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 there-
fore, 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 ob-
jects. 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 ex-
pression of the value of a commodity in another commo-
dity of no known or ascertainable relation to any thing

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