Page:Memoirs of the Geological Survey of Great Britain, Volume 1.djvu/413

400 part of the space now occupied by the British Isles was under water, than they are now or were before, but there is good reason to believe, that so far from those conditions haying continued severe or having gradually diminished in severity southwards of Britain, the cold region of the Glacial epoch, came directly into contact with a region of more southern and thermal character than that in which the most southern beds of glacial drift are now to be met with. This conclusion is directly opposed to that of the Swiss glacialists. Professor Agassiz writes, in his essay entitled 'A period in the History of our Planet,' (Edinburgh New Philosophical Journal, vol. xxxv.) as follows:—

"A crust of ice covered the superficies of the earthy and enveloped in its rigid mantle the remains of organisms which but a moment before had been enjoying existence on its surface. In a word, a period appeared in which the greater portion of the earth was covered with a mass of frozen water; a period in which all life was annihilated, everything organic was put an end to,—the Glacial period.

"This Glacial period is the epoch of separation betwixt the Diluvial period, as it has been termed by geologists and our present period; it is it which, like a sharp sword, has separated the totality of now living organisms from their predecessors, which lie interred in the sand of our plain, or below the ice of our polar regions; lastly, it is it which has left to our times the testimonies of its former greatness upon the tops, and in the valleys of our Alps—the glaciers."—p. 17.

"The British Islands, Sweden, Norway, and Russia, Germany and France, the mountainous regions of the Tyrol and Switzerland, down to the happy fields of Italy, together with the continent of Northern Asia, formed undoubtedly but one icefield, whose southern limits investigation has not yet determined. And as on the eastern hemisphere, so also on the western, over the wide continent of North America, there extended a similar plain of ice, the boundaries of which are in like manner still unascertained. The polar ice, which at the present day covers the miserable regions of Spitsbergen, Greenland, and Siberia, extended far into the temperate zones of both hemispheres, leaving probably but a broader or narrower belt around the equator, upon which there were constantly developed aqueous vapours, which again condensed at the poles," &c.

6. This state of things did not materially differ from that now existing under corresponding latitudes in the North American, Atlantic, and Arctic Seas, and on their bounding shores.

7. The alpine floras of Europe and Asia, so far as they are identical with the flora of the Arctic and sub-Arctic zones of the Old World, are fragments of a flora which was diffused from the north, either by means of transport not now in action on the temperate coasts of Europe, or over continuous land which no longer exists. The deep-sea fauna is in like manner a fragment of the general glacial fauna.

8. The floras of the islands of the Atlantic region, between the Gulfweed bank and the Old World, are fragments of the great Mediterranean flora, anciently diffused over a land constituted out of the up-heaved and never-again submerged bed of the (shallow) Meiocene Sea. This great flora, in the epoch anterior to, and probably, in part, during the