406 Messrs. W. Phillips and S. Woods on the (Dec, 
but including here and there very minute ochreous specks, as 
though one of its ingredients had perished : the soundest speci- 
mens that we could obtain, however, were not without this 
appearance : the rock is sometimes traversed by veins of granu- 
lar quartz, whiter and more compact than the rock itself. 
Between the ferry-house and Lady Bulkeley’s cottage, 
which are scarcely a mile distant, the rock is chloritic, yet often 
assuming the appearance of serpentine; in some places it seems 
to consist almost wholly of slaty chlorite and chlorite slate ; in 
others, it consists of layers of quartz and of chlorite, or of car- 
bonate of lime and chlorite, and occasionally it includes consi- 
derable masses oflimestone. ‘Traversing this rock, we observed 
seven dykes in the distance above mentioned, and reckoning 
from the ferry-house, the first, second, fourth, fifth, and seventh, 
run in the direction of NW and SE; one, the third, NE and 
SW ; and one, the sixth, NandS. The first is about 16 feet 
wide; the second, 8 feet; the third, 1 foot; the fourth, fifth, 
and seventh, about 4 feet each; the sixth, 5 inches. These 
dykes do not all consist of the same variety of rock ; the first, 
second, fourth, and seventh, are constituted chiefly of what may 
be termed a fine-grained basalt, often very beautiful of its kind, 
at once both hard and brittle. The base is a dark substance, of 
which it seems impossible to define the nature by its external 
characters, and it is rendered porphyritic by the presence of 
crystalline calcareous spar, very slender crystals of felspar, and 
small masses of iron pyrites: the whole rock, except the two 
latter substances, yielding pretty readily a grey powder. The 
third and sixth are of a much finer grain, and of a green colour 
almost perfectly agreeing with that of the chlorite slate which 
they traverse. By the assistance of the glass, they can scarcely 
be said to possess a granular texture, and they appear to be per- 
fectly homogeneous without the presence of any imbedded sub- 
stance; their fracture is uneven and splintery ; they are so soft 
as to yleld readily to the knife, and their aspect differs so ver 
little from some of the steatitic rocks already described, that 
every one to whom they have been presented for inspection, 
without any information of their locality, has considered them 
to be merely varieties.of the base rocks of Moel Shabod. A 
rock of the same kind is also connected with the more compact 
substance of the second dyke. The fifth appears to be in a state 
of almost thorough decomposition. 
The walls of these dykes are not all equally well defined; those 
of the small one, the sixth, is the most completely so of the 
whole. In most of the others, there seems more or less an 
intermixture of the chloritic rock they traverse, and we did not 
perceive any instance in which an alteration of texture had taken 
place in the chlorite rock, even where, as in the instance of the 
second dyke, the chlorite rock protruded so far into the dyke as 
almost to cross it. We observed that thin veins of quartz tra- 
