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[Communicated by the permission of the Director-General of the Geological Survey.]
The dependence of the physical features and scenery of a district upon its geological constitution is a subject which has often been treated, and an admirable discussion of it, as applied to Scottish mountains, has indeed already appeared in this Journal. (1) The special aspect of the matter as it affects climbing has, however, rarely been touched, and a few remarks under this head concerning the finest mountain group in the British Islands may therefore be of interest. Although the writer cannot claim to be regarded as a climber, he has become familiar with the Cuillins in the course of some years' work in the service of the Geological Survey of Scotland.
With the exception of certain older and underlying strata, which appear here and there along the coast, the central part of Skye is composed exclusively of igneous rocks - i.e., of rocks consolidated (usually crystallised) from a state of fusion. They are all of Tertiary age, and thus fall within the latest of the great time-divisions of geology. The geological history of the district consists indeed of two chapters - the record of early Tertiary times, when these rocks were formed, and of later Tertiary times, when they were carved into their present forms by the erosive action of running water and finally of ice. The extent of this erosion has been enormous, thousands of feet of rock having been removed from the mountain district; and the existing surface-relief has been evolved during this process on the general principle of the more durable rocks determining the more prominent features. The topography is thus traceable only in an indirect way to the volcanic and allied agencies which gave birth to the constituent rocks, and all comparisons of the mountains with volcanic cones, and of the corries with craters are purely fanciful.
The principal events in the first chapter of the record fall under three heads: 1.) The outpouring of vast floods of lava, which consolidated as basalt, extending over about two-thirds of Skye, and once prolonged even farther (as appears from these rocks terminating abruptly in high sea-cliffs). This lava was not poured out from any great volcano like Etna, but welled up through innumerable fissures, as in Iceland, many small flows from different fissures overlapping one another. 2.) The intrusion or injection among the basalt lava-flows of new material, not very different in chemical composition, but assuming on consolidation the more coarsely crystalline form of gabbro. This difference is due to the fact that the molten material did not reach the surface, but cooled only gradually beneath the weight of a great thickness of basalt, since removed. The gabbro consists of many distinct intrusions, but the whole forms an irregular cake-like mass with basalt below and originally also above it. 3.) The intrusion in similar fashion of molten material of different composition, which crystallised as granite. The granite forms a cake-like mass underlying and partly cutting into the gabbro, but also extending farther eastward. These three groups of rocks are represented roughly by three divisions of the district: - 1) The Moorland Hills; 2) the Cuillins, including the Blaven Range; and 3) the Red Hills; and these represent three strongly contrasted types of scenery.
The differences so conspicuous to the eye depend, however, only in part upon the dominant rocks mentioned above. They are largely related to the very numerous minor intrusions in the shape of parallel sheets and dykes of basalt and diabase, which belong for the most part to a time somewhat later than the last of the events just enumerated. Thus, the strongly terraced appearance of the slopes of the Moorland Hills, and the flat tops of many of them, are due to the great number of intruded sheets or "sills" forced in between the lava-flows, and, by their superior durability, giving rise to salient features. The deep gullies, in which the burns often flow down the slopes of these hills, are often made by the decay of nearly vertical dykes by which the lavas were traversed. A glance at the map shows a strong tendency of the burns to run in straight lines, and to take a N.N.W. or S.S.E. direction, this being the usual bearing of the dykes by which the burns have been guided. The granite is almost free from sheets and dykes, and so the smooth flowing outlines of the Red Hills are determined merely by the crumbling and destruction of the granite itself. Where dykes do occur, they tend rather to project above the granite surface than to form gullies.
The Cuillins exhibit more complexity, and, from their interest to climbers, demand a more detailed notice. It is important to observe that the range extending from Blaven to Belig is geologically and physically a part of the Cuillins, though to some extent separated from the main group by the granite of Marsco, Ruadh Stac, and Meall Dearg. The unique nature of the Skye mountains, both from the scenic standpoint and as a field for climbing, is largely due to the fact that nowhere else in Britain is found so large an area of gabbro. Not only is this rock extremely hard and tough, but also the unequal weathering of its component minerals gives rise to extreme roughness of surface on the small as well as the large scale. Excepting only where the rock has been polished by ice, it gives excellent holds for hand and foot, and so affords security on faces of quite sensational steepness.
