GEOLOGY 



PLEISTOCENE AND RECENT DEPOSITS 



The Lenham Beds, with their tantalizingly fragmentary evidence 

 of extensive submergence, are the latest marine deposits of Kent, if 

 we except the low-level shingle of recent accumulation at Dungeness 

 and the estuarine silt of the marshes of the Thames. All the other 

 remnants of its later geological history tell of the long persistent waste 

 of a land surface shattered by winter frosts and torn down by the 

 gathering of the rains and melting snows into streams, or steadily lowered 

 by the solution of its limestones from the percolation of the sub-aerial 

 waters through its pores, each muddy stream and lime-charged spring 

 incessantly carrying its load of particles downward to the rivers, that in 

 turn sank their channels deeper and deeper into the land as they swept 

 powerfully onward to the sea. 



The Denudation of the Weald. — Let us now consider more fully the 

 eloquent testimony which these rivers in themselves bear to the vast 

 change that the country has undergone since they began to flow in their 

 present courses. Although the plain of Weald Clay lies open eastward 

 to the sea, the Darent, the Medway and the Stour all flow northward 

 from it to break across the high opposing barriers of the Lower Green- 

 sand and Chalk in deep trench-like valleys that they have excavated at 

 right angles to the present escarpments. This behaviour seems inexplic- 

 able until we realize the geological conditions by which their courses 

 were originally determined. We must picture to ourselves the shape 

 of the land after the uplift of the Wealden dome, when the Chalk still 

 formed a continuous arch across the interior, of which only the 

 opposite buttresses now remain in the North and South Downs. From 

 this surface the drainage would necessarily flow northward and south- 

 ward on the opposite sides of the dome, which are precisely the present 

 directions of the principal rivers of Kent on the one side and of Sussex 

 on the other side ; and thus the problem no longer presents any difficulty. 

 Since the courses of these streams were established, the crest of the dome 

 has crumbled away ; formation after formation has been stripped off ; 

 the softer strata have been everywhere lowered relatively to the harder, 

 and longitudinal depressions formed in which tributary streams have 

 been nourished, thereby further accelerating the trenching of the surface ; 

 but still the main rivers have held their original direction and deepened 

 their channels across the broken shell of the land, and they will continue 

 to do so until they have sunk so deeply as to become powerless, or until 

 the country sinks again for renovation beneath the ocean. 



Some relics of this period of erosion — mere shreds of waste left 

 scattered here and there for a while until the elements find time to round 

 off their work — will now claim our attention. 



Clay-'with-F lints and other Hill Drift. — It is in the river valleys that 

 such traces are most abundantly found ; but they are not wanting even 

 on the hills. Thus, as already mentioned, the surface of the Chalk on 

 the Downs, where the ground is not too steep, is very generally over- 

 spread with an irregular sheet, from a few inches to several feet in 



