No botanist hesitates to say that it is the coming of a cold, dry
climate that has thus changed the face of the earth. The
geologist finds more direct evidence. In the Werribee Gorge in
Victoria I have seen the marks which Australian geologists have
discovered of the ice-age which put an end to their Coal-forests.
From Tasmania to Queensland they find traces of the rivers and
fields of ice which mark the close of the Carboniferous and
beginning of the Permian on the southern continent. In South
Africa similar indications are found from the Cape to the
Transvaal. Stranger still, the geologists of India have
discovered extensive areas of glaciation, belonging to this
period, running down into the actual tropics. And the strangest
feature of all is that the glaciers of India and Australia
flowed, not from the temperate zones toward the tropics, but in
the opposite direction. Two great zones of ice-covered land lay
north and south of the equator. The total area was probably
greater than the enormous area covered with ice in Europe and
America during the familiar ice-age of the latest geological
period.
Thus the central idea of this chapter, the destructive inroad of
a colder climate upon the genial Carboniferous world, is an
accepted fact.
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