Varieties of the gabbro differ somewhat in this respect, the most remarkable being perhaps the rusty-weathering rock which occurs on Sgurr Dubh na Dabheinn, Caisteal a' Garbh-choire, and a few other places. Although gabbro is the dominant rock of the Cuillins, there is also a considerable amount of basalt, belonging to the lava-group, in the form of lenticular and irregular patches entangled among the gabbro. The intense heat to which it has thus been subjected has greatly altered its character, making it much harder and more resisting than the corresponding basalt of the moorlands; but it is in general much more brittle and splintery than the gabbro, and affords less secure holds. The upper parts of Alasdair, Tearlach, and Mhic Coinnich consist of basalt, and patches, sometimes of considerable extent, occur in all the western corries and on the branch ridges which divide them, as well as on Gars-bheinn, Bruach na Frithe, &c.
A conspicuous feature in almost any view of the Cuillins is the stratified appearance of the slopes, sometimes carried so far as almost to suggest a rough stairway. This is produced by a great number of parallel sheets of basalt and diabase intruded in such a way as to intersect alike the gabbro and its enclosed patches of basaltic lava. At a given locality these sheets have all roughly the same inclination, usually 20º to 40º to the horizontal, while comparison of different localities shows that they "dip" or incline always towards the centre of the gabbro area. Thus the dip is to the south on Sgurr nan Gillean, east on Sgurr Dearg, north on Sgurr na Stri, and west on Clach Glas. To the climber much depends on these inclined sheets, and especially upon their relation to the trend of the ridge at any place. For example, the western part of the main range, say from Ghreadaidh to Dearg, runs on the whole north to south, while the basalt sheets are inclined eastward. In these circumstances the crest-line is often made by one of the sheets, and the two slopes of the ridge have strongly contrasted characters. On the west side the outcropping ledges present good holds, and form sometimes a kind of natural staircase, besides affording convenient traverses (e.g., on Mhic Coinnich).
On the east side of the ridge the projections slope the wrong way, and climbing is in general much more difficult. To take another illustration, Sgurr a' Mhadaidh has a roughly east to west trend, so that the inclined sheets run athwart the ridge; consequently there is no continuous ridge-line, but a succession of summits, each having a steep drop to the west and a relatively smooth, gentle slope to the east. The rough and broken character of the Sgurr Dubh Ridge results partly from similar conditions.
The dykes which traverse the gabbro and other rocks in a nearly vertical direction are a very important factor in the detailed topography of the mountains. The basalt and diabase of which they are composed are more readily destructible by atmospheric agents than the gabbro, and hence a dyke is often indicated by a trench or fissure. Where a ridge runs athwart the direction of the dykes, it may thus be divided by deep gaps, as in the Pinnacle Ridge of Sgurr nan Gillean. Where, on the other hand, a ridge runs in the direction of the dykes, it sometimes exhibits a vertical face, which represents the bounding wall of a dyke which has been destroyed - the Bhasteir precipice is partly due to this cause. The "Inaccessible" is a mass of gabbro left standing between two such vanished dykes. Deep gullies caused by the weathering away of dykes are seen in Sgurr a' Fheadain, Druim nan Ramh, Sgurr a' Coir' an Lochain, Blaven, and many other places. In the same way arise chimneys such as those in the Bhasteir Tooth and Sgurr a' Mhadaidh. Not all the dykes give rise to gullies. Some are welded in a peculiarly intimate way to the gabbro which they traverse, and do not weather away easily. Again, a large proportion of them are earlier than, and therefore are cut by, the inclined sheets; as a rule only the later dykes, which cut the sheets, give rise to conspicuous gullies.
Although in the carving out of the relief of the district running water has played a vastly more important role than ice, the latter agent, having imparted the final touches to the process, is responsible for many of the surface features. Not only were all the valleys occupied during the Great Ice Age by glaciers, but it is probable that at the stage of maximum glaciation even the highest summits were buried under ice.
