Part 9

From what has now been said, it will readily be understood that there is not much cultivable land in Harris and the hilly parts of Lewis. What little there is occurs chiefly along the west coast, a character which we shall find is common to most of the islands of the Outer Hebrides. In the neighbourhood of Stornoway, and over considerable areas along the whole west coast of Lewis, the moorlands have been broken in upon by spade and plough, with more or less success. But natural meadow-lands, such as are frequently met with on the west side of many of the islands both of the Outer and Inner Hebrides, are not very common in Lewis.

One of the most notable features of the hillier parts of the Long Island are the enormous numbers of loose stones and boulders which are everywhere scattered about on hill-top, hill-side, and valley-bottom. Harris is literally peppered with them, and they are hardly less abundant in the other islands. They are of all shapes and sizes--round, sub-angular, and angular. One great block in Barra I estimated to weigh seven hundred and seventy tons. Many measure over three or four yards across, while myriads are much smaller. These boulders are sometimes utilised in a singular way. In Harris, there being only one burial-place, the poor people have often to carry their dead a long distance, and this of course necessitates resting on the journey. To mark the spot where they have rested, the mourners are wont to erect little cairns by the road-side, many of which are neatly built in the form of cones and pyramids, while others are mere shapeless heaps of stones thrown loosely together. Instead of raising cairns, however, they occasionally select some boulder, and make it serve the purpose by canting it up and inserting one or more stones underneath. Occasionally I have seen in various parts of the mainland great boulders cocked up at one end in the same way. Some of these may be in their natural position, but as they often occupy conspicuous and commanding situations, I am inclined to think that the cromlech-builders may have tampered with them for memorial purposes. The present custom of the Harris men may therefore be a survival from that far-distant period when Callernish was in its glory.

North Uist is truly a land of desolation and dreariness. Bare, rocky hills, which are remarkable for their sterile nakedness even in the Long Island, form the eastern margin, and from the foot of these the low, undulating rocky and peaty land stretches for some ten or twelve miles to the Atlantic. The land is everywhere intersected by long, straggling inlets of sea-water, and sprinkled with lakes and peaty tarns innumerable. Along the flat Atlantic coast, which is overlooked by some sparsely-clad hills, are dreary stretches of yellow sand blown up into dunes. Near these are a few huts and a kirk and manse. Not a tree, not even a bush higher than heather, is to be seen. Peat, and water, and rock; rock, and water, and peat--that is North Uist. The neighbourhood of Lochmaddy, which is the residence of a sheriff-substitute, and rejoices besides in the possession of a jail, is depressing in the extreme. It is made up of irregular bits of flat land all jumbled about in a shallow sea, so that to get to a place one mile in direct distance you may have to walk five or six miles, or even more. I could not but agree with the natives of the more coherent parts of the Long Island, who are wont to declare that Lochmaddy is only "the clippings of creation"--the odds and ends and scraps left over after the better lands were finished. North Uist, however, boasts of some interesting antiquities--Picts' houses, and a great cairn called the Barp, inside of which, according to tradition, rest the remains of a wicked prince of the "good old days." Notwithstanding these, there are probably few visitors who will not pronounce North Uist to be a dreary island.

Benbecula is precisely like North Uist, but it lacks the bare mountains of the latter. There is only one hill, indeed, in Benbecula; all the rest is morass, peat, and water.

Massive mountains fringe all the eastern shores of South Uist, and send westward numerous spurs and foot-hills that encroach upon the "machars," or good lands, so as to reduce then to a mere narrow strip, bordering on the Atlantic. Save the summits of Beinn Mhor (2033 feet) and Hecla (1988 feet), which are peaked and rugged, all the hills show the characteristic flowing outline which has already been described in connection with the physical features of Harris. The low-grounds are, as usual, thickly studded with lakes, and large loose boulders are scattered about in all directions.

Barra is wholly mountainous, and, except that it is somewhat less sterile, closely resembles Harris in its physical features, the hills being smoothed, rounded, and bare, especially on the side of the island that faces the Minch. Of the smaller islands that lie to the south, such as Papey, Miuley, and Bearnarey, the most noteworthy features are the lofty cliffs which they present to the Atlantic. For the rest, they show precisely the same appearances as the hillier and barer portions of the larger islands--rounded rocks with an undulating outline, dotted over with loose stones and boulders, and now and again half-smothered in yellow sand, which the strong winds blow in upon them.

