Loch Corrib, which is the second largest sheet of inland frest water in Ireland, is about thirty-five miles in length from galway to Mám; and varies in breadth from eight miles, as between Uachtar Ard and Cong, to one quater of a mile, as from the Wood of Dún to Corrán Point, where it narrows between the Joyce Country and the Iar-Chonnacht hills. Its general direction is from west-north-west, in a curvature, to south-sour-east. In depth it varies considerable. It is in many parts full of rocky shoals, dry in summer; and, even in the navigation course, having but six or seven feet of water in some places. In other parts it descends to one hundred and fifty-two feet, as between the island of Inis mhic a' trír and Cong, and between Dubhros Island and Fornocht Point, which portions are styled by the fishermen "The Old Loch." The accompanying map, to a scale of half an inch to the statute mile, taken from the Admiralty Chart made in 1846, and the Ordnance Survey Maps, shows the principal islands, the navigation course, the rivers, and the chief objects of interest along its shores.
At the commencement of its tortuous course among the mountains, Loch Coirib has the county of Galway on both sides, along the baronies of Ross and Moycullen. At the north-east, it divides the counties of Mayo and Galway, along the south margin of the barony of Kilmaine in the former, from the river of Cong to the Black-river of Shrule, about a mile to the north of the ruins of Eanach Caoin Castle, on the east shore. From thence southwards, during the remainder of its course, it has the county of Galway on both sides--the barony of Clare on the east, and that of Moycullen on the west; but the river between the south end of the lake and the sea passes through the Barony of Galway.
The old Irish name of this sheet of water was Loch Oirbsen derived from the name of the sea-god, Oirbsiu Mac Allóid, commonly called Manannán Mac Lir, "The Son of the Sea," from whom the Isle of Man is designated. He was slain in conflict by Uillin, grandson of Nuadu of the Silver Hand, King of Tuatha Dé Danann, in a battle on the western margin of the lake; and from that circumstance this district is called Magh-Uillin, the plain or field of Uillin or Magh Cuilinn, and O Flaherty says that in his day a great stone thereon, six miles from Galway, marked the scene; it still exists.
The ancient territories along it were Iar-Chonnacht, comprising Gnó Mor and Gnó Beag--with Conmaicne-Mara, now Conamara, on the west, and Uí Briúin Seóla on the east border, and towards the north-west Dútha Seóigheach, the Joyce Country, between it and Loch Measca; and more to the north-east, Conmaicne Cúile Tola, the barony of Kilmaine, where the first great battle of Moytura was fought.
Loch Coirib covers a space of forty-four thousand acres and its watershed in the counties of Mayo and Galway comprises an area of seven hundred and eighty thousand acres. The summer level of the lake is fourteen feet above the medium data of the sea in Galway Bay, and thirty seven feet below the surface of Loch Measca. This sheet of water formerly extended over a much larger space; but by the drainage operations carried on from 1846 to 1850 it was lowered, much valuable land relieved from flooding, and large tracts rendered capable of cultivation. Its chief western supply is from the great catchment basin of the Valley of Mam, stretching westwards towards the salt water fiord of the Killeries, and affording the vast supply of water from the sea clouds caught on the Joyce Country and Conamara Mountains, and pouring it down through the River Béalánabreac, 'the mouth of the ford of the trout '--(the largest stream in Ireland for its length and its tributary the Faill Mór, into the lake at Bun Bonáin, near Mám, where they coalesce.
On the north-west the principal supply is from the Dumha Éaga, which drains the watershed between the west and south-west sides of Binn Shleibhe and the south shoulder of the hills that run from Loch na Fuathaí [fn4-1] and Loch Measca to Loch Coirib, and which delivers its waters near Corr na Móna -- "the pinnacle of the bog". The great water source is Loch Measca, (surface area twenty two thousand statute acres) that has, with its tributaries and the Partraí range of mountains, a catchment basin of two hundred and twenty-five thousand statute acres, and which, filtering subterraneously through the cavernous limestone neck that divides the two lakes between Ross Hill and Cong, rises in an immense body of water at the latter place, and forms the great river of Cong; besides which, the waters of Loch Measca pour into the Coirib lake in numerous places from Cong to Cross, where there is a small stream feeding it with the various springs and turlochs [fn4-2] of that end of the barony of Kilmaine, and also from the well of St. Fraochan, in the immediate vicinity of the village of Cross.
Still farther to the south-east the rivers of Shrule Cloch- an Uabhair, Coill Rua, Creaga, Claregalway, pour in their tributes; the latter, in particular, which is now partially converted into a canal, and has drained several of the principal turlochs on the eastern border of the lake from Tuaim westwards, is, next to the Loch Measca supply, one of the chief water sources of Loch Coirib and also affords ready transit and good spawning ground for salmon for many miles inland.
