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Scottish Geographical Magazine Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rsgj19 The sculpture of the goat mountain group Frederick Mort M.A., B.Sc., F.G.S., F.R.S.G.S. Published online: 27 Feb 2008.

To cite this article: Frederick Mort M.A., B.Sc., F.G.S., F.R.S.G.S. (1911) The sculpture of the mountain group, Scottish Geographical Magazine, 27:12, 632-643, DOI: 10.1080/00369221108734086 To link to this article: http://dx.doi.org/10.1080/00369221108734086

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in its infancy, their prose narrative often reaches the height of clear simplicity. It is strange, however, that while in the realistic novel of Wineland, the Fortunate Isles have evidently been intermixed with the discovery of America by the Norsemen, the same happy land far out in the ocean west of Ireland was again the luring goal, when the American continent was rediscovered from England. " On the ocean that hollows the rock where ye dwell, A shadowy land has appeared, as they tell; Men thought it a region of sunshine and rest, And they called it 0 Brazil—the isle of the blest. " From year unto year, on the ocean's blue rim, The beautiful spectre showed lovely and dim; The golden clouds curtained the deep where it lay, And it looked like an Eden, away, far away !" It was to find this Fortunate Isle, Brazil, that Bristol sent out expedi- tions in 1480 and later. It was in search of this island of happiness that John Cabot left Bristol in 1497, and he found the continent of America for England. The great illusions have always played an important part in the history of Mankind.

NOTE.—The two illustrations in this paper are drawn from Dr. Nansen's book, In Northern Mists, and for the use of the blocks we are indebted to the courtesy of Mr. W. Heinemann, the publisher.

THE SCULPTURE OF THE GOAT FELL MOUNTAIN GROUP.

By FREDERICK MORT, M.A., B.Sc., F.G.S., F.R.S.G.S.

(With Map and Illustrations.) THE interpretation of the scenery of an area is one of the most fascinating problems in science, particularly when the investigator is dealing with a district so impressively beautiful as North Arran. The features of a landscape may be regarded, in mathematical language, as functions of three independent variables, structure, process, and stage. Structure involves what is generally included under the geology of the area—the nature of the rocks, their arrangement, the way in which they have been affected by subsequent movements—all these have an impor- tant effect in determining the combination of surface features that we know as scenery. Again, the appearance of the landscape depends on the nature of the processes that have been at work. Wind and water Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 carve in very different ways. Ice-work is totally different from either. Just as in the sculpture of the human figure the classic sweetness and grace of Praxiteles is absolutely unlike the powerful impressionism of Rodin, so in the carving of a landscape, nature's sculptors work each THE SCULPTURE OF THE GOAT FELL MOUNTAIN GROUP. 633

in his own characteristic style, recognisable at once by the trained eye. Finally, the stage to which the process has been carried is of great importance. If the erosion of an area is in an incipient stage, the forms produced are very different from those resulting from long-continued denudation. The stage at which erosion has arrived is graphically expressed by the American use of the terms youth, maturity, and old age. The task of the geographer is by examination of the existing land- scape to deduce the original structure, to state what agencies have shaped the finished product now before his eyes, and to decide to what stage their operations have been carried. Obviously the task must often be of extreme difficulty, for one agent obliterates the work of another; it resembles the deciphering of a palimpsest which has been written on again and again. Hence, while many deductions may be soundly based, we are reduced at times to mere conjecture. Goat Fell is the best known of a group of mountains in North Arran, all of which lie within a circle five miles in diameter. Although not a single peak reaches 3000 feet in height, yet by reason of the noble sweep of their outlines, their great precipices and deep valleys, their splintered crests, and the general impression of grandeur produced by the group, they are more worthy of the term mountains than many peaks much superior in actual height. With the exception of Cir Mhor, all the peaks are the culminating points of high and narrow ridges. This arrangement is shown in the map. The ridges radiate out from Cir Mhor in a star-fish-like fashion. To the north runs the ridge of the Castles, swinging to the north-east, and terminating in Suidhe Fhearghas. To the east is the ridge that ends at Cioch na h-Oighe. South-east is the Goat Fell ridge which throws off two easterly spurs culminating in Am Binnein and Meall Breac. South-west from Cir Mhor runs the ridge of A' Chir, which divides into two, the easterly branch forming Beinn a' Chliabhain, the westerly rising into and Beinn Nuis. Between these ridges lie deep glens, coires, and passes, which make North Arran a region of inexhaustible attraction to the student of nature or the mountain wanderer. and Glen are by far the largest of the glens. The other valleys or coires referred to in the text are shown in the map. The structure of this district is fortunately very simple. The whole area consists of coarse granite crossed by numerous dykes of igneous rock. Round the edge of the granite there outcrops a band of schists and sedimentary rocks, but all the high peaks and ridges, and the deep valleys and coires occur in the granite. The ridges of this area are extremely rugged and serrated, giving a character of wildness to the scenery found nowhere else in Arran. The hills to the west are much smoother and softer in outline. Sir A. C. Ramsay in his Geology of Arran (1841) attributed this difference to the fact that the western area consists Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 of fine granite, which is softer than the coarse, thus presenting smoother outlines, and since his time this explanation has been almost universally accepted. That the difference in the grain of the rocks has had some little effect VOL. XXVII. 2 Z Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 FIG. 1.—Map of the Goat Fell area. Scale one inch to a mile. Reproduced with the sanction of the Controller of H.M. Stationery Office. THE SCULPTUEE OF THE GOAT FELL MOUNTAIN GROUP. 635 may be admitted, but it is by no means the dominating influence. For Meall nan Damh occurs in coarse granite, yet no hill in North Arran is smoother in outline. Beinn Bhreac and are within two miles of each other, they are equal in height, and there is practically no difference in roughness of outline between the two, yet one is in the fine granite, the other in the coarse. The same thing holds for the two peaks of Sail Chalmadale. The contrast between the gashed, serrated outlines of the Goat Fell group and the tamer scenery farther west is primarily due not to a difference in structure, but to a difference in process, to a difference in

