VALLEY AND ITS RELATION TO THE WESTLETON EEDS, ETC. 159 



According to the one specimen I kept, this gravel consists of: — 



1. Subangular flints, unstained and stained brown,- — in largest proportion, 



2. A considerable proportion of Tertiary flint-pebbles — some broken and 



worn. 



3. About 10 per cent, of subangular fragments of chert and ragstone. 



With one pebUe of a hard sandstone or quartzite (Tertiary ?) and 

 one small pebble of quartz. 



This gravel extends southward all along the top of this hill, at a 

 height of from 360 to 380 feet above O.D. 



From the Norwood hills we pass westward over a lower tract of 

 country with gravels of later age, as far as AVimbledon Common, 

 which rises to the height of 183 feet above the valley of the 

 Wandle. It is capped by a Drift-gravel, about which I feel un- 

 certain. It has all the elements of the Southern Drift, but in 

 addition it contains quartzite-pcbbles, which have the Triassic 

 characters. It is therefore either of Glacial age, or else a Southern 

 Drift invaded by a later Glacial Drift. It consists, in the order of 

 their relative abundance, of : — 



1. Subangular flints stained yellow. 



2. Tertiary flint-pebbles. 



3. Subangular fragments of cberty ragstone and of a yellow cliert. 



4. Pebbles of white quartz, of dark quartzite, sandstone, and ironstone. 



Imbedded in a ferruginous matrix of coarse worn quartzose sand. 



The next hill to break the uniform level of the later Thames- 

 valley gravels is the isolated and conspicuous hill known as St. 

 George's Hill, which rises 1 J miles to the south of Weybridge to the 

 height of 245 feet, and is capped by a Drift-gravel much like that 

 of Wimbledon, but without the quartzite pebbles. I have less diffi- 

 culty, therefore, in referring it to the Southern Drift, although it 

 contains some small white quartz-pebbles, but these may be derived 

 from the Lower Greensand or Wealden. The gravel is composed 

 as under : — 



per cent. 



1. White and yellow-stained subangular flints 44. 



2. Tertiary flint-pebbles, some broken '30 



3. Subftngular fragments of ragstone and brown chert 15 



4. White quartz-pebbles 5 



5. Pebbles of sandstone, ironstone, &c (i 



100 



in a matrix of quartzose sand. 



The greater part of the Surrey Chalk-Downs are bare, with the 

 exce]jtion of a few Tertiary outliers and the red clay with flints. 

 But on Merrow Down, near Guildford, there is a gravel which 

 seems to belong to this Drift. It consists in large proportion of 

 Tertiary flint-pebbles and subangular flints, mostly Avhite, of some 

 subangular fragments of cherty ragstone, and of a hard sandstone 

 (Tertiary), with a few small rough quaitz-pebbles, imbedded in a 



