﻿284 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Mar. 6, 



hood. This clay of course divides the sand into Upper and Lower 

 Tunbridge Wells Sand. 



VI. Weald Clay of the Neighbourhood of Horsham. 



I have said that the Hastings Sand occupies the surface hardly- 

 further west than Horsham, dipping beneath the "Weald Clay about 

 a mile beyond that town ; in most maps, I believe, it is made to go 

 some miles further on, and the hills about Horsham are put down 

 for Hastings Sand. This difference is due to a slight misunder- 

 standing of the nature of the strata there. The flat on which the 

 town is built is on the uppermost beds of sandstone, which lie very 

 flat, but yet dip gently to the north, and west, and south. The hills 

 around, the most conspicuous of which is that of Den Park, are 

 chiefly of clay; there is 120 feet in thickness of it; but they are 

 capped with a hard stratum, which is no doubt the cause of their 

 standing out as hills. The beds that compose this are not more, 

 taken together, than 10 feet in thickness. They are clay with two 

 or three layers of sandstone, which contain large flat masses of cal- 

 careous grit, just like what occurs in the "Wadhurst Clay. Many 

 quarries are dug in this ; and the ripples and other appearances the 

 hard stone shows, have been described by Mantell, Lyell, and others. 

 This set of beds occupies a great space in the form of a table-land 

 slightly sloping from the edge of the escarpment above Horsham in 

 the same direction as the dip, the width being in one place as much 

 as two miles, and varying from that down to 100 yards. I should have 

 some hesitation in thinking that all this ground was occupied by a 

 stratum no thicker than what I have said, but that Mr* Hay (who was 

 the first to perceive its true position) and myself have traced its 

 upper and lower boundaries for many miles, and have examined every 

 section of it without finding any evidence of, or any necessity for 

 supposing, a greater thickness than I have named. If, therefore, a 

 division is made into Weald Clay and Hastings Sand, this Horsham 

 stone must, at least for the north side of the Weald, be included in 

 the former; for here it is only a 10 ft. bed 120 feet up in the clay, 

 and further east there is nothing but clay at the same horizon ; for, 

 as we go away from Horsham in that direction, the feature it makes 

 becomes less important, and the stone is little worked, and evi- 

 dently thins away : the last signs of it are at Crawley. Behind (on 

 the north of) the course of this bed from near Horsham to Crawley, 

 there is another bine of hill which might easily be mistaken for the 

 feature of the Horsham stone ; it is in fact, although of greater alti- 

 tude tban any made by this stratum, entirely of clay, which is yet 

 higher in the series, the Horsham stone making a step projecting 

 from beneath it. The thickness of Weald Clay above the level of 

 the stone-bed is very great indeed ; I reckon it to be about 500 feet, 

 which will give altogether 600 feet or so for the W r eald Clay here, 

 the same as its thickness was found to be in Kent. 



