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Rise of a new Era
It has seemed advisable to take this further glance at the
general principles and current theories of evolution before we
extend our own procedure into the Tertiary Era. The highest types
of animals and plants are now about to appear on the stage of the
earth; the theatre itself is about to take on a modern
complexion. The Middle Ages are over; the new age is breaking
upon the planet. We will, as before, first survey the Tertiary
Era as a whole, with the momentous changes it introduces, and
then examine, in separate chapters, the more important phases of
its life.
It opens, like the preceding and the following era, with "the
area of land large and its relief pronounced." This is the
outcome of the Cretaceous revolution. Southern Europe and
Southern Asia have risen, and shaken the last masses of the Chalk
ocean from their faces; the whole western fringe of America has
similarly emerged from the sea that had flooded it. In many
parts, as in England (at that time a part of the Continent),
there is so great a gap between the latest Cretaceous and the
earliest Tertiary strata that these newly elevated lands must
evidently have stood out of the waters for a prolonged period. On
their cooler plains the tragedy of the extinction of the great
reptiles comes to an end. The cyeads and ginkgoes have shrunk
into thin survivors of the luxuriant Mesozoic groves. The oak and
beech and other deciduous trees spread slowly over the successive
lands, amid the glare and thunder of the numerous volcanoes which
the disturbance of the crust has brought into play. New forms of
birds fly from tree to tree, or linger by the waters; and strange
patriarchal types of mammals begin to move among the bones of the
stricken reptiles.
But the seas and the rains and rivers are acting with renewed
vigour on the elevated lands, and the Eocene period closes in a
fresh age of levelling. Let us put the work of a million years or
so in a sentence. The southern sea, which has been confined
almost to the limits of our Mediterranean by the Cretaceous
upheaval, gradually enlarges once more. It floods the north-west
of Africa almost as far as the equator; it covers most of Italy,
Turkey, Austria, and Southern Russia; it spreads over Asia Minor,
Persia, and Southern Asia, until it joins the Pacific; and it
sends a long arm across the Franco-British region, and up the
great valley which is now the German Ocean.
From earlier chapters we now expect to find a warmer climate, and
the record gives abundant proof of it. To this period belongs the
"London Clay," in whose thick and--to the unskilled
eye--insignificant bed the geologist reads the remarkable story
of what London was two or three million years ago. It tells us
that a sea, some 500 or 600 feet deep, then lay over that part of
England, and fragments of the life of the period are preserved in
its deposit. The sea lay at the mouth of a sub-tropical river on
whose banks grew palms, figs, ginkgoes, eucalyptuses, almonds,
and magnolias, with the more familiar oaks and pines and laurels.
Sword-fishes and monstrous sharks lived in the sea. Large turtles
and crocodiles and enormous "sea-serpents" lingered in this last
spell of warmth that Central Europe would experience. A primitive
whale appeared in the seas, and strange large tapir-like
mammals--remote ancestors of our horses and more familiar
beasts--wandered heavily on the land. Gigantic primitive birds,
sometimes ten feet high, waded by the shore. Deposits of the
period at Bournemouth and in the Isle of Wight tell the same
story of a land that bore figs, vines, palms, araucarias, and
aralias, and waters that sheltered turtles and crocodiles. The
Parisian region presented the same features.
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