DE RANCE : THE VALE OF CLWYD CAVES. 
5 
lowlands, by the time which it took for the land to subside that 
vertical amount, and that the deposits were thrown down in water of 
a similar shallow depth, in all the sections examined. There is how- 
ever evidence in a large number of borings, especially in the Coal-fields 
of Flintshire, Wigan, and Manchester, that a repetition of conditions 
took place, and that more than two boulder clays exist, and that 
considerably more than one horizon of sand occurs. 
In st)me sections near Brinscall, and in other parts of Lancashire, 
the oldest glacial deposit consists of a tough stiff clay, with local 
fragments, which in places is seen to be overlaid by Lower Boulder 
Clay of the ordinary type, in which obscure traces of stratification 
are to be seen. As I pointed out many years ago [Nature, 1870] 
the same sequence is seen in the glacial drift deposits off the coast of 
North "Wales : a Lower Boulder Clay with northern erratics lying on 
the eroded surface of dark leaden-coloured clay containing local frag- 
ments ; Sands and Shingle Beds resting on the Lower Boulder Clay 
with erratic fragments. These Sands and Shingle attain a thickness 
of nearly one hundred feet at Holywell, in the valley between the 
station and the town ; near Mostyn also they were seen in extensive 
sandpits, and on the opposite side of the Clwyd Valley they are seen 
interstratified with red Boulder Clays between Colwyn Bay and the 
Little Orme's Head. In the neighbourhood of St. Asaph, in the 
centre of the valley, these middle glacial beds have been dug for 
sand, and contain the usual assemblage of shells found in the same 
beds at various Lancashire and Cheshire localities. Between Mostyn 
and St. Asaph these sands were described by Dr. Buckland in the 
Reliquise Diluvianse, London, 1823. He gives the following section 
of the Talargoch Mine, shafts not named : — 
Feet, 
1. Vegetable mould ... 2 
2. Clay ... ... 78 
3. Sand and Gravel .. 204 
284 
He states that pebbles of lead and some pebbles of copper occurred 
in the gravel, and that horns, teeth, and bones of Mammalia occurred 
at from 40 to 70 yards from the surface, and also in the bottom bed 
