282 PERIODS OF JUNCTION AND SEPARATION CHAP. xiv. 



First, a continental period, towards the close of which the 

 forest of Cromer flourished (p. 214) : when the land was at 

 least 500 feet above its present level, perhaps much higher, and 

 its extent probably greater than that given in the map, fig. 41. 



Secondly, a period of submergence, by which the land 

 north of the Thames and Bristol Channel, and that of Ireland, 

 was gradually reduced to such an archipelago as is pictured 

 in map, fig. 40 ; and finally to such a general prevalence of 

 sea as is seen in map, fig. 39. This was the period of great 

 submergence and of floating ice, when the Scandinavian flora, 

 which occupied the lower grounds during the first continental 

 period, may have obtained exclusive possession of the only 

 lands not covered with perpetual snow. 



Thirdly, a second continental period when the bed of the 

 glacial sea, with its marine shells and erratic blocks, was laid 

 dry, and when the quantity of land equalled that of the first 

 period, and therefore probably exceeded that represented in 

 the map, p. 279. During this period there were glaciers in 

 the higher mountains of Scotland and Wales, and the Welsh 

 glaciers, as we have seen, pushed before them and cleared 

 out the marine drift with which some valleys had been filled 

 during the period of submergence. The parallel roads of 

 Grlen Eoy are referable to some part of the same era. 



As a reason for presuming that the land which in map, 

 fig. 41, p. 279, is only represented as 600 feet above its present 

 level, was during part of this period much higher, Professor 

 Ramsay has suggested that, as the previous depression far 

 exceeded a hundred fathoms (amounting in Wales to 1,400 

 feet, as shown by marine shells, and to 2,300, by stratified 

 drift), it is not improbable that the upward movement was on 

 a corresponding scale. 



In passing from the period of chief submergence to this 

 second continental condition of things, we may conceive a 

 gradual change first from that of map 39 to map 40, then 



