OF THE MENAI BASIN. 
sated for by other mineral productions of equal or greater 
value. 
The prevailing rock of the island seems to be the green 
asbestine slate. Good sections of it are exposed to view by 
the road cut along the shore of the Menai Strait, between 
the Iron Suspension-bridge and Beaumaris. It is here pe- 
netrated, from east to west, by frequent narrow veins of 
basalt. 
Two or three great veins of porphyry, steatite^ and horn- 
blende, can be traced across the island, taking the direction 
of east and west. Two of these are well seen to south of 
Amlooch, and within a mile of that town. 
Near Llanerchymead granite occurs, the only place in 
the Menai basin where it is observed. 
Of the secondary rocks we find a great number in the 
island of Anglesea. 
This class, important for the builder and agriculturist, 
is pretty generally diffused through the island. The lime- 
stone first appears on the eastern shore, at Red Wharf Bay, 
where it occurs in great strata, and appears to be the car- 
boniferous limestone that underlies the coal measures. 
In order properly to distinguish it from a reddish va- 
riety occurring at Plas Newydd, we shall call it the upper, 
and the other the under, and above these two will be found 
the coal measures. It ranges from this place northwards 
along the coast, with more or less interruption, to Cemaes, 
the most northerly point of Anglesea. In some places, 
however, along this line of shore it is not seen. It overlies 
the green asbestine slate. From Red Wharf Bay, beds or 
veins of this limestone are often observed, pushing them- 
selves through this slate rock, a considerable distance into 
the interior, as seen from Lluguy to Llanfinnan and Llan- 
gefne. To the south-east of Red Wharf Bay, this lime- 
stone is found at Penmon, nearly opposite to Penmaen 
