VOL. XIV. (1) PRE-RHA:TIC DENUDATION 53 
In the well-known section under Clifton Down, it is mainly 
composed of fragments of limestone and grit, some of them 
of large size, and many of them sub-angular. They have 
been derived from Carboniferous rocks, and have not 
travelled far. The agency of ice as a means of transport 
has been invoked, but, as it seems to me, somewhat super- 
fluously. This conglomerate lies in a hollow between 
Observatory Hill and Durdham Down, and the slopes up 
to these elevations were probably much steeper in Keuper 
times than at present, for the levelling of the Clifton- 
Durdham plateau had not then taken place. The con- 
glomerate accumulated in a deep gorge, flanked on each 
side by high hills of limestone and grit. Fragments 
detached from the overhanging crags would, I think, find 
their way to the bottom by sliding and rolling, and would 
then be somewhat abraded by waves and currents. Whether 
this explanation will account for the origin of the deposit 
in other localities, 1 do not venture to suggest. 
At the close of the Keuper epoch, the subsidence had 
reached the point where the sea gained access to the great 
salt-lake, and spread over all the low-lying ground. The 
age of the English Rhetic now sets in. Prof. Lloyd 
Morgan considers that our meagre Rhetic deposits repre- 
sent only the later part of the true Rhetics. In the 
eastern Alps, Rheetic strata attain a thickness of 2000 feet. - 
_ They thin out in a westerly direction. As submergence 
proceeded, the waters of the Rhetic sea crept up over the 
land, and gave us the attenuated series of beds that inter- 
venes between the Keuper and the Lias. According to 
this view, our Keuper deposits would be in part contem- 
poraneous with the lower Rhetics of the Continent. 
It has already been pointed out that the main features of 
the Paleozoic land in our area were shaped by subaérial 
denudation. The seas of the Permian and Bunter epochs 
would of course act upon their margins in the manner of 
