BEACHES, ETC., OF THE SOUTH OF ENGLAND. 



339 



on one side a short steep slope, and on the other a long slight in- 

 cline, as in the instance of the Chalk Downs of North Kent, the 

 result would be as follows : — 



Yig. 21. — Diagram shoiving the direction of the currents on a 

 hill-range during uplift. 



I 



o being the parting-line or watershed between the superincumbent waters AB, the 

 divergent currents during uplift will be in the directions *• — ^ ; but while A 

 moves down a short steep slope for a distance x, B passes over a surface 

 equal to some multiple of x in the same time. Consequently there will be, 

 independently of other causes, a larger volume of drift collected at the base 

 of a than of a' , and this disproportion is very apparent in the case of most 

 of our Chalk ranges. 



Where the course of the ossiferous drift is along made, narrow channels,, 

 it would pass down them and spread out fan-shaped at their termination, 

 as at Upchurch and Farnham. (See Map, PI. YIII.) 



But if any cavity (m) should exist on the surface of the open 

 ground, the drift in travelling downwards from o will necessarily 

 pass over, fill, and level it ; or if there should be a trough (n) such 

 as that formed by the old clitf of a Eaised Beach, the detrital 

 matter will there accumulate until full to the brim, when the surplus 

 will pass on to the lower level a (see the Brighton and Portland 

 sections, figs. 3 and 6). 



In the same way, if an open fissure should exist on ground over 

 which the body of detritus passes, that detritus will fall into, and 

 will, if sufficiently abundant, level the fissure with the surface. Gene- 

 rally the detritus has fallen in without order and tumultuously, but 

 in the instance mentioned by Buckland (antea, p. 335) there are indi- 

 cations, as in the rubble of the Head, of alternate action caused by 

 successive uplifts, or by oscillations to and fro in the superincumbent 

 body of water. 



The final uplift was the most important, for it moved the largest 

 volume of debris, and propelled it to the greatest distances, though 

 the gradients were often very small, as between Portslade and South- 

 wick (PI. YII. fig. 2) or in the case of the Godrevy outlier (fig. 7). 



Not only is the rubble of a character which can be best explained 

 by the agency of a body of water on a submerged land, but the 

 character of the organic remains likewise accords with what we- 

 might expect to result from the destruction of a land-surface. In. 