There is thus, as I have said, considerable uniformity and even monotony throughout the whole range of the Outer Hebrides. I speak, however, chiefly as a geologist. An artist, no doubt, will find infinite variety, and as he wends his way by moorland, or mountain-glen, or sea-shore, scenes are constantly coming into view which he will be fain to transfer to his sketch-book. The colour-effects, too, are often surprisingly beautiful. When the rich meadow-lands of the west coast are in all their glory, they show many dazzling tints and shades, the deep tender green being dashed and flushed with yellow, and purple, and scarlet, and blue, over which the delighted eye wanders to a belt of bright sand upon the shore, and the vast azure expanse of the Atlantic beyond. Inland are the heath-clad moors, sprinkled with grey boulders and masses of barren rock, and interspersed with lakes, some of which are starred with clusters of lovely water-lilies. Behind the moorlands, again, rise the grim, bald mountains, seamed and scarred with gullies, and in their very general nakedness and sterility offering the strongest contrast to the variegated border of russet moor, and green meadow, and yellow beach that fringe the Atlantic coast.

All through the islands, indeed, the artist will come upon interesting subjects. A most impressive scene may sometimes be witnessed on crossing the North Ford, between North Uist and Benbecula. At low-water, the channel or sound between these two islands, which is five miles in breadth, disappears and leaves exposed a wide expanse of wet sand and silt, dotted with black rocks and low tangle-covered reefs and skerries. On the morning I passed over, ragged sheets of mist hung low down on the near horizon, half-obscuring and half-revealing the stony islets, and crags, and hills that lay between the ford and the Minch. Seen through such a medium, the rocks assumed the most surprising forms, sometimes towering into great peaks and cliffs, at other times breaking up, as it were, into low reefs and shoals, and anon dissolving in grey mist and vapour. At other times the thin cloud-curtain would lift, and then one fancied one saw some vast city with ponderous walls and battlements, and lofty towers and steeples, rising into the mist-wreaths that hung above it, while from many points on the Benbecula coast, where kelp was being prepared, clouds of smoke curled slowly upwards, as if from the camp-fires of some besieging army. The track of the ford winds round and about innumerable rocks, upon which a number of "natives," each stooping solitary and silent to his or her work, were reaping the luxuriant seaweed for kelp-making. Their silence was quite in keeping with the general stillness, which would have been unbroken but for the harsh scream of the sea-birds, as they ever and anon rose scared from their favourite feeding-grounds while we plodded and plashed on our way. The artist who could successfully cope with such a scene would paint a singularly weird and suggestive picture.

But, to return to the physical features of the Long Island, what, we may ask, is the cause of that general monotony of outline to which reference has so frequently been made? At first we seem to get an answer to our question when we are told that the islands of the Outer Hebrides are composed chiefly of one and the same kind of rock. Everyone nowadays has some knowledge of the fact that the peculiar features of any given district are greatly due to the character and arrangement of the rock-masses. For example, who is not familiar with the outline of a chalk country, as distinguished from the contour of a region the rocks of which are composed, let us say, of alternating beds of limestone and sandstone and masses of old volcanic material? The chalk country, owing to the homogeneousness of its component strata, has been moulded by the action of weather and running water into an undulating region with a softly-flowing outline, while the district of composite formation has yielded unequally to the action of Time's workers--rains, and frosts, and rivers--and so is diversified with ridge, and escarpment, and knolls, and crags. When, therefore, we learn that the Outer Hebrides are composed for the most part of the rock called gneiss and its varieties, we seem to have at once found the meaning of the uniformity and monotony. It is true that although pink and grey gneiss and schistose rocks prevail from the Butt of Lewis to Barra Head, yet there are some other varieties occasionally met with--thus soft red sandstone and conglomerate rest upon the gneissic rocks near Stornoway, but they occur nowhere else throughout the Long Island. Now and again, however, the gneiss gives place to granite, as on the west coast of Lewis near Carloway; and here and there the strata are pierced by vertical dykes and curious twisted and reticulated veins of basalt-rock. All these, however, hold but a minor and unimportant place as constituents of the islands. Gneiss is beyond question the most prevalent rock, and we seem justified in assigning the peculiar monotony of the Outer Hebridean scenery to that fact.

