OP EAST BERKS AND WEST STJERET. 559 



accumulations of coarse flint detritus whicli cap the highest ground 

 remaining of the Bagshot terrain, on Caesar's Camp (600', ordn. 

 datum) and Hungry Hills (550', o. d.) above Aldershot *. These 

 vast accumulations (in places cemented into a conglomerate) of 

 almost unworn flints, with scarcely a trace of even the rudest 

 stratification, impress the mind more than anything I have seen in 

 tliis part of England with a vivid idea of the enormous extent of the 

 destroyed Upper-Chalk strata, which once arched over the region 

 lying directly to the south. They may be the remains of the 

 insoluble debris which accumulated under subaerial conditions 

 along the base of the northern slope of the old Miocene Wealden 

 mountain-range : materials, which, by their assortment and trans- 

 port in part across the sloping plateau of the old Tertiary district 

 immediately to the north, furnished the chief constituent, in a more 

 rolled and worn condition, of the Plateau-gravels of the " Southern 

 Drift." I know of nothing with which they compare so well as the 

 old (pre-glacial) " Schotter " (unstratified debris often conglomeratic) 

 of the lower Alpine valleys, which Yon Hauer t and other authors 

 have described under the name " Terrassen-Diluvium." 



Such materials, however, as were carried away northwards and 

 deposited in the lines of river-drainage or spread out on flats, where 

 the declivity of the plateau diminished %, assumed a more or less 

 stratified arrangement. This structural character is of great impor- 

 tance in recognizing the ancient Plateau-gravels in the sections 

 furnished by the numerous gravel-pits opened of late years on the 

 hill- tops, as the demand for road-material has increased with the 

 opening-up of this ancient forest- country. The structural facies they 

 most commonly present is that of interstratified masses of sand § 

 (often loamy) and shingle, the sand-layers being generally coarse and 

 ferruginous, with pronounced oblique lamination or current-bedding. 

 Even where there are not distinct layers of sand in the sections, 

 the stratification is generally manifest from the horizontal position 

 of the longer axis of the pebbles and of the flint and chert fragments, 

 allowance being made for the occasional local disturbance of these 

 by the roots of pine-trees, by " soil-cap " movements on a small 

 scale, and by the formation of talus at the expense of the plateau- 

 gravels, owing to the removal of the sandy materials of the subjacent 

 hill-fianks by ordinary agencies of erosion [j. 



Eurther field-work since 1883 has shown me that the plateau- 

 gravels must be recognized down to levels (as we work northwards) 

 as low as 300 ft. (o.d.) and even lower. These are, of course, the 



* T cannot recollect ever meeting with rolled flint pebbles in these gravels, 

 t See ' Die Geologie,' 1878, p. 704. 



I Somewhat, as I conceive, after the fashion in which the broad expanses of 

 gravelly detritus are formed by the Alpine rivers as they debouch uj)on the 

 Plain of Bavaria. 



§ These are sometimes cemented by ferric oxide into the hard " pan " occa- 

 sionally used for building, and which defies the action of the atmosphere, as 

 in the Roman Wall of Silch ester. 



II Often resulting from the high-level springs which frequently issue from the 

 base of the gravels ; Eupert Jones, Proc. Geol. Assoc, vol. vi. p. 434. 



