Here, fortunately, we meet with a most surprising piece of evidence, which adds enormously to the importance of this plain, and shows that the submergence is no local phenomenon, but a widespread movement of depression which must greatly have altered the physical geography of north-western Europe during times within the memory of man. This evidence deserves a separate chapter. CHAPTER IV THE DOGGER BANK For the last 50 years it has been known to geologists that the bed of the North Sea yields numerous bones of large land animals, belonging in great part to extinct species. These were first obtained by oyster-dredgers, and later by trawlers. Fortunately a good collection of them was secured by the British Museum, where it has been carefully studied by William Davies. The bones came from two localities. One of them, close to the Norfolk coast off Happisburgh, yielded mainly teeth of _Elephas meridionalis_, and its fossils were evidently derived from the Pliocene Cromer Forest-bed, which in that neighbourhood is rapidly being destroyed by the sea. This need not now detain us. [Illustration: Fig. 4.—Showing approximate Coast-line at the period of the lowest Submerged Forest.] The other locality is far more extraordinary. In the middle of the North Sea lies the extensive shoal known as the Dogger Bank, about 60 or 70 miles from the nearest land. This shoal forms a wide irregular plateau having an area nearly as big as Denmark. Over it for the most part the sea has a depth of only 50 or 60 feet; all round its edge it slopes somewhat abruptly into deeper water, about 150 feet in the south, east, and west, but much deeper on the north. This peculiar bank has been explained as an eastward submerged continuation of the Oolite escarpment of Yorkshire; or, alternatively, as a mere shoal accumulated through the effects of some tidal eddy; but neither of these explanations will hold, for Oolitic rocks do not occur there, and the bank has a core quite unlike the sand of the North Sea. When trawlers first visited the Dogger Bank its surface seems to have been strewn with large bones of land animals and loose masses of peat, known to the fishermen as “moorlog,” and there were also many erratic blocks in the neighbourhood. As all this refuse did much damage to the trawls, and bruised the fish, the erratics and bones were thrown into deeper water, and the large cakes of moorlog were broken in pieces. A few of the erratics and some of the bones were however brought to Yarmouth as curiosities. Now the whole surface of the Dogger Bank has been gone over again and again by the trawlers, and very few of the fossil bones are found; unfortunately no record seems to have been kept as to the exact place where these bones were trawled. The species found were:—