But when we come to examine the matter more attentively, we find that there is still some important factor wanting. We have not got quite to the solution of the question. When we study the manner in which the gneiss and gneissic rocks disintegrate and break up at the sea-coast or along the flanks of some rugged mountain-glen, we see they give rise to an irregular uneven surface. They do not naturally decompose and exfoliate into rounded dome-shaped masses, such as are so commonly met with all through the islands, but rather tend to assume the aspect of rugged tors, and peaks, and ridges. The reason for this will be more readily understood when it is learned that the gneissic rocks of the Outer Hebrides are for the most part arranged in strata, which, notwithstanding their immense antiquity--(they are the oldest rocks in Europe)--and the many changes they have undergone, are yet, as a rule, quite distinguishable. The strata are seldom or never horizontal, but are usually inclined at a high angle, either to north-east or south-west, although sometimes, as in the vicinity of Stornoway, the "dip" or inclination of the beds is to south-east. Throughout the major portion of the Long Island, however, the outcrop of the strata runs transversely across the land from south-east to north-west. Now we know that when this is the case strata of variable composition and character give rise to long escarpments and intervening hollows--the escarpments marking the outcrops of the harder and more durable beds, and the hollows those strata that are softer and more easily eroded by the action of the denuding forces, water and frost. When the dip of the strata is north-east we expect the escarpments to face the south-west, and the reverse will be the case when the strata incline in the opposite direction.

Seeing then that the Outer Hebrides are composed chiefly of gneissic rocks and schists which yield unequally to the weather, and which, in the course of time, would naturally give rise to lines of sharp-edged escarpments or ridges and intervening hollows, with now and again massive hills and mountains showing great cliffs and a generally broken and irregular outline, why is it that such rugged features are so seldom present at low levels, and are only conspicuous at the very highest elevations? The rocks of the Outer Hebrides are of immense antiquity, and there has therefore been time enough for them to assume the irregular contour which we might have expected. But in place of sharp-rimmed escarpments, and tors, and broken shattered ridges, we see everywhere a rounded and smoothly-flowing configuration which prevails up to a height of 1600 feet or thereabout, above which the rocks take on the rugged appearance which is natural to them. By what magic have the strata at the lower levels escaped in such large measure from the action of rain and frost, which have furrowed and shattered the higher mountain-tops?

I have said that long lines of escarpment and ridges, corresponding to the outcrops of the harder and more durable strata, are not apparent in these islands. A trained eye, however, is not long in discovering that such features, although masked and obscured, are yet really present. The round-backed rocks are drawn out, as it were, in one persistent direction, which always agrees with the strike or outcrop of the strata; and in many districts one notices also that long hollows traverse the land from south-east to north-west in the same way. Such alternating hollows and rounded ridges are very conspicuous in Barra and the smaller islands to the south, and they may likewise be noted in most of the larger islands also. Looking at these and other features, the geologist has no hesitation in concluding that the whole of the islands have been subjected to some powerful abrading force, which has succeeded to a large extent in obliterating the primary configuration of the land. The rough ridges have been rounded off, the sharp escarpments have been bevelled, the abrupt tors and peaks have been smoothed down. Here and there, it is true, the dome-shaped rock-masses are beginning again to break up under the action of the weather so as to resume their original irregular configuration. And, doubtless, after the lapse of many ages, rain and frost will gradually succeed in destroying the present characteristic flowing outlines, and the islands will then revert to their former condition, and rugged escarpments, sharp peaks, and rough broken hummocks and tors will again become the rule. But for a long time to come these grey Western Islands will continue to present us with some of the most instructive examples of rounded and mammillated rock-masses to be met with in Europe. From Barra Head in Bearnarey to the Butt of Lewis we are constantly confronted by proofs of the former presence of that mysterious abrading power, which has accommodated itself to all the sinuosities of the ground, so that from the sea-level up to a height of 1600 feet at least, the eye rests almost everywhere upon bare round-backed rocks and smoothed surfaces.

II.

