OF VALUE.

111
it appears to require a separate examination. It
is argued, that money or any other commodity
is a good measure of the value of commodities,
only at the same time, because it is liable to
vary; while to perform this function correctly,
there should be a commodity the value of which
did not vary from one age to another; as to
measure the lengths of objects at different pe-
riods, there must be an object of invariable
length *. Let us therefore endeavour to ascer-
tain what this really amounts to. With regard
to the measurement of space, the intervention
of time occasions no alteration in the requisite
conditions. The preceding remarks are as ap-
plicable to the measurement of the length of
objects at different times as to the same time.
The qualification necessary to constitute an
instrument a good measure of space, is in each

® << At the same time and place, money is the exact
measure of the real exchangeable value of all commodi-
ties. It is so, however, at the same time and place only.”
Wealth of Nations, Book i, Chap. 5.