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 periods,
 there must be an object of invariable
length *. Let us therefore endeavour to ascertain
 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 applicable
 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 commodities.
 It is so, however, at the same time and place only.”
Wealth of Nations, Book i, Chap. 5.