WILLIAMS ON THE SALIFEROUS MARLS. 



149 



Section through the Western Extremity of Worle Hill. 

 Horizontal base, \ mile. 



S 



No. 1. is tlie ordinary grey mountain limestone, dipping S. S.W. 

 at an angle of 35°. 



Resting upon this, and dipping at the same angle and in the 

 same direction, are the lower beds of No. 2., consisting of an 

 indurated, red, fine-grained marl, which is succeeded by softer 

 and more marly shales. The harder varieties contain the Tur- 

 binolia ( Cyaihophyllwn) fungitis. Overlying these are beds which 

 have the appearance of a dull brown sandstone ; but which the 

 eye, assisted by a magnifying lens, discovers to be a congeries of 

 minute, red and brown, concretionary, oolitic granules, loosely 

 cemented together by a green, filmy substance, imperfectly filling 

 up the interstices. It acts like a file on the nail, but yields, when 

 triturated, a fine red powder. It effervesces briskly with acids ; 

 and near the overlying bed No. 3., it contains shining facets of 

 plates of a minute encrinite. This series, so far as I could measure 

 it, is from 20 to 25 feet thick. 



No. 3. lies conformably to No. 2., and commonly consists of a 

 pale red, crystalline limestone, sometimes of a bright flesh colour, 

 with small crinoidal plates and stems. Its upper surface is often 

 grey and crystalline, and shows but little alteration from the 

 trappean mass, No. 4., which rests immediately upon it. It dips 

 S. S.W. 35°, towards its outcrop, but not so much below. 



No. 4. is an amorphous mass of red trappean marl, about 30 feet 

 thick, containing numerous globular, angular, and irregularly- 

 shaped concretions, many of them standing in high relief out of it. 

 They are of very varying forms and dimensions, from the size of 

 a pullet's egg to four or more feet in diameter ; and all of them 

 attest their volcanic origin, more or less, by the greater or less 

 abundance of air cells, now filled sometimes by spherical crystals 

 of calcareous spar, and more rarely by red hasmatitic or steel grey 

 iron ore. Sometimes these concretions are slightly vesicular, but 

 at others they are more abundantly so than any trap rock I 

 remember ; and where the original air cells have been left void 

 by the decomposition of the lime and iron, the matrix cannot be 

 distinguished from a recent volcanic scoria. These lump-looking, 



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