30 



aiooLociy of thio avon basjn. 



I.I10 posiliioTi of tlio Dolomifcic C()i\ti^lom(M-a(.o atul Triii-s. So 

 too with tlio physical features. The Battery ridgo, Wood 

 Hill, and Fore Hill, were already marked ont in pro- 

 Mesozoic times. Tlio Portishead-Clevedon ridgo was 

 already in existence, at least in a rongh-hown state. 

 Between it and the Clifton-Clevedon ridgo wore the possibly 

 ico-Iadon waters of the Old Triassic Lake. But as the ages 

 of Mesozoio times passed by those ridgos and islands under- 

 went gradual submergence ; and latter-day denndati(m has 

 boon largely occnpiod in removing tho load of secondary 

 rocks beneath which they wore thus smolliorud. 



