R. H. Chandler—Drift at Bostall Common. 5980 
need not be detailed here. It consists of a coarse, clayey gravel of 
rounded flint pebbles and beds of sand. Some of the pebbles are 
very much corroded outside, split into several pieces, and present 
curious coloured zonings.! Lower Greensand chert and quartz 
pebbles are rare, and quartzite pebbles very rare. A very characteristic 
feature is the presence of the above-mentioned corroded, split, and 
zoned pebbles. The rough cortex of the pebbles show knobs and 
pits as though partly decomposed by an acid, and for which no 
other word than ‘corroded’ seems applicable. The splitting may 
be along any axis, but is frequently parallel to the long one, and is 
not the usual frost shattering or pitting; a pebble may be found 
in three or four pieces and the pieces close together, as though 
the fracture were of recent origin. The zoning is also curious, and 
some pebbles show (on the split surfaces) several differently coloured 
concentric bands, evidently due to weathering and staining. An 
interesting point about these corroded and zoned pebbles is that 
the inner zone is frequently of an opaque cream colour, and is 
surrounded by brown, black, red, or other coloured translucent flint, 
and then comes the cream opaque cortex; whereas in ordinary 
weathered flint pebbles the translucent part is in the centre. These 
three points (i.e. corroding, splitting, and peculiar zoning) at once 
claim attention, and serve to give a characteristic feature to the 
eravel, and to distinguish it from the other ‘Hill’, or ‘ Terrace’ 
gravels of the surrounding district. 
Shoolers Hull 
Bostall 
¥ Cravel, 
Section from Shooters Hill to Bostall Common showing the relation of the 
‘drifts’ and the erosion by the East Wickham stream. Horizontal scale 1inch = 
1 mile, vertical } inch = 100 feet. 
The Shooters Hill gravel rests on about 180 feet of London Clay 
and, as a recent section showed, Bagshot Sand in places.” The 
drift at Bostall Common caps the highest part of the Common, which 
consists of a circular patch of London Clay, about 100 yards in 
diameter and about 10 feet thick, and is separated from Shooters 
Hill by 13 miles of Blackheath, and Woolwich and Reading Beds 
(see Section). The gravel occurs as a thin sprinkling on the surface 
1 Mentioned by Dr. A. E. Salter from notes by Mr. A. L. Leach, Woolwich 
Surveys, 8vo, p. 19, Woolwich, 1909. 
2 A. L. Leach, Gout. Mac., Dec. V, Vol. VII, pp. 405-7. 
