Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/358

Rh not inhabitants of the ancient west of Europe, but of Scandinavia. How did they come? The alpine character of most of them forbids us by any stretch of probability to conduct them across the Germanic plain from its most northern bound, though some few plants, giving a peculiarity to the flora of the north-east of England and south-east of Scotland probably were so derived. But these I regard as Germanic. The plants and animals now under consideration could not have migrated hither after the destruction of the Germanic plains, for by that time the British Isles had assumed their present forms, and the localities of these species had become mountain tops. We have seen that the great Germanic and central British plains themselves were portions of the elevated bed of a pre-existing sea, which sea, when we trace its relics, is found to have covered a great part of the British Isles as now exposed, so that during its existence our mountains must have been comparatively low islands. This was the sea of the Glacial period, properly so styled, when the climate of the whole of northern and part of central Europe, was very different from what it is now, and far colder. The remains of the marine animals found in the strata deposited in that sea indubitably prove this fact, and, as will be seen presently, the flora of its islands as fully bears out such climatal evidence. This was the epoch of glaciers and icebergs, of boulders, and groovings, and scratches. It exhibited conditions physical and zoological, similar—indeed, nearly identical—to those now to be met with on the north-eastern coasts of America within the line of summer-floating ice. Extend that line across the southern half of Ireland and England,—not farther south, as we have evidence to show,—continue it eastwards, so as to strike against the Ural chain (as Sir Roderick Murchison has proved in his great work on Russia), and within that vast area you will have a condition of climate which will account for all the organic phenomena observed in the boulder clays and pleistocene drifts.

Now it was during this epoch (the epoch of my IVth flora), that Scotland and Wales, and part of Ireland, then groups of islands in this ice-bound sea, received their alpine flora and a small portion of their fauna. Plants of subarctic character then would flourish to the water's edge, but when a new state of things commenced, when the bed of the glacial sea was upheaved, its islands converted into mountains, its climate changed, and a suitable population of animals and vegetables diffused over its area, the plants of the colder epoch survived only on the mountain regions which had been so elevated as to retain climatal conditions similar to those which existed when those regions were low ridges or islands in the glacial sea.

The general fauna and flora of our country being accounted for, and