No finer examples can be found of the rounding, smoothing, polishing, and scoring of rock-surfaces by ice action than are displayed about Loch Coruisk and Loch na Creitheach, and in many of the corries of the Cuillins. An extreme case is Coir' a' Ghrundda, the bottom of which is, from this cause, almost impassable. The amphitheatre form usually assumed by the head of a corrie is a result of glacial erosion. So, too, is the longitudinal division of a corrie into two or more portions separated by a steep drop: this is well seen in Coir' a' Ghrundda, Coire Labain, Lota and Harta corries, and others. Another feature connected with the glaciation is the great extent of coarse screes in some parts of the mountains. At a late stage of the Glacial Epoch, when the higher mountains stood out above the ice, these exposed peaks were subjected to the action of frost for a long time, and a great accumulation of fallen blocks resulted from this action. Thus arose the splintered summit-ridges, in such sharp contrast with the rounded rocks below, and thus originated probably the great bulk of such screes as those of Coireachan Ruadha and Garbh-choire. These screes are naturally in greater force on the more difficult side of the ridge, which may thus become the easier side for passes through the gaps.
Much of our information concerning the topography of the Cuillins is due to records in this Journal, and especially to Dr Collie's list of altitudes (Vol. II., p. 168), and Mr Douglas' fuller compilation of names, heights, and positions of peaks (Vol. IV., p. 209), supplemented by a map subsequently issued. Having derived much assistance from these and other items in the Journal, I gladly respond to Mr Douglas' request for corrections and additions.
In the following notes I include such of the altitudes in my note-books as may be of interest to climbers. All are taken with the aneroid, and make therefore no pretence to accuracy. For comparison, I quote in parentheses altitudes already published in the Journal, the sign = being employed to denote exact agreement. Agreement, exact or approximate, may be taken as confirming the earlier figures, and any considerable discrepancy as making a case for further observations.
A few remarks on nomenclature are given in their places. The S.M.C. has done good service in providing names for a number of prominent peaks, and those given on Mr Douglas map may be regarded as established. There still remains certain summits which seem worthy of distinct names, including one which attains the dignity of 3,000 feet - a distinction shared by some fifteen peaks in the Cuillins, besides the outlying Blaven.
One general criticism of Mr Douglas' list, offered with due deference as from a non-climber, concerns the descriptions "easy," "sheep-pass," &c, as applied to passes in the Cuillins. If a pass is to mean, as it surely should mean, a place where any able-bodied man may, without serious difficulty, go up on one side and down on the other, it will properly be described in the language of the ordinary pedestrian, not of the cragsman. Remarks on some of the cols from this point of view will be found below. They may even be of service to climbers as indicating the easiest descent from the ridge in bad weather, and with this object the route down is noted where it is likely to be of help. A map marking these and other pedestrian (not climbing) routes among the mountains, with the speediest ways of access to the several corries, will be deposited with the Editor of this Journal.
The only new altitudes I have here are:
Bealach Coire nan Allt Geala (between Sgurr nan Gillean and Sgurr Beag), 2,360.
Bealach a' Glas-choire (between Sgurr Beag and Sgurr na h-Uamha), 2,050. [Both easy passes.]
[The peak "called something which sounds like Sgurr a' Beoch." has proved an insoluble problem to the Gaelic scholars. On Forbes' little sketch-map of 1846 the small corrie immediately N.E. of this peak is called "Corry Beaoch," and comparison with the text shows this to be a misprint for "Corry Reaoch," evidently a phonetic spelling for Coire Riabhach, of which this small corrie is a branch. This seemed a possible solution of the mystery, but it turns out to be merely an odd coincidence, for Mr Colin Phillip tells me that "Beoch" was simply a mistake for "Beag."]
[The name doubtless suggested by the resemblance to a headsman's axe. This and Druim nan Ramh (gunwale with rowlocks) are almost the only picturesque names among the crowd of "Dubhs," "Deargs," &c]:
Bealach a' Bhasteir.
Bhasteir Rock, 3,050 (3,030, Collie).
Bhasteir Tooth, about 3,000 (2,900, Douglas).
Dip, 2,865 [easy pass beween Coir' a' Bhasteir and Fionn Choire].
