154 TF. H. Hudleston — E. Margin of N. Atlantic Basin. 



latter represents an old area of emergence of considerable antiquity, 

 and although the edge of the platform is not always in exactly 

 100 fathoms, yet it is so nearly on that level for great distances 

 as to give an idea of uniformity. It is obvious that the angle, or 

 ' edge,' formed by the submerged platform with the suboceanic 

 continental slope is a feature of considerable importance, and any 

 marked indentations of this edge are worthy of careful notice. The 

 two indentations of the 100-fathom platform in the mouth of the 

 Channel, near the Sole banks, between Cape Clear and Ushant, have 

 been already mentioned as probably representing the mouths of 

 the rivers of the Irish and English Channels, which seem to have 

 entered the Atlantic Ocean not far from each other. But Professor 

 Hull perceives something more than this. For him these two rivers 

 in early Pleistocene time were draining a highland plateau some 

 6,000 feet above the level of the sea. This, after all, is moderate, 

 being only half of what Professor Spencer requires. The western 

 termination of this elevated plateau was a magnificent ' escarpment,' 

 which, if viewed from the outer ocean, would be found to be 

 ' terrestrial,' not oceanic, in origin. When the two rivers approached 

 the edge of this escarpment they entered the ocean in a series of 

 grand cascades or rapids, which are now represented by the sub- 

 merged caiions that seam the great suboceanic slopes. 



I certainly demur to the view that the suboceanic continental 

 slope represents an 'escarpment' in the geological sense ; ^ but it 

 must be admitted that the soundings beyond the edge of the platform, 

 both at the Sole banks and elsewhere in certain localities round the 

 Bay of Biscay, are curious and perplexing, whether the caiion theory 

 be applicable or not. Thus, there are two tongues of deep water 

 which appear to indent the suboceanic slope in connection with the 

 mouth of one of the Channel rivers. This feature is interpreted by 

 Professor Hull as a river-course with two branches enclosing a kind 

 of island between them, and similar cases occur in connection with 

 supposed canons elsewhere. His drawings are very effective, but 

 the steepness of the supposed gorges is greatly accentuated by the 

 difference between the vertical and horizontal scales. As regards 

 geological age Professor Hull refers the British platform like the 

 American continental shelf to the Mio-Pliocene period. But he 

 refers his 'grand escarpment' to the succeeding early Pleistocene 

 or Glacial stage, when, according to his views, the great continental 

 uplift took place. These conceptions as to the sudden uprise of the 

 sea bed, so as to form an escarpment at that comparatively late date, 

 are certainly opposed to the generalizations of Mr. Jukes-Browne. 

 That author, in "The Building of the British Isles," continuously 

 reduces the land area and increases the sea area from the Oligocene 



occupied by the North Sea to meet the difficulty. If we take the period as Pleisto- 

 cene we are no better ofii. To enable the Eiver of St. George's Channel to surmount 

 the edge of the ' escarpment ' we must raise the drainage area behind, and this it 

 would be difficult to effect without converting the Irish Sea into an inland lake over 

 6,000 feet above sea-level. 

 1 This point is now conceded by Prof. HuU (see Geol. Mag., March, 1899, p. 132). 



