252 NOTES AND ILLUSTRATIONS.

tions as identical. To measure implies, either directly or
indirectly, the ascertainment of a ratio between two objects
by the intervention of a third. We say, it is true, that we
have measured the length of a building, when we have
found its ratio to a yard or a foot, but this is because the
length of other objects in feet is known to us, and therefore,
 when we have the length of the building in feet, we
have it in a common denomination: the ratio of the
building to the foot, determines its place in the common
scale; or, in other words, determines its ratio to a variety
of other objects. We should scarcely consider the length
of a building to be measured, if its ratio was determined
only to a staff or rod, the length of which in relation to
any other object could not itself be ascertained.
In the same way, when we say the value of a commodity
4 is measured when expressed in money, it is because we
know already the relations in value between money and a
variety of other commodities, and therefore the value of a
in money instantly determines its relation to all these objects.
 The idea of intermediation is still implied. But
although to express the value of a commodity in money
may thus be considered as equivalent to measuring it, we
could not with propriety apply the latter term to the expression
 of the value of a commodity in another commodity
 of no known or ascertainable relation to any thing
else.

The following passage from one of Locke’s able tracts on