33 



the flint is strikingly showm hy the way in which the delicate 

 sliells of sea-urchins are found filled up with flint, and by the 

 beautiful casts in flint of spines and other objects. 



The thickness of tlie Clialk in the neighbourhood of London is 

 between six hundred and seven hundred feet. ]>ut at Xorwich it 

 is found to be 1,150ft. thick. 



The Eocene sands, gravels, and clays, overlying tlie Chalk, are 

 seen to abound especially in the neighbourhoods of London and 

 Southampton. They once stretched across the area now occupied 

 by the Chalk of Salisbury Plain, and the beds below the Chalk of 

 the Weald district. When, after the deposition of the Chalk and 

 Eocene beds, the whole area was upheaved, the upheaval was 

 greatest along a line ranging across the middle of Salisbury Plain 

 to the neighbourhood of Winchelsea and Dungeness. Along this 

 line the strata were bent up so as to form an anticlinal fold or 

 ridge, while parallel to and on each side of this line, in the neigh- 

 bourhoods of London and Southampton, they lie in trough-like 

 hollows, or SA'nclinal folds. Hence, the beds along the course 

 of the anticlinal ridge were much more Avasted by the sea, on 

 emergence, than those in the sj'nclinal hollows. The work of the 

 sea, however, as a denuding agent, is to plane down, rocks to a 

 (•ertain level, while the present contours of the ground are due to 

 the subsequent action of rain and rivers. This becomes very plain 

 vn an examination of the Weald district. 



The Weald district is the area bounded on the north by the 

 North Downs, which range from Folkestone to Farnham ; on the 

 south by the South Downs, which stretch from Beachy Head to 

 I'etersfield ; on the east by the sea, and on the west by the escarp- 

 ment between Farnham and Petersfield, connecting the North and 

 South Downs. The North and South Do■\^^ls and the escarpment 

 connecting them are the steep slopes made by the outcrop of the 

 Chalk around and facing the Weald. Within the area bounded by 

 the outcrop of the Chalk are the outcrops of the Upper Greensand, 

 Gault, and Lower Greensand ; all, rouglily speaking, parallel to 

 that of the Chalk. The centre of the district consists of the rolling 

 hills of Hastings sand in the east, and, west of Horsham, of the 

 plain of "Weald clay. East of Horsham the Weald clay occupies a 



