These mountains are almost entirely carboniferous limestone. Much of the group is an elevated plateau, girt round on all sides, or nearly so, by limestone precipices, usually some hundreds of feet high, rising from a long steep slope of débris. The height of the cliff edges is about 1,600 ft., of which the talus occupies about two-thirds. The cliffs are fine, but consist largely of insecure blocks. Occasionally a fissure occurs, permitting ascent or descent, and some very steep ones are used on the south side of the range by turf-cutters.
In consequence of this formation the pedestrian may find himself following a long series of cliff edges, without being able to discover a way of descent. To examine the cliffs the proper course is to follow the sheep walk, which usually occurs at the base of the precipices above the talus. The walk across the range, from Bundoran to Sligo, is full of interest to a mountaineer, and the descent into the valley north of Sligo from King's Mountain is one that will never be effaced from his memory. It is not easy to find the passages leading down. The valley is a vast amphitheatre almost enclosed by cliffs, sheer and, including talus, about 1,000 ft. high.
It is always a pleasant experience to follow the crest of a line of limestone cliffs. Similar cliffs on a smaller scale are those of Moher and Aran, in the county Clare. It is probably owing to the fissures and laminations of the limestone, which afford a perfect system of internal drainage, that such cliffs are not only dry and clean, but also free from the gullies and valleys which, causing frequent ups and downs, sometimes render cliff walks extremely fatiguing—near Waterford, for example. Again, limestone grows no heather and forms little peat, so that the usual footing is clean grass sod—very pleasant after hummocky tussocks—and yielding 'quaas.'
For these mountains Kinlough is perhaps the most convenient centre. Manor Hamilton and Dromahaire may also be utilised, but Bundoran and Sligo, though the latter commands the beautiful Lough Gill, are too distant from the hills.
It may be mentioned here that there are various attractions in Northern Ireland outside the scope of this work. Fishing is always in reach, and of late years golf has thriven apace. No finer links exist than those of Portsalon, Rosapenna, Portrush, and Newcastle, and there are many others of growing excellence.
Ben Bulben is famous for its mountain flora, a valuable report on which, by Messrs. Barrington and Cowell, has been published by the Royal Irish Academy.
Mayo. Here are the highest mountains in the west of Ireland, Mweelrea (2,688 ft.) and Nephin (2,646 ft.)
Nephin is a round, isolated lump of quartzite, becoming schistose, rapidly disintegrating on a northern spur, where the only declivities occur. For the mountaineer it is both distant and unattractive, but on clear days—which are rare—there is an extensive view.