DE RANGE : THE VALE OF CLWYD CAVES. 
3 
down below high-water mark, and doubtless formerly passed beneath 
the level of low water, along which they have since suffered denuda-- 
tion ; borings also at Rhyl at the mouth of the River Clwyd in 
Flintshire establish the same facts, peat beds underlying Blown Sand 
and Estuarine Beds beneath the level of low- water. 
Roman remains occur in the estuarine deposits overlying the 
peat beds of Leasowe, and near Fleetwood, and north of Rossal a large 
number of Roman coins were discovered in marine silt resting on the 
peat, w^hich were probably lost by the Romans slipping about on the 
mud banks, at a period when the levels of land and sea were much as 
at present ; the position of the remains of a Roman Bath at Freckleton, 
west of Preston, points to the same fact, and no change of level 
appears to have taken place since Roman times. 
The coarse gravels at the base of the Ribble Alluvium and the 
shingle in the plains between Garstang and Presall point to a period 
of considerable denudation, the sea wasting the Glacial Drift and 
forming the lowland plain which subsequently constituted an area of 
obstructed drainage, culminating in the growth of peat, and the 
rivers deepening and widening their main valleys to their present 
proportions. 
The previous steps of fluviatile denudation and consequent 
fluviatile deposition of a small portion of the material denuded, 
appears to have proceeded along in similar lines, points to a 
recurrence of physical conditions, first, large gravel formed dur- 
ing a period of denudation, second, peaty beds with trunks of trees 
formed during a period of obstructed drainage, thh^d, a period of 
tranquil deposition of fine loam. These conditions are marked in the 
sequence of deposits in the river terraces of the Ribble and the Irwell. 
Reviewing the whole of the evidence afforded by the Post- 
glacial deposits, it will be seen that no geological work, or physical 
changes in level, or condition of the country appears to have taken 
place since the Roman era, but between the close of the Glacial 
episode, or at all events after the deposition of the latest glacial 
deposit and the advent of the Romans, the wide and deep valleys of 
Western Lancashire were excavated out of the Glacial Drift by 
fluviatile denudation. 
