184 
SUB-AEUIAL DENUDATION 
out the point quite to my satisfaction, nor in the absence of 
organic remains is it easy to come to a decided conclusion. I 
have therefore placed a ? on these patches of rock. And I bring 
this subject in this immature state before the Society, partly 
because, coming as it does within the area of my map, I could 
hardly pass it over without mention, and partly because it is one 
that seems to be worthy of the attention of the Members of the 
Geological Section. For if my views should prove to be correct, 
then coal under the Severn flats is a possible and not uninterest- 
ing corollary. 
6 .- — The Avon Gorge. 
“ The vulgar notion respecting the Avon and its Gorge,’' 
writes Sir Andrew Ramsay, “ is, that before the ravine was 
formed all the low ground through which the river and its 
tributaries flow was a large lake, that ^ a convulsion of nature ’ 
suddenly rent the rocks asunder and formed the gorge through 
which the river afterwards flowed, and so drained the hypo- 
thetical lake.” 
This vulgar notion received its death blow when Professor 
Jukes, in 1867, showed “that the hypothesis of atmospheric 
erosion is applicable to the Clifton Gorge as to all similar 
places.” This is now part of the common stock of geological 
knowledge. But I feel bound to draw attention to it here, 
partly to give unity to my subject, and partly because the truth 
of these views is enforced by the considerations which are to 
follow. I shall, however, content myself with a short quotation 
from Prof. Jukes ; and a very few additional words of my own. 
“ Let the observer then,” I quote from the Oeol. Mag. of 
Oct., 1867, “ stand on the highest point of Clifton Down and 
look up to the superior height of D undry Hill, some six miles to 
the S., and he will see at once that the extension of the old 
oolitic sheet (of which the summit of D undry is but an isolated 
