Geology, Mineralogy, masa of granite which forms the surface-rock of the central district, occupies a tract of varying breadth, Aram 7 to 14 miles, and is the fundamental rock on which the other formations rest; it protrudes in Isolated portions in the districts occu pied by the elates. The granite is in general remarkably pore, and free from minerals not essential to its composition. It varies much in the also of the grain ; some of the largest grained and most beauti ful occora in Gleucree, In the northern part of the county, amid the mountains north of the Dargle ; some of the finest grained, remark ably firm and compact, is found in the Glen of Inside, at the northern side of Keadeen Mountain. The granite is not unfrequently porphy ritic, as in Glencree and Gleumacanass. Schorl, tourmaline, garnet, beryl, rock-crystal, epidote, heavy spar, magnetic re in-ore, galena, copper and iron and other minerals are found in small portions. Contemporaneous veins of granite, and leas frequently of quartz, are found in the granitic) mass. Granite of later formation is occasionally found alternating with the rocks which rest on the fundamental granite.
The mica-slate district on the eastern flank of the granite is in general narrow, never exceeding 3 or 4 miles in breadth : it generally passes into clay-elate, by which it is bounded on the east side through out its course in this county. Hornblende and hornblende-slate, grenatite, emery, andalueite, hollow-spar, talc-slate, which is quarried for chimney-pieces, hearthstones, gravestones, (he., and veins of quartz, occasionally occur in the mica-slate district. The mica-slate on the cap of Keadeen dips 65° to the south-east, and is remarkably full of andaluaite. Brisselstown Hill consists of mica-slate and rocks, namely, fine granular groenatone, greenstone-alate, and green stone-porphyry. Mica-slate and granite are found alternating near Kilranelagh.
The clay-slate on the eastern flank of the granite occupies nearly the whole of that part of the county which lies east of a line drawn from the juuction of the Dargle and Glencree rivers, south-south-west to Tinahely, Shillelagh, and Clonegall in Carlow county. This clay slate is in different parts associated with granite, mica-slate, quartz rock, flinty slate, grauwacke-trap, and porphyry. The strata in the northern part of the elay-slate district, near Bray, are much inflected, but in the middle part, and southern part, so far as concerns this county, they are tolerably regular, dipping to the south-east. In some places the granite acquires a eienitic character ; in others it passes into a true felspar-porphyry; and in others the felspar and mica are so intimately blended as to constitute an apparently homogeneous mineral, in some cases resembling some varieties of the trap-rocks, and in others verging in aspect and texture towards clay-slate. Near
Danganatown, south-west of Wicklow, masses of greeustone and quartz rock are found, gradually passing into hornstone and compact felspar. A mane of greenstene, Inclosing a bed of roofing-slate, which is quarried, is found near the Avon-More; and quartz-rock in combina tion with clay-slate, and abounding in contemporaneous veins of pure white quartz; granite, greenstone, and greenstone-slate, alternating with clay-slate, occur in several places. Arklow rock (411 feet high) on the coast, just south of Arklow, consists of trap rocks, as green stone, farmer, felspar-porphyry, and a variety of trap well entitled to the name of basalt, very similar to the basalt of the Giant's Causeway. Quartz-rock forms the masses of the Great and Little Sugar-Loaf, and of the bill above Bray Head. The clay-slate of the western flank of the granite occupies the most of that part of the county which lies west of the Liffey, the King's River, and the Slaney; grauwacko is found in combination with it.
The reeks on the eastern flank of the granite abound in metals, while on the western flank there is a total absence of them. In tho granite and mica-slate districts the metallic substances are found in veins; the clay-slate district has metalliferous beds, and contem poraneous veins or alluvial deposits. In the granite and mica-slate, galena, green and white lead-ore, and copper pyrites are found. The ore is smelted in small blast-furnaces, with the aid of turf, lime, and a small portion of the purest blind-coal; the lead is obtained by a operation, and is fit for all the purposes of the plumber. The principal lead-mines are In Glonmalure.
The metals obtained from the clay-slate tract are gold, silver, copper, Iron, lead, zinc, tin, tungsten, manganese, arsenic, and anti mony. The metalliferous portion of the clay-slate district is small, extending in length only from the border of the county at Crogbau Kinshala, 10 or 11 miles in a north-north-east direction, and having but a small breadth. The discovery of native gold near Croghan Kimehela Mountain took place about 1796, but the quantity found was very small. Some gold has been found in streams near the moun tain Croghan Moira. Copper pyrites, iron pyrites, and black copper ore are found and wrought at Cronbane and Ballymurtagh, near the Avon-More. The mines employ about 1000 men. Native silver, minutely disseminated, sometimes In particles, sometimes in filaments, was found in the middle of the last century in a brown ludurated oxide of iron at Cronbane. Lead is found and worked at Ilipplagh, or Luganure, near Olenmalure.