must have been bridged in one or two places at least.<8>

The change from Pliocene times to early Glacial was so gradual
that quite a number of animals lived on from one to the other,
and, as we have already stated, one of these species has even
survived to our own times.<9>

But we note the arrival in Europe of a great number of new
animals, and the diversity of species seems at first an
inexplicable riddle. The key, however, is to be found in the
great climatic changes, which we have already mentioned as
occurring during this age. On the one hand, we find such animals
as the musk-sheep, reindeer, and arctic fox, animals whose
natural home is in high northern latitudes, where snow and ice
prevail most of the year.<10> Yet during this age they lived in
Southern France and Italy, which must then have had a far
different climate than that at present.

Were we to confine our attention to these alone we would be
convinced that the climate of Europe at that time was arctic in
its severity. But side by side with the remains of these animals
are found others which imply an altogether different climate.
The hippopotamus, now frequenting the rivers of Africa, during
that period roamed as far north as Yorkshire, England.<11>
This animal could not live in a country where the cold was
severe enough to form ice on the rivers. The remains of a number
of other animals are found whose natural home is in the warm
regions of the earth.<12> These two groups of animals, one from
the north and one from the south, show how varied was the
climate of Europe during the Glacial Age.