322 Messrs. W. Phillips and S. Woods on the (Nov. 
dually aad imperceptibly pass into each other; that hence they 
maintain no uniform or characteristic difference, and that all 
their numerous varieties are interstratified with slates composed 
of the same materials, and consequently that they are all asso- 
ciated in close family alliance, and owe their existence to a 
common origin. There are no indications of any one of these 
slates or rocks being superior or inferior to the rest, and although 
some of these rocks might be pronounced to be greenstone by 
a casual observation of them, yet the occurrence of the same 
organic impressions near the summit of Snowdon and in several 
other places clearly indicate them to be members of one and the 
same series. ‘The greater proportion of these rocks may be 
found within a short compass from Capel Curig, and the situa- 
tions in which from our own limited experience we should 
recommend as the most instructive to observers are, the section 
of the road near Pont y Cyflin; both the new and old road 
towards Bangor, and beyond their junction from the excavated 
pass at Ben Glog to a mile or two beyond the inn at Tan y Maes 
towards Bangor; but above all the mountain close behind the 
inn called Moel Shabod from the base to the summit on every 
side. We had to regret that a continuance of unfavourable 
weather obstructed our visits to the Glyder and the Trefan, but 
from the information of our intelligent friend Mr. Dawson, of 
Bangor, who has accurately surveyed the whole country, and a 
comparison of his specimens, we have every reason to believe 
they would have furnished similar results. We pretend only to 
give a hasty and imperfect sketch ; limited time and abundant 
vain prevented us from attempting more, and we proceed to state 
in detail the evidence we have procured in the hope of stimu- 
lating the lovers of the science to investigations still more 
minute and satisfactory, which will in that delightful region 
carry with them their own reward. 
The general character of the rocks of Snowdonia, and which 
extend even into South Wales, is of a nature that we did not at 
all anticipate. Such as possess little or no appearance of a slaty 
texture, and these are often porphyritic, have for their base a 
substance greatly resembling steatite or potstone,* often so soft 
* Some of the rocks of which this substance forms the base, or which are constituted 
Of it, possess so nearly the characters of some varieties of steatite or potstone, as to pre- 
vent all hesitation in pronouncing them to be allied to those substances, while others 
assume a talcose character; their connexion with chlorite (which almost always accom- 
panies them) seems to authorizethe conclusion that they are all of one family, since the 
greater number of these minerals analyzed by Klaproth, Vauquelin, and Lampadius, 
were found to consist of the same elements; namely, silex, alumine, with 20 to 30 per 
cent, of magnesia, and a small proportion of lime. Hitherto, however, we have been 
speaking of the resemblance of the rocks of Wales to steatite or potstone, only from 
their external characters, and judging by these alone, we repeat that no hesitation would 
be felt in considering them as varieties of those substances. Being anxious, however; 
to ascertain by a reference to chemical agency, how far the chemical characters agree 
with the external, we placed in the hands of Mr, Richard Phillips five specimens, vary - 
ing considerably in aspect, but all allied by interstratification. These were found to 
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