462 GEIKIE 



termed by geologists the Jurassic, we can trace back the 

 origin of a large part of the rock now forming the surface 

 of the continent, from the low plains of Central England 

 up to the crests of the northern Alps, while in the Mediter- 

 ranean basin, rocks of the same age cover a large area of 

 the plateau of Spain, and form the central mass of the 

 chain of the Apennines. It is interesting to know that the 

 north-west of Britain continued still to rise as land in spite 

 of all the geographical changes which had taken place to 

 the south and east. We can trace even yet the shores of 

 the Jurassic sea along the skirts of the mountains of Skye 

 and Ross-shire. 



The next long era, termed the Cretaceous, was likewise 

 more remarkable for slow accumulation of rock under the 

 sea than for the formation of new land. During that time 

 the Atlantic sent its waters across the whole of Europe and 

 into Asia. But they were probably nowhere more than a 

 few hundred feet deep over the site of our continent, even 

 at their deepest part. Upon their bottom there gathered a 

 vast mass of calcareous mud, composed in great part of 

 foraminifera, corals, echinoderms, and molluscs. Our En- 

 glish chalk which ranges across the north of France, Bel- 

 gium, Denmark, and the North of Germany, represents a 

 portion of . the deposits of that sea-floor, probably accu- 

 mulated in a northern, somewhat isolated basin, while the 

 massive hippurite limestone of Southern Europe represents 

 the deposits of the opener ocean. Some of the island 

 spaces which had remained for a vast period above water, 

 and had by their degradation supplied materials for the 

 sediment of successive geological formations, now went 

 down beneath the Cretaceous sea. The ancient high- 

 grounds of Bohemia, the Alps, the Pyrenees, and the 

 Spanish tableland were either entirely submerged, or at 

 least had their area very considerably reduced. The sub- 

 mergence likewise affected the north-west of Britain; the 

 western highlands of Scotland lay more than 1000 feet 

 below their present level. 



When we turn to the succeeding geological period, that 

 of the Eocene, the proofs of widespread submergence are 

 still more striking. A large part of the Old World seems 



