314 SUMMARY OF GEOGRAPHICAL EVOLUTION. [CHAP. XIV, 



The evidence on which to found any conclusions as to 

 the aspect of the country when it emerged from the waters 

 of the Cretaceous sea is of the slenderest, but we may as- 

 sume that England, Scotland, and Ireland were bound 

 together into one mass of land, and that the water- spaces 

 which now separate our islands were then filled up by a> 

 greater or less thickness of Jurassic strata, covered and 

 levelled up by wide- spreading sheets of greensand and 

 chalk. The Atlantic sea-bord then lay considerably to 

 the west of our islands, re-occupying a line along the sub- 

 marine slope which now plunges from 100 to 1,000 fathoms. 

 There is good reason to suppose that there were land con- 

 nections, on the one hand between Scotland and Green- 

 land by way of the Faroes and Iceland, and on the other 

 between Scotland and Scandinavia, thus completely isolat- 

 ing the Arctic Ocean and preventing any influx of cold 

 northern currents into the Atlantic or west European seas. 

 On the south-west also there would appear to have been a 

 continuous tract of land uniting Ireland and Wales with 

 Brittany and the central part of France. 



During the progress of the Eocene period the south-east 

 of England came alternately under the influence of an 

 eastern and a southern sea, but the delimitation of these 

 two seas is one of the most difficult problems of Tertiary 

 geography. With the evidence at our command it is im- 

 possible to say in which direction the great gulf whose 

 waters covered so much of England and Belgium in the 

 time of the London Clay communicated with the open 

 sea ; the probabilities are much against any northward 

 opening ; there is no trace of an easterly one, while the de- 

 posits of Lower Eocene age seem to thin out and disappear 

 in westerly, southerly, and south-easterly directions. The 

 difficulty is in fact such as to raise a doubt whether the 

 accepted views of the correlation of the French and Eng- 

 lish Eocenes are altogether correct. During the formation 



