But recent discoveries indicate that, in the case of the last two extinct quadrupeds, a rude primitive human race may have finished the work of extermination, begun by ante cedent and more general causes.
Flint weapons called " celts," unquestionably fashioned by human hands, have been discovered in stratified gravel, containing remains of the mammoth, in the valley of the Somme near Abbeville and Amiens, at different periods, from the year 1847 (Boucher de Perthes, " Antiquites eel tiques et antediluviennes," Paris, 1847) to the present time.
These evidences of the human species have been extracted from the deposit in question, by Mr. Prestwich (" 17 feet from the surface in undisturbed ground," " Proceedings of the Royal Society," May 26, 1859) ; by Mr. Flower, (" 20 feet from the surface, in a compact mass of gravel," " Times," November 18, 1859) ; by M. Gaudry L'Institut," October 5, 1859) ; and by M. Geo. Pouchet,—all with their own hands in the course of the year 1859. Besides the Elephas primigenius, remains of Rhinoceros tichorhinus, Cervus somonensis, Ursus spelerus, and of a large extinct Bovine animal, have been found in the same bed of gravel.
Mr. Prestwich, F.G.S., after a careful study of the geolo logical relations of this bed, refers it to the post-pliocene age ; and to a period " anterior to the surface assuming its present outline, so far as some of its minor features are con cerned." Similar flint weapons had been discovered by Mr. John Frere, F.RS. (" Archeologia," voL xiii, " An account of flint weapons discovered at Hoxne in Suffolk,' 1800) in a bed of flint gravel, 16 feet below the surface, of the same geological age as that in the valley of the Somme.
Flint weapons have been discovered mixed indiscrimi nately with the bones of the extinct cave-bear and rhino ceros. One in particular was met with beneath a fine antler of a rein-deer, and a bone of the cave-bear, imbedded in the superficial stalagmite in the bone-cave at Brixham, Devon shire, during the careful exploration of that cave conducted by a committee of the Geological Society of London in 1858 and 1859.
Dr. Falconer, F.G.S., has communicated (" Proceedings of the Geological Society," June 22, 1859) the results of his examination of ossiferous caves in Palermo ; and in respect to the " Macca,,omone cave," he draws the following infer ences :—That, "it was filled up to the roof within the human period, so that a thick layer of bone splinters, teeth, land shells, coprolites of hyaena, and human objects, was aggluti nated to the roof by the infiltration of water holding lime in solution ; that subsequently and within the human period, such a great amount of change took place in the physical configuration of the district as to have caused the cave to be washed out, and emptied of its contents, excepting the floor breccia and the patches of material cemented to the roof, and since coated with additional stalagmite." (P. 136.)
Sir Charles Lyell believes "the antiquity of the Abbeville and Amiens flint instruments to be great indeed, if compared to the times of history or tradition. . . ." " It must have re quired a long period for the wearing down of the chalk which supplied the broken flints for the formation of so much gravel at various heights, sometimes 100 feet above the present level of the Somme, for the deposition of fine sediment including entire shells both terrestrial and aquatic, and also for the denudation which the entire mass of stratified drift has under gone, portions having been swept away, so that what remains of it often terminates abruptly in old river cliffs, besides being covered by a newer unstratified drift. To explain these changes, I should infer considerable oscillations in the level of the land in that part of France ; slow movements of up heaval and subsidence, deranging but not wholly displacing the course of ancient rivers. Lastly, the disappearance of the elephant, rhinoceros, and other genera of quadrupeds, now foreign to Europe, implies in like manner a vast lapse of ages, separating the era in which the fossil implements were framed, and that of the invasion of Gaul by the Romans:* As to the successive appearance of new species in the course of geological time, it is first requisite to avoid the common mistake of confounding the propositions, of species being the result of a continuously operating second ary cause, and of the mode of operation of such creative cause. Biologists may entertain the first without accepting any cur rent hypothesis as to the second.