y old pre-Cambrian rocks which appear at the
surface in three areas:--(1) a western region including Holyhead and
Llanfaethlu, (2) a central area about Aberffraw and Trefdraeth,
and (3) an eastern region which includes Newborough, Caerwen and
Pentraeth. These pre-Cambrian rocks are schists and slates, often much
contorted and disturbed. The general line of strike of the formations
in the island is from N.E. to S.W. A belt of granitic rocks lies
immediately north-west of the central pre-Cambrian mass, reaching from
Llanfaelog near the coast to the vicinity of Llanerchymedd. Between
this granite and the pre-Cambrian of Holyhead is a narrow tract of
Ordovician slates and grits with Llandovery beds in places; this
tract spreads out in the N. of the island between Dulas Bay and Carmel
Point. A small patch of Ordovician strata lies on the northern side of
Beaumaris. In parts, these Ordovician rocks are much folded, crushed
and metamorphosed, and they are associated with schists and altered
volcanic rocks which are probably pre-Cambrian. Between the eastern
and central pre-Cambrian masses carboniferous rocks are found. The
carboniferous limestone occupies a broad area S. of Ligwy Bay and
Pentraeth, and sends a narrow spur in a south-westerly direction by
Llangefni to Malldraeth sands. The limestone is underlain on the
N.W. by a red basement conglomerate and yellow sandstone (sometimes
considered to be of Old Red Sandstone age). Limestone occurs again on
the N. coast about Llanfihangel and Llangoed; and in the S.W. round
Llanidan on the border of the Menai Strait. Puffin Island is made
of carboniferous limestone. Malldraeth Marsh is occupied by coal
measures, and a small patch of the same formation appears near
Tall-y-foel Ferry on the Menai Straits. A patch of granitic and
felsitic rocks form Parys Mountain, where copper and iron ochre have
been worked. Serpentine (Mona Marble) is found near Llanfaerynneubwll
and upon the opposite shore in Holyhead. There are abundant evidences
of glaciation, and much boulder clay and drift sand covers the older
rocks. Patches of blown sand occur on the S.W. coast.

[v.02 p.0018]

The London & North-Western railway (Chester and Holyhead branch)
crosses Anglesey from Llanfairpwllgwyngyll to Gaerwen and Holyhead
(Caer Gybi), also from Gaerwen to Amlwch. The staple of the island is
farming, the chief crops being turnips, oats, potatoes, with flax in
the centre. Copper (near Amlwch), lead, silve