FIG. 2.—Looking up Glen Sannox. The peaks shown are, from left to right, Cioch na h-Oighe, Cir Mhor, the serrated ridge leading to , and on the extreme right Suidhe Fhearghas. (Geological Survey Collection.)

the eroding agent at work or in the stage to which the process has been carried. Serrations and peaked contours occur when aretes or sharp edges of any kind are produced by the carving tool. We know that the Goat Fell group was a centre of independent glaciation, and most of the characteristic features of the scenery of the area are, as we shall see, due to ice-work. When a broad-backed, rounded ridge is narrowed into an arete by glaciation in the valleys on each side, the summit almost invariably becomes gashed into the serrated, Alpine character so familiar in many parts of the Highlands of . Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 Two other causes have helped to produce the ruggedness of the Goat Fell group of mountains, the jointing of the granite, and the presence of dykes of igneous rocks. Hardly one of the ridges could be called smooth, yet often on the same ridge there is a sudden increase or diminution in 636 SCOTTISH GEOGRAPHICAL MAGAZINE. ruggedness. In many cases this can be traced to a change in the direc- tion of the dominant planes of jointing of the granite. For example, the south ridge and the actual summit of Goat Fell are fairly smooth in outline, but the ridge running north is strongly serrated; and this corresponds to a rapid change in the direction of the dominant joint planes from nearly horizontal to an angle of forty-five degrees and then to nearly vertical. The ridge along the north-west side of Glen Sannox shows the same change. At Suidhe Fhearghas there is no strongly marked jointing, and the outline is fairly smooth. On the other hand, along the jagged, toothed part of the ridge between Ceum na Caillich and Caisteal Abhail the jointing dips at a high angle.

Fio. 3.—Upper Glen Rosa. The mountain at the head is Cir Mhor. The deep cleft of Ceum na Caillich is seen to the right of Cir Mhor. {Geological Survey Collection.)

Most of the very deep clefts in the ridges are due to the crossing of a dyke that has weathered out more rapidly than the enclosing granite. Ceum na Caillich (the Auld "Wife's Step) is formed by the erosion of a large dyke, as Eamsay long ago recognised. Again, to quote Gunn's words (Geol. Survey Memoir), "A'Chir, the most serrated mountain in the island, is the one most traversed by dykes." Yet it must be remembered that dykes and joints occur in the fine granite without producing markedly rough features. Dykes and joints are only potential causes of serration. Before becoming actual causes they must be given a proper Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 locus. They come into play only when crossing sharp aretes that have been formed by other agents, in this case by the independent glaciation of the Goat Fell group. In the Goat Fell region, as in other parts of Arran, the hills rise THE SCULPTURE OF THE GOAT FELL MOUNTAIN GROUP. 637 sharply from a well-marked plateau. This is one of the most remarkable features of North Arran, and yet it has received hardly any notice in geographical or geological literature. It varies from about 900 feet to about 1100 feet above sea-level, but as a rule it is very nearly 1000 feet above the sea, and will therefore be referred to as the thousand-foot platform. In places it is perfectly flat for long distances. Looking from the north spur of the Castles one sees an absolutely level tableland stretching for a couple of miles from An Tunna (1002 feet), past the Clachan (1013 feet), to Torr Nead an Eoin (1057 feet), the surface diversified only by gleaming pools of water. East and south of Goat Fell again the platform is very plainly marked between Maol Donn and

