"First, a continental period, toward the close of which the forest of Cromer flourished; when the land was at least 500 feet above its present level, perhaps much higher. * * * The remains of _Hippopotamus major_ and _Rhinoceros etruscus_, found in beds of this period, seem to indicate a climate somewhat milder than that now prevailing in Great Britain. [This was a _Preglacial_ era, and may be regarded as belonging to the close of the Pliocene tertiary.] "Secondly, a period of submergence, by which the land north of the Thames and Bristol Channel, and that of Ireland, was generally reduced to * * * an archipelago. * * * This was the period of great submergence and of floating ice, when the Scandinavian flora, which occupied the lower grounds during the first continental period, may have obtained exclusive possession of the only lands not covered with perpetual snow. [This represents the Glacial period; but according to the more extreme glacialists only a portion of that period.] "Thirdly, a second continental period, when the bed of the glacial sea, with its marine shells and erratic blocks, was laid dry, and when the quantity of land equalled that of the first period. * * * During this period there were glaciers in the higher mountains of Scotland and Wales, and the Welsh glaciers * * * pushed before them and cleared out the marine drift with which some valleys had been filled during the period of submergence. * * * During this last period the passage of the Germanic flora into the British area took place, and the Scandinavian plants, together with northern insects, birds, and quadrupeds, retreated into the higher grounds. * * * "Fourthly, the next and last change comprised the breaking up of the land of the British area once more into numerous islands, ending in the present geographical condition of things. There were probably many oscillations of level during this last conversion of continuous land into islands, and such movements in opposite directions would account for the occurrence of marine shells at moderate heights above the level of the sea, notwithstanding a general lowering of the land. * * * During this period a gradual amelioration of temperature took place, from the cold of the glacial period to the climate of historical times."[134] The second continental period above referred to is that which appears on the best evidence to have been the time of the introduction of man; but such facts as that of the Settle Cave, and the implements of the breccia in Kent's Cave, if rightly interpreted, would make man preglacial or "interglacial."