376 MIGRATIONS OF MAN FROM THE CONTINENT. CHAP. xix. 



to have retreated into the higher mountains. During some 

 part of the Post-pliocene ages, the large pachyderms and ac 

 companying beasts of prey, now extinct, wandered from the 

 Continent to England ; but whether the junction of France 

 and any part of the British Isles was as late as the period of 

 the gravels of St. Acheul, or the era of those engulfed rivers 

 which, in the basin of the Meuse, near Liege, swept into many 

 a rent and cavern the bones of Man and of the mammoth 

 and cave-bear, is still doubtful. There have been vast geo 

 graphical revolutions since the times alluded to, and oscilla 

 tions of land, during which the English Channel, which can 

 be shown b} T the Pagham erratics, and the old Brighton 

 beach (p. 280), to be of very ancient origin, may have been 

 more than once laid dry and again submerged since it ori 

 ginated. During some one of these phases, Man may have 

 crossed over, whether by land or in canoes, or even on the 

 ice of a frozen sea (as Mr. Prestwich has hinted), for the 

 winters of the period of the higher level "gravels of the valley 

 of the Somme were intensely cold. 



The primitive people, who coexisted with the elephant and 

 rhinoceros in the valley of the Ouse at Bedford, and who 

 made use of flint tools of the Amiens type, certainly in 

 habited part of England which had already emerged from 

 the waters of the glacial sea, and the fabricators of the flint 

 tools of Hoxne, in Suffolk, were also, as we have seen, post 

 glacial. We may likewise presume, that the people of post- 

 pliocene date, who have left their memorials in the valley of 

 the Thames, were of corresponding antiquity, posterior to the 

 boulder clay, but anterior to the time when the rivers of that 

 region had settled into their present channels. 



The vast distance of time which separated the origin of 

 the higher and lower level gravels of the valley of the Somme, 

 both of them rich in flint implements of similar shape (al 

 though those of oval form predominate in the newer gravels), 



