Professor Edward Hull — Gravel Beds, Isle of Wight, etc. 103 



question, and is to be found in the uplands of the Chalk formation, 

 rising in the case of the Isle of Wight into the ridge which stretches 

 from the l^eedles to Foreland Point, and in the case of the mainland 

 rises into the great expanse of Salisbury Plain. These formed the 

 land-margins of the area at a period of depression to the extent of over 

 400 feet. The epoch of this depression is not difficult to determine. 

 That it was post-Tertiary is clear from the relations of the plateau 

 gravels of the Tertiary beds as seen in the Isle of Wight, and it was 

 after the period of disturbance which raised the Cretaceous and 

 Tertiary beds into their present inclined position, and subjected them 

 to an enormous amount of erosion. Thus we arrive at the conclusion 

 that the plateau gz'avels are the representatives in the South of 

 England of the Interglacial sands and gravels of the centre, east 

 and north of England and Wales. ^ 



Part IV. 



Having thus endeavoured to show that the plateau gravels were 

 deposited under the waters of the sea, and that the materials of which 

 they are composed were derived chiefly from the erosion of the 

 adjoining unsubmerged Cretaceous lands during an epoch of depression, 

 it becomes necessary to refer back to the preceding epoch, in order 

 to determine the physical changes which led up to succeeding 

 conditions, and on this subject the evidence is not less clear and 

 substantial, and while in my handling of this subject I shall adduce 

 the support of an authority of the highest weight, that of the late 

 Mr. Godwin-Austen.* The preceding epoch was one of elevation of 

 the land, and of this the evidence is of two distinct kinds, going to 

 show that the uplift was sufficient to lay dry the bed of the English 

 Channel and bordering sea round the coasts of England and France, 

 producing that remarkable now submerged feature known as the 

 "Continental Shelf". 



This brings me to refer to. the Continental Platform. This 

 physical feature consists of a gently shelving plain extending from 

 the existing coasts, and stretcliing out into the Atlantic for a variable 

 distance, 50 miles or more, and at its outer margin breaking off in 

 a steep, sometimes precipitous, descent into the abyssal depth of the 

 ocean. Its margin generally coincides with the isobathic contour of 

 about 100 fathoms opposite the mouth of the English Channel, and 

 it is traversed not only by channels of rivers continuous with those 

 now entering the Atlantic along the western coast, but also by 

 a submerged river valley which is entirely under water, which I have 



^ In Lancashire these Interglacial sand-beds with marine shells are overlain 

 by an Upper Boulder-clay of marine origin, as shown by the shells it contains 

 {Turritella, Fustis, Ptirpura), and a fine section showing this superposition of 

 the Upper Boulder-clay on the Interglacial sands is laid open on the banks of 

 the Ribble above Preston. I have given an account of these Pleistocene 

 deposits in Ccmtrihutions to the Physical History of the British Isles, 

 1882, chap. xiii. The sands and gravel are probably the representatives of the 

 " Middle Glacial beds " of Messrs. Wood and Harmer, of Norfolk. 



- In his communication to the Geological Society entitled ' ' Valley of the 

 English Channel " : Q.J.G.S., vol. vi, 1850. 



