taining abundant examples of stone showing by their
scratched surface that they have been ground along underneath the
glacier. The rocks on the sides of the mountains are scratched exactly
as are those in the Alps. By observing how high up on the mountains the
striae are, we know the thickness of the ice-sheet; and the direction in
which it moved is shown in several ways.<22>

Briefly, then, the geologist assures us that when the cold of the
Glacial Age was at its maximum glaciers streamed down from all the
mountains of Scotland, Wales, and Northern England; that the ice was
thick enough to overtop all the smaller hills, and on the plains it
united in one great sea of ice some thousands of feet in thickness, that
it stretched as far south as the latitude of London, England. But that
to the west the ice streamed out across, the Irish Sea, the islands
to the west of Scotland, and ended far out into what is now the
Atlantic.<23> But these glaciers, vast as they were, were very small
compared with the glaciers that streamed out from the mountains
of Norway and Sweden. These great glaciers invaded England to the
south-west, beat back the glacier ice of Scotland from the floor of the
North Sea, overran Denmark, and spread their mantle of bowlder clay far
south into Germany.<24>

While such was the condition of things to the north, the glaciers of
the Alps were many times greater than at present. All the valleys
were filled with glacier ice, and they spread far out on the plains of
Southern Germany and westward into France. The mountains of Southern
France and the Pyrenees also supported their separate system of
glaciers. Ice also descended from the mountains of Asia Minor and North
Africa.<25> In America we meet with traces of glaciers on a vast scale;
but we can not pause to describe them here.<26>

It need not surprise us, therefore, to learn of reindeer and musk-sheep
feeding on stunted herbage in what now constitutes Southern France. When
a continuous mantle of snow and ice cloaked all Northern Europe, it
is not at all surprising to find evidence of an extremely cold climate
prevailing throughout its southern borders. We thus see how one piece of
evidence fits into another, and therefore we may, with some confidence,
endeavor to find proofs of more genial conditions when the snow and ice
disappeared, and a more luxuriant vegetation possessed the land, and
animals accustomed to warm and even tropical countries roamed ove