THE AVON AND ITS GRAVELS 
233 
regarding them and not the high level gravels as being 
immediately post-glacial. 
If this conclusion is maintained, then it follows that the 
West of England was a land surface and subject to subaeria] 
denudation, while the south-eastern portion of England was 
submerged. It follows, too, that the Avon during Pleisto- 
cene times was slowly cutting down its bed, and by the 
time the glacial epoch had arrived its waters were within 
one hundred feet or so of their present level. 
With regard to the material of which these high level 
gravels are composed, at least 80 per cent, of the peb- 
bles are of flint which w^ould be derived from the Chalk 
of the neighbouring downs. The accumulation of flints 
after the weathering out of the Chalk is very common, and 
would account for the greater part of this material. It is 
very difficult to locate the source of the quartz-pebbles 
after so much denudation has taken place. They are 
evidently a secondary accumulation bearing marks of 
redistribution. 
The entire deposit bears marks of the sifting process 
which the action of water always effects. In the further 
reaches of the trough or pocket referred to, the fragments 
are comminuted. I regard the high level gravels as a 
record of the work done by the Avon in its early 
days. 
II. The Low Level Gravels.- — These gravels are exceed- 
ingly common on the hillsides near Bath. The deposits 
vary in size from small patches of a few square yards to 
masses which extend across the hillside for half a mile or 
more. They occur at varying heights, but the range is fixed 
by a maximum of one hundred feet or so above the present 
bed of the river. Gravel is largely used for paths and 
public walks locally, and is therefore extracted from open 
pits. I have watched carefully excavations which have 
taken place at three gravel pits in Twerton. They are : — 
