THE VALE OF CLWYD. 7 
No. 5.—The Clwyd and Elwy have cut their channels down 
some 8o feet or so through the old estuarine deposits, 
and have formed alluvial flats which, near their mouth, 
open out into the wide marshy ground known as Morfa 
Rhuddlan. 
Fic. 1. 
Generalized Section E. and W. across the Vale of Clwyd from the 
upper part of the Llwy valley to Caerwys. 
a. Red sand and gravel. 
&. Red clay with stones large and small, some scratched, some not. 
On the West side of the Clwydian range the red sand and 
gravel, with shells, slopes up to the South. The sand and gravel 
is not seen when we get as high as Plas Heaton. On the East 
however, of Moel-y-gaer, the red sand and gravel in which here, 
however, I found no shells, seems to attain a height equal to that 
of Plas Heaton, and runs up the Wheeler Valley in hummocky 
hills, at any rate as faras Caerwys. Standing on Moel-y-gaer 
the highest of these and Plas Heaton seem to form part of an 
old plain stretching away as far as the eye could reach to the 
country S.W. of the Dee. 
c. New Red. d. Carboniferous. ad: Limestone. d* Sandstone. 
a* Conglomerate. 
e. Silurian. Jf. Faults. 
I propose to treat the subject in a very sketchy way, just 
describing a typical section in illustration of each group, or 
calling attention to some sources of error for the guidance of 
future observers who may be beginning to work at the district, 
or pointing out here and there what I think are necessary 
modifications of the interpretation of previous observers. 
I shall begin with the oldest rocks in the district, and describe 
them in ascending order. 
THE BALA SERIES. 
The Bala Beds do not occur in what is popularly known as 
the Vale of Clwyd; but to the W. of Derwen Station and N. of 
Bettws-y-gwerfilgoch the river Clwyd runs through them for 
about two miles. and a belt of rock. to be referred to the same 
age, occurs on Bryngorlan, one of the hills that bar the upper 
end of the vale, 3 miles S. of Llanfair-dyffryn-clwyd (see 
Section fig. 2.) These beds, which belong to the uppermost 
part of the Bala Series, consists of grey or paste-coloured fine 
mudstone, irregularly and roughly but strongly cleaved—often 
showing double cleavage. ~ 
Fic. 2. 
a. New Red Sandstone. 
6. Stained Carboniferous Sandstone seen in cave and on road near 
Penygraig. 
c. Mountain Limestone. 
d. Basement Beds of Mountain Limestone (= Devonian.) 
B2 
