1865,] FOSTER AND TOPLEY JIEDWAY GRAVELS. 445 



northwards to the Chalk near Wrotham, and is thus separated from 

 the basin of the Darent. 



The Chalk forms a steep escarpment facing the Weald to the south, 

 but to the north and north-east the grounds lopes down gradually ; 

 the dip is everywhere into the escarpment, lower beds rising to the 

 south. Through this escarpment the Medway flows at Biu'ham. 

 To the west of the transverse valley thus formed the strike is E. 

 and W. ; on the eastern side it is nearly S.E, and N.W. South of 

 the Chalk we come upon the Gault, forming a flat of low ground 

 averaging three-quarters of a mile in width. The Upper Greensand 

 is here very thin, and makes no feature on the ground ; springs often 

 flow out at the base of the Chalk. The LoAver Greensand rises gra- 

 dually from beneath the Gault, and ends, like the Chalk, in a steep 

 escarpment to the south. The upper part of the Lower Greensand 

 is sandy (Folkestone Beds)*; this division is underlain by a thin bed 

 of clay and sandy clay with fuller's earth (Sandgate Beds) ; and the 

 lower part "of the Lower Greensand (Hythe Beds) consists mainly of 

 beds of limestone and sand, known as "Kentish Rag" and "Hassock." 

 Here the valleys, which do not reach down to the Atherfieid Clay, 

 are often dry, like those of the Chalk. The Kentish Rag country east 

 of the Medway is known as the Quarry Hills. Springs flow out at 

 the junction with the Atherfieid Clay below. This clay is the lowest 

 member of the Lower Greensand, and rests immediately on Weald 

 Clay, which occupies a low and broad plain, varying from four to 

 seven miles in width. The Hastings Sandf, subdivided into beds of 

 clay and sand, rises up on the south from beneath the Weald Clay to- 

 wards the high land of the Forest Ridge. All the streams to the 

 north of this ridge run into the Medway, those to the south drain into 

 the Rother and the Ouse ; the former enters the English Channel at 

 Rye, and the latter at Newhaven. 



The Medway is formed by the junction of a number of small 

 brooks coming down from the high land near East Grinstead ; it 

 flows down past Hartfield to Penshurst, whei-e it receives a large 

 tributary, the Eden, and passing Tunbridge, arrives at Yalding. Here 

 the Beult and the Teise fall into the Medway, which now enters the 

 gorge cut in the Lower Greensand ; it soon reaches Maidstone, re- 

 ceives the Len, and then flows on in a general north-north-westerly 

 direction towards Snodland, where it is joined by the Snodland 

 Brook, The Medway now takes its course along the gorge through 

 the Chalk, passes by Rochester, and finally reaches the Thames at 

 Sheerness. 



/i. Superficial Deposits. — The following different kinds of super- 

 ficial deposits are found in the Medway valley : — 



1. Subaerial beds. 



2. Modern alluvium. 



* For a description of the subdivisions of the Lower Greensand, see Fitton, 

 Trans. Geol. Soc. 2nd ser. vol. iv. 1836, p. 103, and Drew, ' Memoirs of the 

 Geological Survey,' Sheet 4, 1864. 



t For a description of the northern part of the Hastings Sand rountrv, see. 

 Drew, Quart. Journ. Geol. So(>. \cA. xvii. 18G1, p. 271. 



VOL. XXI. PART I. 2 H 



