2 
DE RANCE : THE VALE OF CLWYD CAVES. 
going on until the negative gradient was reached of that particular | 
stream from its source to the sea, below which denudation ceases, so j 
long as the levels of the land- remain constant. i 
Thus it happened that when the cutting bend of the " S " occu- ; 
pied the position of the similar curve of its predecessors, the stream I 
level was vertically lower by the amount denuded during the period \ 
of the seaward progression of the curve to its predecessors position, 
consequently the silt and other material thrown down during floods, 
forming the alluvium of the stream, was deposited successively at 
lower and lower levels ; such portions of these alluvial flats that 
have escaped subsequent denudation form terraces fringing the sides 
of the valley, the varying height of which mark the successive stages 
in the process of deepening the valley. The lowest alluvial flat still 
in process of formation, consists of a bed of loam above a peaty 
horizon, resting on coarse gravel. 
On the western margin of the glacial drift upland-plains, great ; 
marine denudation has gone on, and lowland plains continuous with the \ 
most modern alluvial flat of the Kibble have come into existence, i 
here the sequence is Blowing and Blown Sand, and Scrohiciilaricc ' 
clays resting on thick-beds of peat, which between the Mersey and ; 
the Kibble rests on an ancient Blown Sand, which I have named the i 
" Shirdley Hill Sand " ; and between the Kibble and Wyre, upon an ! 
ancient shingle bed, I named the " Presall Shingle." I 
Following the thick peat of the low-level plains into the Kibble \ 
valley, it is found to be continuous with the peaty horizon of the 
lowest alluvium of that river, proving that the valley had been exca- 
vated to its full width and depth before the growth of the peat out in ; 
the low-level plains. 1 
Examination of the peat deposits on the coasts of North Wales, | 
Cheshire, Lancashire, and West Cumberland point to the land stand- j 
ing at a higher level in regard to the sea than at present. At a 
boring at the Palace Hotel, Birkdale Park, Soutliport, the peat horizon \ 
occurred 69 feet below high- water mark. In Liverpool Bay the fisher- ^ 
men constantly bring up pieces of peat in the trawls, at Kossal, 
Crossens, and Hightown in Lancashire, at Leasowe in Cheshire, and at ■ 
Llanderillo-yn-Khos in Denbighshire, the peat beds are seen extending 
