394 GEOLOGY OF THE ISLE OF PORTLAND. 



elation of the Island, consists of the Kimmericlge 

 clay, which attains a considerable elevation on the 

 north ; this is surmounted by beds of Portland 

 sands, and thick strata of the oolitic limestone so 

 well known as the Portland stone, which is ex- 

 tensively worked in numerous quarries. The 

 strata dip to the south at an angle which corre- 

 sponds with the profile of the Island. The coasts 

 are steep, the base of Kimmeridge clay forming a 

 talus surmounted by perpendicular crags of oolite ; 

 in the north-east cliff, there are beds of bituminous 

 shale like those in Ringstead Bay. The southern 

 extremity consists of low limestone cliffs, which are 

 worn into numerous caverns by the force of the 

 waves. 



The summit of the northern brow to a depth of 

 upwards of twenty feet, is formed of a series of 

 freshwater strata superimposed on the uppermost 

 bed of oolite, which is locally termed "the Cap." 

 These belong to the Purbeck, and present the 

 same remarkable phenomena as were observed 

 in the cliff to the east of Lulworth Cove (see 

 p. 384). Mr. Webster first directed attention to 

 the highly interesting facts here disclosed. 



The Kimmeridge clays of Portland resemble 

 those we have examined in Ringstead Bay, and in 

 the Isle of Purbeck. The lower beds of oolitic 