On the west and south sides are a number of small streams, carrying down the surplus waters of the range of hills that stretch from the village of Magh Cuilinn by Carn Suí Finn till they culminate in Leac Aimhrei, which shadows the upper lake opposite the romantic basin in which rest the island and castle of Caislean na Circe. On this side also underground passages and now a canal carry in the waters of Baile Uí Chuirc Lake, but the chief stream is the Fuathaí, or Abhainn Ruibhe, which, collecting all the waters from the chain of lakes that margin the great road into Conamara, and especially those of Lochs Bó Finne and Gleann Gabhla, to the east of the summit level, enters the lake at Uachtar Ard. The Acha na nIubhar river also affords a full stream. From all this it will be seen that the chief supply to Loch Coirib is independent of springs, and hence the water is remarkably soft.
That portion of the lake bordering on the south and east is low and picturesque, especially along the baronies of Kilmaine, Clareen and Moycullen; but towards the east can from most points be seen the remarkable "Hill of the Fairies," called Cnoc Meadha near Tuaim--a locality very memorable in history, and to which we shall have occasion to refer in another place. The slope of the Magh Cuilinn hills, rising gradually into the great western peaks and highlands, and crowned by Carn Suí Finn, 1,006 feet high, between Uachtar Ard and Dun, relieves the monotony of the south-west bank; and the bold flat-topped outline of Binn Shleibhe, rising 1,O19 feet, at the southern extremity of the Partraí range, commences on the north-west the eminences that shelter the upper waters, and slope down to the wooded point of Dun. Towards the extreme north may be seen, on a clear day, the bulky form of Neifin; and, out-topping the deep blue range of Partraf, the conical top of the Reek, or Cruach Phadraic, standing beside Clew Bay. And looking westward, as we pass between Inis Sean Bó and Inis Uí Chuinn, we obtain glimpses of the peaks of Beanna Beóla, or the "Twelve Bens" of Conamara the topmost of which rises to 2,395 feet. [fn6-1] Viewed frorn any point in Mayo or Galway, on the radius of a circle thirty miles in length, as well as from the midwaters of the lake itself, the mountains that margin the upper portion of Loch Coirib present an outline of great beauty, and when approached nearer fully vie with those of Cill Áirne and Gleann Garbh.
Leac Aimhréi [fn7-1] -- the uneven flagstone -- rising abruptly to a height of 1,307 feet from the south shore of the upper lake, apparently bare, and barren even of heather, forms a step in the ladder of elevations that lead by gradation to Shannanafeola, [fn7-2] in the background of the picture, and on by Mám Tuirc, Cuirceóg Mór, and Binn Bhan, which attains an elevation of 2,307 feet high. From the upper lake, in certain states of the atmosphere, we can see the outline of Maol-Riach that stands by the Atlantic, 2,688 feet high, over the entrance of the "Killaries," Caol-sháile Ruadh, and the rugged scarped sides of the mountains overhanging Mám on the north; and which, when lighted by autumn sunsets playing on the russet tints of the projecting crags, produce flecks of a burnished coppery hue of surpassing loveliness.
These brown hills slope gradually into the valley of Béal a' na breac, towards the west; and on their southeast they end abruptly in the dun of Caislean Circe, where the natural wood descends to the water's edge. [fn8-1]
The lake naturally divides itself into four portions: the upper or Conamara and Joyce Country portion, from Mám to Dún, placid, and untenanted by islands, save the bare rock on which the ancient Hen's Castle of the O Conors and O Flahertys stands; the narrow portion along Dubhros and Ceann Eibhir; the broad "old lake," crowded with islands, that forms its middle portion the rocky narrow gut that commences below Inis Uí Chuinn, and, turning to the south, by the ferry of Cnoc and Coill Beag landing, opens opposite Port Darach, into the broad expanse of the free lower lake that forms its fourth part, and sends its volume of waters through the Coirib and Mionloch Rivers, and the "Friars' Cut," into the Gaillimh, and through it to the ocean, at the estimated quantity of one hundred and twenty-six thousand cubic feet per minute in summer. In the deeper parts the bottom is mud, and in the shallow ones gravel and rock.
The great carboniferous mountain limestone formation occupies all the eastern and southern shores, and the lower portion of the western, in a line drawn from Uachtar Ard to Cunga, occasionally cropping to the surface, and forming stratified fields of smooth bare rock, or where it meets the water being honey-combed like a colander and in other places grooved by the action of water, ice or the attrition of harder bodies passing over it, generally in a S.E. direction.
