Page:Archaeologia volume 38 part 2.djvu/53

Rh flint were comparatively rare, and no pebbles or blocks occurred either within or without the cave; so that there could be but little doubt of the flint flakes being of human workmanship.

The question of the co-existence of man with the extinct animals of the Drift period being thus revived, Mr. Joseph Prestwich, F.R.S., a distinguished geologist, who for years has devoted his principal attention to the more recent geological formations, determined to proceed to Abbeville and investigate on the spot the discoveries of M. Boucher de Perthes, and invited me and several other Fellows of the Geological Society to accompany him. The others were unfortunately prevented from doing so; but at the end of April, 1859, I joined Mr. Prestwich at Abbeville, and with him inspected the collections of M. de Perthes (to whose courtesy and hospitality we were largely indebted), and also visited in his company several of the pits worked for gravel and sand in the neighbourhood of both Abbeville and Amiens, in which the flints in question were asserted to have been found.

Both these towns are situated upon the upper chalk, which is, however, overlaid, as is frequently the case, by beds of drift of a much later period. I need hardly say that drift is the term applied by geologists to those superficial deposits of sands, gravels, clays, and loams which we find to have been spread out over the older rocks in many districts by the driving action of currents of water, whether salt or fresh, or by the drifting action of ice. Though all belonging to a late geological period (the newer Pleiocene, or Pleistocene), these beds of drift are of various and distinct ages, and may be said to range from a point of time antecedent to the Glacial period, when nearly the whole of Britain was submerged beneath an ocean of arctic temperature, to the time when the surface of the earth received its present configuration, and even down to the present day; for the alluvium of existing rivers may be considered equivalent to the fresh-water drift of an earlier age.

The drift-beds occurring in different localities in the neighbourhood of Abbeville and Amiens, do not appear to have been all deposited at the same time, but to be of at least two distinct ages; the series on the lower level being distinguished by the occurrence within it of the bones and teeth of the Elephas primigenius, or Siberian mammoth, and of other extinct animals. These mammaliferous beds of sand, loam, and gravel extend over a considerable tract of country on the slopes of the valley of the Somme, and are worked in several localities for the repair of the roads and for building purposes.