Geology. 7 



foregoing notes have been taken from Mr. Whitaker's Geological 

 Survey Memoir, " The Geology of London and of Part of the 

 Thames Valley " (2 vols., 1889), to which the reader is referred for 

 a more detailed account of this subject. 



3. CHALK. BY G. E. DIBLEY, F.G.S. 



In nearly the whole of the district the Chalk is concealed by 

 the Overlying Tertiary beds ; but it occurs everywhere, and thus 

 forms the ground-floor (so to speak) of the district, and is the source 

 for the water-supply of a large tract, including Woolwich. When 

 the writer resided m Woolwich (1877-83) two pumping stations 

 existed at Chart ton, where the Chalk comes close to the surface ; and 

 at that time the large pits near Hanging Wood Lane were worked, 

 the chalk being conveyed to a riverside-wharf. At the present day 

 a very small quantity is excavated at the base of the Thanet Sand 

 at Cox's Mount (the point at the level-crossing where the North 

 Kent line enters a short tunnel), and many years ago the Charlton 

 pits and Loampit Hill were frequently visited, as the Chalk yielded 

 a good supply of fossils. 



Going eastward, the next section is in the Wickham Valley. 

 The Chalk crops out under Bostal Woods, the top being 60 feet above 

 Ordnance Datum. Continuing eastward, a small exposure is 

 seen at Abbey Wood, while at the Woolwich Co-operative Society's 

 Estate the Chalk is overlaid by about 20 feet of Thanet Sand, and 

 is here worked by a series of tunnels, as at Gregory's Brickyard 

 in Wickham Lane, where the shaft is about 90 feet deep. 



Along a line from St. John's Railway Station, where the Chalk 

 crops out, to Abbey Wood and still eastward, the Chalk suddenly 

 disappears to the north, owing to a fault by which the beds have 

 been dislocated and thrown down to the extent of 100 feet. It 

 is worth while to point out the evidence in reference to this down- 

 throw. At St. John's Station, just after passing the end of the 

 up platform, the Thanet Sand is to be seen in place faulted against 

 the Chalk. At Westcombe Park the North Kent line is laid upon 

 the top of the Chalk, and continues so to a point just east of Cox's 

 Mount. Wells and borings north of the line mentioned above 

 prove a considerable thickness of Tertiary beds beneath Alluvium 

 or gravel. 



So much for the northern limit of the Chalk, and we now turn 

 our attention to the eastern side. Commencing from the Daren t, 

 whose interesting valley and source do not come within the 

 scope of this paper, we proceed westward from Dartford over the 

 outcrop of the Chalk to Crayford, where the Chalk dips northward, 

 being covered by the Tertiary and Pleistocene beds, described 

 further on. 



