1850.] 



PRESTWICH ON THE LOWER TERTIARY STRATA. 



261 



series of the Woolwich fluviatile beds, and the underlying sands re- 

 posing upon the chalk*. 



At Counter Hill, stratum "c" is two feet thick, and shows very 

 distinctly the irregular and worn surface of '*</," on which it reposes ; 

 "</" is there thinner, of a nearly pure white colour, and contains 

 numerous small patches of small round flint pebbles. On the line 

 of the Croydon Railway immediately south of the New Cross Station, 

 is a section of this bed, which has already been described by Mr. 

 Warburton in I844t. For the sake however of showing its con- 

 nexion with the foregoing details, I here give a diagram of that part 

 of the cutting, showing the conglomerate bed at the base of the Lon- 

 don clay. (See fig. 8.) 



Fig. S. — Section at New Cross. 



>b> London clay; tough brown clay with septaria, but without 

 organic remains. 



[remains. 



. Dark ochreous sand full of round flint pebbles. No organic 



^_ / Yellow sand and clays forming the upper part of the series 



_^ '1. of the Woolwich fluviatile beds hereafter to be described. 



The chalk has been reached at a depth of about 100 feet beneath 

 stratum **c." 



We must now make a slight deviation in order to examine a well- 

 section at Hampstead, the particulars of which were communicated 

 to the Geological Society in 1834 by Mr. Wetherell J. It was shown, 

 that the London clay was there underlaid by a compact rock, five 

 feet thick, formed of green sand, with numerous round flint pebbles, 

 and cemented by carbonate of lime, reposing upon a series of sands 

 and mottled clays overlying the chalk. 



The following are the organic remains he gives from this rock : — 



Rostellaria lucida, Sow. (? Sow- Pleurotoma. 



erbyi, Mant.) Venus incrassata, Desk. sp. {} Cytherea 

 Natica glaucinoides, Sovj. obliqua, Desk.) 



Nucula. Scales and teeth of fishes. 



Panopsea intermedia, Sow. Lignite. 

 Cardium nitens, Sow. 



We are now arrived at a point of considerable difliculty. So far 

 the range of this stratum has been regular, and the line of demar- 

 cation between it and the upper part of the mottled clays and sands 

 has been well-marked ; but on reacliing the neighbourhood of Croy- 

 don and London a difFerent order of things commences. The 

 mottled clays disappear except in small quantities, and in a few 

 places ; large and thick beds of round pebbles set in, interstra- 

 tified with a peculiar series of fluviatile and freshwater beds. The 

 London clay recedes further to the north, leaving a large and more 



* For a better section than any now exposed of these beds, see Dr. Buckland's 

 paper in the Trans. Geol. Soc. vol. iv. p. 285 ; also Phillips and Conybeare's Out- 

 lines of the Geology of England, p. 49. 



t Quarterly Journal of the Geological Society, vol. i. p. 1 72. See also Phillips 

 and Conybeare, Geology of England, p. 48. 



t Trans. Geol. Soc. 2nd Series, vol. v. p. 131. 



