heir neighbours are soon obliged to sell at the same price,
though they cannot so well afford it, and though it always diminishes,
and sometimes takes away altogether, both their rent and their profit.
Some works are abandoned altogether; others can afford no rent, and can
be wrought only by the proprietor." If the demand for coal should be
diminished, or if by new processes the quantity should be increased, the
price would fall, and some mines would be abandoned; but in every case,
the price must be sufficient to pay the expenses and profit of that mine
which is worked without being charged with rent. It is therefore the
least fertile mine which regulates price. Indeed it is so stated in
another place by Adam Smith himself, for he says, "The lowest price at
which coals can be sold for any considerable time, is like that of all
other commodities, the price which is barely sufficient to replace,
together with its ordinary profits, the stock which must be employed in
bringing them to market. At a coal mine for which the landlord can get
no rent, but which he must either work himself, or let it alone all
together, the price of coals must generally be nearly about this price."

But the same circumstance, namely, the abundance and consequent
cheapness of coals, from whatever cause it may arise, which would make
it necessary to abandon those mines on which there was no rent, or a
very moderate one, would, if there were the same abundance, and
consequent cheapness of raw produce, render it necessary to abandon the
cultivation of those lands for which either no rent was paid, or a very
moderate one. If, for example, potatoes should become the general and
common food of the people, as rice is in some countries, one fourth, or
one half of the land now in cultivation, would probably be immediately
abandoned; for if, as Adam Smith says, "an acre of potatoes will produce
six thousand weight of solid nourishment, three times the quantity
produced by the acre of wheat," there could not be for a considerable
time such a multiplication of people, as to consume the quantity that
might be raised on the land before employed for the cultivation of
wheat; much land would consequently be abandoned, and rent would fall;
and it would not be till the population had been doubled or trebled,
that the same quantity of land could be in cultivation, and the rent
paid for it as high as before.

Neither would any greater proportion of the gross produce