519 
Quartz Rock of the Lickcy Hill , SsV. 
In over the lowest point of depression of the great escarpment of 
the oolite ; and being deflected thence south-eastwards by the 
elevated ridge of Stow in the Wold, to have gone forward along 
the line of the vale of the Evenlode by Charlbury, till it joined 
that of the Thames at Ensham, five miles north-west of Oxford. 
(See Plate 37.) 
This hypothesis affords the most satisfactory explanation of the 
origin of the great deposits of quartzose pebbles which not only 
cover irregularly the lower regions of the valley of the Evenlode, 
but are scattered abundantly over the surface of the oolite strata 
which rise to a considerable height, and form table-lands on both 
sides that valley along its whole extent. It also accounts for the 
accumulation of beds of similar pebbles on the west and south 
of Oxford, upon the insulated and almost conical summit of 
Wytham Hill, and the ridge of Bagley Wood, by their position ex- 
actly opposite the mouth of the vale of the Evenlode, at its confluence 
with that of the Thames, at the very point on which the driftings 
evacuated from the former valley would be thrown up.* Being 
thus introduced within the escarpment of the oolite, and having 
passed down the vale of the Evenlode, into that of the Thames 
near Oxford, these pebbles may have been forced onwards 
by the retiring diluvian waters, and mixt up with the gravelly 
wreck of the neighbouring hills in each successive district along the 
line of the Thames, from the vale of Oxford downwards to the 
gravel beds of London, their quantity decreasing with the distance 
from their source ; so that in Hyde Park, and at the Kensington 
* Near this same point, pebbles of clear rock crystals occur scattered over the surface 
at Ensham Heath, and are applied to the purposes of jewellery, like the Bagshot Heath 
diamonds, as they are commonly called, being merely similar small pebbles of the same 
substance. 
Vo L. V. 3 u 
