Geology of the Neighbourhood of Weymouth, ^c. 29 



identical^ both in its mineral characters and abundant organic remains, with 

 the cornbrash of Wiltshire^ that no further description need be given of it 

 than may be found in Conybeare and Phillips's account of Cornbrash*. 



2. The middle region, consisting of the usual well-known varieties of forest 

 marble, sometimes constituting thick beds of stone composed of comminuted 

 shells, at other times passing into oolitic and sandy slate. The most perfect 

 condition of this forest marble is exhibited in the quarries of Bothenhampton, 

 one mile south of Bridport, where it contains that remarkable fossil the Brad- 

 ford Encrinite, Apiocrinites rotundus, together with fragments of Pentacrinite, 

 palates of fish, and fragments of lignite, all imbedded in indurated masses of 

 broken shells; it contains also the same Apiocrinite in the under-clifF between 

 Abbotsbury Castle and the sea, and in the cliffs immediately west of Bridport 

 Harbour. 



3. The lower region is composed principally of strata of blue clay and grey 

 marl and marlstone, containing subordinate beds of imperfect stone. 



The best section of this grey marl is seen in the cliff at Watton Hill, close 

 on the west of Bridport Harbour, attaining a thickness of about 150 feet ; it 

 is here capped by an outlying- summit of forest marble, being the extreme 

 south-western termination of this rock on the coast of England f. The base 

 of this marl reposes on the sands of the inferior oolite. This grey marl also 

 forms a cap on the summit of the inferior oolite in Burton Cliff, on the east 

 of Bridport Harbour : it may probably be the equivalent of the Fuller's 

 earth in the vicinity of Bath. The predominating character of these three 

 deposits, which we have grouped together as forest marble^ is clay; the 

 amount of their united thickness may be about 400 feet. 



The extent of this forest marble formation in the Vale of Weymouth is con- 

 siderable ; it occupies a tract near six miles long, and from two to three miles 

 broad, constituting the lowest strata and central belt of that district. This 

 central belt emerges at Radipole from beneath the Oxford clay, and is less 

 elevated than the parallel belts of Oxford oolite and Portland stone, whose 

 escarpments overhang it on the north and south, rising towards each other as 

 if they once had been continuous, and had been separated by the elevation of 

 the central axis of forest marble, over which, if reunited, they would form a 

 continuous ridge. It is not of sufficient importance to trace separately the 

 extent of the individual beds of cornbrash and forest marble throughout this 

 central belt. The cornbrash occupies the uppermost place along the lines of 

 its junction with the Oxford clay, and occurs also on many summits and minor 



* Outlines of the Geology of England, p. 202. f See Plate II. fig. 13 and 14. 



