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and-by, as that land sunk in the sea, buried it perhaps in places 
altogether.*' 
We now find the chalk and the oolites forming long lines of 
hilly ground or escarpments, as they are termed, with here and 
there an outlying hill. The rivers, too, often cut directly 
through them in the most remarkable manner. The rocks 
forming these escarpments dip, on the whole, gently to. the 
south-east, a feature produced, no doubt, during elevation of the 
strata above the sea-level, f 
Before the chalk and other cretaceous strata were deposited 
in the West of England, the oolites and lias had been disturbed 
and denuded, so that the former beds overlap the successive 
members of the latter. The older strata seem ' to have been 
planed off, and probably by the sea, before the chalk and green 
sand were deposited. 
The chalk escarpment was, therefore, no doubt (in certain 
areas) the first escarpment formed. After it had been denuded 
beyond the outcrop of the oolites, then the escarpment of those 
rocks began to be formed. 
Professor Ramsay has. taught us that the reason why so many 
rivers cut through escarpments is that they originated before 
the escarpments were formed, and cut their way down through 
the strata, which afterwards, by atmosjiheric denudation, receded. 
The fact that escarpments have thus receded is plain, although 
rather difficult to account for. Their formation is often at- 
tributed to marine action, but there are so few facts to corrobo- 
rate this notion, that the opinion now generally held is that 
they are, for the most part, due to the silent and slow process of 
atmospheric denudation, of rain and tiny streams and rivers. 
The chalk escarpment, as Professor Ramsay observes, being 
more easily wasted than that of the oolites, its recession east- 
ward has been more rapid. 
The facts that escarpments are formed almost invariably of 
porous rocks, such as limestone or sandstone, while at their base 
is exposed a clayey or marly series of strata impervious to water, 
which, perhaps, again rest on hard rocks, forming another es- 
carpment, the beds in it dipping away from the plain beneath, 
are all-important in forming true notions of their origin.^ 
The beds may have been reduced to a tolerably even level by 
# “ Physical Geology and Geography of Great Britain.” Third Edition, 
pp. 95, 96. Whether the chalk ever covered the whole of Gloucestershire 
and Somersetshire is by no means certain. 
t On this subject see Topley, on “The Correspondence between some 
Areas of Apparent Upheaval and the Thickening of Subjacent Beds.” Quart. 
Journ. Geol. Soc., vol. xxx., p. 186. 
X On this subject see Whitaker, “ Geol. Mag.,” vol. iv., pp. 447, 483. 
