278 PEOr. E. HULL, LL.D., ETC., ON THE SUB-OCEANIC 



annihilated, and their erosive action ceases.* Hence if the 

 soundings enable us to trace out channels of rivers des- 

 cending from (Comparatively shallow levels to those of great 

 depth, we are driven to the conclusion, however unexpected, 

 that the sea-bed was elevated into land to that extent: and 

 the "base-level of erosion " (or ultimate depth) is shown by 

 the position of the einhouclmre where the channel opens out 

 on the abyssal floor. In the region we are now considering, 

 this depth reaches as far down as the 1,500 fathom contour ; 

 in other words, 9,000 feet below the surface ; possibl}^ a little 

 over this. 



I now proceed to give some account of the principal 

 submerged river-channels themselves, from the north to the 

 south of the region here under consideration, taking in 

 succession those of France, the Bay of Biscay, and the 

 coast of Spain and Portugal. 



Having on a former occasion endeavoured to describe 

 the sub-oceanic river-channels to the west of the British 

 Isles as indicated by the Admiralty soundings, it is only 

 necessary for me to refer the reader to the paper in questionf ; 

 but I propose to make an exception in favour of the 

 " English Channel River " for the reason that it in part 

 belongs to the continental system and should not be omitted 

 from a treatise dealing with submerged continental streams. 

 It is also one of peculiar interest, and its existence has been 

 recognised by Professor Boyd-Dawkins, Mr. Jukes-Browne, 

 and Professor T. Rupert Jones definitely. 



{d.) The English Channel River. — 1'his channel may be 

 traced at intervals from the Straits of Dover in a nearly 

 straight course to its embouchure in long. 8° W. l>etween walls 

 of rock about 4,000 feet in height. After passing through 

 a deep canon for a distance of 80-90 miles it received the 

 streams draining the south of England and the north of 

 France, including the Seine, Somme ajid Ranee. Between 

 the Devon and Dorset coast on the north, and the Channel 

 Islands on the south, its course is clearly defined on the 

 Admiralty Chart, by the channel marked as " The Hurd 

 Deep," which is traceable for a distance of 70 miles, with a 

 breadth of about four miles, and a maximum depth of 

 00 fathoms, or 360 feet, below the general floor of the sea- 



* It was lai'gely from this consideration that Professor Spencer was 

 able to demonsti^ate the former great elevations of the American and 

 West-Indian lands and adjoining ocean-bed. 



t Trans. Vict. Inst., vol. xxx (1896-7). 



