The convulsions of a third world; more fertile in animal life than
those which preceded it: but also, more terrible and rapid, if
possible, in its changes.

Of this third world, the one which (so to speak) immediately
preceded our own, we know little yet. Its changes are so
complicated that geologists have as yet hardly arranged them. But
what we can see, I will sketch for you shortly.

A great continent to the south--England, probably an island at the
beginning of the period, united to the continent by new beds--the
Mammoth ranging up to where we now stand.

Then a period of upheaval. The German Ocean becomes dry land. The
Thames, a far larger river than now, runs far eastward to join the
Seine, and the Rhine, and other rivers, which altogether flow
northward, in one enormous stream, toward the open sea between
Scotland and Norway.

And with this, a new creation of enormous quadrupeds, as yet
unknown. Countless herds of elephants pastured by the side of that
mighty river, where now the Norfolk fisherman dredges their teeth
and bones far out in open sea. The hippopotamus floundered in the
Severn, the rhinoceros ranged over the south-western counties;
enormous elk and oxen, of species now extinct, inhabited the vast
fir and larch forests which stretched from Norfolk to the farthest
part of Wales; hyenas and bears double the size of our modern ones,
and here and there the sabre-toothed tiger, now extinct, prowled out
of the caverns in the limestone hills, to seek their bulky prey.