LIMERICK GEOLOGY
In a geological point of view the county comprehends four formations, calcareous, coal, sandstone, and basalt. The calcareous district comprises the greater portion of the champaign part of the entire county, extending with little interruption from Newcastle, in the west, to Abington in the north-east, and from Mount-Trenchard on the Shannon to the eastern boundary of the county south of Kilfrush, comprising the greater part of the vales of the rivers that are tributary to the Shannon. The range is almost uniformly from east to west, and the dip or inclination westward. It presents a great variety both in structure and colour, the stone being raised in some places in blocks of very great size, and in others in thin laminae; the prevailing colour is light grey, and it is susceptible of a high polish. It presents its greatest varieties near Croom and Manister-Nenagh.
Near Askeaton are some indications of lead ore, but not of a character that would encourage any great outlay in tracing the veins: there are indications of a very valuable ore near Tory hill. The coal formation forms the western boundary of the limestone field. The coal lies in thin seams, the lower increasing in goodness of quality and in thickness, but no attempts of any importance have yet been made to raise this mineral except on a small scale and from the upper stratum, which is merely a thin seam of coal shale. The ironstone that alternates with the coal is only used in road-making; nor is it probable that any vigorous researches will be made in quest of coal, while bog fuel can be had in abundance on the surface.
Besides the coal-field above described, there are thin seams in a glen between Castlereagh, Galbally, and the town of Tipperary. The old red sandstone formation comprises the hills of Ballingarry, Knockaderry, and Kilmeedy, which rise abruptly from a limestone plain and range from the Deel to the Maig in a direction east and west. The new red sandstone comprises the mountains of Castle Oliver, the Long mountain, the Black mountain and others from Charleville to Glenbrohane, forming the boundary between Cork and Limerick, and merging into the Galtees. The basalt shews itself in the hill of Ballygooly on the verge of Lough Gur, in those of Knockruadh, Knockgreine, Cahirnarry, Carrigoginniol and the hill of Newcastle.
At Linfield, near the Dead river, it rises to a height of nearly 200 feet, presenting a perpendicular colonnade of massive pillars towards the north, and bearing a striking resemblance to the promontory of Fair head in Antrim. Some of these pillars are 109 feet long, and approximate to a pentagonal or hexagonal form; but in general the basalt of this county is amorphous. To the south-east of this range is Knockgreine, "the Hill of the Sun," 500 feet high, with a base of limestone and a summit of basalt. It everywhere contains a large portion of iron.
Oxyde of iron and iron clay are found in great quantities at the foot of the hills, and near Bohermore are procured specimens containing shells with an appearance of partial calcination. There are appearances of greenstone and millstone grit in several places: near Doon is a very valuable bed of excellent freestone. Specimens of very pure copper ore have been collected near Abington, and some attempts made to trace the vein. At Rathmore, in Manister-Nenagh parish, is a large bed of inferior pipe clay. Slate, but of inferior quality, is obtained in the demesne of Daragh and at Towerlegan; and in the mountains near Athea are procured large, thin, smooth, and very superior flagstones.
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