CHAP. IX.] 



MILD ARCTIC CLIMATES. 



183 



the Pliocene into the glacial epoch in Europe, while in the 

 Arctic zone there is a break in the record between the Miocene 

 and the recent glacial deposits.^ 



Accepting this as a substantially correct account of the 

 general climatic aspect of the Tertiary period in the northern 

 hemisphere, let us see whether the principles we have already 

 laid down will enable us to give a satisfactory explanation of 

 its causes. 



The Causes of mild Arctic Climates. — In his remarkable 

 series of papers on ''Ocean Currents," Dr. James CroU has 

 proved, with a wealth of argument and illustration whose 

 cogency is irresistible, that the very habitability of our globe 

 is due to the equalising climatic effects of the waters of the 

 ocean ; and that it is to the same cause that : we owe, either 

 directly or indirectly, almost all the chief diversities of climate 

 between places situated in the same latitude. Owing to the 

 peculiar distribution of land and sea upon the globe, more than 

 its fair proportion of the warm equatorial waters is directed 

 towards the western shores of Europe, the result being that the 

 British Isles, Norway, and Spitzbergen, have all a milder climate 

 than any other parts of the globe in corresponding latitudes. 

 A very small portion of the Arctic regions, however, obtains 

 this benefit, and it thus remains, generally speaking, a land 

 of snow and ice, with too short a summer to nourish more than 

 a very scanty and fugitive vegetation. The only other opening 

 than that between Iceland and Britain by which warm water 



1 It is interesting to observe that the Cretaceous flora of the United 

 States (that of the Dakota group), indicates a somewhat cooler climate 

 than that of the following Eocene period. Mr. De Ranee (in the geological 

 appendix to Capt. Sir G. Nares' Narrative of a Voyage to the Polar Sea) 

 remarks as follows : " In the overlying American Eocenes occur types of 

 plants occurring in the European Miocenes and still living, proving the 

 truth of Professor Lesquereux's postulate, that the plant types appear in 

 America a stage in advance of their advent in Europe. These plants 

 point to a far higher mean temperature than those of the Dakota group, 

 to a dense atmosphere of vapour, and a luxuriance of ferns and palms." 

 This is very important as adding further proof to the view that the 

 climates of former periods are not due to any general refrigeration, but 

 to causes which were subject to change and alternation in former ages 

 as now. 



