During the first or main Inter-glacial Period was deposited the “modified drift.” In a terrace of this material on the Mississippi, near Little Falls, Minnesota, Miss Babbitt found numerous quartz chips regarded by competent archæologists as artificial products.[13] They represent the refuse of an early workshop near the quartz veins in that vicinity, and were cast aside by the pristine implement-maker when the Minnesota glacier was receding for the last time, but still lifted its icy walls five or ten miles above the present site of Little Falls. The extensive beds of loess which cover many thousand square miles in the Central United States are referred to the second Glacial Epoch. Professor Aughey reports the finding of rudely chipped arrowhead in this loess as it occurs in the Missouri Valley. They lay immediately beneath the vertebra of an elephant, an animal, I need scarcely add, long since extinct. Another proof of man’s presence about that date is a primitive hearth discovered in digging a well along the old beach of Lake Ontario. According to that competent geologist, Professor Gilbert, this dated from a period when the northern shore of that body of water was the sheer wall of a mighty glacier, and the channel of the Niagara river had not yet begun to be furrowed out of the rock by the receding waters.[14] Other finds which must be referred to about this epoch are those by McGee of a chipped obsidian implement in the lacustrine marls of western Nevada; and that of a fragment of a human skull in the westernmost extension of the loess in Colorado.[15] More conclusive than these are the repeated discoveries of implements, chipped from hard stones, in deposits of loess and gravels in Ohio and Indiana, which deposits, without doubt, represent a closing episode of the last Glacial Epoch. There may be some question about the geologic age of the former finds, but about these there is none. They prove beyond cavil that during the closing scenes of the Quaternary in North America, man, tool-making, fire-using man, was present and active.[16] This decision is not only confirmed, but greatly extended, by the researches of Dr. C. C. Abbott and others in the gravels about Trenton, on the Delaware. These were laid down contemporaneously with the terminal moraine in Ohio and Indiana, from which the palæoliths were exhumed. Abbott’s discoveries include several hundred stone implements of the true palæolithic or “Chelléen” type, and some fragments of human skeletons.[17] They reveal to us not only the presence of man, but a well defined stage of culture strictly comparable to that of the “river drift” men of the Thames and the Somme in western Europe, which has been so ably described by De Mortillet.[18]