al intercourse.

Now, on the other hand, having thus noticed the question, what
commercial value has China irrevocably for England, next in the reverse
question--namely, what commercial value does England bear to China?--I
would wish to place this in a new light, by bringing it for the first
time into relation to the doctrine of rent. Multitudes in past days,
when political economy was a more favoured study, have spoken and
written upon the modern doctrine of rent, without apparently perceiving
how immediately it bears upon China, and how summarily it shatters an
objection constantly made to the value of our annual dealing with that
country. First, let me sketch, in the very briefest way, an outline of
this modern doctrine. Two men, without communication, and almost
simultaneously, in the year 1815, discovered the law of rent. Suddenly
it struck them that all manufactured products of human industry must
necessarily obey one law; whilst the products of land obey another and
opposite law. Let us for a moment consider arable land as a natural
machine for manufacturing bread. Now, in all manufactures depending upon
machinery of human invention, the natural progress is from the worse
machines to the better. No man lays aside a glove-making machine for a
worse, but only for one that possesses the old powers at a less cost, or
possesses greater powers, let us suppose, at an equal cost. But, in the
natural progress of the bread-making machines, nature herself compels
him to pursue the opposite course: he travels from the best machines to
the worse. The best land is brought into cultivation first. As
population expands, it becomes necessary to take up a second quality of
land; then a third quality; and so on for ever. Left to the action of
this one law, bread would be constantly growing dearer through a long
succession of centuries. Its tendency lies in this direction even now;
but this tendency is constantly met, thwarted, and retarded, by a
counter-tendency in the general practice of agriculture, which is always
slowly improving its own powers--that is, obtaining the same result at a
cost slowly decreasing. It follows as a consequence, when closely
pursued, that, whilst the products of pure human skill and human
machines are constantly, by tendency, growing cheaper, on the other
hand, by a counter-tendency, the products of natural machines (as the
land, mines, rivers, &c.) are constantly on the ascent. Another
consequence is,