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.

4. First Sort

The first sort of rude produce of which the price rises in the progress of improvement is that which it is scarce in the power of human industry to multiply at all. It consists in those things which nature produces only in certain quantities, and which, being of a very perishable nature, it is impossible to accumulate together the produce of many different seasons.

Such are the greater part of rare and singular birds and fishes, many