FIG. 4.—Goat Fell from Bay. In the middle distance the thousand-foot platform is seen running right across the photograph. (Geological Survey Collection.)

Glenshant Hill. On the other side of Glen Eosa it envelops the south ridge of Beinn Chliabhain, and then is splendidly developed round the southern slopes of Beinn Nuis. It can be traced also to the west, but there it passes out of the special area at present under consideration. Many of the North Arran lakes (Loch Tanna, Dubh Loch, Loch Nuis, Loch nam Faoileag, and a host of smaller pools) lie upon its surface, their levels in all cases being just over 1000 feet above the sea. The origin of the thousand-foot platform presents an interesting problem. The only reference to it made in the Geological Survey Memoir is Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 as follows : " These rocks (the schists) often occupy a kind of plateau rising to over 1000 feet in the district reaching from Glenshant Hill to "." From this remark one might conclude that the platform is a structural feature due to the outcropping of the schists at a uniform 638 • SCOTTISH GEOGRAPHICAL MAGAZINE.

height around the granite. But this is by no means the case. The level surface of the platform is an erosion feature that has been cut in rocks of very different kinds. The plateau is formed not only by the schists but by the Old Eed Sandstone, the Triassic rocks, and the granite itself. It marks a former base level of erosion later in time than the 3000 feet base-level from which the Highlands of Scotland have been carved. The thousand-foot platform is pre-glacial, for it is overlaid by boulder-clay and moraine stuff, and has been eroded by the glaciers moving down the main valleys; but it is of later age than the granite, since it is partly carved from that rock. The granite has now been

FIG. 5.—The valley of the White Water (Coire Lan) seen from above. The small stream is a "misfit" in the wide, deep valley. Part of the thousand-foot platform is seen beyond the valley mouth.

demonstrated to be of Tertiary age, so that the platform may be assigned to late Tertiary times. The drainage of the thousand-foot platform is remarkably immature. The plateau has hardly been touched by stream erosion. Most of it consists of a level marsh, the surface of which is scarcely incised at all by the few streams that cross it. It presents a perfect example of extremely youthful topography, and this also indicates a comparatively recent date of origin. When we consider the total amount of erosion accomplished in Tertiary times we cannot help being convinced that this Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 peneplain must have been formed practically at the close of that epoch. Does the thousand-foot platform represent a peneplain of sub-aerial erosion, or is it an example of a shelf of marine denudation ? Formerly all such plateaux were referred to marine action, but in recent years, THE SCULPTURE OF THE GOAT FELL MOUNTAIN GEOUP. 639 following the American school of physiographers, the tendency has been to class them as of sub-aerial origin. In Arran the platform is so level that if it is an old land, surface reduced to a peneplain then the stage of the denuding processes involved must have been one of extreme old age, the very end of the cycle of erosion. The profile of the land surface should therefore show a very gentle, continuous curve from the centre to the sea. But this does not agree with the observed facts, for round the inner edge of the platform there is a sudden rise to the mountains of the interior. This is more in harmony with the belief that we are dealing with a peneplain of marine denudation. The valleys of the Goat Fell mountain group are particularly beautiful. The upper part of Glen Rosa, at the head of which Cir Mhor seems to mount guard, is a splendid bit of composition, while Glen Sannox in some aspects is distinctly grander. The rounded swell of Cioch na h-Oighe (the Maiden's Breast) forms a fine contrast to the splintered ridge that runs past Ceum na Caillich to the Castles. The valleys are deep but widely opened, the cross-profile sweeping

50OO •Goat Fell -

2IOO s-Chll.bK«m

20OO / / 5oo i5CK>

IOOO IODO

Boo

FIG. 6.—Section across Glen Rosa. Vertical and horizontal scales the same. The characteristic catenary curve is well shown.

