belong to
the Glacial Age. They seem first to become numerous in the interglacial
period, and continue to increase and become diversified as we descend
lower in time. How long ago it was that the sea of ice began its
downflow over the earth it is impossible to say. Some place it back six
hundred thousand or seven hundred thousand years. Some seek to bring it
down to a quite recent date. It is still so uncertain and such a matter
of controversy that the utmost we are able definitely to say is that it
was very long ago.

While there is no positive proof that men dwelt in Europe before the
coming on of the glacial chill, we have no just reason to doubt it. That
he lived there during glacial times is unquestionable, and we may be
very well assured that a naked tropical animal, destitute of the hairy
covering of the other animals, would not have chosen that frozen period
to migrate to the north. The fact that he was there during the ice age
seems satisfactory evidence that he was there before that age, during
the mild climate of late Tertiary times, and that--for a reason which we
shall hereafter consider--he was caught there and unable to retreat, and
was forced to adapt himself to the new conditions.

During the warm preceding period he probably wandered as a hunter
through the European forests. But with the gradual coming on of a wintry
chill, as the advance of the ice began, shelter of some kind became
necessary, and he sought refuge in caves. From being a forest wanderer
he became a troglodyte. Everywhere in southwestern Europe we find traces
of this period of man's existence. There is hardly a cave or rock
shelter in that region within which he has not left his marks. He made
his way to England, which was probably then connected by land with
Europe, and dwelt long in its caverns. His period of cave residence,
indeed, appears to have been a very extended one. While it continued,
deposits many feet in depth gradually accumulated on the floors of the
caverns, slowly filling them up. And that, in some cases at least, this
cave residence ended a very long time ago, we are assured, for since
then a great thickness of stalagmite, which is deposited with extreme
slowness, has spread over the lower cave deposits and sealed them in.

It is in these caves that we find, not only the rude stone spearheads,
scrapers, hammers, etc., the bone awls, borers, and other implements of
palaeolithic man, but the bones of man himself. And i