oy 
43 
give place to a blue vein discovered in the metalliferous slate, at Dolmynach and 
Cwmparadwys. This slate is of excellent quality and durability, in every way 
equal to that from North Wales. This stratum also abounds in lead and copper 
ore, which is one of the characteristics of this formation. Cwm Elan and Nanty- 
car Lead Mines are in this neighbourhood, as is also the Dalrhiw Copper Mine 
which has been lately discovered. 
There is a paucity of fossils here. There are, however, a few Graptolites, 
which belong to one of the lowest orders of organization—the Paleozoic. We find 
in geology that the fauna ascend in the scale of organization as the geological forma- 
tions ascend in the order of time by gradual development, until we reach the 
alluvial deposits, which contain the skeletons of fauna resembling those of the 
present time. The hills here were formed by an upheaval long before there was 
dry land, which, no doubt, was caused by the expansion of subterranean heat and 
gases. All stratified rocks were formed by an aqueous deposit, the deposit of mud 
in shallow or calm seas, and by pressure these slaty strata were formed. No doubt 
the layers were formed horizontally ; since then, from internal disturbance, they 
were raised and contorted, producing the anticlinal and synclinal of the Plinlim- 
mon group. The synclinal extends as far as Rhayader from the hill; the dip of 
these beds is inclined to the east. The valleys were produced by denudation from 
the action of ice, frost, rain, and the river. There is every evidence that ice had 
a great deal to do in scooping out these valleys. Professor Ramsay thinks that 
the lakes on the hills were formed from the same cause, such as the Cerrigllwydon 
Pools, Gwengy Pool, and the Teifi Pools in this locality, and all other lakes or 
pools in a similar way. We have evidence of large boulders in great thickness 
through the valley of Cwm-ar-lechwedd down to Llanwrthwl. Most of us have 
observed the deep channels cut in brooks and rivers after each heavy flood ; what 
would be the effect of this in thousands or millions of years? You have only to 
observe how the Elan has worn down the rock into deep pot-holes, and that very 
deep channel at Pontyrhyllfan (the bridge of the awful place). I cannot do 
better than here quote a few of the descriptive lines of Bowles on this place :— 
And now a little onward, where the way 
Ascends above the oaks that far below 
Shade the rude steep, let Contemplation lead 
Our footsteps—from this shady eminence. 
*Tis pleasant and yet fearful to look down 
Upon the river roaring, and far off 
To see it stretch in peace, and mark the rocks, 
One after one, in solemn majesty 
Unfolding their wild reaches, here with woods 
Mantled, beyond abrupt and ‘bare, and each 
As if it strove, with emulous disdain, 
To tower in ruder, darker a: uplitude. 
Pause, ere we enter the long craggy vale: 
It seems the abode of Solitude. So high 
The Rock’s bleak summit frowns above our head, 
Looking immediate down, we almost fear 
Lest some enormous fragment should descend 
With hideous sweep into the vale, and crash 
The intruding visitant. No sound is here, 
Save of the stream that shrills, and now and then 
A cry as of faint wailing, when the kite 
Comes sailing o’er the crags, or straggling lamb 
Bleats for its mother. 
