146 HISTORY OF THE EUROPEAN FAUNA. 



Any one who has read the writings of the late Dr. 

 Croll cannot help being struck by the facts he adduces 

 to show the importance of ocean currents in relation 

 to the distribution of heat over the globe, and it seems 

 to me that the view which attributes the mild climate 

 prevailing in former times in Greenland to warm 

 ocean currents reaching the Polar Circle is the 

 one least open to serious objections. If we suppose 

 that the North Atlantic Ocean was bridged by a 

 land-connection between Scandinavia and Greenland 

 by way of Spitsbergen, and between Greenland and 

 North America, the Polar Ocean would be practically 

 a closed sea. If, then, a wide passage existed some- 

 where about Behring Straits to allow a warm current 

 to enter and circulate within the Arctic Seas, we 

 should have the southern shores of Greenland washed 

 by the warm Atlantic current and the northern shores 

 by a warm Pacific current, which combination would 

 undoubtedly produce the effect of raising the tem- 

 perature throughout the Polar Regions very con- 

 siderably; and especially would that be the case 

 with regard to Greenland and the neighbouring 

 islands. 



It might be urged that the constant darkness 

 during winter must have had an injurious action 

 upon the flora, but it is found that in countries 

 such as Northern Russia, where southern plants are 

 housed during winter in greenhouses, the light being 

 almost entirely excluded by a covering of straw, no 

 serious damage is done thereby to the plants. 



