The prevalent phenomena of any given period are those which give it its character, and by which we distinguish it. But this fact does not exclude the coëxistence of other phenomena belonging to prior or subsequent stages. Thus, during the many stages of human progress there have been men more or less in advance of the general body, and their characteristics have given a peculiar stamp to the later and higher condition of the whole. It furnishes no objection to this view that we find, as might have been anticipated, the stone, bronze and iron periods overlaping one another, or men of an inferior culture supplanting in some cases a superior people. A case of this kind is seen in North America, where the existing “Indians,” stone-men, have succeeded the mound-builders, copper-men. The successional relation of discoveries is all that it is necessary to prove, and this seems to be established. The period at which the use of metallic implements was introduced is unknown, but Whitney says that the language of the Aryans, the ancestors of all the modern Indo-Europeans, indicates an acquaintance with such implements, though it is not certain whether those of iron are to be included. The dispersion of the daughter races, the Hindoos, the Pelasgi, Teutons, Celts, etc., could not, it is thought, have taken place later than 3000 B. C.—a date seven hundred years prior, to that assigned by the old chronology to the Deluge. Those races coëxisted with the Egyptian and Chinese nations, already civilized, and as distinct from each other in feature as they are now.