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SUB-AERIAL DENUDATION 
limestone ridge, and cuts the deep trench of Coomb Dingle, 
through the Blaize Castle woods. It is scarcely necessary again 
to point out that this is due to the fact that the low ground 
above is due to the action of general denudation, and that its 
gradual lowering was effected during, and not before, the time 
that the Henbury Trym was exerting its special denuding 
influence on the Blaize Castle ridge. 
It only remains in this connection to point out that the 
depression to the South of the Blaize Castle eminence may be 
due to the incoming of the Middle Limestone Shales at this 
point. 
There is one other minor depression on the Gloucester side 
of the Avon, namely that in the Lower Limestone Shales S. of 
the Penpole Down. Here we have evidence, from the way in 
which the Dolomitic Conglomerate is disposed ( see map ), that 
the Old Bed Sandstone ridge was notched before the deposition 
of that Triassic deposit. 
9 . — The Curves of the Avon. 
The curves and bends of the Avon, as it passes through the 
Clifton Gorge, and thence to the Severn, are of interest. Mr. 
Tawney suggested that in the limestone they might have been 
determined by joint planes. But the point to which I would 
rather draw attention is that they are very closely connected 
with the incoming of harder and softer beds. 
From the beginning of the Gorge to somewhat beyond the 
the Suspension Bridge, the river cuts across the strata nearly 
along the line of their dip. Then it is forced over somewhat to 
the Somerset shore, probably by the incoming of those upper and 
harder beds of the Upper Limestone Shales which, as we have 
seen, are more extensively brought down by the fault on the 
Clifton than on the Leigh side of the river, and are now being 
blasted in the river bed near the Gloucester shore. 
