GEOLOGY. 



Edited by W. WHITAKER, B.A., F.R.S., F.G.S. 



GENERAL REMARKS. BY W. WHITAKER. 



The boundaries of the district dealt with in the following notes 

 are the Thames on the north, the Ravensbourne on the west, the 

 Cray on the east, and the outcrop of the Chalk between the last 

 two rivers on the south, near Keston and Farnborough. This 

 roughly triangular area is between 50 and 60 square miles in extent. 



The geologic formations that form the surface of the district are, 

 from the most recent downward, the ALLUVIUM of the rivers, the 

 various gravels and loams of the DRIFT, the LONDON CLAY, the 

 LOWER LONDON TERTIARIES (Blackheath Beds, Woolwich Beds, and 

 Thanet Sand), and the UPPER CHALK. 



But this series is not geologically continuous, there being a great 

 gap between the London Clay and the Drift, a gap represented in 

 some other parts of the London Basin by the Bagshot and 

 Bracklesham Series and the Crag, and in the Hampshire Basin 

 also by a great set of beds between the Bracklesham Beds and the 

 Crag in age. 



Besides these, however, other formations have been proved, by 

 means of deep borings. These comprise the MIDDLE and LOWER 

 divisions of the CHALK, and the GAULT, beneath which last we 

 again find a great gap, including the whole of the Lower Cretaceous, 

 the Jurassic and Liassic Series, and perhaps also the Triassic and 

 the Carboniferous, a set of red beds of doubtful age being then 

 reached. 



The scenery of the district of course depends on the geology, 

 and there are some well-marked features. Beginning at the lowest 

 level is the Alluvial plain of the Thames, due to the deposition by 

 the river of the various constituents of the marshes. Then there is 

 the plateau of Blackheath, Plumstead Common, Bexley, etc., due 

 to the erosion of the London Clay from off the pebble-beds, and the 

 capacity of the latter to withstand erosion, except at the edges, 

 where a sharp slope is generally formed, as is markedly shown by 

 the southern escarpment at and near Keston. In the immediate 

 neighbourhood of Woolwich the crowning feature is Shooter's Hill, 



