Ixii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



statement of the author's views as to the mode of migration of the 

 alpine flora, which we find when he treats of that of the other 

 floras. He tells us that the plants of this flora could not have been 

 inhabitants of the ancient west of Europe, but of Scandinavia. "The 

 alpine floras of Europe and Asia," he says, " so far as they are 

 identical with the floras 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 tempe- 

 rate coasts of Europe, or over continuous land which no longer exists." 

 But he had already stated, that during the glacial epoch, when Scot- 

 land and Wales, and part of Ireland, received their alpine flora and 

 a small portion of their fauna, they were groups of islands in an 

 ice-bound sea ; and that in an after-state of things these islands 

 were upheaved and converted into mountains, and 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. Thus the only modes of migration, according to this view of a 

 group of islands, must have been by currents or by the transporting 

 agency of icebergs ; and from what he states (p. 351), in speaking of 

 the origin of the alpine floras of the Alps and Carpathians, and some 

 other mountain ranges, it is evident that, though not directly ex- 

 pressed, an iceberg is the mode of transport that is chiefly in the au- 

 thor's mind in that part of his essay. Icebergs have been seen par- 

 tially covered with alluvial soil, on which plants were growing. Are 

 we therefore to suppose, that the alpine flora was transferred from 

 the land now called Scandinavia to that now called Britain, by such 

 icebergs as chanced to carry plants with soil suflScient to preserve 

 their vitality, and as chanced to be stranded on the islands ? This 

 mode of transmission appears to have been felt to be unsatisfactory 

 and inadequate by the author, for towards the conclusion of the 

 essay we find the following passage: — " The pheenomena of the gla- 

 cial formations, the peculiarities in the distribution of the animals 

 of that epoch, and in the relations of the existing fauna and flora 

 of Greenland, Iceland, and Northern Europe, are such as strongly 

 to impress upon my mind, that the close of the glacial epoch was 

 marked by the gradual submergence of some great northern land, 

 along the coasts of which the littoral mollusks, aided by favouring 

 currents, migrated, whilst a common flora became diffused over its 

 hills and plains. Although I have made icebergs and ice-floes the 

 chief agents in the transportation of an Arctic flora southwards, 

 I cannot but think that so complete a transmission of that flora as 

 we find in the Scottish mountains was aided perhaps mainly by 

 land to the north, now submerged." I am inclined to the opinion, 

 that this last view of the author, the former existence of land to- 

 vvards the north pole, from which there was a continuous communi- 

 cation with the land of our island, is the more probable hypothesis; 

 and many phsenomena of the northern drift, especially the difficulty 

 of conceiving any other source for the origin of the vast mass of 

 detrital matter, water-worn stones and boulders, which are found in 



