1822.] Geology of Snowdon, and the surrounding Country. 417 
In the first three or four miles from Harlech towards Barmouth, 
a rock in situ is scarcely perceptible near the high road, the 
country being considerably flat, and affording a scarcely inter- 
rupted covering of herbage. If, however, we may be allowed to 
judge in some degree of the nature of a country by the rocks 
composing its stone fences, which in Wales present almost 
every variety that is to be seen 2 situ, it may be concluded that 
the same rocks still prevail. The remaining part of the way, 
there was not sufficient light for us to observe any thing cor- 
rectly. The road, however, is by far more rugged than we had 
found any road in any other part of North Wales. The cause of 
this was perceived the next morning on retracing our steps 
about a mile, in which the granular rock prevails in most, if not 
all, the varieties observed at the base of Moel Shabod. Insome 
places, however, quartz entered into its composition in greater 
abundance than in any rock perceived by us on that mountain. 
On quitting Barmouth for Dolgelly, we found that the very 
last house stands on the termination of the granular rock, and 
that the slates perceptible on the hill behind the town descend to 
this place, and repose on the rock in a line perfectly consonant 
with the plane of the slaty cleavage, which as usual runs NE 
and SW, and dips towards the SE at an angle of 68°. The 
slate here is somewhat coarse, though with a completely slaty 
structure: it is translucent on the thin edges, and of a green 
colour by transmitted light. 
Slates continue to prevail along the road from Barmouth 
to Dolgelly, and they are in many places newly laid open by the 
recent widening of the road, and for materials for its repair. 
The direction of the laminz continues, as we observed it imme- 
diately on quitting Barmouth, the whole of the way with the 
same dip, the angle somewhat declining in approaching Dol- 
elly. 
. But though slates prevail in the mountains on our left from 
the base to the summit, we were able, in several instances, to 
perceive, before our arrival at it, a change in the nature of the 
rock, by the appearance up the side of the mountain of a ridge 
differing manifestly from the slates, and which, on examination, 
bees to be a rock of the same nature as the base rock of Moel 
habod, but often without any appearance of quartz or chlorite, 
and interstratified with the slates in the direction of NE and 
SW. The rock of the only ridge which we carefully examined, 
appears to consist of steatite occasionally mixed with carbonate 
of lime, since it effervesces in patches. Itis fine-grained, yields 
readily to the knife, of a greyish colour, and translucent on the 
edges. 
n approaching Dolgelly, we had a good view of the summit 
of Cader Idris, and of some ranges of lower mountains, which 
may be considered as forming a part of its northern side. These 
| possess a character different to that of the summit of the moun- 
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