Vol. 54.] GEAVELS IN BEEK8HIRE AND OXFOEDSHIEE. 597 



has been cut back since the time of the Quartzite-gravel. If this be 

 so, it must mark a very considerable lapse of time. 



The flint-gravel would seem to be in part a reconstruction of old 

 hill-gravels, but very largely, particularly at Turner's Court, a 

 residuum left after the dissolution of the Chalk ; and the deposit in 

 its present position would necessarily be subsequent in date to the 

 Quartzite-gravel. 



On the south side of the Thames also, the Quartzite-gravel comes 

 into relation with the old flint-gravels in a very interesting manner. 

 In the district south of Streatley and west of Pangbourne we come 

 upon gravels of a ' Southern ' type. Pits in this gravel may be 

 seen near Bere Court, 2 miles south-west of Pangbourne, and another 

 I mile south-west of Upper Basildon. The gravel at the latter place 

 is at an elevation of about 350 feet above Ordnance-datum. 



Similar gravel occurs on Ashampstead Common at about the same 

 level, but the two deposits are separated by a dry Chalk-ravine. 

 The highest parts of this common consist of loamy or sandy gravel, 

 of which a thickness of 4 or 5 feet may be seen in an old pit. It 

 was found to have the following composition : — 



Per cent. 



Flint-pebbles 32 



Subangular flints, rather small 61 



Large flint-pebble 1 



Subangular sarsens 3 



Veined grey quartzite-pebble 1 



Quartz-pebble 1 



Purplish chert 1 



It will thus be seen that some of the ' Northern ' material has 

 reached this gravel. The pit near Upper Basildon, on the other 

 side of the dry chalk-valley, showed a thickness of 6 or 7 feet of 

 email subangular gravel of the flinty type, but the upper 3 feet of it 

 appeared to have been disturbed, and was found to contain here and 

 there quartzite-pebbles. Immediately under this upper part of the 

 gravel I found a large white qnartzite, a flint-flake, and also a flint- 

 ' core,' from which flakes had apparently been struck. There were 

 also a few large unrolled flints, some of them 15 inches long. 



This intrusion of the quartzite-material is not remarkable, when 

 it is considered that at Basildon Kiln there is, at a level 100 feet 

 higher, a remnant of a gravel of an intensely quartzitic type, less 

 than a mile distant from this point. What is noticeable is that the 

 gravels have mingled so little, so that in walking over the fields 

 the surface-drift is found to alter its character suddenly. 



One cannot avoid being impressed, both here and elsewhere, with 

 the great physical changes which have taken place since the time of 

 the deposition of the Quartzite-gravel. Valleys must have been 

 scooped out, filled with ' Southern ' debris, and, as a result of further 

 denudation, formed into plains since the gravel of Upper Basildon 

 was deposited. Assuming the gravel which flanks that hill to be not 

 so old as the gravel on its summit, yet a large amount of time must 