In the preceding article I have described the peculiar configuration of the Long Island--rounded and flowing for the most part--and have pointed out how that softened outline is not such as the rocks would naturally assume under the influence of the ordinary agents of erosion with which we are familiar in this country. The present contour has superseded an older set of features, which, although highly modified or disguised, and often well-nigh obliterated, are yet capable of being traced, and are, no doubt, the conformation assumed by the rocks under the long-continued action of rain and frost and running water. We have now to inquire what it was that removed or softened down the primal configuration I refer to, and gave to the islands their present monotonous, undulating contour.

Any one fresh from the glacier-valleys of Switzerland or Norway could have little doubt as to the cause of the transformation. The smoothed and rounded masses of the Outer Hebrides are so exactly paralleled by the ice-worn, dome-shaped rocks over which a glacier has flowed, that our visitor would have small hesitation in ascribing to them a similar origin; and the presence of the countless perched blocks and boulders which are scattered broadcast over the islands would tend to confirm him in his belief. A closer inspection of the phenomena would soon banish all doubt from his mind; for, on the less-weathered surfaces, he would detect those long parallel scratches and furrows which are the sure signs of glacial action, while, in the hollows and over the low-grounds, he would be confronted with that peculiar deposit of clay and sand and glaciated stones and boulders which are dragged on underneath flowing ice.

Having satisfied ourselves that the rounded outline of the ground is the result of former glacial action, our next step is to discover, if we can, in what direction the abrading agent moved. Did the ice, as we might have supposed, come out of the mountain-valleys and overflow the low country? If that had been the case, then we should expect to find the glacial markings radiating outwards in all directions from the higher elevations. Thus the low-grounds of Uig, in Lewis, should give evidence of having been overflowed by ice coming from the Forest of Harris; the undulating, rocky, and lake-dappled region that extends between Loch Roag and Loch Erisort should be abraded and striated from south-west to north-east. Instead of this, however, the movement has clearly been from south-east to north-west. All the prominent rock-faces that look towards the Minch have been smoothed off and rounded, while in their rear the marks of rubbing and abrading are much less conspicuous. It is evident that the south-east exposure has borne the full brunt of the ice-grinding--the surfaces that are turned in the opposite direction, or towards the Atlantic, having been in a measure protected or sheltered by their position. The striations or scratches that are seen upon the less-weathered surfaces point invariably towards the north-west, and from their character and the mode in which they have been graved upon the rock, we are left in no doubt as to the trend of the old ice-plough--which was clearly from south-east to north-west. Nor is it only the low-grounds that are marked in this direction. Ascend Suaina (1300 feet), and you shall find it showing evident signs of having been abraded all over, from base to summit. The same, indeed, is the case with all the hills that stretch from sea to sea between Uig and Loch Seaforth. Beinn Mheadonach, Ceann Resort, Griosamul, and Liuthaid, are all strongly glaciated from south-east to north-west.

North and South Harris yield unequivocal evidence of having been overflowed by ice which did not stream out of the mountain-valleys, but crossed the island from the Minch to the Atlantic. A number of mountain-glens, coming down from the Forest of Harris, open out upon West Loch Tarbert, and these we see have been crossed at right angles by the ice--the mountains between them being strongly abraded from south-east to north-west. It is the same all over South Harris, which affords the geologist every evidence of having been literally smothered in ice, which has moved in the same persistent direction. The rock-faces that look towards the Minch are all excessively naked; they have been terribly ground down and scraped, and the same holds good with every part of the island exposed to the south-east.

Now, the mode in which the rocks have been so ground, scraped, rounded, and smoothed betokens very clearly the action of land-ice, and not of floating-ice or icebergs. The abrading agent has accommodated itself to all the sinuosities of the ground, sliding into hollows and creeping out of them, moulding itself over projecting rocks, so as eventually to grind away all their asperities, and convert rugged tors and peaks into round-backed, dome-shaped masses. It has carried away the sharp edges of escarpments and ridges, and has deepened the intervening hollows in a somewhat irregular way, so that now these catch the drainage of the land and form lakes. Steep rocks facing the Minch have been bevelled off and rounded atop, while in their rear the ice-plough, not being able to act with effect, has not succeeded in removing the primeval ruggedness of the weathered strata.

