forward uninterruptedly. Doubtless very
gradually, from century to century, the seasons grew more and more
severe, until, finally, the Summer's sun no longer cleared the mountains
of the Winter's snow. This was the beginning of the Glacial Age proper.

The best authorities also suppose that the reign of snow and ice was
broken by at least one return (possibly more) of genial climate,
when animals and plants from the south again visited the countries of
Northern Europe--only, however, to be once more driven forth by a return
of arctic cold. But finally, before the increasing warmth of a genial
Climate, the glaciers vanished, not to return again, and the Glacial Age
became merged in that of the present.

It is no longer a question that man lived in Europe during the largest
portion of this age, if not from the beginning. It is necessary, then,
to come to a clear understanding of the successive stages of this entire
age, and to trace the wonderful cycles of climate--the strange mutation
of heat and cold, which must have exerted a powerful influence on the
life, both animal and vegetable, of the period--and see when we first
find decisive proofs of man's presence, and learn what we can of his
condition.

The map of Europe, at the close of Pliocene times and the commencement
of the Glacial Age, is of interest to us in several ways. From this it
will be seen that it was considerably more elevated than at the present.
As this is no fancy sketch, but is based on facts, it is well to outline
them. Without the aid of man, land animals can not possibly pass from
the mainland of a continent to an island lying some distance off the
shore. But it is well known that animals like the rhinoceros, and
several others, wandered as well over the surface of the British Islands
as on the adjacent coast of Europe. We are therefore compelled to
assume, that at that time the English Channel and the Irish Sea were not
in existence. This necessitates an elevation of at least four hundred
feet, which would also lay bare a large portion of the North Sea.<5>
In proof of this latter statement is the fact, that, at a distance from
land in the North Sea, fishermen at the present day frequently dredge up
bones and teeth of animals that then roamed in Europe.<6>

Map of Europe------------------

While there is no necessity for supposing an elevation greater than that
required to lay bare a passage for animals back and forth, yet soundings
underta