OF VALUE, 
97 
first to one and then to the other: it is far from 
being so much as this: it is merely like calcu- 
lating the ratio of length between the two 
pieces of timber, after we are informed how 
many feet are contained in each. For of each 
commodity A and c the value in relation to B 
must be given, or, in other words, their value 
must be expressed in a common denomination, 
before their mutual relation can be ascertained ; 
just as in the case supposed the relation of each 
piece of timber to the foot-rule must be given, 
before their relation to each other can be de- 
duced. The actual application of the foot rule 
is that part of the process which is alone en- 
titled to the appellation of measuring, the rest 
being mere calculation, but to this there is no- 
thing at all analogous in any possible attempt 
to ascertain value. The way in which the 
commodity B would be used, in the above 
instance, is in truth as a medium of compari- 
son, not a measure, yet it is the only process 
which bears any analogy to measurement. 
It appears, therefore, that all we can under-