190 
SUB-AEBIAL DENUDATION 
minor points whicli may serve to illustrate it. The gully, for 
example, near the Sea Wall, is in this respect of interest. It 
will be seen to ow'e its existence to a band of soft shaley beds 
(which might be locally termed the Middle Limestone Shales) 
which here occur in the Mountain Limestone. These beds 
being more readily denuded than the massive limestone have 
given origin to a line of drainage. The water which has flowed 
along this line of drainage has cut its way downwards, from the 
point of junction of the softer and harder beds on the surface of 
the Down, into the solid limestone. Thus the notch was started 
in the Middle Limestone Shales, but has been carried down into 
the underlying Mountain Limestone. A very similar gully may 
be seen on the other side of the river, entering the Avon a little 
further down stream. It is worth noting that the Middle 
IMountain Shales form a more gentle and more retreating slope 
than the harder limestone on either side. And this can be seen 
on both sides of the Avon. In fact this band of Middle Lime- 
stone Shales is most valuable to the geologist as completely 
disproving the hypothesis of a fault along the Avon Gorge. 
The beds answer point for point on either side of the river. 
There is no displacement — no dislocation of the beds. 
The most important tributary on the Gloucester side of the 
Avon is the Trym, which falls into the river at Sea Mills. Close 
to its mouth it receives a Stoke branch. This branch rises in 
the softer band of Old Ked ; and, from the present contour of the 
land, it would seem its natural course to follow this line of 
depression to the Avon. But instead of doing so, it leaves the 
line of depression and cuts a prettily wooded valley through the 
Dolomitic Conglomerate, which may be seen near the head of the 
notch to rest on the Old Red. Thus the Stoke Trym does on a 
small scale exactly what the Avon does on a large scale. The 
natural course of the Avon from Bristol would seem to be to 
flow into the sea by Nailsea, thus avoiding altogether the ridge 
