Ediforidl Comment. 257 
Instead of regarding this h3'pf)tljesis as possibly acceptable, 
the present writer sees an apparently crucial and insuperable 
objection to it in the great and sudden changes oi' climate 
which we know to have taken place in Arctic regions within 
the Pleistocene period. It has been generally held, and no 
doubt rightly, that the oncoming of the Glacial period was 
quite gradual and slow, and that its termination, with the 
melting awa^^ of the ice-sheets during the Champlain epoch, 
was geologically ver)^ sudden. This would perhaps accord 
with Culverweirs suggestion of slow loss of the earth's atmos- 
phere while the ice-sheets were being amassed, and witii sud- 
den increase of the atmosphere bringing the Ice age to its end. 
Better, however, as I think, these wonderful climatic results 
can be shown to have depended on great epeirogenic uplifts 
of the land areas which became glaciated, and on the depres- 
sion of these areas in the Champlain epoch, giving again a 
genial climate and melting away the ice. The observations 
which appear fatal to CulverwelTs explanation, but not incon- 
sistent with my epeirogenic theory, are those of Dall in 
Alaska and of Baron Toll in the New Siberia islands. After 
a stage of glaciation in each of these regions, there supervened 
H temperate climate, mostly melting away the ice-sheets; veg- 
etation flourished on the drift which had been englacial and 
finally became superglacial ; and herds of mammoths and 
othe-r large animals pastured on the shrubs ami herbage. 
Then suddenly came a much colder climate, after the culmina- 
tion of the Ice age, under which the mammoths were over- 
whelmed and became extinct; but their frozen bodies, un- 
thawed to the present day, are occasionally washed out of 
alluvial river banks. It is the .sudden chanye froin vn'ld con- 
ditions to those of secere raid which the atmospheric theory 
cannot account for, and it ma}' be confessed that we should 
not expect such a change to result even from any combina- 
tion of epeirogenic movements, variations in volume and di- 
rection of sea currents, ciianges in prevailing courses of winds, 
exceptional storms, etc.; but the latter class of causes is un- 
doubtedly the more probable, and the ver}' deep fjords and 
continuations of river valleys beneath the sea tell unmistaka- 
bly of great elevation of the glaciated lands immediately 
preceding the Ice age. 
