Fig. 2.—Ice-Gorged River.
Reproducing on a small scale the conditions of the Glacial epoch.
It has been stated in the most positive manner, which only positive evidence could warrant, that so-called paleolithic implements have not been found in situ in gravel deposits at a distance from the river, and such, if there were such, as appeared to be in the gravel, were recent intrusions. This statement, in its several parts and its entirety, is absolutely incorrect, and no excuse can be offered for its publication. It is to be explained, however, because avowedly predetermined. Wherever the glacial gravel of the Delaware tide-water region is found, there paleolithic implements occur, as they also do on and in the surface of areas beyond the gravel boundary. We accept, notwithstanding the unscientific source of the suggestion, the statement that post-glacial floods inhumed all traces of man found beneath the superficial soils, and find that, if these traces are considered in that light, some mysterious power was behind the senseless flood, and always buried argillite paleolithic implements far down in the gravel, and then selected argillite artifacts of more specialized forms for the overlying sands and reserved the pottery and jasper arrow points for the vegetation-sustaining soil. This, as stated, is absurd, but such is the order of occurrence of the traces of early man in the upland fields, and these are to be considered carefully before a final conclusion can be reached. The broad, elevated plateau extending eastward from the present bank of the river offers facilities for studying the evidences of man's occupancy in this region such as are to be found in few localities. The principal reason for this is that almost no local disturbance has occurred since the original deposition of the sand that overlies the gravel and underlies the soil. The natural history of these underlying sands has recently received a good deal of attention, because, unlike the deeper gravels, there is perfect accord as to the occurrences therein of artificially chipped objects; and the suggestion that they are of intrusive origin being set aside as untenable, the geologists are now divided on the question whether the sand is wind-blown, a modified dune, and so not necessarily old even in years, or the result of intermitting overflow of water, usually carrying a considerable amount of sand and often heavy with washings from some distant clay bank. The objections to the "eolian" theory are that pebbles and bowlders, even of considerable weight, are scattered at all elevations through the sand, and these pebbles, as a rule, do not present any evidence of exposure to eroding sands, but are smooth and glassy, or the typical water-worn pebbles of a brook or the river bed, and more significant is the fact that the sands themselves are of different degrees of fineness, layer upon layer, and are nowhere clean or free from clay; and finally the thin layers of clay are clearly continuous over such extensive areas that in no sense can they be called segregations of that material. On the other hand, a carefully instituted comparison of the sand from the surface of the field to its junction with the gravel proper shows its identity with a deposit made by water in comparatively recent times. No difference whatever could be detected. The sand dune, modified by rains and finally leveled to a plain, presents, in section, no such appearance as the sands that overlie the gravels of glacial origin. Without a scintilla of reason, however, many geologists declare that no deposit of sand can be of any geological significance if it contains traces of man not clearly intrusive. The latter fact necessitates the former claim, all of which, I submit, is nonsense.
Fig. 3 illustrates how artificially chipped pebbles occur in this underlying sand. The upper portion shows the superficial soil removed to its point of contact with the sand. This is determined by the change of color from dark brown to light yellowish brown, and it is generally so very abrupt a change that no doubt arises as to where the soil ends and the sand begins. The sand proper is shown by the position of the object—the measuring rule and trowel. It will be noticed that the implement is lying flat, as such an object would almost necessarily be if transported by water, and not perpendicular, as would be the case if it had fallen down some root-hole, animal's or insect's burrow, or opening in the earth from any cause, and now obliterated.
Fig. 3.—Occurrence of an Argillite Implement in Glacial Stratified Sand.
The presence of these artificial flakes, blades, and other forms of simple implements can only be explained by considering them as a constituent part of the containing bed, having been brought hither by the same agency that brought the sand, pebbles, and clay. When standing before a newly made section of this implement-bearing deposit it is easy to picture the slow progress of its accumulation. The broad plain has been subjected to overflow, now of water bearing only sand, and then of muddy water; now with current strong enough to roll small pebbles from some distant point, and then periods when the sun shone on the new deposit, dried it, and the loose sand was rippled by the wind. Floods of greater volume occasionally swept across the plain, and ice-incased pebbles were dropped upon its surface, and with this building up of the plateau to a higher level there were also brought to it traces of man's handiwork. Of this, I think, there can be no doubt now. Years ago I endeavored to show from the distribution of rude argillite implements of specialized forms, as arrow points and small blades, trimmed flakes and scrapers, that these objects were older, as a class, than jasper and quartz implements and weapons, and that pottery was made only in the rudest way before "flint" chipping—jasper and quartz—was established. The more exhaustively this subject was followed up, the proposition became more evidently true, and to-day it is unqualifiedly confirmed by the results obtained from systematically digging deeply over wide areas of country. The fact that argillite continued in use until the very last does not affect this conclusion.
As the high land, now forty or more feet above the river and beyond the reach of its floods of greatest magnitude, was once continually overflowed and gradually built up by the materials the water spread upon it, it is evident that the conditions were materially different when such things happened from what now obtains, and the whole configuration of the country to-day points to but the one conclusion: that these plateau-building floods occurred so long ago as when the river flowed at a higher level and possessed a greater transporting power than at present. This, it is true, was long after the coarse gravel and huge bowlders were transported from the hillsides of the upper valley, but it was before the river was confined to its present channel, and more significantly before what may be called the soil-making period, itself of long duration and the time of the Indian as such. Not an argillite chip from the sands beneath the soil but speaks of the distant day when this plateau was an almost barren plain, and man saw it, roamed over it, and perhaps dwelt upon it, when but the scantiest vegetation dotted its surface, and only upon the hills beyond its boundary were there trees and herbage.