Scottish Geographical Magazine

ISSN: 0036-9225 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/rsgj19

Notes on the physiography of Arran

Alexander Scott M.A. D.Sc.

To cite this article: Alexander Scott M.A. D.Sc. (1918) Notes on the physiography of Arran, Scottish Geographical Magazine, 34:3, 90-99, DOI: 10.1080/14702541808555203

To link to this article: http://dx.doi.org/10.1080/14702541808555203

Published online: 30 Jan 2008.

Submit your article to this journal

Article views: 13

View related articles

Citing articles: 2 View citing articles

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=rsgj19

Download by: [The University Of Melbourne Libraries] Date: 18 June 2016, At: 01:48 90 SCOTTISH GEOGRAPHICAL MAGAZINE.

all its fortified lines. The battle of the Marne has often been described as a miracle; eyen the geographer may be excused for saying that it suggests that might lies not only in the sword and in the fort, but in something deeper. Turned back from Paris, the German armies estab- lished themselves on the Aisne, and to-day still hold Laoi~, on the edge of the westernmost barrier. The Argonne played its part in the battle of the Marne, despite its relative insignificance. On September 8, 1914, the Chief War Lord stood waiting, wrapped in his .martial cloak, we are told, to make that triumphant entry into Nancy which was to mark the conquest of the continuation of the rampart which runs north and south from Metz. That triumphant entry has been indefinitely postponed. The siege of Verdun was in part an attempt, due to the failure of the first offensive, to make that direct western attack on Paris from which the German staff shrank in August 1914. Summary as these notes are, they may serve to suggest the strategic value of the moderate elevations which guard Paris from the east, and are themselves due to differential erosion in the rocks of the Paris Basin and its margins. (To be continued.)

NOTES ON THE PHYSIOGRAPHY OF ARRAN. By ALEXANDER SCOTT, M.A., D.Se. FROM the point of view of both geological structure and physiography the island of Arran may be divided into two parts of approximately equal area. The contrast in scenery is very pronounced, the northern portion consisting of a number of rugged peaks and ridges, rising to almost 3000 feet and interspersed with deep valleys; while the southern portion is mainly moorland with rounded hills which seldom exceed 1500 foot in height. The geological structure of the former has been described in detail by the Geological Survey (Gunn, 1903),

Scottish Geographical Magazine 1918.34:90-99. and although no systematic description of the latter has appeared, several papers on the sedimentary and intrusive rocks have been pub- lished in recent years (Gregory, 1915 ; Tyrrell, 1915). Apart from the Glacial and Raised Beach deposits, the .youngest rocks in the island are the Cainozoic dykes and sills, and these are not later than Miocene. The northern half of the island consists of a great circular dome of granite surrounded on the north, west, and south by metamorphic rocks of pre-Cambrian age; while on the east it abuts transgressively on Palmozoie sediments. The mountains, all of which are found in the granite area, are divided into two groups by the long north and south depression which runs up Glen Easan Bioraeh from Loch Ranza and down Glen Iorsa, culminating at Loch Iorsa. The eastern group comprises a number of ridges radiating from Cir Mhor, one running north-north-west over Caisteal Abhait to Creag Dubh, one south-south-east to Goatfell, and one south-south-west over A' Chir and to Beinn Nuis. Subsidiary ridges branch off from NOTES ON THE PHYSIOGRAP]~tY OF ARRAN, 91

