116 ROCK-METAMORPHISM. 



Influenced by objections to all the hypotheses that have been 

 offered in explanation of these climatal interchanges, I find a 

 much more tenable one in that which attributes them mainly to 

 the aforementioned vertical movements. 



Confining myself to the climatal conditions which charac- 

 terized Grinnell Land, Spitzbergen, and other Arctic areas 

 during the Miocene period, as indicated by their plant-remains, 

 I make the suggestion that these and adjacent areas stood at a 

 somewhat lower level relatively to the sea than at present, and 

 formed an archipelago, freely permitting currents with a tem- 

 perature slightly more elevated than that of the gulf-stream 

 where it now strikes the west coast of Ireland to bathe the 

 coasts of its islands. Climatal amenities now prevail in Arctic 

 Scandinavia, the Kara Sea, and on the western border of the 

 Taimyr peninsula in Asiatic Russia : the last place, the most 

 northern continental land of the globe, now supports an 

 exuberant forest vegetation in a much higher parallel than 

 anywhere else within the Arctic circle, and only about 16 or 17 Q 

 short of the North Pole the fact being seemingly due to the 

 presence of warm water, carried by ocean-currents and by rivers 

 (as the Yenissei) from the south. Boreal Siberia, in direct 

 communication with southern lakes, inland seas, and ocean- 

 streams charged with warm water, and in the condition of an 

 archipelago, why may not its great forest belt be extended up to 

 Spitzbergen and Franz -Joseph Land to parallels corresponding 

 with those in Grinnell Land, which formerly supported the 

 growth of a vegetation approximately similar in some respects 

 to that now characteristic of Northern Italy and the Southern 

 States of North America ? 



As to the long winter-night of darkness and the long summer- 

 day of sunlight, I feel satisfied from adducible evidences that, 

 other things being favourable, such conditions would rather 

 favour than impede vegetable growth. Areas favourably 

 situated as to shelter, meteoric influences, soil, proximity 

 to warm currents, &c., and especially where a thick covering 

 of snow prevailed during the severe months of winter, would, 

 in my opinion, become genial oases supporting an exceptional 

 vegetation : such I look upon were the places in Grinnell 

 Land and Spitzbergen where, during the Miocene or early 

 portion of the Pliocene period, flourished guelder roses, water- 



