284 The Rev. W. Buckland on the Plastic Clay Formation. 



Blackheath, Lewisham, Charlton, Woolwich, and on the east of 

 Plumsted. In all these places the thin bed next above the chalk, 

 which at Reading contains fishes teeth and oysters, is seen com- 

 posed of a similar substance of ioose green sand mixed with chalk 

 flints, both rolled and angular, and generally coated with a dark 

 green crust ; but here they contain no organic remains, and seldom 

 exceed two feet in thickness. Above this thin bed is a thick stra- 

 tum of fine grained ash coloured sand, destitute of shells or pebbles, 

 and varying in thickness generally from 30 to 40 feet. This stra- 

 tum is seen to the greatest advantage in the Woolwich sand pits, 

 where is an enormous artificial section, presenting the following 

 order of succession : * 



Section of the Woolwich Pits, asct7iding from the lowest Strata. 

 (See coloured Section, PI. 13, No. 1). 



No. Feet. 



1. Chalk with beds and nodules of black flint - - — 



2. Green sand of the Reading oyster bed, containing green 



coated chalk flints but no organic remains 1 



3. Light ash coloured sand without shells or pebbles - -35 



4. Greenish sand with flint pebbles 1 



5. Greenish sand without shells or pebbles - - - 8 



6. Iron-shot coarse sand, without shells or pebbles, and con- 



taining ochreous concretions disposed in concentric la- 

 minae - - - -- - - -9 



* Although a Section of these pits is already before the Society, it seemed necessary to 

 insert that I am now giving, as it differs from Mr. Webster's (Geol.Trans.vol.2, p. 195.) 

 in a few minute particulars, and was the result of a careful examination by the Rev. Win. 

 Conybeare and myself, in April, 1815. I have also the sanction of Mr. Conybeare's 

 authority, and am indebted to his observations, confirmed subsequently by my own, for 

 the Notices, Map, aud Sections, which I have given of the neighbourhood of Blackheath. 



