VOL. XIV. (1) 
Fic. 2. SECTION ACROSS SITE OF AVONGORGE IN PRE-RHATIC TIMES. , 
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PRE-RHETIC DENUDATION 55 
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level than the section, and 
were deposited lateron, when 
the waters of the creek had 
risen further up in its valley. 
Theriver that had previously 
excavated this valley must 
therefore have flowed to the 
east, that is, right across the 
direction of the present 
gorge (Fig.2). As the land 
was subsiding, and con- 
tinued to subside far on 
into Mesozoic time, it is 
certain that the valley of the 
Avon could not have been 
carved out until the re- 
elevation of the land per- 
mitted the play of sub-aérial 
agents of denudation. This 
probably did not take place 
before Tertiary times. 
The first stage in the 
excavation of the Bristol 
Channel was due to pre- 
Keuper denudation. Prob- 
ably as early as the Permian 
epoch, the site of at least the 
eastern half of the Channel 
was occupied by a river flow- 
ing eastward. The existence 
of a valley along this line 
is indicated by the fringe 
of Liassic and Upper Triassic 
strata on both sides of the 
Channel at sea-level, and 
never much above it. Some 
