The valley of the Somme, between Abbeville and Amiens, is occupied by beds of peat, some twenty or thirty feet deep, resting on a thin bed of clay which covers other beds, of sand and gravel, and itself rests on white Chalk with flints. Bordering the valley, some hills rise with a gentle slope to a height of 200 or 300 feet, and here and there, on their summits, are patches of Tertiary sand and clay, with fossils, and again more extensive layers of loam. The inference from this geological structure is that the river, originally flowing through the Tertiary formation, gradually cut its way through the various strata down to its present level. From the depth of the peat, its lower part lies below the sea-level, and it is supposed that a depression of the region has occurred at some period: again, in land lying quite low on the Abbeville side of the valley, but above the tidal level, marine shells occur, which indicate an elevation of the region; again, about 100 feet above the valley, on the right bank of the river, and on a sloping surface, is the Moulin-Quignon, where shallow pits exhibit a floor of chalk covered by gravel and sand, accompanied by gravel and marly chalk and flints more or less worn, well-rounded Tertiary flints and pebbles, and fragments of Tertiary sandstone. Such is the general description of a locality which has acquired considerable celebrity in connection with the question of the antiquity of man.
The Quaternary deposits of Moulin-Quignon and the peat-beds of the Somme formerly furnished Cuvier with some of the fossils he described, and in later times chipped flint-implements from the quarries and bogs came into the possession of M. Boucher de Perthes; the statements were received at first not without suspicion—especially on the part of English geologists who were familiar with similar attempts on their own credulity—that some at least of these were manufactured by the workmen of the district. At length, the discovery of a human jaw and tooth in the gravel-pits of St. Acheul, near Amiens, produced a rigorous investigation into the facts, and it seems to have been established to the satisfaction of Mr. Prestwich and his colleagues, that flint-implements and the bones of extinct Mammalia are met with in the same beds, and in situations indicating very great antiquity. In the sloping and irregular deposits overlooking the Somme, the bones of Elephants, Rhinoceros, with land and fresh-water shells of existing species, are found mingled with flint-implements. Shells like those now found in the neighbouring streams and hedge-rows, with the bones of existing quadrupeds, have been obtained from the peat, with flint-tools of more than usual finish, and together with them a few fragments of human bones. Of these reliquiæ, the Celtic memorials lie below the Gallo-Roman; above them, oaks, alders, and walnut trees occur, sometimes rooted, but no succession of a new growth of trees appear.
The theory of the St. Acheul beds is this: they were deposited by fluviatile action, and are probably amongst the oldest deposits in which human remains occur, older than the peat-beds of the Somme—but what is their real age? Before submitting to the reader the very imperfect answer this question admits of, a glance at the previous discoveries, which tended to give confirmation to the observations just narrated, may be useful.
Implements of stone and flint have been continually turning up during the last century and a half in all parts of the world. In the neighbourhood of Gray’s Inn Lane, in 1715, a flint spear-head was picked up, and near it some Elephants’ bones. In the alluvium of the Wey, near Guildford, a wedge-shaped flint-tool was found in the gravel and sand, in which Elephants’ tusks were also found. Under the cliffs at Whitstable an oval-shaped flint-tool was found in what had probably been a fresh-water deposit, and in which bones of the Bear and Elephant were also discovered. Between Herne Bay and Reculver five other flint-tools have been found, and three more near the top of the cliff, all in fresh-water gravel. In the valley of the Ouse, at Beddenham, in Bedfordshire, flint-implements, like those of St. Acheul, mixed with the bones of Elephant, Rhinoceros, and Hippopotamus, have been found, and near them an oval and a spear-shaped implement. In the peat of Ireland great numbers of such implements have been met with. But nowhere have they been so systematically sought for and classified as in the Scandinavian countries.
The peat-deposits of those countries—of Denmark especially—are formed in hollows and depressions, in the northern drift and Boulder clay, from ten to thirty feet deep. The lower stratum, of two or three feet in thickness, consists of sphagnum, over which lies another growth of peat formed of aquatic and marsh plants. On the edge of the bogs trunks of Scotch firs of large size are found—a tree which has not grown in the Danish islands within historic times, and does not now thrive when planted, although it was evidently indigenous within the human period, since Steenstrup took with his own hands a flint-implement from beneath the trunk of one. The sessile variety of the oak would appear to have succeeded the fir, and is found at a higher level in the peat. Higher up still, the common oak, Quercus robur, is found along with the birch, hazel, and alder. The oak has in its turn been succeeded by the beech.
Another source from which numerous relics of early humanity have been taken is the midden-heaps (Kjökken-mödden) found along the Scandinavian coast. These heaps consist of castaway shells mixed with bones of quadrupeds, birds, and fishes, which reveal in some respects the habits of the early races which inhabited the coast. Scattered through these mounds are flint-knives, pieces of pottery, and ashes, but neither bronze nor iron. The knives and hatchets are said to be a degree less rude than those of older date found in the peat. Mounds corresponding to these, Sir Charles Lyell tells us, occur along the American coast, from Massachusetts and Georgia. The bones of the quadrupeds found in these mounds correspond with those of existing species, or species which have existed in historic times.
By collecting, arranging, and comparing the flint and stone implements, the Scandinavian naturalists have succeeded in establishing a chronological succession of periods, which they designate—1. The Age of Stone; 2. The Age of Bronze; 3. The Age of Iron. The first, or Stone period, in Denmark, corresponded with the age of the Scotch fir, and, in part, of the sessile oak. A considerable portion of the oak period corresponded, however, with the age of bronze, swords made of that metal having been found in the peat on the same level with the oak. The iron age coincides with the beech. Analogous instances, confirmatory of these statements, occur in Yorkshire, and in the fens of Lincolnshire.
The traces left indicate that the aborigines went to sea in canoes scooped out of a single tree, bringing back deep-sea fishes. Skulls obtained from the peat and from tumuli, and believed to be contemporaneous with the mounds, are small and round, with prominent supra-orbital ridges, somewhat resembling the skulls of Laplanders.
The third series of facts (Lake-dwellings, or lacustrine habitations) consisted of the buildings on piles, in lakes, and once common in Asia and Europe. They are first mentioned by Herodotus as being used among the Thracians of Pæonia, in the mountain-lake Prasias, where the natives lived in dwellings built on piles, and connected with the shore by a narrow causeway, by which means they escaped the assaults of Xerxes. Buildings of the same description occupied the Swiss lakes, in the mud of which hundreds of implements, like those found in Denmark, have been dredged up. In Zurich, Moosseedorf near Berne, and Lake Constance, axes, celts, pottery, and canoes made out of single trees, have been found; but of the human frame scarcely a trace has been discovered. One skull dredged up at Meilen, in the Lake of Zurich, was intermediate between the Lapp-like skull of the Danish tumuli and the more recent European type.
The age of the different formations in which these records of the human race are found will probably ever remain a mystery. The evidence which would make the implements formed by man contemporaneous with the Mammoth and other great Mammalia would go a great way to prove that man was also pre-glacial. Let us see how that argument stands.