328 Messrs. W. Phillips and S. Woods on the (Noy. 
we found in a mass of rock perfectly resembling some of the 
varieties plentifully distributed at its base, the impression of a 
shell, much resembling those which have been so abundantly 
discovered in what hitherto has been termed greywacke, near 
the summit of Snowdon. 
In the loose masses lying beside the road near Pont y Cyftin, 
we found several shells, some resembling those just mentioned ; 
others differing from them. These masses had apparently been 
cut from the rocks on the side of the road; some of them were 
slaty ; others were not, but perfectly resembled the base rocks 
of Moel Shabod, from which their locality was separated only by 
the road and the river. The slate is occasionally hard enough 
to scratch glass, is translucent on the edges, and green by trans- 
mitted light, but externally has the character of ordinary slate. 
In one of the stones used in the construction of “ the tap,” 
belonging to Capel Curig Inn, near the door, we observed a con- 
siderable mass containing the impressions of several shells. 
The sides of Moel Shabod are in so considerable a degree 
covered by herbage,—by grass, by fern, and here and there by 
heath,—as on a very large proportion of its surface to hide very 
completely the rocks from observation : this, we cannot donbt, 
has arisen from the decomposition chiefly of the slates prevalent 
in the middle region of the mountain. On the northern side of 
it (we had not an opportunity of observing the southern side at 
about the same height), there appears a sort of terrace covered 
by long grass, hiding from view the summit of the slates, and 
between them and the porphyritic rocks constituting the upper 
part of the mountain. Above this terrace, we found no appear- 
ance of herbage, nor any slaty rock ; the whole consisting of 
loose blocks of the rock already described as constituting the 
upper third part of the mountain. These blocks are of very con- 
siderable size generally, lying without regularity, and they had 
no appearance of the columnar form, except, perhaps, in a very 
few instances ; but on a considerable part of what may be termed 
the long line of its summit, which is often less than 20 feet in 
breadth, large and apparently columnar masses were ranged side 
by side in a horizontal position, across the ridge in north and 
south direction, and always presenting an edge uppermost. 
The seeming difference in the mineralogical characters of the 
rocks of the summit to those of the rocks cf the base, their sepa- 
ration from the slates by a grassy terrace, and the disappearance 
of all slaty recks on the upper third of the mountain, induced 
the suspicion that the rocks of the summit might possibly form 
the nucleus of the mountzvin, and if so, that the slates and rocks 
of the base might, perhaps, have been deposited upon them. If 
this were the case, analogy led us to expect that a careful exa- 
mination of the southern side of the mountain, which is far more 
precipitous, and, therefore, in its upper part less covered by 
herbage than its northern side, would expose the slates and 