from one ridge to the other in a beautiful catenary curve. The sides are smooth and uninterrupted by tributary glens. As one ascends a glen to its head the valley sides do not contract as normal valleys should, but rather widen, and the glen ends suddenly in an abrupt, rounded amphitheatre. Towards its lower end a large valley often terminates all at once, the stream cascades openly down a rock- step, and then occupies an incision in the rocks that is quite out of proportion to the deep and wide valley higher up the stream. (See Fig. 7.) The White Water (Corrie Burn of the O.S. maps) and Coire nan Larach are good examples. The tributaries do not join the main streams at accordant junctions, but tumble down the main valley sides from openings higher up, in short they are "hanging valleys." The wide, main valleys give the observer an impression of harmony and proportion until the actual stream is noticed, when a disturbing sense of incongruity is felt. The valley seems too large for the tiny Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 stream that flows down it; it is a misfit, the disproportion in some instances being almost ludicrous. Can these small streams possibly have excavated the wide and deep valleys in which they flow 1 Seventy years ago Eamsay seems to have asked himself the same question, 640 SCOTTISH GEOGRAPHICAL MAGAZINE.

and he suggests that perhaps the material in the glens was softer than the surrounding rocks. Needless to say there is no basis of observation for this hypothesis. If the valleys are due to normal stream erosion then the process must have reached a high degree of maturity, for the valleys are widely opened and flat-bottomed. But the other features that should accompany a mature topography are entirely absent. The tributaries should enter their mains with accordant junctions instead of forming hanging valleys. The rock-steps should long ago have disappeared. The streams should flow in swinging meanders down the flat floors of the valleys. Instead of that they flow with fair rapidity in straight courses, and are cutting young

FIG. 7.—The valley of the White Water seen from below. In its lower course instead of becoming larger the valley practically vanishes. Compare Fig. 5.

valleys in the large, old valley-floors. Increased velocity and consequent cutting power may be due to rejuvenation, but (with an unimportant reservation considered later) this explanation does not apply to the Goat Fell valleys, for in the stage of maturity they must have reached, assuming normal stream erosion, rejuvenation would produce incised meanders such as we find so well developed in the upper Thames basin. The hypothesis, then, that these valleys have been eroded by normal river action completely breaks down. We are forced to the conclusion that they have been excavated by ice. On this Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 theory the peculiar features enumerated are easily accounted for, and many other details of the landscape difficult to understand on any other hypothesis receive a reasonable explanation. The course of the Rosa Water may be taken as typical of the THE SCULPTURE OF THE GOAT FELL MOUNTAIN GROUP. 641 larger streams of the Goat Fell area. A section along the river bed is shown in Fig. 8. The first part of its course (until about 1250 feet above sea-level) is in the coire at its head. The step at the mouth of the coire is •well shown; it ends approximately 1000 feet above the sea. The gradient although not so steep is still considerable until 600 feet is reached, for the stream up to that point flows in the wide amphitheatre at the head of Glen Rosa. From 600 feet to the sea the river runs along the floor of the valley and the slope is therefore much gentler. One abnormal feature of this part of the stream's course is shown clearly by the diagram—namely, that from 300 feet to about 50 feet the gradient increases. An examination of the glen at this point reveals no apparent cause for an increase of slope. It may with some probability be attributed to a slight rejuvenation of the stream caused by the very recent uplifts that gave rise to the raised beaches of the Clyde area. In fact in its lower

500

1000

SOO Mm,' dccjjen ,fig of Gfen Rosa

• —

FIG. 8.—Section along the Rosa Water and its tributary the Garbh Allt.

course the river is now actively cutting through the alluvium of the raised beaches. Fig. 8 also shows the discordant junction of the Garbh Allt with its main river. The steepest part of this stream's course is at its mouth where it joins the Rosa Water. The diagram shows that there is a sudden fall from 700 feet to less than 200 feet. This plainly affords a minimum value for the glacial erosion of Glen Rosa at this point, while the presence of the pre-glacial thousand-foot platform, at this point well developed, fixes a maximum. The pre-glacial junction of the stream must have been between 700 feet and 1000 feet above sea-level, and therefore at this point Glen Rosa has been deepened by not more than 800 feet and not less than 500 feet. One of the most characteristic features of a glaciated region is the Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 presence of rounded, bowl-shaped excavations known in Scotland as coires (or corries), in "Wales as cwms (kooms), and in France as cirques. These almost invariably occur at the heads of valleys, and in addition are frequently found situated on valley-sides or on mountain slopes. G42 SCOTTISH GEOGRAPHICAL MAGAZINE.