I have said that the movement of the ice was from south-east to north-west. But a close examination of the ice-markings will show that the flow was very frequently influenced by the form of the ground. Minor features it was able to disregard, but some prominent projecting rock-masses succeeded in deflecting the ice that flowed against them. For example, if we study the rocks in North Harris, we shall find that the Langa and the Clisham have served as a wedge to divide the ice, part of which flowed away into Lewis, while the other current or stream crept out to sea by West Loch Tarbert. The Langa and the Clisham, indeed, raised their heads above the glacier mass--they were islets in a sea of ice. It is for this reason that they and the Tarcull ridge in South Harris have not been smoothed and abraded, but still preserve their weathered outline. All surfaces below a height of 1600 feet which are exposed to the south-east, and which have not been in recent times broken up by the action of rain and frost, exhibit strongly-marked glaciation. But above that level no signs of ancient ice-work can be recognised.

We see now why it is that the hill-slopes opposite the Minch should, as a rule, be so much more sterile than those which slope down to the Atlantic. The full force of the ice was exerted upon the south-east front, in the rear of which there would necessarily be comparatively "quiet" ice. For the same reason we should expect to find much of the rock débris which the ice swept off the south-east front sheltering on the opposite side. Neither clay nor sand nor stones would gather under the ice upon the steep rocks that face the Minch. The movement there was too severe to permit of any such accumulation. But stones and clay and sand were carried over and swept round the hills, and gradually accumulated in the rear of the ice-worn rocks, just in the same way as gravel and sand are heaped up behind projecting stones and boulders in the bed of a stream. Hence it is that the western margin of Harris is so much less bleak than the opposite side. Considerable taluses of "till," as the sub-glacial débris is called, gather behind the steeper crags, and ragged sheets of the same material extend over the low-grounds. All the low-grounds of Lewis are in like manner sprinkled with till. Over that region the ice met with but few obstacles to its course, and consequently the débris it forced along underneath was spread out somewhat equally. But wherever hills and peaks and hummocks of rock broke the regularity of the surface, there great abrasion took place and no till was accumulated.

Thus the position and distribution of this sub-glacial débris or bottom-moraine tell the same tale as the abraded rocks and glacial striæ, and clearly indicate an ice-flow from the south-east. This is still further proved by the manner in which the upturned ends of the strata are frequently bent over underneath the till in a north-westerly direction, while the fragments dislodged from them and enclosed in the sub-glacial débris stream away as it were to the same point of the compass. Not only so, but in the west of Lewis, where no red sandstone occurs, we find boulders of red sandstone enclosed in the till, which could not have been derived from any place nearer than Stornoway. In other words, these boulders have travelled across the island from the shores of the Minch to the Atlantic sea-board.

Having said so much about the glaciation of Lewis and Harris, I need not do more than indicate very briefly some of the more interesting features of the islands further south.

I spent some time cruising up and down the Sound of Harris, and found that all the islets there had been ground and scraped by ice flowing in the normal north-west direction, and sub-glacial débris occurs on at least one of the little islands--Harmetrey. But all the phenomena of glaciation are met with in most abundance in the dreary island of North Uist. The ridge of mountains that guards its east coast has been battered, and ground down, and scraped bare in the most wonderful manner, while the melancholy moorlands are everywhere sprinkled with till, full of glaciated stones, many of which have travelled west from the coast range. Benbecula shows in like manner a considerable sprinkling of till, and the trend of the glacial striæ is the same there as in North Uist, namely, a little north of west. There are no hills of any consequence in Benbecula, but the highly-abraded and barren-looking mountains that fringe the eastern margin of North Uist are continued south in the islands of Roney and Fuiey, either of which it would be hard to surpass as examples of the prodigious effect of land-ice in scouring, scraping, and grinding the surface over which it moves.

South Uist presents the same general configuration as North Uist, its east coast being formed of a long range of intensely glaciated mountains, in the rear of which ragged sheets and heaps of sub-glacial débris are thrown and scattered over the low, undulating tract that borders the Atlantic. No part of either Benbecula or North Uist has escaped the action of ice, but in South Uist that knot of high-ground which is dominated by the fine mountains of Beinn Mhor and Hecla towered above the level of the glacier-mass, and have thus been the cause of considerable deflection of the ice-flow. The ice-stream divided, as it were, part flowing round the north flank of Hecla, and part streaming past the southern slopes of Beinn Mhor. But the ice-flow thus divided speedily reunited in the rear of the mountains, the southern stream creeping in from the south-east, and the northern stream stealing round Hecla towards the south-west. The track of this remarkable deflection and reunion is clearly marked out by numerous striæ all over the low-grounds that slope outwards to the Atlantic coast. The till, it need hardly be added, affords the same kind of evidence as the sub-glacial deposits of the other islands, and points unmistakably to a general ice-movement across South Uist from the Minch to the Atlantic.

