If you except corn, and such other vegetables as are raised altogether by human industry, that all other sorts of rude produce, cattle, poultry, game of all kinds, the useful fossils and minerals of the earth, etc. naturally grow dearer, as the society advances in wealth and improvement, I have endeavoured to shew already. Though such commodities, therefore, come to exchange for a greater quantity of silver than before, it will not from thence follow that silver has become really cheaper, or will purchase less labour than before; but that such commodities have become really dearer, or will purchase more labour than before. It is not their nominal price only, but their real price, which rises in the progress of improvement. The rise of their nominal price is the effect, not of any degradation of the value of silver, but of the rise in their real price.
Different Effects of the Progress of Improvement upon three different sorts of rude Produce.
These different sorts of rude produce may be divided into three classes. The first comprehends those which it is scarce in the power of human industry to multiply at all. The second, those which it can multiply in proportion to the demand. The third, those in which the efficacy of industry is either limited or uncertain. In the progress of wealth and improvement, the real price of the first may rise to any degree of extravagance, and seems not to be limited by any certain boundary. That of the second, though it may rise greatly, has, however, a certain boundary, beyond which it cannot well pass for any considerable time together. That of the third, though its natural tendency is to rise in the progress of improvement, yet in the same degree of improvement it may sometimes happen even to fall, sometimes to continue the same, and sometimes to rise more or less, according as different accidents render the efforts of human industry, in multiplying this sort of rude produce, more or less successful.