banks or great
beds of loam, and would sweep any plants which might be washed into its
floods far out to sea; or if by chance they should become buried in such
gravel beds, the action of water would speedily cause the decay of the
tender portions, such as leaves, bark, and soft wood, in which case no
profitable investigation could be made. Occasionally, however, around
the shores of old lakes, vegetable beds have been buried, and we know
that some mineral springs deposit a sort of protecting sediment on every
thing with which they come in contact. By such means, at rare intervals,
leaves, seeds, and fruits have been sealed up for future inspection, and
from a careful study of all such instances much valuable information has
been obtained. At one place in the valley of the Seine was discovered,
under a bed of tufa, the remains of a forest growth. It is not doubted
that the deposit belongs to the Glacial Age.<17>

Yet the forest growth reminds us of that prevalent during the Miocene
Age. The fig-tree, canary, laurel, and box-tree grew in profusion. These
are all southern forms. One severe winter would kill them all, and even
hard frosts would prevent the ripening of their fruits.

Neither were the Summers hot and dry. This is shown by the presence of
numerous plants which can not thrive in hot and dry localities, but live
in the shady woods of Northern France and Germany. The evidence of this
forest growth surely presents us an inviting picture of Europe during a
portion of the Glacial Age.

We are not without evidence, also, of a much more severe climate. In a
lignite bed (a species of coal) found in nearly the same latitude as the
forest growth just mentioned, we detect the presence of trees that grow
only in cold northern climates, such as birch, mountain pine, larch, and
spruce.<18> And in some peat-bogs of Southern Europe belonging to this
age<19> are found willows now growing only in Spitzbergen, and some
species of mosses that only thrive far to the north. It is quite evident
that this deposit testifies to an altogether different climate from that
indicated by the deposit before mentioned. No theory of migration can
explain this assemblage of plants, unless it be migration taking place
very slowly, in consequence of an equally slow change of climate.

From what we have just learned of the animals and plants living in
Europe during this age, we can frame some conception of the different
climatic conditions of Eur