The influence which an irregular surface has in causing local deflections of an ice-flow is also well seen in Barra, where the striæ sometimes point some 5° or 10°, and sometimes 25° and even 35° north of west--these variations being entirely due to the configuration of the ground. This island is extremely bare in many places, more especially over all the region that slopes to the Minch. The Atlantic border is somewhat better covered with soil, as is the case with South Uist and the other islands already described.

Vatersey, Saundry, Papey, Miuley, and Bearnarey, are all equally well glaciated; but as they show little or no low-ground with gentle slopes, they have preserved few traces of sub-glacial débris. In this respect they resemble the rockier and hillier parts of the large islands to the north. Till, however, is occasionally met with, as for example on the low shores of Vatersey Bay, and on the southern margin of Miuley. Doubtless, if it were carefully looked for it would be found sheltering in patches in many nooks and hollows, protected from the grind of the ice that advanced from the south-east. I saw it in several such places in the islet of Bearnarey, where the striæ indicated an ice-flow as usual towards the north-west.

We have now seen that the whole of the Long Island has been ground, and rubbed, and scraped by land- or glacier-ice which has traversed the ground in a prevalent south-east and north-west direction. We have seen also that this ice attained so great a thickness that it was able to overflow all the hills up to a height of 1600 feet above the sea. It is needless to say that such a mass could not have been nurtured on the islands themselves. They have no gathering grounds of sufficient extent, and if they had, the ice would not have taken the peculiar direction it did. Instead of flowing across the islands it would have radiated outwards from the mountain-valleys. Where, then, did the ice come from?

Looking across the Minch we see Skye and the mountains of the north-west Highlands, and those regions, as we know, have also been subjected to extreme glaciation. From the appearances presented by the mountains of Ross-shire we are compelled to believe that all that region was buried in ice up to a height of not less than 3000 feet--the ice-sheet was probably even as much as 3500 feet in thickness. The evidence shows that the under portion of this vast ice-sheet flowed slowly off the country into the Minch by way of the great sea-lochs. Thus we know that an enormous mass crept down Loch Carron and united with another great stream stealing out from the mountains of Skye, to flow north through the hollows of Raasay Sound and the Inner Sound into the Minch. So deep was the ice that it completely smothered the island of Raasay (1272 feet high) and overflowed all the lofty trappean table-lands of Skye. From the Coolins, as a centre-point, another movement of the ice-sheet was towards the south-west, against the islands of Rum, Cannay, and Eigg. Further north similar vast masses of ice streamed out into the Minch, from Loch Torridon, Gairloch, Loch Ewe, and Loch Broom. The direction of the glaciation in the north of Skye, which is towards north-west, shows that the glacier-mass which overflowed that area must eventually have reached the shores of the Long Island. In short, there cannot be a reasonable doubt that the immense sheet of ice that streamed off the north-west Highlands must have filled up entirely the basin of the Minch, and thereafter streamed across the Outer Hebrides. But it may be objected that if the Outer Hebrides were overflowed by ice that streamed from the mainland across the north end of Skye, we ought to get many fragments of Skye rocks and Ross-shire rocks too in the sub-glacial débris or till of Lewis and Harris, and the north end of North Uist. But all such fragments are apparently wanting. True, there are bits of stone like the igneous rocks of Skye often met with in the Hebridean till, but as veins or dykes of precisely the same kind of rock occur in the Long Island itself, we cannot say that the stones referred to are other than native. A little reflection will show us, however, that it is extremely improbable indeed that stones derived from Skye and the mainland should ever have been dragged on under the ice, and deposited amongst the till of the Long Island. There is only one part of the whole Outer Hebrides where we might have anticipated that fragments from the mainland should occur; and there, sure enough, they put in an appearance.