standard, indicating correctly the
variations of other things; the latter is subject to as many
fluctuations as the commodities compared with it. Adam Smith, after most
ably shewing the insufficiency of a variable medium, such as gold and
silver, for the purpose of determining the varying value of other
things, has himself, by fixing on corn or labour, chosen a medium no
less variable.

Gold and silver are no doubt subject to fluctuations, from the discovery
of new and more abundant mines; but such discoveries are rare, and their
effects, though powerful, are limited to periods of comparatively short
duration. They are subject also to fluctuation, from improvements in the
skill and machinery with which the mines may be worked; as in
consequence of such improvements, a greater quantity may be obtained
with the same labour. They are further subject to fluctuation from the
decreasing produce of the mines, after they have yielded a supply to the
world, for a succession of ages. But from which of these sources of
fluctua