CHAP. VII.] DYASSIC PERIOD. 107 



formed first and the second set by a separate and subse- 

 quent movement, but it is certain that the interference or 

 combination of these axes has produced the broad basins 

 in which the Coal-measures are now found. 



The system of east and west flexures is particularly well 

 marked in Ireland, the pre-Dyassic movements acting most 

 forcibly over the northern and southern districts, and 

 raising the whole central mass of country between them. 

 In the south of England there is a set of ridges similar to 

 those in the south of Ireland, passing from Devon and 

 Somerset beneath the newer rocks of the southern counties 

 into Belgium and the north of France. It is also very 

 likely that the tract of Palaeozoic rocks which underlies 

 the east of England was elevated at this epoch. 



Simultaneously with these upheavals it is very probable 

 that the ancient Atlantic continent was broken up, sub- 

 merged, and converted into an open ocean ; the depression 

 of this Atlantic area being in fact the proximate cause of 

 the upheavals on either side. Such, according to Professor 

 Hull, was the genesis of the North Atlantic Ocean, 1 and, 

 apparently, it has never ceased to be an ocean from that 

 time to the present day, though throughout the Mesozoic 

 periods there was a large continuous tract of land to the 

 west of England, of which Ireland, Wales, and Cornwall 

 are now the sole remnants. 



It may, in fact, be said that the rock-masses out of which 

 Ireland, Scotland, and the greater part of England have 

 been hewn, were now, for the first time, brought into con- 

 nection as a compact mass of land. The greater part of 

 this land region lay to the south and west, spreading from 

 the north of France, through the south of England, to 

 Wales and Ireland, and thence, by way of the Hebrides, 

 to Scotland and the Border counties. It was not Britain, 



1 " Physical History of the British Isles/' 1882, p. 44. 



