72 



Cutch, and in fhe passes leading to Cabul. (Lyell's Elements, 

 page 305.) This great thickness and extent of rock, the eleva- 

 tion of the greatest mountain ranges from the ocean's depths, 

 the change and development of whole species of animals and 

 plants, both of sea and land, are only some of the events that 

 happened between the deposition of the London Claj- of the 

 Sheppey and Whitstable cliffs, and the gravels and brick-earths 

 that furnish the road making and building materials of the dis- 

 trict. It is necessary to impress upon the mind this immense 

 period of time, in order that we may the better understand how 

 the denudation of the Weald was brought about. 



The great disturbance of the strata at the close of the cre- 

 taceous period, that resulted in the upheaval of such vast 

 mountain ranges, is supposed to have been brought about by 

 contractions going on in the earth's crust. As the skin of an 

 apple shrivels up, or wrinkles gather on our own faces, as we 

 with our mother earth grow older, so a wrinkle passed across 

 this portion of the world, in a north-westerly direction, in a line 

 from Hastings to near Farnborough, constitutes the anticlinal 

 axis of the AVeald. This seems to have been a gradual upheaval, 

 for the sea planed the strata off as they were brought near its 

 surface and consequently within range of the action of its waves, 

 rolling the flints off the chalk, and the chert of the Lower Green- 

 sand until nothing of them was left but their very hard hearts, 

 the Eocene pebbles of the Woolwich and Old Haven beds. This 

 upheaval and depression was probably repeated several times, 

 for a depression seems again to have followed, when the London 

 Clay was deposited in deep and quiet water. We must stUl bear 

 in mind the length of time occupied by these changes. The 

 debris of the cretaceous and Wealden rocks, as attested by the 

 flint pebbles, contributed materials for filling the depression in 

 the chalk to the north and south, known as the London and 

 Hampshire basins. The Wealden district having in this manner 

 been denuded of thirteen hundi-ed feet of cretaceous and 

 Wealden rocks was reduced to an elevated jplain, having 

 its watershed to the north-east and south-west of the 

 anticlinal ridge. The water running down these slopes 

 like the roof of a house cut out the river channels at 

 right angles to the strike of the rocks, and consequently in the 

 same direction as their dip, which is to the noith-east on the one 

 side of the anticlinal and to the south-west on tlie other. We 

 have five rivers to the north, the Stour, Medway, Darent, Mole, 

 Wey, and four corresponding ones on the south, the Arun, 

 Adur, Ouse, Cuckmere, and probably once a fifth corresponding 

 to the Stour, the seaward portion of which through encroach- 

 ments of the sea has ceased to exist. The relative and opposite 

 positions of these rivers is most remarkable, they do not flow out 



( 



