AND THE AVON GOEGE. 
187 
Mountain Limestone, and Upper Limestone Shales, relatively 
shifted downwards, are not the same as on the opposite shore. 
They are: — 
On the Sornerset Side. 
Mountain Limestone ... ... 770 feet. 
Upper Limestone Shales ... ... 330 ,, 
Total ... ... 1100 ,, 
The difference of 50 feet in the total may be due to the 
dying out of the fault westwards, or it may he due to errors 
of observation. Since the total thickness of the Upper Lime- 
stone Shales is 600 feet, of which 330 are faulted down below 
high-water mark, there remains a thickness of 970 feet above 
high-water mark, which will extend to the top of the gorge 
in Leigh Woods. We should not expect therefore to find 
Millstone Grit on this side of the river. Nor have I been 
able, on careful search, to discover any of the characteristic 
beds of this rock, though several of the silicious bands of the 
Upper Limestone Shales — similar to those which are now being 
blasted in the river bed — crop out at the surface. 
Now the Upper Limestone Shales, brought down to the N. of 
the fault, are softer than the massive Mountain Limestone 
which bounds them on either side. We should therefore expect, 
on the principles of denudation, that these softer rocks would 
have their physical expression in the contour of the land. 
And tins is so. A marked depression, largely occupied -with 
Dolomitic Conglomerate, separates Clifton Down from Durdham 
Down. And if we look across from Leigh Woods to the opposite 
side of the river we see that, betw^een the bold bluff of Lime- 
stone of Observatory Hill, and the Limestone Cliffs of the 
Great Quarry, there is a wide space where the slope is more 
gentle. And this is the space occupied by the Upper Limestone 
