412 Messrs. W. Phillips and S. Woods on the ~~ [Drc. 
been described : the run of the slaty cleavage is of remarkable 
uniformity every where. . 
Not very far beneath the summit of Snowdon are the workings 
of acopper mine still carried on. An examination of the refuse 
thrown out by the miner produced no rock that is not manifestly 
connected in character and composition with those found on the 
surface. The principal part of the rock immediately connected 
with the ore is slaty, of a greenish colour, often includes multi- 
titudes of minute crystals of iron pyrites, yields easily to the 
knife, is translucent on the edges, and it is evident by trans- 
mitted light and the assistance of the glass, that the colouring 
matter of the rock is a green substance, arranged in irregular 
lines, and we are confirmed in the opinion of its beg chlorite, 
from having found masses of slaty chlorite enclosing yellow cop- 
per ore, and veins of quartz. We are not enabled to state any 
thing respecting the veins of this mine, not having been so for- 
tunate as to meet with the captain, either on the mine, or at 
his residence in Beddgelert. 
During our descent, we observed on the summit of the ridge 
which unites the Lluwydd (Cleweth) with the Widdfa, the sum- 
mit of Snowdon, an appearance of stratification which, as viewed 
in the distance, may be termed basin-shaped, and which from 
its complete disagreement with all that we had hitherto observed, 
seemed to justify the conclusion that some important difference 
existed in that place in the nature of the rocks. It may be 
represented by the following rough sketch : 
This remarkable appearance excited the wish to examine the 
spot, and a future opportunity permitted our ascent to it. 
We began to rise at the bridge, about four miles from Beddge- 
lert, on the road to Capel Curig; and after carefully observing 
the rocks in our progress, we may safely assert that no rock 
was apparent but such as have been already noticed at the base 
of Moel Shabod, and on Snowdon. On examining the spot above 
alluded to, we found the rock to be essentially of the same 
nature ; but being of a darker colour, and as it should appear 
containing more iron, it had become more subject to decay, 
producing on the surface an ochreous-brown colour. very 
observable at a distance; and by a comparison of it with other 
rocks of a similar nature in other places, might be said to be 
considerably brittle. Still, however, it remains for us to account 