each of these, as, for example, the Suidhe Fheargus ridge from The Castles, Cioch na h'Oighe, and Am Binnein from Goatfell, and Beinn a Chliabhain from A' Chir. The eastern group includes a curvilinear ridge which proceeds in a general northerly direction from over Beinn Breac (2333 ft.)1 to Meall nan Damh, and another from Beinn JTarsuinn (1819 ft.) 1 to Meall 1V[hor. The area of high land is bounded on the north by the Chalmadale- depression between which and the coast is a range of tow hills: On the southern edge is a broad plateau, about 1000 feet above sea level, and terminating in the through valley which carries the "String Road." The hills of the southern portion only attain a maximum height of under 1700 feet, and may also be divided into two groups. Situated immediately to the south of the String Road is a large Cainozoie vol- canic vent, the igneous and pyroclastie material of which gives rise to the Ard Bheinn group of hills, while to the south-east, and separated from the latter by another depression, is the Tighvoin group. This is formed by a large series of Cainozoic sills which have been intruded into the Triassic sediments. The contrast between the two types of scenery may be paralleled, to some extent, by a similar contrast which is found in Skye, where the mountainous region of the Cuillins is sculptured out of a great gab- bro laecolite, while the monotonous plateaux to the north-west are made up of the Cainozoie sills and dykes. The two districts present several other analogies, which will be discussed later. In endeavouring to determine the history of the topography of Arran, it is necessary to take into consideration, firstly, the effect of the dissection of the ancient Highland peneplain, and of the denudation which occurred prior to the separation of Arran from the mainland ; and, secondly, the effect of the denudation which has taken place since the separation of the island. It is generally recognised that the Scot- tish Highlands have been carved out of a plateau, which may have originally been a peneplain, and the present average height of which is

Scottish Geographical Magazine 1918.34:90-99. between 2000 and 3000 feet. This tableland sloped gently from north-west to south-east, and many of the higher peaks of the High- lands stood out as monadnocks in the undulating plateau. It prohably extended much farther to the north-west than the present land surface, and many of the north-west south-east through valleys of the Highlands were initiated by the consequent streams which drained this plateau. Superimposed on this drainage system is a series of subsequent valleys with a general north-east and south-west trend, following the direc- tion of the strike of the Dalradian rocks, and parallel to a series of faults. In the south-west Highlands the trend is rather south-south- west. According to Peach and Horne (1910), the second base-level of erosion occurs approximately at the 1000-feet level, but these writers

1 As there are several hills of these names in the island, the heights are inserted in order to indicate which is referred to. 92 8(DTTISH GEOGRAPttlCAL MAGAZINE,

give few details. Various high-level platforms have been described from the south-west of England and the Snowdon district. More ([914) has discussed the origin of the 1000-feet platforfn in Arran, but the first writer to describe the occurrence of such a platform in Arran was Smith (1896), who remarks upon " the immense amount of marine denudation which has taken place . . . when the sea worked between the 600-feet and the 1.300-feet contour lines." A third base-level probably occurs at some depth below sea-level, but the present level of this is variable owing to the submergence being differential. So far as Arran is concerned, there is little residual trace of the Highland peneplain. The mountains of the granite area probably existed as rounded hills, rising some distance above the general level, but all other traces have tong vanished owing to the enormous amount of denudation which has occurred since the uplift of the plateau. The 1000-foot platform, however, is very obvious, and can be seen at many places round the margins of the granite, and also some considerable way up Glen Iorsa. A detailed description of its extent in the northern half of the island is given by Mort (1914). In the southern area the platform is not so obvious, but in many places the land rises steeply to about 800 to 900 feet, and then a fairly abrupt change in gradient takes place, the slopes above 1000 feet being very gentle. This is clearly seen along the eastern margin of the Vent, while in the south- eastern corner of the island a broad extent of moor at the same level is found. There is no very definite evidence as to the age and origin of the piatform. The generally flat surface suggests a high degree of maturity, while the small amount of dissection which it shows in the granite area --save where cut by the deep glens--is indicative of a comparative recent uplift. The comparatively steep gradients by which the moun- tains of the interior rise from the surface of the platform are favourable to the marine origin of the latter, but, on the other hand, the general structure of the southern tableland points to an advanced stage of sub~erial denudation. The absence of shore deposits, cliffs, and so forth,

