OF THE MENAI BASIN. 
239 
its summit ; and on its north-east side, it there exists as 
sulphuret and sulphate of copper. The other vein is at the 
foot of Snovvdon, on the west bank of the upper lake of 
Llanberris, and within half a mile of the village of the 
same name. It occurs also in this, in the state of sulphate 
and sulphuret. 
These veins of copper are followed in galleries cut hori- 
zontally into the heart of Snowdon, passing through hard 
basalt and slaty hornblende, which form the walls of the 
veins. The matrix of the copper is quartz. From the ir- 
resistible nature of the enclosing rocks, much gunpowder is 
required. When the metal is thus raised, it is broken with 
hammers into small pieces, and, by means of a stamping- 
mill, moved by water, which is brought nearly a mile in a 
wooden aqueduct, it is reduced into a fine powder, and well 
washed. The metallic copper-ore thus prepared is packed 
up in bags, and is put on board small boats, sent down the 
two lakes, and afterwards carted to Carnarvon, whence it 
is exported to the founderies at Swansea. 
Somewhat connected with the last described metal, we 
find on the south bank of the Ogwen, above a mile from 
Dolawen slate-quarry, and more than seven from Bangor, 
the arseniate of copper. It is included between hard rocks 
of slate. It was not long ago that it was raised, roasted, 
and by process of sublimation pure oxide of arsenic was 
obtained. But the preparation requiring much chemical 
skill, was not properly conducted, and it has lately been 
abandoned. 
There remains only to be considered, iron, manganese, 
lead, and calamine, all which are found in this side of the 
Menai basin, but in very inconsiderable quantities, and 
hardly deserving observation. 
In the secondary rock along the Carnarvon side of the 
