mantle were removed the country would appear deeply intersected with
fiords in the manner exhibited in the regions to the south of
Greenland or the Scandinavian peninsula. The ice comes down to the
sea through the valleys, often facing the ocean for great distances
with its frozen cliffs. Entering on this seaward portion of the
glacier, the observer finds that for some distance from the coast line
the ice is more or less rifted with crevices, the formation of which
is doubtless due to irregularities of the rock bottom over which it
moves. These ruptures are so frequent that for some miles back it is
very difficult to find a safe way. Finally, however, a point is
attained where these breaks rather suddenly disappear, and thence
inward the ice rises at the rate of upward slope of a few feet to the
mile in a broad, nearly smooth incline. In the central portion of the
region for a considerable part of the territory the ice has very
little slope. Thence it declines toward the other shore, exhibiting
the same features as were found on the eastern versant until near the
coast, when again the surface is beset with crevices which continue to
the margin of the sea.

Although the explorations of the central field of Greenland are as yet
incomplete, several of these excursions into or across the interior
have been made, and the identity of the observations is such that we
can safely assume the whole region to be of one type. We can
furthermore run no risk in assuming that what we find in Greenland, at
least so far as the unbroken nature of the central ice field is
concerned, is what must exist in every land where the glacial envelope
becomes very deep. In Greenland it seems likely that the depth of the
ice is on the average more than half a mile, and in the central part
of the realm the sheet may well have a much greater profundity; it may
be nearly a mile deep. The most striking feature--that of a vast
unbroken expanse, bordered by a region where the ice is ruptured--is
traceable wherever very extensive and presumably deep deposits of ice
have been examined. As we shall see hereafter, these features teach us
much as to the conditions of glacial action--a matter which we shall
have to examine after we have completed our general survey as to the
changes which occur during glacial periods.

In the present state of that wonderful complex of actions which we
term climate, glaciers are everywhere, so far as our observations
enable us