204 DE. R. L. SHERLOCK AND MR. A. H. NOBLE ON THE [JuDG I912, 



with-Elints. The relation of the two deposits seems fairly clear ; 

 when both occur together the gravel, except in the case of pockets, is 

 below the Clay-with-Flints and towards the south-east replaces it. 



The gravel is essentially composed of well-ronnded flint pebbles 

 derived from the Heading Beds and set in Reading-Bed detritus, 

 either clay or sand. Prequently there are in addition subangular 

 flints, especially towards the southern border. Sandstone and 

 quartzite pebbles are found near the junction with the Pluvioglacial 

 deposits into which the gravels pass. 



The gravel can best be seen in some small pits in the wood 

 south-east of Hazlemere Church, near High Wycombe. In one pit 

 there is some bedded loam like that of Walter's Ash, and this is 

 obliquely cut off by gravelly clay. There are a few green-coated 

 flints. In one place the Chalk projects upward to within 4 feet 

 of the surface of the ground, but elsewhere it was not touched at 

 a depth of 10 feet. The general aspect of the deposit is that of 

 Glacial Drift, and it differs from the so-called Clay-with-Flints 

 as seen at Walter's Ash, in containing more sand and flint pebbles 

 and fewer unworn flints — that is, more Eocene and less Cretaceous 

 material. 



Other sections may be seen in the small outlier a little south of 

 Kayner's Park, Penn ; in two pits 700 yards east of the outlier ; 

 at Tyler's Green ; Egham's Earm, Knotty Green ; Hill Earm, 

 Chalfont St. Giles ; and other places. 



III. The Eltjvioglacial Gravels. 



Eollowing on to the south of the Glacial Gravels, and in some 

 cases separable with difiiculty from them, are large spreads of 

 gravel with associated masses of sand and loam, which slope very 

 gently, from a height of 400 feet down to less than. 200 feet above 

 Ordnance datum, towards the south. jN'ear Marlow they attain an 

 elevation of about 300 feet above the present Thames. The spread 

 of gravel has no relation to the present valleys, but is dissected by 

 them. It agrees with the Glacial Gravels in its components being, 

 like them, chiefly derived from the Beading Beds and Chalk, but 

 these components are present in difi'erent proportions. 



The gravels which we are now describing difi'er from the Glacial 

 Gravels in the following characters : — 



(1) They contain scarcely any clay, but brick-earth is found in them. 



(2) Tlie flints are generally subangular, unworn ones being vmcommon, 



(3) They contain a proportion, up to 5 per cent, or more, of pebbles 



derived from a distant source. 



(4) They lie more nearly horizontaUy. 



In composition they vary among themselves mainly in the 

 relative proportion of flint pebbles to subangular flints, sometimes 

 one and sometimes the other predominating. The proportion of 

 far-travelled pebbles, such as sandstones and Bunter quartzites, 

 is also variable, and their distribution is shown on the map (PL 

 XIV). The far-travelled pebbles occur abundantly in a belt from 



