THE VALE OF CLWYD. 13 
i.c., the thickness of the strata from the Bala Beds of Bryngorlan 
to the highest Silurian seen on Moel Ganol, would be about 
1% miles; but much of the denudation that exposed the edges 
of the Cambrian Rocks all over North Wales probably belongs 
to this interval also, in which case we are speaking of a thick- 
ness of 8 or 9 miles. What was that ancient land like, and 
what plants and animals lived on it ? 
Dawson has described a plant from the Silurian of America ; 
so we need not be surprised to find remains of vegetation in the 
much later period of continental conditions that preceded the 
formation of the Devonian and Carboniferous. But we are not 
left in doubt to speculate on the probability of there having been 
plants in that old land in our district. In the sand of the sea 
that washed its shore we may gather for ourselves the leaves and 
sticks that were carried down from it, The sea sand, it is true, 
has long been hardened into sandstone, and the wood is 
blackened and charred by the slow combustion which chemists 
call oxidization. 
It is probable that the Southern area (South Wales and 
Devonshire) went down before our district ; perhaps much of it 
never got fairly above the sea level at all. For whereas in our 
area we have evidence of great denudation of the underlying 
Silurian, in the South there does not appear to be this sweeping 
away of the older rocks, and so we find there the Silurian passing 
up into a vast and generally unfossiliferous series of deposits 
known as the Lower Old Red. In our area again there are only 
thin patches of coarse sediment forming the basement beds of 
the Carboniferous, while in the South there are such enormous 
deposits of sediment at the base of the Carboniferous series 
that they have been exalted into a separate formation, under the 
title of Upper Old Red Sandstone or Devonian. 
CARBONIFEROUS SERIES. 
The above considerations having led us to infer that there 
was in our area an enormous interval between the Silurian and 
Carboniferous Periods, we are prepared to expect that there 
will be no great difficulty in separating them. There might 
have been, it is true, a recurrence of similar lithological 
character, and the base of the newer series, being made up of 
the underlying rocks, might have been hard to distinguish from 
them, but it does not happen to have been so. The palzonto- 
logical break is almost complete. 
I have dropped the name Old Red for any of these beds, 
considering them to be simply the irregular basement beds of 
the Carboniferous Rocks, as I long ago pointed out in the 
similar case in the North of England. [Notes on the Geology 
of Parts of Yorkshire and Westmorland, Geol. P. of Soc. West 
Riding, 1867.—Mem. Geol. Survey, Expl. 98 S.E., p. 16, 1872.] 
The beds we have are merely the patches of sand and shingle 
