This rise of the land involved a great decrease in the proportion
of moisture in the atmosphere. The sea surface was enormously
lessened, and the mountains would now condense the moisture into
snow or cloud to a vastly greater extent than had ever been known
before There would also be a more active circulation of the
atmosphere, the moist warm winds rushing upward towards the
colder elevations and parting with their vapour. As the
proportion of moisture in the atmosphere lessened the
surface-heat would escape more freely into space, the general
temperature would fall, and the evaporation--or production of
moisture would be checked, while the condensation would continue.
The prolonging of such conditions during a geological period can
be understood to have caused the accumulation of fields of snow
and ice in the higher regions. It seems further probable that
these conditions would lead to a very considerable formation of
fog and cloud, and under this protecting canopy the glaciers
would creep further down toward the plains.
We have then to consider the possibility of a reduction of the
quantity of carbon-dioxide in the atmosphere The inexpert reader
probably has a very exaggerated idea of the fall in temperature
that would be required to give Europe an Ice-Age.
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