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, 
while preserving all or almost all the interglacial 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 climates 
have been explained by Dr. Croll as due to periods of high 
excentricity with winter in perihelion, 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, 
