The preceding résumé shows pretty conclusively that the American peoples and the American civilizations, if not indigenous to the New World, were introduced from the Old at a period long preceding any to which we are carried by the traditional or monumental annals of either continent. We have found no evidence of any populating or civilizing migration across the ocean from east or west, north or south, within historic times. Nothing approaching identity has been discovered between any two nations separated by the Atlantic or Pacific. No positive record appears even of communication between America and the Old World,--intentionally by commercial, exploring, or warlike expeditions, or accidentally by shipwreck,--previous to the voyages of the Northmen in the tenth century; yet that such communication did take place in many instances and at different periods is extremely probable. The numerous trans-oceanic analogies, more or less clearly defined, which are observed, may have resulted partially from this communication, although they do not of themselves necessarily imply such an agency. If scientific research shall in the future decide that all mankind descended from one original pair, that the centre of population was in Asia rather than in America, and that all civilization originated with one Old World branch of the human family--and these are all yet open questions--then there will be no great difficulty in accounting for the transfer of both population and culture; in fact the means of intercontinental intercourse are so numerous and practicable that it will perhaps be impossible to decide on the particular route or routes by which the transfer was effected. If, on the other hand, a contrary decision be reached on the above questions, the phenomena of American civilization and savagism will be even more easily accounted for. [Sidenote: THE MYSTERY OF ANTIQUITY.]