Scottish Geographical Magazine 1918.34:90-99. as pointed out by Mort, cannot be considered strong evidence in favour of the latter, as the platform was covered by the main ice-sheet of the Clyde area, and probably modified to a certain extent. The uplift is certainly pre-Glaeial in age, and as it is later than the Cainozoie igneous rocks, iV probably belongs to Pliocene Limes. The existence of platforms at lower levels, such as the fairly well marked one which can be seen between and at a height of 300 to 400 feet, and the one, at 350 to 450 feet., west of Corrie, cannot be regarded as indicative of the marine origin of the 1000-foot platform. The latter, if a peneplain, must have been worn down to base-level, and there seems to be no reason for assuming that, prior to the uplift, the base-level was at any considerable height above the sea ; in fact it would probably be near sea-level. Taking the evidence of the southern plateau into account it is probable that the whole areahad reached an advanced stage ofsubwrial denudation, and was then partly submerged, the eastern and western mountains standing out as high NOTES ON THE PHYSIOGRAPHY OF ARRAN. 93

islands, their lower slopes being steepened into cliffs, and the submerged portions modified by s_ea action. At the same time, the hills of the Vent and of the Tighvein district probably stood up as low rounded islets. The granite of the mountain area apparently was so much more resistant than the superimposed rocks that, as soon as the rivers had cut down to the former, the topography was determined to a great extent by the shape of the upper surface of the granite. Before the Highland peneplain'had reached such an advanced stage of dissection, several of the old consequent rivers must have flowed across the Firth of Clyde. One, for example, occupied the lower part of Loch Fyne, and traversed ~ho Sound of Bute ; a second probably rose somewhere to the west of Kintyre, and flowed through Glen Chalmadale and North Glen Sannox ; it is possible that a third traversed , passed to the west of the Clauchland Hills, and then between Holy Island and King's Cross p~int. The North Channel was occupied by a fourth, and it seems feasible that part of the Firth of Clyde, at least, is due to the tribu- taries of the latter cutting back and capturing the head waters of the more northerly streams. Kilbrannan Sound may be accounted for in this way. When the granite was reached, however, the drainage was diverted so that it followed the form of the granite surface. Mort has assumed that the granite was originally a dome, and that this, by river action, was cut down so that the highest land was no longer central, but occupied several isolated areas. This involves the existence of a radial drainage, but it is somewhat difficult to class the river systems of North Arran as radial. There is a very decided north and south trend in most of the valleys. For example, Glen Cataeol and Glen Seaftigill are in a north-south line i so are Glen Easan Bioraeh and Glen Iorsa i Glen Rosa and part of North Sannox. The only valleys of any size in the' granite area, whose main trend is other than north and south, are South S~nnox and the White Water Glen. It seems preferable to adopt the idea put forward by Smith (1896) with regard Co the upper surface of the granite without at the same time

Scottish Geographical Magazine 1918.34:90-99. adopting Smith's argument in all its detail. In some laeeolites, the main direction of jointing is, undoubtedly, parallel to the original sur- face of the igneous rock, but it is by no means proved that it is always so. Nevertheless it seems very probable that the original surface of the Arran granite was not dome-shaped but undulatirig, the axes of the crests and troughs being approximately north and south. The Beinn Bharrain ridge would then be an anticline, as would also be the Beinn Nuis-Tarsuinn ridge, Bcinn a Chliabhain, and possibly Goatfell. The north and south valleys, such as Glen Iorsa, upper Garbh Allt, and Glen Rosa would occur in synclines, the chief exception being the Glen Scaftigill-Glen depression. The last seems to lie along a shatter-belt which extends from the foot of Glen Scaftigitl to Meall Mhor. That the major direction of weakness in the granite was north and south seems to be indicated by the fact that the majority of the long dykes have this trend. For instance, one runs from Ceum na Caillieh to 94 SCOTTISH GEOGRAPHICAL MAGAZINE.

