1822.] Geology of Snowdon, and the surrounding Country. 329 
lower rocks in mantle-shaped masses; we did not, however, 
succeed in realizing this expectation, for on both sides, the 
cleavage of the slate is in the direction of north-east and south- 
west, being on the northern side nearly or quite vertical in their 
nearest apparent place to the summit, while on the southern 
side, the dip is towards the mountain itself at a considerably low 
angle. There were, however, some circumstances which tended 
to confirm, though they did not fully satisfy us, of the correct- 
ness of the notion, that the rocks of the summit constitute the 
nucleus of the mountain. On the south-east side, there is a 
small lake, called Llyn y Foel, perhaps 1000 feet below the 
summit of the mountain. About 300 feet beneath this Llyn, 
we observed a rock much resembling that of the summit, as it 
were, protruding from the side of the mountain, but did not per- 
‘ceive the mode of connexion between it and the slates on each 
side and above it. Again, above the Llyn, we found the same 
rock, dipping down in continuity, from the summit, and also 
apparently beneath a vast mass of slates, their actual contact 
being covered only by about three feet of alluvial matter. 
Again, having crossed the dip of this apparent buttress of the 
summit rock, above Llyn y Foel, we descended over slates and 
slaty rocks perfectly resembling those already described, the 
slaty cleavage being constantly north-east and south-west ; but 
in our long walk in returning to Capel Curig down the slant of 
the mountain, we perceived what we supposed to be still another 
buttress of the summit rock, covered on both sides by slates. 
Notwithstanding these repeated appearances of this rock in the 
manner above described, it would require a much longer time 
than we could devote to the investigation to ascertain whether 
or not the nucleus of the mountain be of the rock appearing on 
the summit, and we wish to recommend this examination to 
future observers. 
It may be mentioned, that in traversing the long and narrow 
ridge which constitutes the summit of Moel Shabod, we per- 
ceived two chasms, at a little distance apart, from 10 to 20 feet 
wide each, and traversing the summit in nearly a north and south 
direction. The continuation of these chasms was soon lost 
beneath the grass covering to a great height the more easy 
slope on the northern side, but they were perceived to a great 
depth down its precipitous side on the south. They descend 
nearly to Llyn y Foel, though in great degree filled by ruin and 
alluvial matter, as we could perceive in looking upwards from 
the banks of that Lake. These chasms appeared to be the con- 
sequence merely of the separation of the rocks. The rubbish 
with which they were filled at the summit appeared on exami- 
nation to consist altogether of fragments of the adjacent rocks, 
which, however, might possibly hide the substance of which 
they may be filled (if indeed they be dykes), except where it 
