110 EARLY MAN IN BRITAIN. [CHAP. v. 



remote parts of the world, points with unerring certainty 

 to great geographical and climatal changes. Nearly all 

 ^the temperate, northern, and mountainous species can 

 be traced to northern and central Asia, and for their 

 migration it is necessary to suppose that a very close 

 connection with Asia was caused by the elevation of land 

 at the close of the Pleiocene age. 



This, probably, is indicated by the low tract of 

 country uniting the northern end of the Caspian with 

 the Sea of Aral, and reaching through the salt steppes 

 of Ishim into the valley of the Irtisch, and thence to 

 the Gulf of Obi and the Arctic Sea. Britain also formed 

 part of the mainland, and the bottom of the Pleiocene 

 sea (Fig. 10) became the feeding-grounds of the animals 

 which have left their remains in the forest bed of Nor- 

 folk and Suffolk, as well as in the Dogger Bank off Yar- 

 mouth. Ireland also must have been united to Britain 

 to have allowed of their finding their way so far to the 

 west. The elevation above the present sea-level, neces- 

 sary to account for this distribution of the animals, is 

 not less than 600 feet or 100 fathoms. At this depth 

 the soundings show the presence of a line of submarine 

 cliffs which form the margin of the plateau of the 

 British Isles, and which mark the probable Atlantic 

 coast-line of north-western Europe, during a large part 

 of the Pleistocene age, as represented in the accom- 

 panying map (Fig. 24). 3 



The invasion also of Europe by southern animals, 

 whose headquarters are in Africa, proves an intimate 

 connection between the two continents. The Straits of 

 Gibraltar could not have been in existence when the 

 African elephant ranged as far north as Madrid, and the 



1 Dawkins' Cave-hunting, p. 362 et seq. 