the foot of Glenshant Hill, the present bed of the Rosa in fact following the line of this dyke for a considerable distance. Another can be traced from the summit of Beinn a Chliabhain suuthwards for two miles, while a third of the same length also runs southward from Beinn Tarsuinn. The general consequence was that as soon as the granite became exposed the drainage tended to be diverted to the southward, and it is probable that the original Iorsa was initiated at this time as a tributary of the river which flowed do~m Kilbrannan Sound. How fat" back this stream cut is uncertain, but it is possible that it may have beheaded the Chal- madale-Norgh Sannox stream~ and thus formed the broad valley which separates the eastern hills from the western. At this period the water- shed must have been farther to the north-west, as there is evidence of the existence of some considerable tributaries which flowed in a south- easterly direction into the Iorsa. The col at the head of Glen Diem- hen, between Beinn Bhreac (1881 ft.) and Beinn Tarsuinn (1819 ft.), is probably the remnant of the valley of one of these. Another may have occupied the gap between Meall nan Damh and the ridge north-east of Coirein Loehan as well as the col between Glen Catacol and Loch Iorsa, while the shallow depression between Ceann Reamhar and Beinn Bhar- rain may be due to a third. The north-east south-west depression which runs from Catacol to Thundengray resembles the high level channels which are found in many Highland valleys at some considerable elevation above the present valley floor. We would thus have two areas of high ground, one a long ridge trending north and south in the region of Beinn Bharrain, and the other a more dome-shaped mass with its centre to the north-west of Goatfell, and already partly trenched by the Rosa burn. The drainage of this may to a certain extent have been radial, for we have the North Sannox burn draining northwards, the South Sannox to the north-west, the White Water to the east, and the Rosa Burn and the Garbh Allt to the southwards. There seems little doubt that the Garbh Allt originally drained southwards to Glen Eas- buig, and has been captured at a very late date by a small stream cutting back from the Rosa. In the first place, there are traces of a ridge

Scottish Geographical Magazine 1918.34:90-99. connecting the north-south portion of the Garbh Allt with Glen Easbuig, and this may be a residual portion of the old valley wall, and, secondly, the E~sbuig burn begins to cut a trench in the 1000-foot platform very near its present source. As none of the smaller streams have been able to dissect the 1000-foot platform to any extent, it seems probable that Glen Easbuig was cut out by a larger stream than the present one, and theft this stream was beheaded by one of the small burns flowing down the west slope of Glen Rosa. The original tributary of the Rosa was probably similar to the burn which drains the small corrie at the south end of the Beinn a Chliabhain ridge. The Garbh Allt has been assumed to be a hanging valley (Mort, 1914), and the amount of glacial over- deepening of the Rosa has been calculated from it, but it seems to the writer that the above explanation is much more satisfactory, and that all that the calculation gives is the depth of the Rosa valley at that point below the 1000-foot platform. It is, of course, evident that most of the present valleys have been NOTES ON THE PHYSIOGRAPHY OF ARRAN. 95

considerably modified by glacial erosion, but at the same time they are all long pro-Glacial. After the 1000 foot uplift, the streams underwent a great rejuvenation, deep gorges were cut in the platform, giving rise to the present valleys of the Iorsa, Rosa, Sannox Burn, Easan Biorach and Cataeo]. During the Glacial period most of the terries were formed, and these have generally an east or north-east aspect. The result is ~hat 6hose ridges which originally trended, for example, north-west and south-east, now have a smooth, spurless, south-west face, while the north-east face consists of projecting spurs and deep corrie indentations alternately. Thus the south-west face of has no spurs, while the north-east face, on the other hand, has at least four, Craig Dubh being the most northerly and Suidhe Fheargus the largest. Simi- larly, the Goatfell group has one spur on the western side and four on the eastern. A parallel state of affairs can be seen in many other parts of . In the south end of Rum, for example, all the projecting spurs are on the north-east side of the chief range ; in Sutherland the Foinne Bheinn group has a smooth south-west face (the wall of an old consequent valley), while the north-eas~ is intersected by numerous terries. There seems little doubt that the formation of these corries should be attributed to ice action, and it is more probable that localised frost action, such as is postulated by Johnson, has been the chief agent, than that they have formed mainly by plucking or grinding. The eorries which face south and west, such as the one at the head of the Barbh Allt, and Coire Chattan, south of Goatfel], have been formed chiefly by river action. On the whole, the slopes of the latter are by no means so steep as those of the former, but locally they show signs of steepening through the action of landslides, and it is very probable that many of these landslides occurred in pro-Glacial and Glacial times. The east face of Beinn Tarsuinn and Beinn Nuis has probably developed in this way, but a prominent factor has been the direction of jointing of the granite, the main direction being almost vertical on these slopes. There is no doubt that the slope on many of the valley walls is directly due to the inclination of the joint planes, as where these are nearly

