﻿1861.] 



DREW HASTINGS SAND. 



275 



at Tunbridge "Wells, from the great descent there is between the out- 

 lier of Weald Clay at the top of the Common, by the corner of Bishops - 

 down, and the valley of the Wells ; and even in this the base of the 

 sand is not reached, while the dip is in that direction which would 

 make out the thickness more than the fall of the ground. At Groom- 

 bridge Hill too, where the strata are about flat, there is 180 feet of 

 vertical height from the top to the bottom of the sand. At Eridge 

 Rocks, however, and at some other places, there can hardly be so 

 great a thickness. 



I should here mention those natural sections so well known to 

 every one who has been in the neighbourhood of Tunbridge Wells : 

 they are lines of projecting rock sometimes showing a quite perpen- 

 dicular face. From their having a grey weathered surface, and from- 

 the way in which the vegetation is combined with them, clothing 

 and hanging over the summits, they form, in several places, exceed- 

 ingly pretty groups. All of these (namely those on Tunbridge Wells 

 and Rusthall Commons, Eridge Rocks, Harrison's, Penn's Rocks, &c.) 

 belong to one stratum, namely the top bed of the sands that I have 

 before described; and it is to be remarked that these bare rocks 

 occur where the bed is not in its hardest form (namely a good 

 sandstone), but they are almost in every case composed of rock-sand, 

 which would seem to resist the degrading action of the weather by 

 the solid mass it presents without planes of division. It will gene- 

 rally be found that the rocks are capped with an outlier of clay, which 

 is of course the Weald Clay. There is one more circumstance about 

 the Tunbridge Wells Sand which I would have borne in mind, be- 

 cause it bears on a question we shall come to discuss ; it is that some- 

 times at a level quite low down in this subdivision another bed of 

 rock-sand occurs ; it does not, however, form any natural rocks. It 

 may be seen by Groombridge, Speldhurst, rTashes near Penshurst,. 

 and at other places. 



3. Wadhurst Clay. — We now come down to a clay stratum, which 

 I call "Wadhurst Clay." The bottom of the sand is generally loamy, 

 this being the passage (not a very gradual one) to the clay that suc- 

 ceeds. This last is, both in the upper part and through all its thick- 

 ness, stiff brown clay, or brown or blue shale ; it ends sharply against 

 the next sandy stratum, good clay or else shale resting on sand or 

 sandstone. The thickness was proved by a well-sinking at Pellet 

 Gate, Pembury, to be 160 feet; but I do not think it is everywhere 

 quite so much ; I should say that in the neighbourhood of Tunbridge 

 Wells it varied between that and 120 feet. There occurs a little of 

 three different kinds of stone in this clay, — first, a calcareous grit, 

 or a fine, hard, calcareous sandstone, which is seen in thin beds every 

 here and there ; but just in the neighbourhood of Beech Green, 

 Withyham, it forms beds of two or three feet, much worked for 

 roadstone. Secondly, a shelly limestone, containing Cyrena chiefly, 

 of which I only saw a few two- or three-inch layers. Thirdly, a 

 smooth grey clay-ironstone, generally in small nodules or layers 

 of nodules. It was this kind of ironstone, and chiefly stone from 



