KERRY GEOLOGY

From A Topographical Dictionary of Ireland, 1837

The western portion of the north of the county, which has been described as lying low, is a great limestone basin, the eastern boundary of which is formed by a line from Knockanure hill southward to Listowel, and thence south-westerly to Ardfert, where it sinks under the ocean in Ballyheigue bay. This limestone is secondary, with marine remains and calc spar, usually of a light blue or smoke-grey colour: it seldom rises more than forty or fifty feet above high water, appearing sometimes in crags and low cliffs, but mostly concealed by a cover of yellow clay. Its northern boundary, the hill of Knockanure, about 700 feet high, is composed of grey sandstone; the junction on that side is every where concealed by a deep cover of clayey loam.

To the west of that hill, the contiguous rock sinks under the level of the ocean, and permits the tide to enter the mouth of the Cashen, the navigation of which is obstructed by sand hills; but these, being partly calcareous, afford a useful supply of manure to the upper country. From the Cashen to Kerry Head stretches a bank of upland, which, as it proceeds westwardly, becomes chiefly a heathy moor, rising to a considerable height at its termination: it is composed of thick beds of argillaceous sandstone, nearly horizontal, in the partings of which the beautiful quartz crystals called Kerry stones are found: they are transparent and regular, and very hard.

Steel-grained lead is also found traversing this formation. On its southern side this bank is more slaty and somewhat calcareous, being mixed, near Ballyheigue, with lesser masses of close-grained conglomerate. On the west is a low sandy flat and salt marsh, defended from the ocean by a screen of sand hills extending from Ballyheigue to Barra harbour. In the northern upland formation of the middle district of Kerry are beds of culm, which has been worked only in its eastern range, in the county of Cork. Specimens of the culm from Killarney, Tralee, and Castleisland were nearly incombustible, which may be accounted for from their having been taken from the surface. In a drift in the river Awineeghrea, a branch of the Flesk, the specimens resemble plumbago. It is possible, by sinking, to obtain coal like that of Kilkenny.

A band of limestone, containing a few organic remains, traverses the southern part of this formation: it is chiefly blue, compact, with chert over it, and to the west partly regularly stratified. Where it shows itself in the middle of the Slieve Lughar bogs, in Lord Kenmare's quarries, it is also blue and compact, without any chert, but a good deal of calcareous spar. It next appears about two miles west of Killarney, on the Flesk, much intermingled with horn-stone or chert, and, finally, constitutes the great deposition which forms nearly all the islands and promontories on the north side of the Lower lake. The limestone there meets the brown transition rocks of the mountains; and near the junction it is traversed by metallic veins of copper and lead. A second band is found in various places along the course of the Gheestan, where it is blackish and mingled with chert.

The whole bottom of the valley of the Maine consists of limestone lying in strata, which, though generally confused, appear to lap on each side above those of the mountain. The limestone is generally compact, much impressed with marine remains; black and hard towards Tralee, where it is dressed as marble; whitening and more tender towards Castleisland and the Maine, and of course more readily calcined: both kinds are excellent and nearly pure. Towards the northern side of the beds they become more flinty, and are separated from the mountain rocks by thin beds of Lydian stone, black or blueish grey, with the cross fracture slightly conchoidal. Towards Tralee this becomes a complete horn slate, the shiver of which is highly valued for road gravel. There are large banks of shell sand in Castlemaine bay: it is of a muddy blueish cast, containing numerous whole shells of the species of cardium. One of the Skellig rocks, which has often been called marble, contains nothing but bolts of quartz traversing the brown slate.

The mountain of Slieve Mish, which runs parallel to the Maine on its northern side, and terminates in the peninsula of Corkaguiney, is composed of old sandstone or grit, dipping about 40° to N. 8° W.: towards the interior the dip is greater, and the rock more indurated. It is covered with thick beds of millstone grit, or coarse-grained conglomerate, with pebbles of quartz, jasper, and feldspar. The component rock of the mountains which form nearly the whole of the southern part of the county is of the transition class, being a clay-slate or ardesia, which dips to the S. 55° E., at an angle of 68° from the horizontal; so that, though nearly on edge, it presents its cliffs and sections to the north-west. This position is favourable to its decomposition. From the facility with which the water penetrates, the strata split and crumble down the mountain side, leaving a considerable detritus at the foot of all the cliffs, finally decomposing into an adhesive loam well suited to the production of grain crops, and forming a principal component of many fertile soils in the South of Ireland.

