CHAP, ii.] THE MOUNTAINS. 23 



island and Norway ; the soundings being respectively 

 2650 and 1760 fathoms. 1 The elevation of this tract 

 of land would afford a means of free migration of animals 

 and plants from Europe to America, or from America to 

 Europe. I have therefore taken the 500-fathom line 

 to mark the probable boundary of the Eocene Atlantic, 

 as well as the southern extension of the Eocene North 

 Sea in the direction of the Shetlands. The enormous 

 depth of the Atlantic between Ireland and the United 

 States forbids the hypothesis that the line of communi- 

 cation was in that direction. 



From these considerations Eocene Britain may be 

 taken to have formed part of a great continent, 

 extending northwards and westwards to America by 

 way of Iceland and Greenland, while to the north- 

 east it was continuous with Norway and Spitzbergen. 

 It extended also to the south-west, across what is now 

 the Channel, to join the western parts of France. This 

 great north-western continent, or northern Atlantis as 

 it may be termed, existed through the Eocene and 

 Meiocene ages, offering a means of free migration for 

 plants and animals, and it was not finally broken up by 

 submergence, as we shall see in the course of this work, 

 until the beginning of the Pleiocene age. 



The Mountains. 



The highlands of Britain in the Eocene age were in 

 their present positions. The older Palaeozoic strata of 

 Cornwall, Wales, Cumberland, and Scotland had already 

 been cut up into hill and valley before the deposit of 

 the Triassic rocks, and constituted a broken chain of 



1 H. Mohn, Nature, vi. p. 526. 



