34 



belt of country both north and south of tlie underlying Hastings 

 sand, and between that formation and the Lower Greensand. 

 North of a line drawn across the centre of this district (east and 

 west) the beds have a northerly, south of it a southerly, dip. And 

 Avherever we stand on the edge of the Chalk escarpment and look 

 towards the Weald, we always have a belt of much lower ground 

 at our feet. Now we find the rivers of this district, instead of 

 nanning out to sea along the plains of Gault or Weald clay, rise in 

 the centre and run either north or south, crossing the lofty Chalk 

 escarpment. Hence, as rivers can never have run up hill, it is 

 obvious that the work of the sea must have been finished Avhen it 

 had planed aM'ay the Tertiary beds and much of the Chalk, leaving 

 the centre of the district rather higher than the present height of the 

 Chalk escarpment around it. And, consequently, to the varying 

 effects of the action of rain and rivers on hard and soft rocks the 

 present contours of the ground are due. 



Our views southward from the neighbourhood of Greenwich 

 are bounded by the edge of the escarpment of the North Downs. 

 The well-known landmark, Knockholt Beeches, stands near the 

 brow of the escarpment. Looking northward from Knockholt 

 Beeches we see the Lower Tertiary escarpment rising above the 

 dip-slope of tlie Chalk about Farnborough and Keston. Under 

 London the Chalk bends do\vnward in a synclinal fold, and is 

 covered by Tertiary beds, again rising from beneath them in the 

 neighbourhood of Watford. But a local upturn of the Chalk along 

 the valley of the Thames caiises its appearance at the base of the 

 Tertiary ' plateau extending between Erith and Greenwich. At 

 Greenwich a line of fault, ranging nearly east and west, and with 

 a downthrow on its northern side, causes the top of the chalk to 

 be about 125ft. below at the Eoyal Naval College, instead of close 

 to the surface as might be anticipated from the position of the 

 chalk-pits of Westcombe Park, Blackheath Hill, and Loampit Hill, 

 LeAvisham. 



The highest of the Eocene beds in this neighbourhood^ is the 

 London clay, which rises above the Blackheath pebble beds at 

 Shooter's Hill, and is itself capped there by gravel of much later 

 date. Of still more recent date is the gravel of the Thames valley, 



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