The geology of the upper lake is of a totally different character. "At Oughterard," writes Mr. Kinahan, "the limestone becomes inter-stratified with sandstone; and immediately north of that village is replaced by granite, which at Glan gives place to fossiliferous Silurian rocks, that lie uncomfortably on older gneiss, schist, quartz rock and primary limestone, with dykes and masses of vario igneous rocks. On the north of the lake the geology is similar, fossiliferous Silurian rocks occurring at the north west end of the Mám valley and extending by Kilbride and Loch Mask to Ben Levi and Cong, under which, bounding Loch Corrib, are found gneiss, schist, and primary limestone; and, extending from Ben Levi Lodge on Loch Mask to Cong, the mountain limestone is found capping the primary rocks. In the small eastern tract between the River of Cong and the stream at Cross, a detailed list gives an epitome of nearly all the rocks entering into the structure of the district about Loch Corrib: carboniferous limestone, yellow sandstone and fossiliferous Silurian grits and shales in sandstone, and a variety of whinstone similar to Cotta's description of diallage rock.
"In the townland of Gortachurra there are carboniferous limestone, conglomerates, and diallage rock- and in that of Ballymagibbon South, and the islands adjoining, granite, gneiss, schist, fossiliferous Silurian grits and shale with igneous (diallage) rocks, and conglomerates. There is also, in a boss of primary rocks at the north-west corner of this townland, a small mineral vein containing lead ore, and a trace of copper and mundic.
"Good Silurian fossils, supposed to be of Upper Llandovery age, have been found at Currareavagh and New Village in Glan, on the west of the lake; also at Kilbride, on Loch Mask; Benlevi, more especially about Coolin Loch, and from that to Ashford Demesne; also in Lisloughery, and Gortachurra townlands, and the adjoining islets. West of Ashford rare trilobites occur; and in the carboniferous limestone in that demesne I was fortunate enough to find a Chiton, this being the second locality where chitons are recorded as found in the carboniferous limestone, the other being near Rathkeale, Co. Limerick. Black limestone, that will take a fine polish, and form good marble, occurs at Menlough and Anglingham, which quarries are at present worked; also at Rushveala and Cregg, near Oughterard. The serpentine, or green calcareous rocks, commonly called `Connemara marble,' are found in various places between Lissoughter and Clifden; and at present a company is about to open works on these at Lissoughter and Ballinahinch, whence it is intended to carry the blocks to the sea, and ship them at Cashel, near Roundstone.
"In the primary rocks, and in some of the carboniferous limestone adjoining the lake on the north, nort-west and east, mineral indications are frequent; but up to the present no deep workings have been carried out, therefore it is impossible to speak positively on the mineral resources of the district. In the carboniferous limestone, on east of the lake, lead and sulphur ores have been found in the neighbourhood of Ballycurran; and on the west of the lake, at Gortmore, Drumeillstown, Moyvoon, Portacarron, Lemonfield, Ardvarne, and Eighterard, and in most of these places small trials have been made on the veins. In all the primary rock the indications of lead, copper, and sulphur are more or less plentiful, and small trials have been made at Doorus, and other places on the north of the lake. At Leackavrea, and in Glann, Mr. Hodgson carried on mining operations for some time, and shipped some copper and sulphur ore from the port of Galway, having for the time a steamer plying on the lake to carry the ore to that port. During his operation the hills were burrowed in various directions, and more money spent than, if put in a deep working, would have proved whether the country contains good mines or not. The deepest working in the district is that at Glangowla, in Mr. O'Flahertie's mine, where large bunches of lead were found some years ago."
Bogs are scarce, and consequently fuel dear, on the south-east shore of the lower moiety of the lake, but plentiful on the west and south, and near Uachtar Ard supply good turf in púcáns, or large lug-sail boats, to the surrounding districts, and even to the town of Galway from whence they bring back cargoes of seaweed for manure. Turf is procured in three ways, accordng to the nature of the boggy material: by the down-cutting or foot slane, a sharp narrow spade, with a wing on one side; by the broad flat "breast slane," which cuts it out in front of the worker; and by raising, mixing, kneading, and forming into loaf-like lumps and then drying, the black mud of old cut-away bogs, and this is called "hand turf." There are several varieties of peat, either owing to the nature or age of the bog: as spadach, a whitish towy stuff, composed of the latest layer of uncompressed sphagnum; brown turf; and black or stone turf, the latter being often used, when charred, for forge purposes.
A project was entertained of opening up a free communication through the great chain of lakes--Coirib, Measca, and Cearra--with the harbour of Gaillimh and much expense was incurred in constructing a canal, locks, and other works for that purpose. Before they were completed it turned out to be a failure--for it was discovered, that like many other undertakings, the great canal at Cunga "would not hold water." [fn12-1]