We have already seen that the greater the extent of
the eccentricity the greater is the effect resulting from
the actimia of the physical causes, whether this effect
be the production of ice on the cold hemisphere, or its
removal from the warm. It is evident that the same
thing must necessarily hold true in regard to the
mntual reactlonis of the physical causes. Conse-
quently, if the mutual actions and reactions of the
physical causes, brought into operation during a high
state of eccentricity, led at the Glacial Epoch to the
great accumulation of ice when the wintera were in
aphelion, they must have led to an equally great
melting and dispersal of that ice when precession
brought the winters round to perihelion. These
causes would be as efficient in the removal of the
ice as they were in its production. In so far as the
physical and astronomical causes were concerned, the
greater the amount of ice formed during the cold
periods the greater would be the amount melted
during the warm interglacial periods.
This conclusion follows so obviously from the fore-
going principles that it seems almost superfluous to
dwell further on the subject, the more so as it will be
seen in the next chapter that the correctness of the
conclusion is established by the facts of geology and
palfoontology.
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DISCUSSIOIfS IN CLIMATOLOGY.
