16 The Ancient Fauna of Essex.
seems to be this: these animals were not only more active,
but the majority of them were nocturnal in their habits ; and
no doubt when the Herbivora were overtaken by floods it was
frequently in the night when they were asleep—just the
time when the Tigers, Lions, Bears, and Wolves would be
wide awake; and they would probably get up the nearest tree
or escape to the higher ground, 'or some other suitable place,
and so avoid the catastrophe. And, indeed, many of them
must have escaped, or we should have a far larger proportion
of their remains ; though it must always be borne in mind
that one pair of Lions or one pair of Bears occupied a very
large tract of country; and therefore we should not expect
them to be in such numerical abundance as the Herbivora on
which they fed.
It may be interesting to inquire how it happens that the
remains of both northern and southern forms are found com-
mingled together in these deposits. When those immense
herds of Mammoths occupied the North Sea Valley and the
adjacent countries, it seems probable that the conditions of
climate in the extreme North of Europe and Asia had
previously become unbearable for them, and they had been
driven south. At any rate, if they did not remain all the
year, they migrated south every winter. All the Arctic
species would come down into this country for the winter,
and stay here until the summer invited such animals as
the Reindeer, the Elk, and the Musk-Ox to migrate north-
ward in great herds, as they do at the present day on the
Continent, towards the feeding grounds, which in winter are
uncongenial to them, but in summer afford them rich
pasturage. In the same way, in the summer season, the
Rhinoceros, the Hippopotamus, and other more southern
animals, with great herds of Wild Horses, would no
doubt advance northwards and westwards with the change
of season. Such climatal and physical conditions enable
us to explain that curious admixture of animal-remains
found in these deposits, which otherwise would not be
so easy to comprehend. We are moreover confirmed
in this view . by the fact that we find the same state