multiply at all. Such are the greater part of rare and singular birds and fishes, game, wildfowl and birds of passage, as well as many other things. The high price paid by the Romans, in the time of their greatest grandeur, for rare birds and fishes, may in this manner easily be accounted for. Seius gave what 66 l. 13 s. 4 d. would purchase in the present times for a nightingale. 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. When the price of cattle, for example, rises so high that it is as profitable to cultivate land in order to raise food for them, as in order to raise food for man, it cannot well go higher. If it did, more corn land would soon be turned into pasture. Till the price of cattle, indeed, has got to this height, it seems scarce possible that the greater part, even of those lands which are capable of the highest cultivation, can be completely cultivated. The hog, that finds his food among ordure, and greedily devours many things rejected by every other useful animal, is, like poultry, originally kept as a save-all. As long as the number of such animals, which can thus be reared at little or no expence, is fully sufficient to supply the demand, this sort of butcher?s-meat comes to market at a much lower price