Several good examples occur in the Goat Fell area, perhaps the finest in Arran being the beautiful little coire on the slopes of Cioch na h-Oighe, known locally as the Devil's Punchbowl, A consideration of the direction in which these coires face gives an interesting result. The name coire is often applied to a short, deep, well-opened valley, but limiting the term at present to a detached amphitheatre or a bowl- shaped hollow, we find that in the Goat Fell area there are about ten good examples. Of these ten only one (a small coire on the north ridge of Goat Fell) faces west; the others face north-east or east, that is the direction away from the sun and the warm winds, and most favourable to the accumulation of snow and ice. The same relation obtains in the case of many of the ridges. In general the ridges show a pronounced asymmetry, one side being much steeper than the other. The steep side almost invariably faces in a direction between north and east. This phenomenon is forcibly brought home to those visitors to North Arran who cross from Glen Eosa to Glen Sannox by the col known as the Saddle. The south slope from Glen Rosa is easy, but the Glen Sannox side which faces north is steep and in places dangerous. Fig. 9 shows a rough sketch of the same thing as seen in the Bealaeh an Fhir-bhogha (the Archer's Pass), and many other ex- amples could be given. It would not be easy to ex- plain facts such as these on any theory but that of ice-erosion. The phenomenon known as "spur truncation" is frequently encountered in glaciated regions. A valley formed by normal stream erosion is more or less Flo. 9.—View looking east from the Bealaeh an Fhir- winding, and at the bend bhogha. The asymmetry of the slopes is very spurs run down first from marked. The steep slope faces north. one side of the valley, then from the other. When such a valley is heavily glaciated it is straightened by the less mobile medium which cannot flow round the curves and therefore simply cuts away the ends of the spurs. Truncated spurs of this kind are quite common in the Scottish Highlands, and beautiful examples occur also in Wales. In the Goat Fell region they are rare. Only one fairly good example has been observed by the writer—namely, the ridge that forms the north-eastern extremity of Beinn a' Chliabhain. In the foregoing pages an effort has been made to show that the Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 surface features of the Goat Fell mountain group have been profoundly modified by ice-sculpture in comparatively recent times, geologically speaking. May there not, however, be some portions of the area left to indicate the contours of the hills before modification? Obviously THE SCULPTURE OF THE GOAT FELL MOUNTAIN GROUP. 643

where two large glens approach each other the probabilities are that the dividing ridge has been so sharpened that its original appearance has been entirely destroyed. The most likely hill in the area is the ridge running from the north summit of Goat Fell towards Cioch na h-Oighe. On the west this has been rendered precipitous by backward cutting in Coire nan Fuaran, but on the east it is untouched save by Coire nan Larach and the little Punchbowl, which are too small to have produced an arete. At a height of over 2500 feet this ridge is quite unserrated. It is broad, smooth, round, and heather-clad. One is tempted to think that here we have an indication of the nature of the original hill contours before the ice-age had sharpened them into the striking and beautiful forms that we now see. In fact we reach the same conclusion as Professor W. M. Davis in his brilliant essay on the group x—namely, " that a large-featured, round-shouldered, full-bodied mountain of pre-glacial time had been converted by erosion during the Glacial Period—and chiefly by glacial erosion—into the sharp-featured, hollow-chested, narrow-spurred mountain of to-day."

NOTES ON THE GEOGRAPHY OF THE EDINBURGH DISTRICT.

By JAMES COSSAR, M.A., F.R.G.S. (With Map and Illustrations.) Continued from p. 600.

CLIMATE. THERE is a very intimate relation between the configuration of the region and the distribution and character of its climatic phenomena. For our knowledge of the climate we are almost entirely dependent upon the records of the Scottish Meteorological Society and upon the vast amount of data contained in Mr. Mossman's classic paper on "The Meteorology of Edinburgh," from which most of the following figures have been taken. Unfortunately meteorological records are wanting for many parts of the region, but the main facts that have been estab- lished for the city of Edinburgh can be applied with local modifications to most of the area. The controlling factor in the climate of the region is the direction and character of the prevailing winds. As appears from the following table of the mean percentage frequency of the winds throughout the

Downloaded by [Computing & Library Services, University of Huddersfield] at 06:22 29 December 2014 year, deduced from the means of a hundred years, the prevailing winds in Edinburgh are from the west and south-west; 6 6 per cent, are

1 " Glacial Erosion in North Wales." By Prof. William Morris Davis. (Quart. Journal Geol. Soc, vol. 65, 1909.)