The range of mountains which separates the bay or river of Kenmare from Bantry bay is composed of beds of schist and sandstone of various clay-slate is quarried for roofing in some places, but as the works have seldom proceeded far below the surface, that raised is generally shivery and small, yet much of it is equal in quality to the Easdale and Ballahulish, in the West of Scotland. It is blue, purple, and green, according to the intermixture of iron or chlorite; splits readily and bears piercing, is slightly foliated or wavy, harder and more silicious than Bangor slate, and very durable. The convenience of export has hitherto only admitted of quarries being opened at Cahir, Begnish, and Valencia; at the last place flags of large dimensions are quarried, which find a ready market in London.

The general slate rock, especially towards the south and centre, is in many places penetrated with veins of quartz; is highly indurated, and in some places the traces of stratification are entirely obliterated in the smaller specimen, though always recognizable in the great, where the rock is found in situ. From the colour communicated by the chlorite, the rock is provincially called greenstone, being similar in aspect, though of different composition, to that so called by mineralogists. When the red oxyde is more abundant, it is called brownstone. Where the induration is not so great as to destroy the schistose as well as the lamellar structure, the rock is used as flag or rubble stone. Flags of this sort are common on the surface. But the most common land stones here are the blocks of more highly indurated rocks, which, parting from the mass by cracks and fissures, have had their angles decomposed and worn off, and are to be met with in the form of round boulders at great distances from their original seat in the mountain.

One of the most singular rocks occurs close to the road from Killarney to Ballyvourney, at the head of the glen of Glenflesk: it rests on the transition slate of the county, and is a close-grained compact sandstone, imbedded in which are minute prismatic crystals of flesh-coloured feldspar, and here and there geodes, six or eight inches in diameter, containing sparry iron-ore and white quartz. It thus comes under the description of porphyritic rocks, and is the only one at present known in the South of Ireland. It may also be mentioned that in all the mountains the common grit-stone contains large quantities of spar or crystal, or both; also sparry iron-ore, and iron pyrites in crystals. The Roughty stream separates beds of limestone from others of clay-slate; and near the head of the Kenmare river are several islands abounding with limestone and beautifully variegated marbles. Limestone occurs on other parts of this coast.

Iron is found plentifully in the southern baronies, where there were two manufactories of it, one at Killarney, the other at Blackstones, but both have been long since, discontinued from want of fuel. Lead-ore is found in many parts. Copper of a golden colour was raised at Muckross, and when the mines were worked, grey cobalt and cobalt bloom were found in considerable quantities; purple copper at Ardfert, and marcasites of copper in Glanerought. The marble of Tralee has spots like that of Kilkenny, but larger and fuller of sparry substance: it takes a high polish. Marble of inferior quality is found in several other parts. In some of the islands in the bay of Kenmare is a variegated marble of red and white, interspersed with yellow, green and purple spots. A grey marble in Cappanacoss island was formerly extensively worked by Sir William Petty. Near Castleisland is found the Lapis Hibernicus auctorum, or "Irish slate:" its taste is sour, and it abounds with common green copperas, for extracting which works were erected at Tralee, but were relinquished for want of a market. Pipe-clay, potters'-clay, fullers'-earth, brown ochre, and rotten stone, like tripoli, are met with in various places. Very fine amethysts have been found in the cliffs near Kerry Head; and sulphur appears on the north of Cashen river, near Ballybunnian.

A kind of whetstone used for razors is found near the Devil's Punch Bowl. Fossil shells are to be met with in most places where there is limestone: they are chiefly of the cockle kind, and generally consist of lumps of sparry matter, the shell being wholly decomposed, and only the shape remaining. Coraloids are also discernible. Of the plants peculiar to this county, or only found on the ridge that separates it from the county of Cork, the most remarkable is the arbutus, which, with the yew and holly, gives a perpetual verdure to the natural woods of Killarney. The prostrate juniper occurs on the shore near Derriquin, on the Kenmare estuary. Saxifrages in numerous varieties descend from the summit of the Reeks to the sea shore; and those plants that luxuriate in a moist climate are more numerous and diversified in Kerry than in any other county in Ireland: such are of the orders Musci, Hepaticae, and Lichenes, and of these, several new species have been added to the British list.

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