Between outpours of volcanic floods he finds, after a
time, traces that an ocean and rivers are wearing away the land.
He finds seams of carbon among the rocks of the second division
of the Archaean (the Keewatin), and deduces from this that a
dense sea-weed population already covered the floor of the ocean.
In the next division (the Huronian) he finds the traces of
extensive ice-action strangely lying between masses of volcanic
rock, and sees that thousands of square miles of eastern North
America were then covered with an ice-sheet. Then fresh floods of
molten matter are poured out from the depths below; then the sea
floods the land for a time; and at last it makes its final
emergence as the first definitive part of the North American
continent, to enlarge, by successive fringes, to the continent of
to-day.*
* I am quoting Professor Coleman's summary of Archaean research
in North America (Address to the Geological Section of the
British Association, 1909). Europe, as a continent, has had more
"ups and downs" than America in the course of geological time.
This meagre picture of the battle of land and sea, with
interludes of great volcanic activity and even of an ice age,
represents nearly all we know of the first half of the world's
story from geology.
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