Now the traces of the existence of men in North America during the Glacial epoch have in recent years been discovered in abundance, as for example, the palaeolithic quartzite implements found in the drift near the city of St. Paul, which date from toward the close of the Glacial epoch[6]; the fragment of a human jaw found in the red clay deposited in Minnesota during an earlier part of that epoch;[7] the noble collection of palaeoliths found by Dr. C. C. Abbott in the Trenton gravels in New Jersey; and the more recent discoveries of Dr. Metz and Mr. H. T. Cresson. [Footnote 6: See Miss F. E. Babbitt, "Vestiges of Glacial Man in Minnesota," in _Proceedings of the American Association_, vol. xxxii., 1883.] [Footnote 7: See N. H. Winchell, _Annual Report of the State Geologist of Minnesota_, 1877, p. 60.] [Sidenote: Discoveries in the Trenton gravel.] [Sidenote: Discoveries in Ohio, Indiana, and Minnesota;] The year 1873 marks an era in American archaeology as memorable as the year 1841 in the investigation of the antiquity of man in Europe. With reference to these problems Dr. Abbott occupies a position similar to that of Boucher de Perthes in the Old World, and the Trenton valley is coming to be classic ground, like the valley of the Somme. In April, 1873, Dr. Abbott published his description of three rude implements which he had found some sixteen feet below the surface of the ground "in the gravels of a bluff overlooking the Delaware river." The implements were in place in an undisturbed deposit, and could not have found their way thither in any recent time; Dr. Abbott assigned them to the age of the Glacial drift. This was the beginning of a long series of investigations, in which Dr. Abbott's work was assisted and supplemented by Messrs. Whitney, Carr, Putnam, Shaler, Lewis, Wright, Haynes, Dawkins, and other eminent geologists and archaeologists. By 1888 Dr. Abbott had obtained not less than 60 implements from various recorded depths in the gravel, while many others were found at depths not recorded or in the talus of the banks.[8] Three human skulls and other bones, along with the tusk of a mastodon, have been discovered in the same gravel. Careful studies have been made of the conditions under which the gravel-banks were deposited and their probable age; and it is generally agreed that they date from the later portion of the Glacial period, or about the time of the final recession of the ice-sheet from this region. At that time, in its climate and general aspect, New York harbour must have been much like a Greenland fiord of the present day. In 1883 Professor Wright of Oberlin, after a careful study of the Trenton deposits and their relations to the terrace and gravel deposits to the westward, predicted that similar palaeolithic implements would be found in Ohio. Two years afterward, the prediction was verified by Dr.