stone, such weapons naturally soon became media of exchange; when the ox and the sheep, the swine and the goat are tamed, large additions are made to the circulating media of the more advanced communities; then come the metals; the older ornaments of shells and implements of stone are replaced by those of gold (and much later by silver) and by weapons of bronze as in Asia and Europe, and by those of iron in Africa. Copper and iron circulate either in the form of implements and weapons, such as the axes of West Africa, the hoes of the early Chinese and modern Bahnars, and the ancient Chinese knives, all of which remind us of the axes and half-axes in Homer; or in the form of rings and bracelets, like the manillas of West Africa and the ancient Irish fibulae; or else in the form of plates or bars of metal, ready to be employed for the manufacture of such articles, as we saw in the case of the iron bars of Laos, the iron discs of the Madis, and the brass rods of the Congo. Again we are reminded of the mass of pig-iron, which Achilles offered as a prize2.
It is of the highest importance to observe that such pieces of copper and iron are not weighed, but are appraised by measurement. We shall find that it is only at a period long subsequent to the weighing of gold that the inferior metals are estimated by weight. The custom of capturing wives which prevails among the lowest savages is succeeded by the custom of purchasing wives. The woman is only a chattel on the same footing as the cow or the sheep, and she is accordingly appraised in terms of the ordinary media of exchange employed in her community, whether it be in cows, horses, beads, skins or blankets. Presently male captives are found useful both to tend flocks and, as in the East and in the modern Soudan, to guard the harem. With the discovery of gold, ornaments made at first out of the rough nuggets supersede other ornaments, and presently either such ornaments or portions of gold in plates or lumps are added to the list of media, and the same follows with the discovery of silver. Such ornaments or pieces of gold and silver are estimated in terms of cattle, and the standard unit of the bars or ingots naturally is adjusted