TERTIARY FORMATION—CHALK. 63 
by the drainage of the glaciers and the floods of running 
water, which at one time increased periodically to a 
degree truly colossal. The diluvial period, as it seems, 
includes, both in Europe and America, a repeated glaci- 
fication of countries and vast portions of the world, of 
which the present. state of Greenland may now give 
some idea. 
The period of the series of strata, comprised under 
the name of the tertiary formation, may be regarded 
as that during which, at least, the skeleton of the pre- 
sent continents finally attained its integral configuration. 
Within its limits fall the erection and upheaval of the 
great mountain chains, the Cordilleras, Alps, Himalayas, 
and others ; the outlines of the continents were, mean- 
while, in constant movement. This phenomenon, how- 
ever, persists throughout all formations, and, as the 
geological characteristic of the tertiary formation, more 
Stress should be laid on the separation of the earth’s 
surface into climatic zones, approximating to the zones 
of the present age. The names of the subdivisions are 
intended to indicate the relation of the animals then 
living to those of our world, as it was supposed that in 
the eocene the first animals identical with present 
species were to be found, more in the miocene, and, yet 
more, in the pliocene. 
To the chalk formation belong rocks of very various 
kinds, which can be reduced to one great. geological 
period by means of their contents. If the quartzose 
sandstone of Saxon Switzerland represents this forma- 
tion in the centre of Germany, it is from the white chalk 
of England and Northern France that it took its name. 
In America, the sandstone has been in a great measure 
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