The Rev. W. Buckland on the Plastic Clay Formation. 289 



No. 12 at Loam Pit Hill. This sand lies on a bed of plastic clay 

 which supports the water of the well in Mr. Conybeare's garden, 

 and of all the wells on the plain of Blackheath at no great depth ; 

 it possesses the same peculiar dark red colour, with the plastic clay 

 of Reading, Corfe Castle, and Paris, and has been used for pottery.* 

 Beneath this clay the Woolwich shell beds and subjacent thick ash 

 coloured sand are to be seen in several parts of the sloping terrace 

 that surrounds the Blackheath plain. Under these on the north and 

 west sides appears the chalk, separated from the ash coloured sand 

 by the same thin pebble bed as at Reading. This pebble bed not 

 attaining the thickness of one foot may be seen at the junction dis- 

 played by the descent to some ancient subterraneous quarries in 

 chalk, called the caves, on the north side of the road ascending to 

 Blackheath from Deptford ; it may be seen also on the south side of 

 the same road in some chalk pits on the slope of the hill : in both 

 places it is covered by the thick ash coloured sand. 



In the lane that leads down from the village of Charlton to the 

 Thames, is a good section shewing the Woolwich shell beds incum- 

 bent on the ash coloured sand which appears there in great thickness. 



The church of Charlton is on the edge of the continuation of the 



* It is probable (hat the plastic clay contains at Blackheath as at Corfe Caslle, Alum 

 Bay and Loam Pit Hill, the remains of vegetable matter in a state approaching to coal ; 

 and that this circumstance has ^iven origin to the erroneous opinion so preralent, that 

 there is good coal at Blackheath if Government would allow it to be worked. 



The very high improbability of finding good coal above the chalk is acknowledged by 

 all who have even the smallest acquaintance with the geological relations of the English 

 coal mines. The presence of black vegetable matter in a state approaching charcoal 

 in almost all our secondary argillaceous strata, has caused endless vain attempts to search 

 for useful coal in formations where the discovery of that substance would be contrary to 

 all experience in this country. No good coal has I believe been yet found in England 

 in any stratum more recent than the new red sandstone, or red rock marl. That of the 

 Cleveland Moors in Yorkshire, being above lias and in the oolite formation, is of so bad 

 a quality as scarcely to form an exception to this position. 



