drift period, but to those of the bone caves, and of the early shell-heaps and peat-bogs. But it may he remarked that geological evidence, though capable of showing the lapse of vast periods of time, has scarcely admitted of these periods being brought into definite chronological terms; yet it is only geological evidence that has given any basis for determining the absolute date at which the makers of the drift implements lived in France and England. In an elaborate paper published in 1864, Mr. Prestwich infers, from the time it must have taken to excavate the river-valleys, even under conditions much more favourable than now to such action, and to bore into the underlying strata the deep pipes or funnels now found lined with sand and gravel, that a very long period must have elapsed since the implement-bearing beds began to be laid down. But his opinion is against extreme estimates, and favours the view that the now undoubted contemporaneity of man with the mammoth, the Rhinoceros tichorhinus, etc., is rather to be accounted for by considering that the great animals continued to live to a later period than had been supposed, than that the age of man on earth is to be stretched to fit with an enormous hypothetical date. Mr. Prestwich thus sums up his view of the subject, "That we must greatly extend our present chronology with respect to the first existence of man appears inevitable; but that we should count by hundreds of thousands of years is, I am convinced, in the present state of the inquiry, unsafe and premature."[1]
A set of characteristic drift implements[2] would consist of certain tapering instruments like huge lance-heads, shaped, edged, and pointed, by taking off a large number of facets, in a way which shows a good deal of skill and feeling for symmetry; smaller leaf-shaped instruments; flints partly shaped and edged, but with one end left unwrought, evidently for holding in the hand; scrapers with curvilinear edges; rude flake-knives, etc. Taken as a whole, such a set of types would be very unlike, for instance, to a set of chipped instruments belonging to the comparatively late period
