210 
ON THE GEOLOGY OF THE 
Wales, taken as a whole, may be considered as a moun- 
tain group of land, separated from England by the valleys 
or basins of the Dee and the Severn, much in the same 
manner as Galloway is disjoined from the rest of Scotland 
by the basins of the Ayr and the Nith ; and Cumberland 
and Westmoreland from the north of England by the 
basins of the Lune and the Eden. As England is ob- 
served to be divided into very unequal portions by a ridge 
of hills which traverse it nearly from north to south, having 
to the east the principal level tracts of our island, — so we 
observe in Wales a similar mountainous range in a direc- 
tion parallel to the central one of England, to which it is 
connected by a slightly elevated tract running betwixt the 
basins of the Dee and the Severn. From this central 
mountain-ridge of Wales, individual ridges branch off on 
each side, which are found generally to take the direction 
of SW. and NE. 
One of these ridges, which cross the central range, viz. 
that which is most northerly, and forms the counties of 
Carnarvon and Anglesea, we propose to make the subject 
of our observations in this paper. 
That we may have a clear idea of the district of North 
Wales we are about to describe, we cannot perhaps do 
better than ascend the summit of Snowdon, situate in the 
southern border of Carnarvonshire, and from this com- 
manding height survey the surrounding country. From 
its lofty peak, 3546 feet above the sea, at Carnarvon 
Quay, we shall observe stretching in one direction SW., 
and in another NE., a lofty chain of mountains, some of 
them little inferior in elevation to Snowdon itself, and 
having it for a centre. On the NE. this range is termi- 
nated by the bold face of Penmaen Maur, rising almost 
perpendicularly from the sea to the elevation of 1200 feet ; 
and on the SW. by the Rivels, equally elevated, and 