Scottish Geographical Magazine 1918.34:90-99. vertical or inclined to a high angle there is a much greater tendency for landslides to occur. The well-known contrast between the two types of scenery may be mainly ascribed to the same cause. Various explanations of this have been given. It has been assumed that smooth ridges were due to the presence of fine granite, and the serrated ridges to coarse granite, but as Mort has shown, this explanation does not hold. The latter writer ascribes the difference to the stage of erosion, holding that the smooth outlines indicate a very immature stage of glacial erosion, while the rugged hills are characteristic of an advanced stage. This involves the idea that the topography of the western hills has been much less altered by glacial erosion than is the case in the eastern hills, nevertheless, the ridge on the east side of Coire Roinn on Beinn Bharrain is one of the most rugged parts of the island, and it is difficult to see why the erosion should have been so advanced on this particular ridge and elsewhere in the same neighbourhood so slight. On the other hand, when the direc- 96 SCOTTISH GEOGRAPHICAL MAGAZINE,

tion of jointing is considered, it is found that on all the serrated ridges the granite slabs are inclined at a very high angle, while on the smooth ridges the slabs are often more nearly horizontal. Dykes have often been a secondary cause, but the jointing must be considered to be the main factor. On the A' Chit ridge the main joints are nearly vertical, while the ridge is traversed by a number of dykes, the two faetors producing the most serrated ridge on the island ; on the Caisteal Abhail- Creag Dubh ridge the main joint planes are inclined at a low angle to the horizontal, and though the ridge is cut by numerous dykes it presents a comparatively smooth longitudinal outline. While many of the ridges, such as A' Chit, have been narrowed by the cutting back of two corries, this is not the chief reason for the serrated appearance. Beinn Tarsuinn has a typicallyserrated ridge, though the gradient of the slope towards Glen Iorsa is not steep in comparison with the perpen- dicular crags of the eastern face. Hence the most potent factor has been the vertical jointing of the granite. On the whole, the rugged hills owed their appearance and structure mainly to the nature of the jointing, but the ridges may be narrowed by the cutting back of corries and serrated by differential weathering due to the presence of dykes. The valleys show many of the usually accepted signs of glacial erosion. The walls are steep and the floors fiat, so that the general cross-section is a eatenary ; longitudinally they are straight and spurs are conspicuous by their absence, particularly in Glen Rosa and Glen Sannox, where the sheer smooth walls constitute the most prominent features of the valleys. The valley heads have often been widened by the formation of eorries, and the presence of hanging iralleys suggests that there may have been some overdeepening. It is, however, very doubtful if the latter has occurred to any extent. As has been noticed elsewhere (Bailey, 1916), for example, in the Ben Naris district, hanging valleys are not necessarily the result of Glacial action, and may arise in other ways. This has already been discussed in the case of the Garbh A_llt, and other explanations can be found for the other examples. The stream from Loch Nuis originates on the 1000-foot platform, and drops down the

Scottish Geographical Magazine 1918.34:90-99. steep east face of Glen Iorsa. As the stream is small, and has been unable to cut a valley on the platform, it is difficult to understand how it could cut a graded valley any more than the other small burns which flow down the slopes of the Iorsa. Many of the so-called hanging valleys are simply small streams which originate on the 1000-foot plat- form, and are unable to cut trenches either there or on the slopes of the valley into which they drain. The case of Glen Diomhan is rather different. The tributary valley, above the junction, increases its grade, and falls 200 feet in a series of cascades. The lower part of the glen is broad and U-shaped, as it also is at its head, but the intermediate part is V-shaped. The most obvious explanation of this is that the lower mature portion is cut in the more yielding shattered area of the granite, and the remainder in the more resistant normal granite, the steep portion of the thalweg being near the eastern margin of the al6ered area. In the ease of the discordant junction of Glen Easan Bioraeh, and Glen Chalmadale, the explanation given in NOTES ON THE PHYSIOGRAPHY OF ARRAN. 97

