182 
SUB-AEEIAL DENUDATION 
depression, and is found in patches on the southern flanks of 
the Leigh Down limestone ridge. 
Overlying the Dolomitic Conglomerate in larger or smaller 
patches are the Keuper Marls, as at Pill and to the S.W. of 
Westbury ; and they form the low-lying band from Easton-in- 
Gordano through Shirehampton, King’s Weston, and Lawrence 
Weston. This band dips gently down beneath the yet more low- 
lying fringe of Severn flats. 
Overlying this again, N. of Blaize Castle, is a small patch of 
Rhoetic ; while the Lower Lias Clay rests directly on Mountain 
Limestone in the area to the E. of Westbury. 
A comparison of this section with the last, and a reference 
to the map, will show how clearly the general physical features 
of the area are determined by the general geological structure. 
So that the geological colouring in our map at once indicates the 
nature of the physical contours ; while, vice versa, contouring 
would at once indicate geological structure. 
5 . — The Age of the Bocks at King's Weston, 
In the map I have in the main followed Mr. Sanders and the 
Geological Survey. There are, however, one or two points in 
which I have made some slight alterations ; and of some of 
these I would now say a few words. 
In the first place, I have given a separate colouring to the 
Upper Limestone Shales, chiefly because the effects of the 
Clifton Fault thereby become more obvious. The line of division 
between these beds and the Mountain Limestone is, however, 
approximate. 
Secondly, I have introduced a slight alteration where the 
Westbury Trym, after passing through the notch in the 
Mountain Limestone, passes out into the Dolomitic Con- 
glomerate. Both Mr. Sanders and the Survey, map the Moun- 
tain Limestone in contact with Old Red at this point. 
