ON THE GEOLOGY AND STATISTICS 
length, transported to Port Penryn, within a mile of Ban- 
gor, where it is shipped for all quarters of the globe. 
At this quarry a useful piece of machinery, put in m.o- 
tion by water, is employed for sawing and cutting slate 
into tombstones, jambs, and such like. Near Port Penryn 
is a writing-slate manufactory. Of the refuse slabs of slate 
very good fences are made ; some that are long enough are 
fastened together with iron-nails, like post and rails, and in 
that form look well, and answer a good purpose. 
The returns from this quarry in the course of a year are 
immense, many thousand tons being sold and exported. 
Nearly a thousand men are daily to be seen at w^ork ; and 
from the interesting appearance of the various workings of 
the Dolawen slate-quarry, and the great extent of the ope- 
rations, few places can afford a higher treat to the practical 
mineralogist. 
Were instances wanting to exemplify the vast advantage 
iron-railways confel* in prosecuting great works, at less ex- 
pense, and with greater expedition, over common roads, 
repaired and engineered on the best principles, the iron- 
railway at Dolawen slate-quarry may be adduced. It is 
said, that, before the present one was laid do\vn, nearly 400 
horses were required to convey the slates from the quarry 
to Port Penryn ; but with the assistance of the railway, 20 
horses can do all the carriage. 
The next slate-quarry worthy of examination is that of 
Alt Dhu, belonging to Mr A. Smith, situate on the east- 
ern bank of the lower lake of Llanberris, on the steep de- 
clivity of a mountain rising not much less than 2000 feet 
above the level of the sea. This slate-vein, which is evi- 
dently the continuation to the south-w^st of Dolawen vein, 
on the Ogwen, first described, passes along the Alt Dhu 
mountain. In thickness it is 300 yards, and in height not 
much less. It consists, like that of Dolawen, of three 
