422 — Messrs. W. Phillips and S. Woods on the [Dec. 
Within a mile of Built, the soil begins to be tinged of a reddish 
colour, and about three miles from it we observed a small 
quarry on the top ofa hill, and near the road side, situated in a 
sandstone perfectly resembling the old red. It afforded two or 
three varieties ; one of them consists apparently of an indi - 
rated clay or marl of a red colour, enclosing specks of mica; — 
another of grains of siliceous sand, and an ochreous substance 
connecting them ; a third resembling the sandy variety, exc ep 
that it was rendered slaty by the intervention of close layers « 
mica; these varieties are interstratified, and dip at about 15° to 
the SW. 
_ In conclusion, we have to observe, that previously to our 
quitting the hospitable roof of Mr. Dawson, at Bang » he 
informed us that some varieties of the rocks of the district we 
visited had been pronounced by certain French geologists to_ 
the steaschiste of Brongniart. Since committing the foregoing” 
pages to the press, we have consulted the description by that 
eminent mineralogist of the Geology of the Cotentin inserted 
in the 35th yolume of the Journal des Mines, and his particular 
description of the steaschiste to be found in his “ Ess i d’une 
Classification Mineralogique des Roches mélangés,”’ in the pre- 
ceding volume. The perusal of these at once convinced us of 
the relation existing between the rocks of North Wales and 
those of the Cotentin, and even of their identity in so far as 
related to their actually consisting of the steaschiste, and of 
that alone ; for we did not perceive any rock whose character 
sufficed to raise a doubt of the whole being of one formation, 
We refer the reader to the two memoirs above cited, the ae j 
of which will readily satisfy him of the correctness of our present 
_ views of the nature of the rocks in question, and that their pro- 
perand expressive designation is steaschiste ; of which we have 
described most of the varieties mentioned by Brongniart : they 
are as follow: Steaschiste rude ; porphyroide; noduleux ; steatr- 
teux; chloritique; diallagique (ours is rather augilique); ophio- — 
din; phytladien, nt Sees ete 
— 
; 04 a SC a overs 
Having sent to Mr. G. B. Sowerby, of King-street, Coven a 
garden, all the impressions of shells found by usin Wales, and 
requested of him some remarks upon them, which his intimate _ 
acquaintance with conchology well qualifies him to afford, we — 
annex the communication received from him on the subject, first _ 
observing that the impressions figs. 1, 2,3,4, 5, and9 (PI. XVII), — 
are from the summit of Snowdon ; 6,7, 8, 10, 11, 12, and 15 
from the road side near Pont y Cyffin; fig. 13 is from about 
midway between the Devil’s Bridge and Rhyader; fi y 14 
from Cader Idris. Pe oe ie 
my 
