Page:Early Man in Britain and His Place in the Tertiary Period.djvu/276

248 be remarked, are merely the outer signs or symbols of three phases of culture, each of which was higher and better than that which went before. The history of Britain begins late in the Iron age.

The Prehistoric period is separated from the Pleistocene by a long interval, during which, not merely great changes in the zoology of Britain took place, but also corresponding changes in the geography.

At the close of the Pleistocene age (Fig. 32), the valleys which united Britain to North France, Germany, and Scandinavia, as well as to Ireland, were gradually depressed beneath the sea-level; and the North Sea, the British Channel, the Irish Sea, and the Western Atlantic coast-line generally became very much as we find them now (see Fig. 95). An examination, however, of the submerged forests and peat-bogs proves that the downward movement had not ceased until a late period in the Neolithic age.

We can approach this interesting question most conveniently by examining the evidence as to the submarine forest exposed between tide-marks on the coast of west Somerset, admirably described by Sir Henry de la Beche and by Mr. Godwin-Austen.

It was shown by the latter to be rooted on "an