228 THE STORY OF THE EARTH AND MAN. 



slowly accumulating a chalky mud or slime. That 

 such a rock should occur over vast areas of the con- 

 tinental plateaus, that both in Europe and America it 

 should be found to cover the tops of hills several 

 thousand feet high, and that its thickness should 

 amount to several hundreds of feet, are facts which 

 evidence a revolution more stupendous perhaps than 

 that at the close of the PalaGozoic. For the first time 

 since the Laurentian, the great continental plateaus 

 changed places with the abysses of the ocean, and the 

 successors of the Laurentian Eozoon again reigned on 

 surfaces which through the whole lapse of Palaeozoic 

 and Mesozoic time had been separated more or less 

 from that deep ocean out of which they rose at first. 

 This great Cretaceous subsidence was different from 

 the disturbances of the Permian age. There was at 

 first no crumpling of the crust, but merely a slow 

 and long-continued sinking of the land areas, followed, 

 however, by crumpling of the most stupendous cha- 

 racter, which led at the close of the Cretaceous and 

 in the earlier Tertiary to the formation of what are 

 now the greatest mountain chains in the world. As 

 examples may be mentioned the Himalaya, the 

 Andes, and the Alps, on all which the deep-sea beds 

 of the Cretaceous are seen at great elevations. In 

 Europe this depression was almost universal, only very 

 limited areas remaining out of water. In America 

 a large tract remained above water in the region of 

 the Appalachians. This gives us some clue to the 

 phenomena. The great Permian collapse led to the 



