Narrative and Critical History of America, Vol. 1 (of 8) / Aboriginal America

by Unknown

There has been much discussion among geologists in regard to both the duration and the conditions of the glacial period, but it is now the settled opinion that there have been two distinct times of glacial action, separated by a long interval of warmer climate, as is proved by the occurrence of intercalated fossiliferous beds; this was followed by the final retreat of the glacier.[1482] The great terminal moraine stretching across the United States from Cape Cod to Dakota, and thence northward to the foot of the Rocky Mountains, marks the limit of the ice invasion in the second glacial epoch. South of this, extending in its farthest boundary as low as the 38th degree of latitude, is a deposit which thins out as we go west and northwest, and which is called the drift-area. The drift graduates into a peculiar mud deposit, for which the name of “loess” has been adopted from the geologists of Europe, by whom it was given to a thick alluvial stratum of fine sand and loam, of glacial origin. This attenuated drift represents the first glacial invasion. From Massachusetts as far as northern New Jersey, and in some other places, the deposits of the two epochs seem to coalesce.[1483]

The interval of time that separated the two glacial periods can be best imagined by considering the great erosions that have taken place in the valleys of the Missouri and of the upper Ohio. “Glacial river deposits of the earlier epoch form the capping of fragmentary terraces that stand 250 to 300 feet above the present rivers;” while those of the second epoch stretch down through a trough excavated to that depth by the river through these earlier deposits and the rock below.[1484]

As to the probable time that has elapsed since the close of the glacial period, the tendency of recent speculation is to restrict the vast extent that was at first suggested for it to a period of from twenty thousand to thirty thousand years. The most conservative view maintains that it need not have been more than ten thousand years, or even less.[1485] This lowest estimate, however, can only be regarded as fixing a minimum point, and an antiquity vastly greater than this must be assigned to man, as of necessity he must have been in existence long before the final events occurred in order to have left his implements buried in the beds of débris which they occasioned.

In April, 1873, Dr. C. C. Abbott, who was already well known as an investigator of the antiquities of the Indian races, which he believed had passed from “a palæolithic to a neolithic condition” while occupying the Atlantic seaboard, published an article on the “Occurrence of implements in the river-drift at Trenton, New Jersey.”[1486] In this he described and figured three rude implements, which he had found buried at a depth as great in one instance as sixteen feet in the gravels of a bluff overlooking the Delaware River. He argued that these must be of greater antiquity than relics found on the surface, from the fact of their occurring in place in undisturbed deposits; that they could not have reached such a depth by any natural means; and that they must be of human origin, and not accidental formations, because as many as three had been discovered of a like character. His conclusion is that they are “true drift implements, fashioned and used by a people far antedating the people who subsequently occupied this same territory.”

After two years of further research he returned to the subject, publishing in the same journal, in June, 1876, an account of the discovery of seven similar objects near the same locality. Of these he said: “My studies of these palæolithic specimens and of their positions in the gravel-beds and overlying soil have led me to conclude that not long after the close of the last glacial epoch man appeared in the valley of the Delaware.”[1487]

Most of these specimens were deposited by Dr. Abbott in the Peabody Museum of American Archæology and Ethnology at Cambridge, Massachusetts; and the curator of that institution, Professor Frederick W. Putnam, in September, 1876, visited the locality in company with Dr. Abbott. Together they succeeded in finding two examples in place. Having been commissioned to continue his investigations, Dr. Abbott presented to the trustees, in November of the same year, a detailed report On the Discovery of Supposed Palæolithic Implements from the Glacial Drift in the Valley of the Delaware River, near Trenton, New Jersey.[1488] In this, three of the most characteristic specimens were figured, which had been submitted to Mr. M. E. Wadsworth of Cambridge, to determine their lithological character. He pronounced them to be made of argillite, and declared that the chipping upon them could not be attributed to any natural cause, and that the weathering of their surfaces indicated their very great antiquity. The question “how and when these implements came to be in the gravel” is discussed by Dr. Abbott at some length. He argued that the same forces which spread the beds of gravel over the wide area now covered carried them also; and he predicted that they will be met with wherever such gravels occur in other parts of the State. He specially dwells upon the circumstances that the implements were found in undisturbed portions of the freshly exposed surface of the bluff, and not in the mass of talus accumulated at its base, into which they might have fallen from the surface; and that they have been found at great depths, “varying from five to over twenty feet below the overlying soil.” He also insisted upon the marked difference between their appearance and the materials of which they are fashioned and the customary relics of the Indians. The conditions under which the gravel-beds were accumulated are then studied in connection with a report upon them by Professor N. S. Shaler, which concludes, from the absence of stratification and of pebbles marked with glacial scratches, that they were “formed in the sea near the foot of the retreating ice-sheet, when the sub-glacial rivers were pouring out the vast quantities of water and waste that clearly were released during the breaking up of the great ice-time.” This view regards the deposits as of glacial origin, and as laid down during that period, but considers that they were subsequently modified in their arrangement by the action of water. In such gravel-beds there have also been found rolled fragments of reindeer-horns, and skulls of the walrus, as well as the relics of man. Dr. Abbott accordingly drew the conclusion that “man dwelt at the foot of the glacier, or at least wandered over the open sea, during the accumulation of this mass of gravel;” that he was contemporary of these arctic animals; and that this early race was driven southward by the encroaching ice, leaving its rude implements behind. Thus it will be seen that Dr. Abbott no longer considers man in this country as belonging to post-glacial, but to interglacial times.

Continuing his investigations, in the following year Dr. Abbott gave a much more elaborate account of his work and its results, in which he announced his discovery of some sixty additional specimens.[1489] To the objection that had been raised, that these supposed implements might have been produced by the action of frost, he replied that a single fractured surface might have originated in that way or from an accidental blow; but when we find upon the same object from twenty to forty planes of cleavage, all equally weathered (which shows that the fragments were all detached at or about the same time), it is impossible not to recognize in this the result of intentional action. Four such implements are described and figured, of shapes much more specialized than those previously published, and resembling very closely objects which European archæologists style stone axes of “the Chellean type,” whose artificial origin cannot be doubted.

THE TRENTON GRAVEL BLUFF.