Yol. 54.] 



HIGH-LEVEL GRAVELS 11^ BEEKS AND OXON. 



589 



feet above Ordnance datum), and that at Bell Bar (378 feet) 

 have been included for purposes of comparison : — 



Flint-pebbles 



Subangulai* flints . . . 



Quartz-pebbles 



Do> (viti-eous) 



Sandstone , 



Soft do 



Purple quartzite 



Brown do 



Pale do 



Chert, etc 



Lydite 



Grit 



Shale, etc 



Chalk and other ] 



soft rocks J 



Sarsens 



College 





Bowsey 



Ashley 



Merrill 



Bell 



Wood. 





Hill. 



Hill 



Hill. 



Bar. 



Per cent. 



Per cent. 



Percent. 



Per cent. 



Per cent. 



Per cent. 



13 



n 



35 



35 



47 



37 



23 



12^ 



17| 



19 



2 



5 



28 



33^ 



29 



21 



28 



27 



9 



7 



8 



7 



n 



5 



H 



10 



H 



4 



H 



8 



1 



4 





1 









2 



1 



¥ 



1 

 a 



... 



... 



n 



1 





1 



1 



1 



4 



n 



6 



6 



4* 



9 



H 



4 



3 



2 



• t • 



2 



1 













5 



H 





3 



H 



1 



1 



3 



... 



X 

 2 





4 



1 



2 



2 



... 



... 



1 



1 



1 





... 



... 



... 



... 



When we consider the great variety of material composing this 

 gravel, and that sometimes more than half of this is not flint, 

 there seems to be some ground for supposing that it was formed 

 under conditions different from those which prevailed when the 

 pebble-gravel was accumulated. The quartz-pebbles are frequently 

 more numerous than those of flint, and some of the quartz-pebbles, 

 as mentioned by Mr. Salter,^ are not of the ordinary opaque kind, 

 but transmit a certain amount of light, sometimes having a quasi- 

 granular appearance. This gravel also contains a varying — but 

 always a small, sometimes a very small — proportion of brown or 

 purplish quartzite-pebbles, resembling those from the Bunter con- 

 glomerate. It is also in some places closely associated with deposits 

 recognized as Glacial. 



It is natural to ask from what source or sources the characteristic 

 materials of this gravel have been derived. In order to ascertain 

 whether the Ardennes were a probable source, I visited that dis- 

 trict, and showed a few pebbles from Bowsey Hill to Prof. 

 Dewalque, at Liege. He informed me that some pebbles of grey 

 grit might be Gedinniau, and I afterwards noticed the same resem- 

 blance in rocks of that age near Vireux and elsewhere ; but, 

 taking the hard rocks of the Ardennes as a whole, it did not 

 appear to me necessary to conclude that they had furnished much, 

 if any, of the materials of the gravel. 



The high-level gravels near Liege proved to be of interest. 

 A deposit at Crotteaux contained about 50 per cent, of quartz- 

 pebbles, of which some were of the vitreous kind. This variety of 

 quartz occurs in the Norfolk Forest Bed ; but it is found also in the 



Proc. Geol. Assoc. toI. xiv (1896j p. 389. 



