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 have 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 Croll obtained the details of about 250 
bores put down in all parts of the mining districts of Scotland 
for the purpose of discovering minerals. 1 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 
day.” 
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 
1 Transactions of the Edinburgh Geological Society , Vol. I. p. 330. 
