les traces du moyen-âge. Cinquante centimètres plus bas, on commence à trouver des déris romains, puis gallo-romains. On continue à suivre ces derniers pendant un mètre, c'est a dire jusqu'au niveau de la Somme. Après eux, viennent les vestiges gaulois purs qui descendent sans interruption jusqu'à près de 2 mètres audessous de ce niveau, preuve de la longue habitation de ces peuples dans la vallée. C'est à un mètre plus bas, ou a 4 mètres environ audessous de ce même niveau, qu'on arrive au centre du sol que nois avons nommé Celtique, celui qui foulèrent les Gaulois primitives ou les peuples qui les précédèrent;" and which belonged therefore to the ordinary stone period. It is, however, hardly necessary to add that these thicknesses are only given by M. Boucher de Perthes "comme terme approximatif"
The "Antiquités Celtiques" was published several years before the Swiss Archæologists had made us acquainted with the nature of the Pfahlbauten; but, from some indications given by M. Boucher de Perthes, it would appear that there must have been, at one time, lake-habitations in the neighbourhood of Abbeville. He found considerable platforms of wood, with large quantities of bones, stone implements, and handles closely resembling those which come from the Swiss lakes.
These weapons cannot for an instant be confounded with the ruder ones from the drift gravel They are ground to a smooth surface and a cutting edge, while the more ancient ones are merely chipped, not one of the many hundreds already found having shown the slightest trace of grinding. Yet though the former belong to the stone age, to a time so remote that the use of metal was apparently still unknown in Western Europe, they are separated from the earlier weapons of the upper level drift by the whole period necessary for the excavation of the Somme Valley, to a depth of more than 100 feet.
If, therefore, we get no definite date for the arrival of man in these countries, we can at least form a vivid idea of his antiquity. He must have seen the Somme running at a height of, in round numbers, a hundred and fifty feet above its present level. From finding the hatchets in the gravel up to a level of a hundred feet, it is probable that he dates back in Northern France almost, if not quite, as long as the rivers themselves. The face of the country must have been indeed unlike what it is now. Along the banks of the rivers ranged a savage race of hunters and fishermen, and in the forests wandered the mammoth, the two-horned, woolly, rhinoceros, a species of tiger, the musk ox, the reindeer, and the urus.
Yet the geography of France cannot have been very different from what it is at present. The present rivers ran in their present directions, and the sea even then lay between the Somme and the Adur, though the channel was not so wide as it is at present.
Gradually the river deepened its valley; ineffective, or even perhaps constructive, in autumn and winter, the melting of the snows
