CHAP. XVI.] 



THE BRITISH ISLES. 



317 



away. This plain may have continued down to very recent times, 

 since the whole of the Bristol Channel to beyond Lundy Island 

 is under twenty-five fathoms deep. In the east of England 

 we ha,ve a similar forest-bed at Cromer in Norfolk ; and in the 

 north of Holland an old land surface has been found fifty -six 

 feet below high- water mark. 



Buried River Channels. — Still more remarkable are the buried 

 river channels which have been traced on many parts of our 

 coasts. In order to facilitate the study of the glacial deposits 

 of Scotland, Dr. James CroU obtained the details of about 250 

 bores put down in all parts of the mining districts of Scotland 

 for the purpose of discovering minerals.^ These revealed the 

 interesting fact that there are ancient valleys and river channels 

 at depths of from 100 to 260 feet below the present sea-level. 

 These old rivers sometimes run in quite different directions from 

 the present lines of drainage, connecting what are now distinct 

 valleys ; and they are so completely filled up and hidden by 

 boulder clay, drift, and sands, that there is no indication of their 

 presence on the surface, which often consists of mounds or low 

 hills more than 100 feet high. One of these old valleys connects 

 the Clyde near Dumbarton with the Forth at Grangemouth, and 

 appears to have contained two streams flowing in opposite directions 

 from a watershed about midway at Kilsith. At Grangemouth 

 the old channel is 260 feet below the sea-level. The watershed 

 at Kilsith is now 160 feet above the sea, the old valley bottom 

 being 120 feet deep or forty feet above the sea. In some places 

 the old valley was a ravine with precipitous rocky walls, which 

 have been found in mining excavations. Dr. Geikie, who has 

 himself discovered many similar buried valleys, is of opinion 

 that they unquestionably belong to the period of the boulder 

 clay." 



We have here a clear proof that, when these rivers were 

 formed, the land must have stood in relation to the sea at least 

 260 feet higher than it does now, and probably much more ; and 

 this is sufficient to join England to the continent. Supporting 

 this evidence, we have freshwater or littoral shells found at great 

 depths off our coasts. Mr. Godwin Austen records the dredging 

 ^ Transactions of the Edinburgh Geological Sociefg, Vol. I. p. 330. 