Sgurr a' Bhasteir, 2,950 (2,900, Douglas).
Dip, 2,030.
Meall Odhar, 2,060.
Bealach a' Leitir, 2,940 (2,700, Douglas; perhaps a clerical error for 2,900). [Easy pass. Descent into Lota Corrie; keep left side of gully (scree), the other side (rock) in ascending. Going down from Lota Corrie, keep to burn, on left side of it.]
Sgurr a' Fionn Choire, 3,050 (3,000, Douglas).
Dip, 2,970.
Bruach na Frithe (3,143, T.S.). Breach na Frithe Ridge runs N.W. to Meall a' Tobar nan Uaislean (1,682, T.S.), and Bealach a' Mhaim, 1,150.
On Mr Douglas' map the name An Caisteal is attached to the southerly summit of Bruach na Frithe; it belongs to the more detached peak some 200 yards farther S. The S. summit of Bruach na Frithe might well be named Sgurr na Bhairnich (i.e., Limpet). In the part of the range which next follows, and especially about the peaks of Bidein Druim nan Ramh and their connections, the O.S. map is far from accurate. (2) Mr Pilkington's rough sketch-map is in some points more correct. I have few altitudes in this neighbourhood. Sgurr na Fheadain is about 2,215, and the dip just S.E. of it 2,100. These are on the short branch ridge which divides Coir' a Mhadaidh on the N.E. from Tairneilear on the S.W. [Certain writers in this Journal have taken exception to these last two names, and even proposed to interchange them, so as to bring Coir' a' Mhadaidh next to Sgurr a' Mhadaidh; but the O.S. map certainly follows local usage, the ultimate court of appeal. It is probable that the former name covered originally not only the small corrie, but its continuation, now called Coire na Creiche (a name of suspiciously new appearance).
The conspicuous mountain above this large corrie would, according to common practice, be styled Sgurr a' Mhadaidh, and this name, too, may once have been more comprehensive; indeed the old O.S. map makes it embrace Bidein and the Fheadain Ridge.]
Bealach na Glaic Moire has two branches - the N.E. one 2,510 (= Collie), the S.W. 2,515. [Easy pass. Descent into Tairneilear; keep well up to right until the deep gully from Bidein is crossed and a second gully reached; then go down on top of screes of Sgurr na Fheadain. Descent into Coruisk, use N.E. branch of pass, and for ascent the other.]
Of Sgurr a' Mhadaidh I have only verified the altitudes of the two western summits. From the northerly one of the two the Thuilm Ridge runs off to the right, N.W., with dip, 2,515. [Easy pass. Descent into Coir' a' Ghreadaidh; from lowest point of col go down about 20 or 30 feet, and then turn sharply to left along a sloping ledge. Descent into Tairneilear; go 70 or 80 yards along ridge towards Sgurr Thuilm, then down, bearing to right.]
Bealach, 2,760 (= Collie). This is the "An Dorus" of the O.S. [Easy descent into Coir' a' Ghreadaidh. Descent into Coir' an Uaigneis troublesome owing to slippery slabs; in corrie take left side of burn.]
Gap (the "An Dorus" of Douglas, a term which seems to be applied generically to any narrow pass; this may be called Macleod's Gap for distinctness), 2,890 (= Collie). [Easy descent into Coir' a' Ghreadaidh by scree-gully.]
The O.S. map is far from correct in the part of the range next following. Sgurr a' Ghreadaidh has not a round top, but a narrow crest-line with two summits, 3,190 and 3,180 in order (= Collie), besides a wart-like prominence N. of the chief summit. From this prominence a spur runs off to the right, N.W., with successive points at about 2,870 and 2,770. From the S. summit of Sgurr a' Ghreadaidh a shorter spur runs off to the left, E.S.E., dividing Coir' an Uaigneis from Coireachan Ruadha.
Dip, lowest point of ridge, 2,810 (2,800, Collie). [Not a pass, but possible descent into Coir' a' Ghreadaidh.]
Small prominence on ridge.
Dip, 2,930.
