consider that if a similar advantage were extended to other countries,
they would employ it above all in the production of those articles, in
which they had already the greatest natural advantages; and if the
former country would be a loser by their improvements in the production
of articles which it sells, it would gain by their improvements in those
which it buys. The exportation of machinery may, however, be a proper
subject for adjustment with other nations, on the principle of
reciprocity. Until, by the common consent of nations, all restrictions
upon trade are done away, a nation cannot be required to abolish those
from which she derives a real advantage, without stipulating for an
equivalent.

7. The case which we have just examined, is an example in how remarkable
a manner every cause which materially influences exports, operates upon
the prices of imports. According to the ancient theory of the balance of
trade, and to the associations of the generality of what are termed
practical men to this day, the sole benefit derived from commerce
consists in the exports, and imports are rather an evil than otherwise.
Political economists, seeing the folly of these views, and clearly
perceiving that the advantage of commerce consists and must consist
solely of the imports, have occasionally suffered themselves to employ
language evincing inattention to the fact, that exports, though
unimportant in themselves, are important by their influence on imports.
So real and extensive is this influence, that every new market which is
opened for any of our goods, and every increase in the demand for our
commodities in foreign countries, enables us to supply ourselves with
foreign commodities at a smaller cost.

Let us revert to our earliest and simplest example, but which displays
the real law of interchange more luminously than any formula into which