on. In America the change is
even greater. A vast ridge rises along the whole western front of the
continent, lifting and draining it, from Alaska to Cape Horn. It is
the beginning of the Rocky Mountains and the Andes. Even during the
Cretaceous period there had been rich forests of Mesozoic vegetation
covering about a hundred thousand square miles in the Rocky Mountains
region. Europe and America now begin to show their modern contours.

It is important to notice that this great uprise of the land and the
series of disturbances it entails differ from those which we summed
up in the phrase Permian Revolution. The differences may help us to
understand some of the changes in the living population. The chief
difference is that the disturbances are more local, and not nearly
simultaneous. There is a considerable emergence of land at the end of
the Jurassic, then a fresh expansion of the sea, then a great rise of
mountains at the end of the Cretaceous, and so on. We shall find our
great mountain-masses (the Pyrenees, Alps, Himalaya, etc.) rising at
intervals throughout the whole of the Tertiary Era. However, it suffices
for the moment to observe that in the latter part of the Mesozoic and
early part of the Tertiary there were considerable upheavals of the land
in various regions, and that the Mesozoic Era closed with a very much
larger proportion of dry land, and a much higher relief of the
land, than there had been during the Jurassic period. The series of
disturbances was, says Professor Chamberlin, "greater than any that had
occurred since the close of the Palaeozoic."

From the previous effect of the Permian upheaval, and from the fact that
the living population is now similarly annihilated or reduced, we should
at once expect to find a fresh change in the climate of the earth. Here,
however, our procedure is not so easy. In the Permian age we had
solid proof in the shape of vast glaciated regions. It is claimed by
continental geologists that certain early Tertiary beds in Bavaria
actually prove a similar, but smaller, glaciation in Europe, but this is
disputed. Other beds may yet be found, but we saw that there was not
a general upheaval, as there had been in the Permian, and it is quite
possible that there were few or no ice-fields. We do not, in fact, know
the causes of the Permian icefields. We are thrown upon the plant
and animal remains, and seem to be in some danger of inferring a cold
climate from the organic re