CHAPTER V.

ON COMPARING COMMODITIES AT DIF-FERENT
 PERIODS.

PeruaPps no part of their investigations has
perplexed political economists more than their
attempts to compare the value of the same
object at different periods of time.
It is a direct inference from the explanation
of value in the preceding chapters, as denoting
 a relation between two commodities, a
relation incapable of existing when there is
only one commodity, that it cannot exist between
 a commodity at one period and the same
commodity at another period. We cannot
ascertain the relation of cloth at one time to
cloth at another, as we can ascertain the relation
 of cloth to corn in the present day. All