Oolitic Escarpment and Tableland. 3 1 7 



the nearest Lias, near Droitwich in Worcestershire. 

 Indeed, I firmly believe that the Lias and Oolites 

 entirely surrounded the old land of Wales, passing 

 westwards through what is now the Bristol Channel on 

 the south, and the broad tract of New Red formations, 

 now partly occupied by the estuaries of the Dee and 

 Mersey, that lie between Wales and the Carboniferous 

 rocks of the Lancashire hills. 



The strata that now form the wide Oolitic tableland, 

 have a slight dip to the south-east and east, and great 

 atmospheric denudations having in old times taken 

 place, and which are still going on, a large part of the 

 strata, miles upon miles in width, has been swept away, 

 and thus it happens that a bold escarpment, once for 

 a time in Yorkshire and the Yale of Severn an old line 

 of coast cliff, overlooks the central plains and undula- 

 tions of England, from which a vast extent and thick- 

 ness of Lias and Oolite have been removed. That the 

 sea was not, however, the chief agent in the production 

 of this and similar escarpments will be shown further on. 



An inexperienced person standing on the plain of the 

 great valley of the Severn, near Cheltenham or Wotton- 

 under-edge, would scarcely expect that when he ascended 

 the Cotswold Hills, from 800 to 1 ,200 feet high, he would 

 find himself on a second plain (9, fig. 57, p. 304) ; that 

 plain being a high tableland, in which here and there 

 deep valleys have been scooped, chiefly opening out 

 westward into the plain at the foot of the escarpment. 

 These valleys have been cut out entirely by frost, rain, 

 and the power of brooks and minor rivers. 1 



If we go still farther to the east, and pass in 



1 Such valleys are necessarily omitted on so small a diagram, 

 and the minor terraces on the plain, especially such as 7, are ex- 

 aggerated. 



