26 Outlines of Geology. 



scape which they constitute, peculiar for the smooth and rounded 

 outline of its hills, their monotony of surface, and for the singular 

 cup-shaped concavities and deep hollows in which their sides 

 abound. The situation and extent of the chalk in England is 

 best shown by reference to coloured geological maps. Salis- 

 bury Plain and Marlborough Downs form a centre, as it were, 

 from which the chalk emanates in a north-east direction, through 

 Buckingham, Bedford, and Cambridgeshires, and terminates on 

 the coast of Norfolk in one direction. Another branch, inter- 

 rupted by the Valley of the Humber, traverses Lincolnshire, 

 terminating at Flamborough Head in Yorkshire. 



The extreme western point of the chalk is not far from Honiton 

 in Devonshire, whence it branches off toward the south-east to 

 the Isle of Purbeck, and again appears, forming a ridge that 

 crosses the Isle of Wight. Near Hungerford, in Berkshire, 

 another range of chalk commences, and passes by Alton and 

 Rochester to the coast of Kent, forming the cliffs between 

 Folkstone and Deal. From near Alton, another branch passes 

 off, and ends at the lofty promontory of Beachy Head on the 

 Sussex coast. In this chalk district there are some considerable 

 elevations. Near Dunstable and Shaftesbury, for instance, it 

 forms hills nearly 1000 feet above the level of the sea. Between 

 Lewes in Sussex, and Alton in Hampshire, there are several 

 similar elevations. Between Alton and Dover, the highest point 

 is about S00 feet, and the Castle Hill is about 470 feet high. The 

 chalk cliffs near Folkstone, and those near Lyme in Dorsetshire, 

 are between 5 and 600 feet high. 



Chalk, like the strata that lie upon it, abounds in organic 

 remains, but they are of a different and more ancient character, 

 exhibiting many new genera, and scarcely a single species quite 

 identical with any that now exist. They are chiefly as follow : — 

 Remains of vertebral fish, such as teeth of a species of 

 shark. 



Among the testaceous mollusca, are ammonites and belemnites, 

 generally in the lower strata only ; a few spiral univalves and 

 several bivalves. 



