racter pervades all the extensive Tertiary
deposits of temperate North America, we shall, I think, be forced to the
conclusion that no general glacial epochs could 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 completely 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 observations 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 {71} 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 considerably milder climate than now
prevails could alone have enabled them to do so. How long ago this occurred
we do not know, but one of the last intercalated mild periods of the
glacial epoch itself seems to offer all the ne