OF THE MENAI BASIN. 
2SS 
Carnarvon Slate. 
One of the finest and most extensive slate- quarries of 
this range is that at Dolawen, belonging to Mr D. Pennant, 
on the south bank of the river Ogwen, about six miles from 
Bangor. 
The quarry is situate on the face of a lofty hill. The 
vein ranges from south-west to north-east, as do all the 
slate veins of this district ; and its dip is nearly vertical to 
the horizon. It is included in a hard blackish greywacke 
sort of rock. The breadth of the quarry, now working, 
and which has been opened considerably more than forty 
years, is no less than 300 yards, and about 100 in depth. 
In colour it is blue, reddish, and green ; but these varie- 
ties occur generally in separate veins, though occasionally 
passing into each other. The blue, which predominates, 
is excelled in hardness and durability 'by no other slate 
anywhere found. It splits readily and easily into the thin- 
nest laminae or plates, and may be obtained of any size ; 
and almost any kind of architectural article can be made 
of it, as roofing-slate, flooring-flags, window and door jambs, 
chimney-pieces, tombstones, and various other articles. 
This great vein of slate is penetrated about the middle, 
from south to north, by a hard quartzy vein, having occa- 
sional traces of sulphuret of lead. The slate in immediate 
contact with this dike or vein of quartz is much inferior 
in quahty, as it splits less readily. 
The slate of this quarry cannot be raised without the 
assistance of gunpowder. Though great quantities are 
thus separated and brought down, much is shattered and 
rendered useless by the explosion. Being removed from 
the quarry, and prepared for architectural purposes, it is 
then^ by means of an iron-railway, upwards of six miles in 
