Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/365

352, when we consider that the greater part of the northern hemisphere was under such climatal conditions during the epoch referred to, the undoubted evidences of which have been made known in Europe by numerous British and Continental observers, on the bounds of Asia by Sir Roderick Murchison, in America by Mr. Lyell, Mr. Logan, Captain Bayfield, and others; and that the botanical (and zoological as well) region essentially northern and alpine, designated by Professor Schouw that "of saxifrages and mosses," and first in his classification, exists now only on the flanks of the great area which suffered such conditions; and that, though similar conditions reappear, the relationship of alpine and Arctic vegetation in the southern hemisphere with that in the northern is entirely maintained by representative and not by identical species; (the representation, too, being in great part generic, and not specific), the general truth of my explanation of the origin of alpine floras, including identical species, becomes so strong, that the view proposed acquires fair claims to be ranked as a theory, and not considered merely a convenient or bold hypothesis.

Assuming as well founded the origin and general diffusion during the glacial epoch of a flora and fauna of subarctic and Alpine type throughout the northern and central regions of the old world, an important corollary follows, respecting the relative antiquity of the flora and fauna now general throughout the British Isles (which I have termed the Germanic), derived by migration over the upheaved bed of the glacial sea, from the central regions of Europe, viz.,—that the Germanic fauna and flora, equivalent to a part of the second botanical province in Professor Schouw's arrangement, not only migrated at a later epoch, but also originated later in time than the Scandinavian flora, which now clothes the summits of our mountains.

If the views I have ofiered respecting the origin and distribution of our terrestrial fauna and flora be correct, we might expect to find evidence in their favour when we inquire into the distribution of the marine plants and animals now inhabiting the British Seas. Especially ought we to discover important facts bearing upon the soundness of the propositions respecting the origin of our alpine flora, for we have already seen that the conversion from a general flora, clothing most parts of the area as were then above water, into a limited assemblage of plants almost all confined to the mountain summits, was owing to an elevatory action by which the bed, or a great part of the bed of the glacial sea, was left high and dry. The remains of that ancient sea bottom, in the form of stratified and unstratified masses of clay, sand, and gravel, often including large boulders, and presenting in many places considerable thickness and superficial extent; are to be met with in many parts