occasioned the use of various commodities for this purpose in the early periods of society.
Of these, cattle seem to have been the most general. Among pastoral nations, they are not only kept without difficulty or loss by those who obtain them, but as they form the principal possessions and wealth of society in this stage of its progress, they must naturally have been the subject of frequent exchanges, and their exchangeable value in consequence compared with other commodities would be pretty generally known.
It seems to be quite necessary indeed that the commodity chosen for a medium of exchange should, in addition to the other qualities which may fit it for that purpose, be in such frequent use that the estimation in which it was held, founded on the desire to possess it, and the difficulty of obtaining it, should be tolerably well established.
A curious and striking proof of this is, that notwithstanding the peculiar aptitude of the precious metals to perform the functions of a medium of exchange, they had not been used for that purpose in Mexico at the period of its conquest by the Spaniards, although these metals were in some degree of plenty as ornaments, and although the want of some medium of exchange was clearly evinced by the use of the nuts of cacao for that purpose.*
It is probable, that as the practice of smelting and refining the ores of the precious metals had not yet been resorted to, the supply of them was not sufficiently steady, nor was the use of them sufficiently general, or the degree of difficulty with which they were obtained sufficiently known, to fit them for the purpose required.
In Peru, where the precious metals were found by the Spaniards in much greater abundance, the practice of smelting and refining the richest ores had begun to prevail, although no shafts had been sunk to any depth in the earth.† But in Peru the state of