the Geological Survey memoir (Ounn, 1903) seems more satisfactory than that offered by the hanging valley hypothesis (Mort, 1914) According to the former, the waterfall is due to the presence of a band of schist indurated by contact-metamorphism, The argument that such a band should induce a similar fail in Glen Cataeol, which has been advanced against this view, is scarcely valid, as the amount of meta- morphism induced by the intrusion of the granite is very variable, a contact metamorphosed aureole 300 yards wide being found at some p~rts, while in others unaltered rocks are found Within a few yards of the granite. Further, the nature of the schists, and consequently their resistance to erosion, is by no means uniform round the granite margin. The general conclusion is that, while the valleys have been broad- ened by glacial erosion, the spurs being truncated and the walls steepened to some extent, there is very little evidence that there has been any great amount of over-deepening. Many of them must have developed their present courses and have been cut down to their present levels in poe-Glacial times, and it is possible that some of the through valleys which now form cnls have, in the neighb0urhood of the latter, been subjected to [ittl~ dowueutting since the ] 000-foot uplift. In the southern half of the island the topography at the time of the Plioeene uplift must, have been very mature. The whole area hart been worn down to b~se-level with the exception of a few low hills in the region of the great Cainozoic vent and the neighbourhood of Tighvein. The persistence of these must be ascribed to the superior resistance of the underlying rocks, the vent consisting mainly of granite and agglomerate with a mass of diorite on the eastern margin, and the Tighvein district of an igneous coroplex of granophyre and dolerite allied to the Marseo complex in Skye. These rocks would be better able to resist erosion than the soft Permian and Triassic sediments which surround them. Apart from the vent, the present drainage is moulded on the structure of' the underlying rocks. The prevalent dip of the s)diments throughout the whole area is approximately south-west, and the intercalated Cainozoie sills seem to have the same inclination.

Scottish Geographical Magazine 1918.34:90-99. As the main streams flow south-west, they are therefore consequent, and flow down a dip-slope. The watershed runs north-west and south- east along a belt containing many igneous intrusions and stretching from Tighvein to Dippin Head, and a number of smaller streams flow down the scarp to the east. This escarpment seems to be migrating to the south-west, as there is a col at waterhead which cannot have been lowered by the present streams which flow from it, and Which was probably formed by the action of a stream whose source was further to the north-east. The two chief south-westerly streams, the Sliddery Water and the Kilmory waters, are normal dip streams, and the valleys are ordinary river-cut valleys. The Ashdale burn is mainly a strike stream in the upper (north-west and south-east) part of its course, but the position ot~ the actual gorge is determined by a number of dykes of similar trend. The lower part 0f the course, where the flow is eastwards, is at right angles to the strike of rocks and against the dip, and a numbe~ of water~ VOL XXXIV. tt 98 SCOTTISH GEOGRAPHICAL bIAGAZINE.

falis are formed by the basaltic sills which arc cut through. The final part of the course is a fairly deep V-shaped valley cut in the sediments. Of the streams which debouch in Bay, the Benlister burn is an obsequent stream which has cut through the original watershed and diverted part of the headwaters of the Clauchan Burn. A series of thin sills and dykes form a number of cascades in the stream, which falla rapidly from the 1000-foot level to the 200-foot level. The other valley, Monamore Glen, is of a different type, and seems to be along the iine of an older valley. It is a deep, V-shaped valley, with great broad meanders for the main part of the course, but the upper portion is an immature gorge draining the Tighvein complex. The Cainozoic Vent at the commencement of the present cycle of erosion seems to have been of the nature of a dome, and this haa been dissected by an approximately radial drainage. The harder rocks of the eastern margin, however, seem to have constituted a barrier, as the streams to the east have not been able to cut back into the vent to any extent, while, on the other hand, Glen Craigag and Ballymichael Glen, draining north and west respectively, are typical deep river-cut valleys. These originally drained into a stream which rose in the northern granite area, occupied the middle part of the present course of the , and {lowed southward past Blaekwaterfoot. The consequent Clauchan Burn, draining the southern margin of the vent, was also a tributary of this stream. At a comparatively recent date the latter was intercepted by a ~mall stream cutting back from Machrie Bay; the recent date is proved by the fact that the old river alluvium north of is partly below the level of the 100-foot raised beach, tteneo tire capture must have occurred since the deposition of the 100-foot beach. The valleys of the southern part of the island have undergone little modification by glacial action, with the notable exceptions of Glen Dubh and Glen Ormidale, draining into Glen Cloy, and to a less degree Benlister Glen. In the two former there are numerous moraines; in Glen Dubh a large crescentic series must have dammed up a lake at one time. The head of the glen forms a corrie, which is due partly, at

