The
work is the finest manual in modern geological literature. I have
used it much, in conjunction with the latest editions of Geikie,
Le Conte, and Lupparent, and such recent manuals as Walther, De
Launay, Suess, etc., and the geological magazines.
The exception which Professor Chamberlin has in mind when he says
"most of the data" is that we find deposits of salt and gypsum in
the Silurian and Lower Carboniferous, and these seem to point to
the evaporation of lakes in a dry climate. He admits that these
indicate, at the most, local areas or periods of dryness in an
overwhelmingly moist and warm earth. It is thus not disputed that
the climate of the earth was, during a period of at least fifteen
million years (from the Cambrian to the Carboniferous),
singularly uniform, genial, and moist. During that vast period
there is no evidence whatever that the earth was divided into
climatic zones, or that the year was divided into seasons. To
such an earth was the prolific life of the Coal-forest adapted.
It is, further, not questioned that the temperature of the earth
fell in the latter part of the Carboniferous age, and that the
cold reached its climax in the Permian.
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