[Footnote 16: According to Dr. Rink the Eskimos formerly inhabited the central portions of North America, and have retreated or been driven northward; he would make the Eskimos of Siberia an offshoot from those of America, though he freely admits that there are grounds for entertaining the opposite view. Dr. Abbott is inclined to attribute an Eskimo origin to some of the palaeoliths of the Trenton gravel. On the other hand, Mr. Clements Markham derives the American Eskimos from those of Siberia. It seems to me that these views may be comprehended and reconciled in a wider one. I would suggest that during the Glacial period the ancestral Eskimos may have gradually become adapted to arctic conditions of life; that in the mild interglacial intervals they migrated northward along with the musk-sheep; and that upon the return of the cold they migrated southward again, keeping always near the edge of the ice-sheet. Such a southward migration would naturally enough bring them in one continent down to the Pyrenees, in the other down to the Alleghanies; and naturally enough the modern inquirer has his attention first directed to the indications of their final retreat, _both_ northward in America and northeastward from Europe through Siberia. This is like what happened with so many plants and animals. Compare Darwin's remarks on "Dispersal in the Glacial Period," _Origin of Species_, chap. xii. The best books on the Eskimos are those of Dr. Rink, _Tales and Traditions of the Eskimo_, Edinburgh, 1875; _Danish Greenland_, London, 1877; _The Eskimo Tribes, their Distribution and Characteristics, especially in regard to Language_, Copenhagen, 1887. See also Franz Boas, "The Central Eskimo," _Sixth Report of the Bureau of Ethnology_, Washington, 1888, pp. 399-669; W. H. Dall. _Alaska and its Resources_, 1870; Markham, "Origin and Migrations of the Greenland Esquimaux," _Journal of the Royal Geographical Society_, 1865; Cranz, _Historie von Groenland_, Leipsic, 1765; Petitot, _Traditions indiennes du Canada nord-ouest_, Paris, 1886; Pilling's _Bibliography of the Eskimo Language_, Washington, 1887; Wells and Kelly, _English-Eskimo and Eskimo-English Vocabularies, with Ethnographical Memoranda concerning the Arctic Eskimos in Alaska and Siberia_, Washington, 1890; Carstensen's _Two Summers in Greenland_, London, 1890.]