Vol. XL] 
[Part L 
PROCEEDINGS 
OF THE 
YORKSHIRE 
GEOLOGICAL AND POLYTECHNIC SOCIETY. 
Edited by JAMES W. DAVIS, F.S.A., F.G.S., &c. 
1888. 
NOTES ON THE VALE OF CLWYD CAVES, BY C. E. DE RANGE, F.G.S., 
ASSOC.INST.C.E., F.R.G.S., HONORARY MEMBER MANCHESTER 
GEOLOGICAL SOCIETY. 
To realize the full significance of the facts lately discovered at 
Tremeirchion, on the east side of the Vale of Clwyd, and half-a-century 
ago at Cefn, on its western slope, it is necessary to review the evidence 
that has been obtained in other parts of North Wales, in Cheshire, 
in Cumberland, and especially in Lancashire, in which county a com- 
plete sequence of deposits can be determined from the commencement 
of the Glacial conditions down to the present time. 
The upper portions of the Lancashire valleys are found to be 
what Professor Green has well called ''valleys within valleys," the more 
ancient depression having been filled up with Glacial Drift,, which has 
been re-excavated out, by the gradual denudation of the rivers running 
through them. The work ot widening is effected by the outer bends 
of the " S "-like curves of the rivers, these slowly move their position 
in the direction of the flow of the stream, so that after a sufficient 
time has elapsed, the cutting bend of the "S" reaches the precise 
point which its predecessor occupied. 
The Lancashire rivers have not only excavated wide valleys more 
than a mile across, like that of the Ribble at Preston, but have 
excavated them vertically to a depth of nearly 200 feet, the process 
