Since this interesting discovery was made in New Jersey we have received news of similar discoveries in Minnesota. A lady, Miss Frank Babbitt, has found in the modified drift of the Mississippi River, at Little Falls, Minnesota, evidence of the existence of Paleolithic man. The implements are made of quartz, and not argillite, but closely resemble implements made of this later material as described by Dr. Abbott. It is, to say the least, an interesting coincidence that one of a very few flint implements found in the Trenton gravel by Dr. Abbott should be identical in shape with some of the flint implements in Minnesota.55
This point being determined, others at once spring up asking solution. Among the very first is the question of age. The river terrace on which Trenton is built is a geological formation, and if we can determine its age we shall also determine at least one point in the antiquity of man, for we know the implements are as old as the gravels. It is not necessary for our purpose to give more than the results of the careful labors of others in this direction. We may be sure that this question has been carefully studied. When the implements were first discovered, the gravels were considered of glacial origin, and to that period they were assigned by Dr. Abbott. Subsequently Prof. Lewis, a member of the Pennsylvania State survey, decided that they were essentially post-glacial—that is, more recent in time than the Glacial Age.56 Still more recently Prof. Wright, of Oberlin, but also of the State survey of Pennsylvania, concludes that they are, after all, a deposit made at the very close of the Glacial Age.57
He thinks the sequence of events were about as follows: When the ice of the Glacial Age reached its greatest development, and came to a pause in its southward march, it extended in an unbroken wall across the northern part of New Jersey, crossing the Delaware about sixty-five miles above Trenton. In front of it was accumulated the great terminal morain—a long range of gravelly hills still marking its former presence.
It is certain that the close of the Glacial Age was comparatively sudden, and marked by floods far exceeding any thing we are acquainted with at the present day. For, when the formation of the ice ceased, we must bear in mind that the country to the north of the terminal morain was covered with a great glacier, in some places exceeding a mile in thickness. When glacial conditions were passing away, and the ice commenced to melt faster than it was produced, the thaw would naturally go on over the entire field at an increasing rate, and hence would result floods in all the rivers.