Scottish Geographical Magazine 1918.34:90-99. least, to glacial action. These moraines, and the lateral ones which occur in Benlister Glen, are due to a local glaciation, proceeding from the vent. Although the whole area must have been covered by the main icesheet during the Glacial Period, the main function of the latter seems to have been protective, and there was probably no great amount of erosion during that period. The area is chiefly interesting on account of the close dependence of the topography on the geological structure, and in this respect it presents many analogies with the basaltic plateaux of Skye (Harker, 1904). In both cases the intrusive sills dip gently in on6 direction, with a steep escarpment in the opposite ; the thicker sills form sea-cliffs, as at Druma- doon, or inland escarpments, and the thinner sills, which give rise to such well raarked terraces as in Glen Varrigill (Skye), have their counter- part in the prominent terraces on the south side of Glen Ashdale. In both eases the dykes give rise to gullies and ravines, and the present s~reams are often entrenched along the lines of these dykes. In Arran NOTES ON THE PHYSIOGRAPHY OF ARRAN. 99

most of the waterfalls can be traced to the effect of the sills, the one notable exception being the lowest fall in Glen Ashdale, which is due to a band of hard sandstone (Tyrretl, 1915). Throughout the whole area there zre pr~ctic~Uy no topographical features which cannot be accounted for on the basis of the geological structure.

REFERENCES. B~L~r~ E.B. 19t0. In "The Geology of Ben Nevis and Glen Coe." Mesa. Geol. Survey~ Scotland, pp. 1~13. GR~oRr, J.W. 1915. "The Permian and Triassic Rocks of Arran." Trans. Geol. Soc. Glasgow, vol. xv. pp. 174-87. Gu~, W. i903. Ia "The Geology of North Arr~n~ etc." Mem. Geol. Survey, Scotland. 200 pp. [tA~KER, A. 1904. "The Tertiary Igneous Rocks of Skye." Mere. Geol. Survey, Scotland. Pp. 434-51. Moa r~ F. 1914. "l~he Sculpture of NorSh Arran." ~cot. Geog. Mag.~ vol. xxx. pp. 393-404. PE~CH, B. N., a~d HO~SE, J. 1910. In The Bathymetrical Survey of the Scottish Fresh-water Lochs, vol. i. pp. 439-5 i3. SMITg, J. 1896. " A New View of the Arran Granite Mountains." Trans. Geol. Soc. Glasgow, vo]. ~. pp. 216-56. TYRRnLL~ G. W. 1915. "On . . . the Red Rock Series in Arran." Trans. Geol. Soc. Glasgow, vo]. xv. pp. 188-99.

SOUTHERN PALESTINE: SOME NOTES ON HISTORICAL GEOGRAPHY.

By Captain W. R. KERMACK.

ONE result, at any rate, of the war, which is, perhaps, not wholly on the bad side is that, with its will or against its will, the great British pub- lit'has been taught or rebaught a certain amount of classical and Bibli-

Scottish Geographical Magazine 1918.34:90-99. cal geography. One British army nearly at the site of Troy, another in Macedonia, a third in Mesopotamia, yet a fourth in Egypt and Pales- fine, must have compelled many a paterfamilias to turn his mind pain- fully back to schoolboy days, and furbish up again his rusty armbury of classical information. Specially true, perhaps, is this in the case of the campaign in Palestine ; and those who agree with Sir George Adam Smith, that "History never repeats, without explaining, itself," and who feel that the explanation of the history lies often in geography, will see with interest, but without surprise, our troops reaching in burn Beersheba, Ascalon~ Ashdod, and Ekron, fighting in the footsteps of Joshua at Beth-heron, and facing Jerusalem, where Cceur-de-lion hid his face from the city he might not win on Nebi Samwil. To the ancients Syria was first and foremost a bridge, between the two great river-eivilisations of Mesopotamia and Egypt, with the desert on one hand, the Mediterranean on the other. Palestine, which is the southern portion of this bridge, consists of an inland strip of mountain