"North top, Sgurr na Banachdich," 3,040 (= Collie). [This peak seems to deserve a distinctive name, especially as Sgurr na Banachdich is otherwise well provided with summits. Mr Colin Phillip, who has already stood sponsor for more than one peak, suggests "Sgurr a' Leighiche," the Doctor's Peak, in honour of Dr Collie. (3)] From here a short spur runs off to the right, Ghreadaidh.
Bealach (2,920, Collie). [Descent into Coir a' Ghreadaidh; first a short rough scramble; then easy, turning to right round spur just mentioned. Descent into Coireachan Ruadha not difficult.]
Sgurr na Banachdich (3,167, T.S.). The branch ridge of Sgurr nan Gobhar runs off to right, W., terminating at cairn (2,047, T.S.). From this ridge, at about 2,700, the shorter spur of An Diallaid runs off to N.W.; saddle 2,365, summit 2,375. [Easy descent from Sgurr na Banachdich by Coir' an Eich. Note that the "pock-marked" rock occurs in Coire na Banachdich, the mountain being, of course, named after the corrie.] After the "third" and "fourth" tops of Banachdich comes
Dip, 2,865 [alternative pass].
S. termination of Banachdich part of range, 2,900. From here a spur, about 2,650, runs off to left, E.N.E., dividing Coireachan Ruadha into two smaller corries. [This spur is conspicuous as seen from the E., owing to a broad horizontal band of orange-yellow, with darker rock above and below. It might be named Sron Bhuidhe.]
Bealach Coire na Banachdich, 2,815 (2,810, Collie), not as marked on map, but in next gap to S. [Easy pass. Descent into Coire na Banachdich; avoid obvious way by central gully, and keep well up to left until reaching another gully, which comes down from Sgurr Dearg. Descent into Coireachan Ruadha over easy screes; keep to right until past some smooth rocks at about 1,800.]
Gap just before precipice of Dearg, 2,940. [The map is faulty about here, the high part of the Dearg Ridge being carried too far northward, and the westward sweep to the gap and pass not indicated.]
runs S. from summit cairn (3,234, T.S.) to a point 3,165; then after a dip, 3,135, runs W. from a point 3,160 to a marked summit (3,042, O.S.), continues to a point 2,535, from which a short spur runs off to N.W., and terminates at the cairn (2,012, T.S.).
The O.S. map immediately E. of the Sgurr Dearg Ridge is very difficult to understand. The Inaccessible Pinnacle, which seems to be only about 100 feet distant from the summit cairn, is not marked, and the strongly accentuated point on the map to which Mr Douglas has attached the name has apparently no existence on the ground, though there is a small pinnacle at or about the site. The other point on the map, farther east, corresponds pretty nearly with the position of the nameless peak, 3,155, below and S.E. of the Inaccessible. [Easy descent from Sgurr Dearg to Coire Labain over screes, skirting W. base of Inaccessible and peak just mentioned, and bearing to left until near the pass. Avoid the scree leading more directly down towards the corrie.]
Watershed passes N.E. of the Inaccessible and its anonymous neighbour to:
Bealach Coire Labain, 2,680 (2,690, Collie). [Descent into Coire Labain easy. Descent into Coireachan Ruadha troublesome for the first 300 or 400 feet (until joining the Coire na Banachdich Pass), having rotten rock at top and smooth slabs at bottom; the latter may be avoided by keeping away to left.]
Gap about 120 yards S.E. of Bealach; lowest point of ridge, 2,620; not a pass.
Sgurr Mhic Coinnich.
Dip, about 2,935, not checked. [Possible pass. Descent into Coire Labain, first a short rock-climb, then a scree-gully joining the Alasdair Stoneshoot at about 2,500. Descent on other side on to col of Sgurr a' Coir' an Lochain presents no difficulty.]
runs N.E. and then N:
Dip, about 2500. [Easy pass between Coir' an Lochain and Coireachan Ruadha. Going down from Coir' an Lochain, leave burn where it begins to descend steeply, and strike over rocks to right, N.E., until a grassy ledge is struck; a zigzag along such ledges leads easily to the head of Loch Coruisk.]
Sgurr a' Coir' an Lochain, chief summit, about 2,575 (wants checking).
