1822.] Geology of Snowdon, and the surrounding Country. 407 
versed the small dyke, and the rock including it, without any 
alteration either of texture or direction. 
At Lady Bulkeley’s cottage, we ascended to the road which 
is from 80 to 100 feet above the sea, and walked back to the 
ferry-house. The first object that attracted our attention was a 
Jarge mass of limestone which had been cut through in forming 
the road. To this succeeded chloritic rocks, of the same varie- 
ties.as those below, and often including masses of limestone, 
‘but, where these were absent, exhibiting curious contortions, 
and in one instance the series of vandykes noticed by Mr. Hen- 
slow. We looked attentively for the continuance of the dykes, 
but could perceive only two ofthe seven, which from their situa- 
tion, width, and the nature of the rock, we considered to be the 
first and second, consisting here and below of the same firm 
basaltic rock. In neither instance was the including rock altered 
in its direction, but in one place its texture certainly appeared 
to have suffered materially. Three or four feet from the dyke, 
it had its usual appearance of slaty chlorite of a green colour ; 
but close to the dyke, it had no longer the appearance ofa chlo- 
ritic rock ; it had become less firm in its texture, very brittle, 
and of a dingy-brown hue ; and even the dyke itself at the imme- 
diate contact appeared to be less crystalline than in the interior. 
Returning to Garth Ferry on the Bangor side of the Menai, 
we walked along the shore to Bangor Ferry, near the bridge now 
erecting over the Menai. For some distance, we passed only 
the broken edges of rocks and slates, almost perfectly resem- 
bling those of the base of Moel Shabod, to which we have been 
compelled so often to allude. In one instance at least, the rock 
had the appearance of a conglomerate, but it was acknowledged 
by all that the included nodules or masses were often of the same 
nature as the rock itself, though considerably harder, sometimes 
of the substance resembling hornstone occurring on the hill 
above Conway, the rock itself often partaking of the same nature. 
The plane of the slaty cleavage is here also NE and SW. 
. We were conducted by Mr. Dawson a little above the shore of 
the Menai to view a siliceous sandstone enclosing rounded masses 
of quartz, and having the characters of the millstone grit of 
Shropshire, being connected with a limestone and shale enclos- 
ing thin layers of coal. It has been described by Mr. Henslow, 
and apparently with much justice, as belonging to a regular coal 
formation, though of small extent, and without possessing any 
beds of workable coal. We had no opportunity of perceiving 
its connexion with the rocks and slates of its neighbourhood, 
but we visited the dyke which traverses the shale and limestone, 
which are quarried for building upon a large scale close to the 
shore. In some places the substance of the dyke is very com- 
pact, and then appears to consist chiefly of crystals of black 
augite enclosing carbonate of lime and iron pyrites, but is mostly 
in a decomposed state, and has much the appearance of a loose 
