The city of Trenton, New Jersey, is built on a gravel terrace whose surface is between forty and fifty feet above the flood plain of the Delaware. We are told that this gravel is clearly a river deposit, and must have been laid down by the Delaware at some former time in its history. It is in this gravel deposit that quite a large number of Paleolithic implements have been found.
This cut is a representation of one of them, found under such circumstances that there can be no question about its antiquity. We are told it was taken from the face of the bluff fronting the river. Owing to heavy rains, a large section off of the front of the bluff became detached just the day before this specimen was discovered. It was found in the fresh surface thus exposed, twenty-one feet from the surface, almost at the bottom of the gravel. Immediately above it, and in contact with it, was a bowlder estimated to weigh over one hundred pounds. Immediately above this last was a second and much larger bowlder. It is manifest the implements could never have gotten in the place found after the gravel had been deposited.54
This is only one of the many examples that could be given. But it is to be noticed that implements of the Neolithic type do not occur in the gravel, except on the surface. Dr. Abbott is not the only one who has found those implements. Many of our best American scholars have visited the locality and secured specimens, amongst others, Prof. Boyd Dawkins, of England, who is so familiar with this class of relics in Europe. We may consider it proven, then, that in this country there was also a Paleolithic Age. Our present information in regard to it is only a beginning.
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.
He considers the gravels in question to have been deposited near the close of this flooded period, when the land stood at about its present level and the glaciers had retreated perhaps to the Catskill Mountains. The rivers were still swollen and would be heavily charged with coarse gravel brought from the morains and lying exposed on the surface of the ground vacated by the glaciers.58