TERTIARY FORMATION — CHALK. 6^) 



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 tlicir 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 



