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Second sort.-The second sort of rude produce, of which the price

rises in the progress of improvement, is that which human

industry can multiply in proportion to the demand. It consists in

those useful plants and animals, which, in uncultivated

countries, nature produces with such profuse abundance, that they

are of little or no value, and which, as cultivation advances,

are therefore forced to give place to some more profitable

produce. During a long period in the progress of improvement, the

quantity of these is continually diminishing, while, at the same

time, the demand for them is continually increasing. Their real

value, therefore, the real quantity of labour which they will

purchase or command, gradually rises, till at last it gets so

high as to render them as profitable a produce as any thing else

which human industry can raise upon the most fertile and best

cultivated land. When it has got so high, it cannot well go

higher.