CHAP. IX.] 



MILD ARCTIC CLIMATES. 



175 



have occurred during their formation. It must be remembered 

 that the "imperfection of the geological record " will not help 

 us here, because the series of Tertiary deposits is unusually 

 complete, and we must suppose some destructive agency to have 

 selected all the intercalated glacial beds and to have so com- 

 pletely made away with them that not a fragment remains, 

 Avhile preserving all or almost all the interglacicd beds ; and to 

 have acted thus capriciously, not in one limited area only, but 

 over the whole northern hemisphere, with the local exceptions 

 on the flanks of great mountain ranges already referred to. 



Temperate Climates in the Arctic regions. — As we have just 

 seen, the geological evidence of the persistence of sub-tropical 

 or warm climates in the north temperate zone during the 

 greater part of the Tertiary period is almost irresistible, and we 

 have now to consider the still more extraordinary series of ob- 

 servations which demonstrate that this amelioration of climate 

 extended into the Arctic zone, and into countries now almost 

 wholly buried in snow and ice. These warm Arctic ch mates 

 have been explained by Dr. Croll as due to periods of high 

 excentricity with winter in j)erihelion, a theory which implies 

 alternating epochs of glaciation far exceeding what now prevails ; 

 and it is therefore necessary to examine the evidence pretty 

 closely in order to see if this view is more tenable in the case 

 of the north polar regions than we have found it to be in that 

 of the north temperate zone. 



The most recent of these milder climates is perhaps indicated 

 by the abundant remains of large mammalia — such as the 

 mammoth, woolly rhinoceros, bison and horse, in the icy alluvial 

 plains of Northern Siberia, and especially in the Liakhov 

 Islands in the same latitude as the North Cape of Asia. These 

 remains occur not in one or two spots only, as if collected by 

 eddies at the mouth of a river, but along the whole borders of 

 the Arctic Ocean ; and it is generally admitted that the animals 

 must have lived upon the adjacent plains, and that a consider- 

 ably milder climate than now prevails could alone have enabled 

 them to do so. At what period this occurred we do not know, 

 but one of the last intercalated mild periods of the glacial 

 epoch itself seems to offer all the necessary conditions. Again, 



