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



plain of Blackheath, which extends thence eastward to Plumsted 

 Common and Boston Heath. (See map, PI. 13.) 



On the inner edge of this platform at the Plumsted Common 

 brick kilns, which are at the base of the north-east extremity of 

 Shooter's Hill, a large section exposes the London clay, abounding 

 in selenites and septaria. This clay is dug for brick tiles and coarse 

 pottery. In the same field with the clay pits and on the north side 

 of them a shaft is sunk 120 feet to the surface of the subjacent chalk, 

 which has been extracted to the further depth of 24 feet, being the 

 object for which the shaft is made. The upper portion of this shaft 

 is in alluvial gravel, between which and the chalk occur the Wool- 

 wich sands. Another shaft was begun in the same fields still nearer 

 to the base of Shooter's Hill, but abandoned from the quantity of 

 water that came in when they were at a depth of which the plastic 

 clay should be found if continued to this point from Woolwich in 

 the same relative position which it there occupies. The same thing 

 happened in an adjoining field, where the shaft for chalk was stopped 

 by the water at the depth of 36 feet. 



In a ravine at the east end of Plumsted Common that falls towards the 

 Thames, the plastic clay that upholds the water of these wells and shafts, 

 is laid open on each side of the hollow way, and throws out a line 

 of springs at its junction with an incumbent stratum that is identical 

 with the bed covering the plastic clay at Blackheath and Woolwich. 

 On the east of this ravine in a deeper hollow called the King's Highway 

 we recognise the sand and gravel beds below this plastic clay corres- 

 ponding with Nos. 4, 5, 6, of the Woolwich Pit, and 4, 5, 6, of the 

 Loam Pit Hill section ; beneath these is the ash coloured sand No. 3 

 of Woolwich. The King's Highway descends into a still deeper 

 valley (through which runs the road leading from Plumsted to 

 Wickham) j this valley is cut to a considerable depth in the chalk. 



