﻿Vol. 66.~] THE WESTERN END OF THE WEALD. 655 



Swanscombe Hill (320 feet), 8^ miles from the summit, we have an average of 

 only 55 feet per mile. The mean of the two calculations is 75 feet per mile. 



2. Morant's Court Hill (704 feet) to 480 feet, at a distance of 

 3f- miles. Average gradient — 71 feet per mile. 



3. Titsey Hill (878 feet) to 523 feet at 41 miles. Gradient = 83 feet 

 per mile. 



4. Botley Hill (882 feet) to 539 feet at 4 miles. Gradient = 86 feet 

 per mile. 



5. Gravelly Hill (778 feet) to 445 feet near Eeedham Asylum (4f miles). 

 Gradient = 72 feet per mile. 



6. EeigateHill (763 feet) to 478 feet near Banstead, 4| miles away. 

 Gradient = 60 feet per mile. 



It may be objected that several of the localities selected are 

 decidedly below the plain-level, as indicated by the dotted lines in 

 tigs. 1 & 2 (p. 642) ; but there are one or two points to be considered 

 in this connection. In the first place, one of the summits used 

 (Morant's Court Hill) is a mile to the north of the main escarpment- 

 line, and allowance must be made for this. Secondly, the fact that 

 there are large areas of evenly bevelled ground below the theoretical 

 level of the plain seems to point, either to local warpings — which 

 very probably occurred but are difficult to prove ; or to lowering of 

 these areas by various subaerial agencies. The extensive sheets 

 of Clay-with-Plints which cover much of the Chalk in this region 

 may point in this direction ; while, when we have an opportunity of 

 examining the surface of the Chalk below the superficial drifts, we 

 always find it rising into a series of pinnacles, like the teeth of a 

 gigantic saw ; and this very strongly suggests that the process of 

 solution, which must be constantly going on, may sometimes have 

 caused a uniform lowering of the plain without much disturbance 

 of the surface. Mr. Monckton (15, pp. 124-26) attributed to such 

 action the lowness of the Tertiary beds at Tot Hill, and I incline 

 to the belief that its effects are often very extensive. 



In order, however, to prove that the conclusions reached in this 

 paper do not depend on such debatable arguments as this, I will 

 proceed to show how little the gradients are altered if we take the 

 dotted lines in figs. 1 & 2 (p. 642) as our starting-point, instead of 

 the actual summits. 



1. Terry's Lodge Hill actually touches the dotted summit-line, so 

 there is no correction to be made. 



2. Morant's Court Hill is quite a mile to the north of the escarpment 

 line, being in the re-entering angle cut by the Darent. Making allowance for 

 this, and estimating the theoretical summit at 810 feet, -we obtain a revised 

 gradient of 80 feet per mile. 



3 & 4. Botley Hill and Titsey Hill touch the summit-line ; therefore 

 no change is required. 



5. G-ravelly Hill. Theoretical summit, 840 feet; revised gradient — 85 feet 

 per mile. 



6. Reigate Hill. Theoretical summit, 810 feet; revised gradient = 70 feet 

 per mile. 



It will be seen, then, that the two methods of calculation lead to 

 but slight differences in the results, although the second method 

 tends to greater uniformity. 



