124

ON MEASURES
cause of the change in the relation between
cloth and silver had been in the former, and as
labour is, by the supposition, the sole cause of
value, we might more particularly infer, that
the producing labour of cloth had been abridged
to half its former quantity.

A commodity, therefore, under these con-
ditions, produced by an invariable quantity of
labour, would enable us to ascertain, not the
fluctuations in value between two or more com-
modities (for these are facts to be gathered
from appropriate evidence), but the fluctuations
in the quantity of labour which produced them:
and in truth, if we examine what is the par-
ticular advantage which Mr. Ricardo himself
supposes we should be able to derive from the
possession of such a commodity, we shall find
it to be in reality that which is here described,
the power of ascertaining, not the variations in
value, but the variations in the producing la-
bour of commodities. Speaking of the inter-
change of game and fish, in the earlier stages
of society, he says,—