PHYSICAL CONDITIONS— POSTGLACIAL. 509 



tion that the Asturian or Iberian flora, or even that of the 

 Devonshire and Kentish types, could possibly have survived the 

 Ice Age in Britain. The Asturian saxifrages and heaths of the 

 west and south-west of Ireland grow upon mountains which are 

 glaciated, and in the valleys of which morainic detritus abounds. 

 The only flora which, as I have said, could possibly have out- 

 lived that Age in Britain would be high-alpine or Scandinavian. 

 It was this flora which, upon the gradual disappearance of arctic 

 conditions, slowly migrated north, ascending the mountains as 

 the temperate group advanced and pressed it out of the low 

 grounds. The Germanic, Gallican, and Iberian types may quite 

 well have migrated during one and the same period, although it 

 is most probable that the Germanic flora would be first on the 

 march. But before the plants coming from Spain and Northern 

 France could immigrate hither, it is evident that the British area 

 must have been considerably more extensive than it is at present. 

 Mr. Godwin -Austen, many years ago, showed that shell -sand 

 (with littoral shells, such as limpets and periwinkles) occurs 

 upon the western slope of the Little Sole Banks at a depth of 

 100 fathoms and more. This sand, he thinks, marks a former 

 coast-line, when the shores of our area advanced to a point 180 

 miles south of Galley Head in Ireland, and some 200 miles west 

 of Ouessant Island. 1 Again, Dr. Gwyn Jeffreys has recorded 

 the occurrence of littoral shells of arctic species in about 90 

 fathoms of water off the Shetland Islands 2 — an interesting fact 

 which goes to show that the North Sea may have vanished be- 

 fore the climate of Northern Scotland had quite lost its arctic 

 character. The Irish Sea and the English Channel had thus 

 ceased to exist, and in place of the North Sea there appeared a 

 broad undulating plain, traversed by one or more rivers, which 

 carried the tribute of our English and Scottish streams down to 

 the deep gulf that circles round the south part of the Scan- 

 dinavian peninsula, and even to the shores of the Northern 

 Ocean, beyond the Orkney and Shetland Islands. In like 



1 Quart. Journ. Geol. Soc, vol. vi. p. 69. 

 2 Brit. Ass. Rep., 1867, p. 431. 



