ANGLESEY, or ANGLESEA  , an insular northern county of Wales . Its area is 176,63o acres or about 276 sq. m . Anglesey, in the see of Bangor, is separated from the mainland by the Menai Straits (Afon Menai), over which were thrown Telford's suspension bridge, in 1826, and the Stephenson tubular railway bridge in 1850 . The county is flat, with slight risings such as Parys, Cadair Mynachdy (or Monachdy, i.e . " chair of the monastery "; there is a Nanner, " convent," not far away) and Holyhead Mountain . There are a few lakes, such as Cors cerrig y daran, but rising water is generally scarce . The climate is humid, the land poor for the most part compared with its old state of fertility, and there are few industries . As regards geology, the younger strata in Anglesey rest upon a foundation of very 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 fclsitic rocks form 1'arys 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 .

The

London & North-Western railway (Chester and Holy-head 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, silver, marble, asbestos, lime and sandstone, marl, zinc and coal have all been worked in Anglesey, coal especially at Malldraeth and Trefdraeth . The population of the county in 1901 was 50,606 . There is no parliamentary borough, but one member is returned for the county . It is in the north-western circuit, and assizes are held at Beaumaris, the only municipal borough (pop . 2326) . Amlwch (2994), Holyhead (10,079), Llangefni (1751) and Menai Bridge (Pont y Borth, 1700) are urban districts . There are six hundreds and seventy-eight parishes . Mon (a cow) is the Welsh name of Anglesey, itself a corrupted form of O.E., meaning the Isle of the Angles . Old Welsh names are Ynys Dywyll (" Dark Isle ") and Ynys y cedairn (cedyrn or kedyrn; " Isle of brave folk ") . It is the Mona of Tacitus (Ann. xiv .

29, Age. xiv . 18),

Pliny the Elder (iv . 16) and Dio Cassius (62) . It is called Mam Cymru by Giraldus Cambrensis . Clas Merddin, Y vel Ynys (honey isle), Ynys Prydein, Ynys Brut are other names . According to the Triads (67), Anglesey was once part of the mainland, as geology proves . The island was the seat of the Druids, of whom 28 cromlechs remain, on uplands over-looking the sea, e.g. at Plas Newydd . The Druids were attacked in A.D . 61 by Suetonius Paulinus, and by Agricola in A.D . 78 . In the 5th century Caswallon lived here, and here, at Aberffraw, the princes of Gwyneddlived till 1277 . Thepresentroadfrom Holyhead to Llanfairpwllgwyngyll is originally Roman .

British and Roman camps, coins and ornaments have been dug up and discussed, especially by the Hon . Mr Stanley of Penrhos . Pen Caer Gybi is Roman . The island was devastated by the Danes (Dub Gint or black nations, genies), especially in A.D . 8J3 . See Edw . Breese, Kalendar of Gwynedd (Venedocia), on Anglesey, Carnarvon and Merioneth (London, 1873) ; and The History of Powys Fadog . ANGLESI'I E, a mineral consisting of lead sulphate, PbSO4, crystallizing in the orthorhombic system, and isomorphous with barytes and celestite . It was first recognized as a mineral species by Dr Withering in 1783, who discovered it in the Parys copper-mine in Anglesey; the name anglesite, from this locality, was given by F . S . Beudant in 1832 . The crystals from Anglesey, which were formerly found abundantly on a matrix of dull limonite, are small in size and simple in form, being usually bounded by four faces of a prism and four faces of a dome; they are brownish-yellow in colour owing to a stain of limonite .

Crystals from some other localities, notably from Monteponi in

Sardinia, are transparent and colourless, possessed of a brilliant adamantine lustre, and usually modified by numerous bright faces . The variety of combinations and habits presented by the crystals is very extensive, nearly two hundred distinct forms being figured by V. von Lang in his monograph of the species; without measurement of the angles the crystals are frequently difficult to decipher . The hardness is 3 and the specific gravity 6.3 . There are distinct cleavages parallel to the faces of the prism { r ro 1 and the basal plane ) oor t, but these are not so well developed as in the isomorphous minerals barytes and celestite . Anglesite is a mineral of secondary origin, having been formed by the oxidation of galena in the upper parts of mineral lodes where these have been affected by weathering processes . At Mon teponi the crystals encrust cavities in glistening granular galena; and from Leadhills, in Scotland, pseudomorphs of anglesite after galena are known . At most localities it is foundas isolated crystals in the lead-bearing lodes, but at some places, in Australia and Mexico, it occurs as large masses, and is then mined as an ore of lead, of which the pure mineral contains 68 % .