192 THE STORY OF THE EARTH AND HAN. 



eastwards. Thus this later Jurassic period was the 

 culmination of the Mesozoic, the period of its most 

 perfect continental development, corresponding in this 

 to the Carboniferous in the Palaeozoic. 



The next or closing period of this great Mesozoic 

 time brought a wondrous change. In the Cretaceous 

 period, so called from the vast deposits of chalk by 

 which it is characterized, the continents sunk as they 

 had never sunk before, so that vast spaces of the great 

 continental plateaus were brought down, for the first 

 time since the Laurentian, to the condition of abyssal 

 depths, tenanted by such creatures as live in the 

 deepest recesses of our modern oceans. This great 

 depression affected Europe more severely than Ame- 

 rica; the depression of the latter being not only less, 

 but somewhat later in date. In Europe, at the period 

 of greatest submergence, the hills of Scandinavia and 

 of Britain, and the Urals, perhaps alone stood out of 

 the sea. The Alps and their related mountains, and 

 even the Himalayas, were not yet born, for they have 

 on their high summits deep-sea beds of the Cretaceous 

 and even of later date. In America, the Appalachians 

 and the old Laurentian ranges remained above water ; 

 but the Eocky Mountains and the Andes were in 

 great part submerged, and a great Cretaceous sea 

 extended from the Appalachians westward to the 

 Pacific, and southward to the Gulf of Mexico, opening 

 probably to the North into the Arctic Ocean. 



This great depression must have been of very long 

 continuance, since in Western Europe it sufficed for 



