522 
Mr. Buckland on the 
the denuding agency which they exerted during the period of 
their retreat.* 
It is here important to remark, that although the valley of the 
Evenlode from its commencement to its termination is thus strewed 
over with quartzose pebbles, the parallel valley of the Windrush, 
which is closely adjacent to it on the west, and separated only by 
the lofty ridge of Stow in the Wold, affords not a single pebble 
that is not derivative from the oolite strata by which it is inclosed : 
this arises from the circumstance of its upper extremities taking 
their origin entirely within the high escarpment of the elevated 
ridge of the Cotswold and Campden Hills, whilst an interruption 
of the continuity, or at least a depression of this escarpment at the 
head of the vale of Evenlode, has permitted the diluvian current 
from Warwickshire there to pass on without obstruction into the 
area of the oolite, f and bring with it the wreck of the districts over 
which it had advanced. In the upper part also of the valley of 
the Thames, from that part where the driftings of the Evenlode 
Gap have fallen into it above Oxford, to the sources of its many 
tributary streams, no traces of this gravel are to be discovered; 
nor is there any depression along the line of the Cotswold Hills on 
the west of Stow in the Wold, by which any such current as that 
which entered by Moreton and the vale of the Evenlode could 
have gained admittance. 
# For a detailed and excellent description of the gravel beds of the plain of Oxford, 
I beg to refer to the preface of Dr. Kidd’s Elements of Mineralogy, and to Chap. 17, 
of his Geological Essays. 
+ Although the oolite vallies which lie on the south-west of that of the Evenlode, 
are not strewed over like it with quartzose pebbles, they still afford equally convincing 
proofs of extensive and deep-cutting denudations taking their origin, not from a current 
rushing in over the high crest of the lofty escarpment that bounds their upper extremities, 
but simply from the weight and force of an immense volume of water subsiding within it 