Gap.
Sgurr a' Coir' an Lochain, N. summit, 2,440 (2,450, Douglas).
Gap, head of Alasdair Stoneshoot, 3,150 ( = Collie). [Easy descent to Coire Labain tarn; no way to Coir' a' Ghrundda.]
Sgurr Alasdair, 3,275 (= Collie).
Dip, 3,010 (3,050, Collie). [Easy pass; on Coire Labain side joins Alasdair Stoneshoot.]
Sgurr Sgumain, chief summit (3,104, T.S.), with a short spur running W. into Coire Labain.
Dip, head of Sgumain Stoneshoot, E. branch 2,770, W. branch 2,720. [Easy pass. Going down to Coire Labain, choose E. branch of stoneshoot; keep to left at bottom.]
Sgurr Sgumain lower summit, just W. of above dip, 2,780.
The lower cairn (2,507, T.S.) is not on any true summit.
Gap (" Alasdair-Dubh Gap"), not a pass.
Bealach, 2,830 (2,810, Collie). [Descent into Coir' a Ghrundda easy. Going down from Coir' a' Ghrundda, leave the burn where it turns to left after first steep descent, and, passing just below a rough bit of scree, keep up on right side of corrie, thus avoiding all slippery slabs. Descent into Coir' an Lochain rough.]
I have no altitudes to record for the Sgurr Dubh ridge. The summit of Sgurr Dubh Mhor I should place farther west than it is marked on Mr Douglas' map.
Dip, 2,560. [Bealach a' Garbh-choire is not here, as marked on map, but 200 yards farther S.]
Bealach a' Garhh-choire, 2,620 (= Collie). [Easy on both sides, but of little use as a pass owing to the extremely rough scree, a mile long, occupying all the floor of Garbh-choire.]
Sgurr nan Eag (3,036, T.S.) has a nearly level summit ridge running S.E. for 300 or 400 yards; to give it two tops is rather a needless refinement.
Dip, 2,555 (2,550, Collie). ["Sheep pass" of Douglas. I cannot regard it as a real pass, since there is no direct approach from Coire nan Laogh -.without climbing. Going down to Garbh-choire, bear to left for the first 100 feet.]
Sgurr a' Coire Bheag, 2,875 (2,870, Collie), with branch ridge running off to left, N.E., dividing Garbh-choire from Coire Beag.
Dip, 2,760 (2,750, Collie). [A possible pass. Descent into Coire nan Laogh; at first keep well up on slopes of Gars-bheinn. Descent into Coire Beag difficult at first, keeping close under Sgurr a' Coire Bheag; then bear well to right to avoid slippery slabs.]
Gars-bheinn (2,934, T.S.), with small peak on ridge immediately W. of summit, 2,890.
The six-inch O.S. map seems to be fairly accurate here, except that the summit of Gars-bheinn is not sufficiently isolated, nor the S.E. precipitous termination of Sgurr nan Eag indicated, while the burns in Coire nan Laogh are unrecognisable. The one-inch reduction has been made with gross carelessness. Gars-bheinn being placed 200 yards too far to the S.E.
From a point a little S. of summit a branch ridge runs off to left, N.E., dividing Coire Beag from Coir a! Chruidh, and terminating in a prominent crag, about 2,125.
Prominent point on ridge, about 2,665. A little beyond this another branch ridge runs off to left into Coir' a' Chruidh, terminating in a knoll at about 1,850.
Ridge continues E.S.E. with a prominent point at 2,485, and another (termination) at 2,275.
In conclusion, I give approximate altitudes for some of the mountain tarns:
Coir' a' Bhasteir, 2,250
Coir' a' Ghrundda, 2,220
Coir' an Lochain, 1,815
Coire Labain, 1,805
Loch an Fhir Bhallaich, 895 ["Loch of the Spotted Folk", probably trout].
(1) Sir A. Geikie, Vol. IV., p. 113.
(2) The worst errors of the old six-inch map are corrected in later issues, but the one-inch map is still hopelessly misleading here.
(3) Or, on the model of Alasdair and Tearlach, we might say Sgurr Thormoid (Norman's Peak).
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