DRIFT-STAGES OF THE DAKENT VALLEY. 1 37 



is ])crfectly homogeneous, and allows the surface-water to pass 

 through it and descend to the underground Matcr-level, iv I — a 

 level governed by that of the adjacent stream ; and I can only 

 account for a spring in the liigh position of (*) by supposing that one 

 may have broken out there at the time when tlie bed of the valley had 

 not been excavated to below that point, when the line lu I' would 



Fig. 4. — Section of Meenfold Hill, Shoreham. 



Meenfold 

 Darent R. Hill. 



w^_ *J^--'--—'lf 



'2 

 - -Z 



im===^ 



a. Red Clay-with-flints. 

 *. Compact Chalk breccia. 

 w I. Present bne of water-level. 

 ul' V . Supposed former line of water-level. 

 2. Chalk. 



represent the then level of the underground water, and consequently 

 of the springs ; for in that case springs would be thrown out on the 

 higher level \v' l\ as they are now on the lower one lu ?, indepen- 

 dently of any impervious stratum. This, therefore, may be taken 

 as some evidence of the higher level probably occupied by the 

 stream at that period. 



§ 4. The High-Level or Limpsfield-Gravel Stage. 



I have already had occasion to notice in a former paper * some of 

 the few drift-beds in that branch of the Darent Valley which runs 

 eastward from Otford to its watershed with the Shode — a tributary 

 of the MedAvay. Those of the more important western or main 

 branch of the Darent Yalley running up to "Westerham and Liraps- 

 field Common have now to be noticed. (See Map, PI. YII.) 



The first appearance of a well-marked drift connected with the 

 river-erosion of the Darent Valley is the high-level gravel on the 

 watershed at Limpsficld Common. The denudation of the area had 

 by that time made considerable progress ; for the Chalk escarpment 

 ri'ses 200 to 300 feet, and the Lower Greensand 100 to 200 feet, 

 above the level of this gravel-bed. With the exception of the few 

 isolated traces named in preceding paragraphs, there is nothing to 

 record the work of early excavation of the valley, though it is 

 obvious, for the reasons before given, that the valley-erosion, which 

 followed on the pre-Glacial rise of the land, must have continued 

 through the succeeding Glacial epoch ; and as there is evidence to 

 show that extreme climatal conditions prevailed during that period 

 in the Thames Valley, it may be presumed that ice and snow were 



* Quart. Journ. Geol. See. vol. xlv. (1889) p. 270. 



