THT5 MEN.DIPS : A GEOLOGICAL KEVERIE. 



265 



(perhaps at tho timo of the Oxford Clay) beneath sucli de- 

 posits was it buried. 



There is indeed no definite evidence of tlie final sub- 

 mergence of the island ; and it may be that, as Charles 

 Moore was inclined to believe, it was not submerged at all 

 in Jurassic times. The Oxford Clay is, however, a formation 

 of wide extent, and of comparatively uniform thickness and 

 character. Undoubtedly it was formed in deeper water than 

 the oolitic limestones that un'Herlie it and preceded it in time. 

 And since the Inferior Oolite and Fullers Earth tell us that 

 tho sea had in their day crept far up the flanks of Mendip 

 it would seem probable that, by further subsidence of the 

 land, tho island completely sank beneath the deeper waters 

 of the Oxford Clay sea. In any case, it is not probable that 

 Mendip was long submerged; and when ere long (perhaps 

 in tlie age of the Portland Oolites) upheaval again lifted the 

 area above the waters, it must have formed a fertile lowland 

 district, contrasting strongly with the mountainous parts of 

 Cornwall, Devon, and Wales, which had not been thus sub- 

 merged and smothered in Jurassic deposits. 



I mitst now content myself with sketching very briefly, in 

 a couple of paragraphs, the events which led up to the second 

 submergence and the final re-emergence of the Mendips. 



Probably the upheaval that re-elevated the Mendips above 

 tho waters of the oolitic sea converted nearly the whole of 

 England north of London and the Vale of Wardour into a 

 rich and fertile land surface, bordering an eastern sea which 

 occupied the site of part of the North Sea, and formed a 

 Speeton Bay over parts of Yorkshire and Lincolnshii-e. To 

 the west there was, in Mr. Jukes-Brown's opinion, a lake in 

 the area which is now the Irish Sea between the Isle of 

 Man, Anglesea, and Lancashire. To the south lay an inland 

 sea, soon to be converted into a Wealden Lake (Map 5) 



