1822.] Geological Society. 67 
what extent the discontinuity of the strata and the formation 
of the valley, beyond the limits of the escarpments are attribu- 
table to the last of the above recited causes; for we know not 
how far the strata originally extended beyond their present 
frontier, nor how much of the subjacent valley is referable to 
other causes than the most recent diluvian agency. But when 
a valley occurs within the limits of the escarpment of strata, 
which are horizontal, or nearly so, and which bear no marks 
of having been moved from their original position, by eleva- 
tion, depression, or disturbance of any kind ; and when such 
valley is inclosed along its whole course by hills that afford an 
exact correspondence of opposite parts, it must be referred ex- 
clusively to the removal of the substance once filling it, and 
the cause of that removal appears to have been a violent and 
transient inundation. The author contends, that vallies, such 
as those last described, cannot have been formed in any con- 
ceivable duration of years, by the rivers now flowing through 
them, since each individual stream owes its existence to the 
prior existence of the valley through which it flows. But for 
further proofs and illustrations of the diluvian theory, he refers 
to the works of Catcott and Dr. Richardson, and of Mr. 
Greenough. 
Of the same nature with those last described, are the val- 
lies which form the principal subject. of the present communi-_ 
cation. Their main direction is from north to south, at right 
angles to the coast, and nearly in the direction of the dip of 
the strata in which they are excavated. The streams that dow 
through them are short and inconsiderable, and incompetent, 
even when flooded, to move any thing more weighty than mud 
and light sand. 
The greater number of these vallies, and of the hills that 
bound them, are within the limits of the escarpment of the 
green sand formation, and in their continuation southwards cut 
down into oolite, lias, or red marl, according as this or that 
formation, constitutes the substratum over which the green sand 
originally extended. 
There is usually an exact correspondence in the structure of 
the hills inclosing each valley, so that whatever stratum is 
found on one side, the same is discoverable on the other side, 
upon the prolongation of its plane. Whenever there is a want 
correspondence in the strata on the opposite sides of a 
valley, this is referable to a change in the substrata, upon 
which the excavating waters had to exert their force. The 
section of the hills presents in general an insulated cap of 
chalk, or a bed of angular and unrolled chalk-flints, reposing 
on a broader bed of green sand ; this, again, reposes on a still 
broader base of oolite, lias, or red marl. With the exception 
of the very local depression of the chalk, and the subjacent 
strata on the west of the Axe at Beer Cliffs, the position of 
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