Page:The American Cyclopædia (1879) Volume IX.djvu/364

 350 IRELAND barrier is broken only by the limestone plain of Mayo, extending to the shore of Clew bay. Mica slate and granitic ridges extend north- ward and eastward through Sligo to Donegal, forming almost the entire surface of the latter county and a great portion of Londonderry and Tyrone. In the N. W. part of this district the granite and quartz are intermixed with veins of primitive limestone, which also mingles with the mica slate constituting the remainder. East of this granite and mica slate district lies the great trap field of Antrim, the erupted rock over an extent of 800 sq. m. capping a stratum of in- durated chalk, which rests on lias. Patches of the same metamorphie rocks also appear on the coast of Kerry, and on that of Antrim, where they terminate in Fair head. The ancient Irish annals contain many accounts of land erup- tions proceeding from volcanic action ; and in more modern times two are noticeable : one in 1490 at the Ox mountains, Sligo, by which 100 persons and numbers of cattle were de- stroyed; and a volcanic eruption in May, 1788, on the hill of Knocklade, Antrim, which poured a stream of lava 60 yards wide for 39 hours, and destroyed the village of Ballyowen and all the inhabitants save a jnan, his wife, and two children. The immense extent of bog is a great obstacle to a perfect knowledge of Irish geology. The coal fields, with the exception of a small field of bituminous coal in the west and a few patches in the north, are south of the centre of the island. The quality of the coal is inferior. The most valuable bed is in Kilkenny, and is made up of seven workable seams of anthracite, the coal containing from 94 to 96 per cent, of pure carbon. The largest field covers a consid- erable tract in the southwest ; but the coal is not well adapted for domestic use, and is chiefly em- ployed in malting and lime burning. In Ty- rone, the district of Coal Island produces coal of good quality used in the neighborhood ; the beds seldom exceed a few inches in thickness. In 1772, at Ballycastle, Antrim, a colliery was discovered, with gallery and branches, which, from the stalactite pillars and the sparry in- crustations on the sides and supports, is believed to have been worked before the Norman inva- sion. Lignite, the only tertiary deposit, is found on the 8. shore of Lough Neagh. The clay-slate formation contains copper ore, the chief mineral wealth of Ireland, the principal mines of which are in the counties of "Wicklow, "Waterford, Cork, and Tipperary. Lead is more abundant than copper ; but in Ireland the mountain lime- stone is much less liberally supplied with it than in England. The coal measures are rich in iron ; and silver is found in connection with lead ore in proportions varying from 7 to 120 oz. per ton. Native gold associated with mag- netic ironstone was found toward the end of the last century in Wicklow, but all the efforts of the government to discover an available vein proved fruitless. Tinstone also exists in the same locality, but no working deposits have been discovered. Recent explorers have found in the new red sandstone beds of salt promis- ing an inexhaustible supply. The other mine- rals known to exist are antimony, zinc, nickel, iron pyrites, alum, clays of various kinds, gyp- sum, ochre, building stone, marble, and paving and roofing slates. Mineral springs occur at Mallow, where the water is 20 warmer than the atmosphere, and at Castle Connell, near Limerick, where the waters are chalybeate ; and sulphur springs at Swanlinbar in Cavan, and at Lucan near Dublin. Of the two kinds of bogs, the red or fibrous consists chiefly of bog moss (sphagnum palustre) ; it is reddish brown, ap- proaching to olive when dry. Its surface is generally covered with heath. The black bog varies from dark brown to perfect black ; in the latter case it becomes very hard and close- grained, and breaks into angular fragments. The deepest layers are still denser and darker, and very compact, resembling pitch or coal, and emitting when lighted an offensive odor. The average depth of these bogs is 25 ft. ; in some places they attain a depth of 40 ft. They are always above the sea level, their greatest height being 488 ft. and lowest 25 ft. The peat is found to rest on a blue clay, and ulti- mately on gravel. The area of bog available for peat fuel is about 2,830,000 acres. This physical disposition accounts for the hydro- graphic features of Ireland. From any part of the country navigable water can be reached within a distance of 50 m. Few countries. are so well supplied with rivers and lakes. The principal river is the Shannon, the largest in the United Kingdom, which has its source in the county Cavan at the foot of Mt. Cuilcagh, and in a course of 250 m. forms Loughs Allen, Ree, and Derg. The other principal streams are the Blackwater, which has its estuary near Youghal ; the Suir, the Nore, and the Barrow, which have their estuary near the city of Wa- terford ; the Slaney, emptying into St. George's channel at Wexf ord ; the Boyne, flowing N. E. from the elevated plain of Leinster into the Irish sea at Drogheda ; the Bann, rising in the Mourne mountains, and flowing northward through Lough Neagh till it empties into the Atlantic at Coleraine ; the Foyle, emptying into the lough of that name, and formed by the union of four streams from the interior of Ulster ; the Erne, falling into Donegal bay; and the Liffey, flow- ing into Dublin bay. The principal of the nu- merous lakes are Lough Neagh in Ulster, the largest lake in the United Kingdom, covering 98,255 acres, and exceeded in extent on the continent of Europe by only a few lakes out- side of Russia and Sweden ; Lough Erne in Fer- managh, consisting of two lakes 5 m. apart, con- nected by the fine river of that name; Lough Corrib and Lough Mask in the west of Con- naught, separated by an isthmus 3 m. broad; Lake Conn in the north of the same province ; and the lakes of Killarney in Kerry, renowned for their beauty. Giraldus Cambrensis praises the mild and equable climate of Ireland. At Dublin the mean annual temperature is a little