SCIENCE-GOSSIP. 



by Mr. A. E. Salter, B.Sc. at Thornton Heath (-). 

 The drift of Wandsworth Common has yielded a 

 large number of flint implements, but it belongs to 

 the Thames rather than the Wandle. 



The Lower Terrace. — After the formation 

 of what is now known as the upper terrace, the 

 deposition of gravel for some reason or other 

 temporarily stopped, and thus failed to counteract. 

 as it had hitherto, the erosive action of the running 

 water on the channel in which it flowed, so that 

 the subsequent accumulation of gravel took place 

 at a considerably lower level. The lower sheet of 

 gravel not only occupies the river valley, but also 

 extends into the dry valleys to the south. It may 

 be divided into two contemporaneous sections, viz. 

 •(«) the angular detritus of the chalk area which 

 comprises the dry valleys and coombes which 

 penetrate the chalk plateau, and (5) the subangular 

 gravel of the Eocene tract. 



There is one deposit which cannot be definitely 

 referred to either of the above sections. Cloth- 

 ing the eastern end of the chalk slope which 

 extends from Sutton to Carshalton, between the 

 Upper (or Carshalton) and Lower Roads, and rest- 

 ing on the London Clay at its foot, is a mass of 

 rearranged Kentish Tertiaries. This is evidently 

 the deposit which was exposed during the exca- 

 vation for a new sewer described by Mr. TV W. 

 TVatts at a meeting of the Geological Society in 

 l v '.'S. "These excavations are situated at a spot 

 which on the Geological Survey map is coloured 

 as London Clay, and the features of the ground 

 fully justified this conclusion. The excavations, 

 however, have shown that there are loamy and 

 sandy beds of a light yellow colour, some 14 or 

 15 feet in thickness. At the base these sandy 

 beds become dark and clayey in places, and include 

 flints and pebbles, while below this is London 

 Clay. In the dark pebbly layer were found" 

 various mammalian remains, which Mr. E. T. 

 Newton. F.R.S.. determined to be the bones of 

 two or three horses (JEquus cabailus), the skull 

 and part of the skeleton of a woolly rhinoceros 

 (Rhinoceros antiquitatis), and a piece of an 

 elephant's tusk. This deposit, some small sections 

 of which are exposed at the present time, was 

 probably found in the same way as the angular 

 detritus about to be described. 



The Angular Detritus of the Dry 

 Valleys. — South of the railway station at Cars- 

 halton one of those small coombes that form so 

 picturesque a feature of the North Downs opens 

 on to the river valley. Lining this and projecting 

 on to the lower ground is a mass of angular 

 detritus, which is well exposed in the two pits 

 sunk in the triangular piece of land situated 

 between the Shorts. Alma, and Carshalton roads. 

 The larger section is nearly 120 feet long and 

 15 feet in depth. It shows a confused mass 



( 2) - Pebbly and other Gravels in Southern England."—"' Proe. 

 •Geologists' Assoc," voL sv. (1898). 



of flints and chalky sand, from 5 to 7 feet in 

 thickness, overlaid by alternations of the same 

 materials charged with chalk shots. The majority 

 of the flints, though broken, are but little worn or 

 weathered, and are almost as fresh as those that 

 still remain embedded in the parent limestone. 

 The fine buff-coloured sand, the abundance of 

 green-coated flints, and of small flint pebbles, 

 being all characteristic constituents of the 

 Kentish Tertiaries, point to the destruction and 

 subsequent incorporation of large masses of these 

 very much older strata, such as still exist not far 

 away. The only other foreign materials present are 

 pieces of a compact ironstone. I have obtained from 

 here a trim m ed flake of Palaeolithic type. 



Similar angular detritus, in which the sand is 

 replaced by loam — evidently decomposed chalk — 

 covers the whole of the bottom of the Chipstead. 

 Hooley, and Caterham valleys. These are the 

 valleys I have previously referred to as converging 

 south of Croydon. The Caterham Valley sheet 

 contains in addition a great number of boulders of 

 pebble-conglomerate. In a now partially filled-in 

 pit at TVhyteleafe rounded masses of chalk were 

 also frequently exhumed, and I once noticed one 

 of those blocks of hard sandstone known as grey- 

 wethers or sarsens. At the bottom of the pit I 

 obtained teeth of the wild ox {Bos primigeniag) 

 and of the woolly rhinoceros. Dr. Hinde mentions 

 getting a portion of the antler of a reindeer 

 (Rangtfer tarandus) together with remains of the 

 horse and ox, of Rhinoceros leptorMnus, and of the 

 mammoth (Eleplias priviigenius). Mr. A. E. Salter 

 also records being shown a tooth of the last by the 

 workmen. In the Horniman Museum there is. 

 from Coulsdon, a portion of the jaw of the same 

 species of animal retaining one molar. This deposit 

 is identical with the typical rubble-drift of the 

 Hants Basin, and was undoubtedly formed in the 

 same way. It has, however, been suggested that 

 this detritus is of fluviatile origin, that the Wandle 

 during the lower terrace period extended up the 

 Hooley Valley, and that tributary streams occupied 

 the bottom of the Chipstead and Caterham Valleys. 

 The appearance at intervals of a small stream, the 

 Bourne, in the Caterham Valley would at first seem 

 to support this view. It is indeed quite feasible 

 that a small stream might in time remove much 

 of the soluble limestone from the valley bottom, 

 leaving the imperishable flints little, if at all, worn : 

 but in this instance the occurrence of mammalian 

 bones at the base of the deposit precludes the 

 possibility. On the other hand, a river strong 

 enough to drag stones along its bed and bury 

 animal remains beneath twelve feet of gravel, 

 would certainly impart a considerable amount of 

 wear to the flints. Hence one is forced to fall 

 back on the subaerial theory in order to explain the 

 phenomenon ( 3 ). 



(3) See C. Reid, F.R.S., " Origin of Dry Chalk Valleys and at 

 Coombe-rock [= Rubble-drift]." — "Quart. Jour. GeoL Soc." 



