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Netherlorn and its Neighbourhood
Chapter III - The Slate Islands: Seil


"And a record of commotion
Which a thousand ridges yield;
Ridge, and gulf, and distant ocean
Gleaming like a silver shield."

- WORDSWORTH, Poems of the Imagination.

The western shore of the island of Seil, notably the part fringing the lands of Kilbride, presents an excellent example of "raised beach." It is striking on account of its extent and uniformity, and the battlemented character of the precipices, which, 200 yards and more from the present shore-line, rise abruptly from it. Scattered over it we find numerous "pot-holes," polished dykes and boulders, left as they were when the slow elevation of the land had placed them beyond the reach of breaker action. These precipices show natural sections of the strata, and no better place can be found for the study of the geology of slate.

The strata of rock vary in thickness from an inch or less to many feet. The native workmen call the smaller seams "bands," the larger "stones." It requires a considerable amount of practice to detect the line of division between the various strata, and this line must not be confounded with the cleavage planes; the latter are usually quite apparent, and pass across large tracts of rock quite irrespective of the foldings and contortions which the strata may undergo. The cleavage planes, having been super-induced long after the deposition of the clay which ultimately hardened into slate, have no connection with the bedding. The strike of these planes is exactly parallel to the characteristic indentations of the coast-line, and probably the titanic forces which squeezed or thrust the strata into folds produced a rearrangement of the axes of the particles of the slate at right angles or tangential to the direction of the force.

The strata are seen to be folded in an inverted manner, the arches (anticlines) being bent towards the north-west. To the different parts of these folds the quarrymen have given characteristic names: thus the middle limb, which has a more or less perpendicular but overhanging dip, is called the "beul" (mouth); as the fold turns at the bottom of the trough (syncline) it is called "bonn" (sole); while the ascending limb, which generally approaches the horizontal, is called a "sgreab" (crust).

The inversion of these anticlines explains the peculiar outline of the Slate Islands as viewed from the south-west. The series of parallel ridges which traverse the islands, with steep western sides and sloping declivities to the east, are the remains of the folds; the perpendicular parts of the arches, owing to the cleavage planes and the dip approximating, presenting much greater resistance to the powers of erosion than the horizontal folds with intersecting cleavage.

Speaking of the geological characteristics of slate rock, but with special reference to Easdale, Mr. Whyte, in his letters already referred to, says: -"It is well known to slate miners that roofing slates are usually distributed in bands through other rocks of a slaty character of little or no economic value, and not infrequently associated with quartzite and limestones more or less impure. In the island of Easdale there are two such seams which may be traced through their various contortions from one end of the island to the other. These seams are made up of different beds varying in thickness from a few inches to many feet; and it may be noticed as an indication of the sedimentary character of these slate rocks that there is a decided difference in the quality of the upper and lower portions of the thicker beds, the former being fine-grained and smooth, and the latter coarse and gritty: a feature which we recognise as analogous to that exhibited by other rocks of sedimentary origin.

"Although the slate-seams are so much contorted as to be found at various angles with the horizon, the cleavage plane invariably maintains an angle of 37" to a vertical line. Where the rock has been least disturbed from the horizontal position it is more easily quarried, and yields better slates. In some instances a space, which must originally have measured several feet, has been compressed into a few inches, and yields an inferior quality of slate. These 'bands' are from a quarter of an inch to a few inches in thickness, they are harder than the general mass, are much more thickly studded with cubes of iron pyrites, and form a sort of selvage on the slates. In both of the Easdale slate-seams there are beds composed of irregular nodules, half-slate, half-limestone" (the nodules are called "neasgaidean" (boils) by the quarriers). "These are continuous, accompanying the slate in all its undulations; some have a curved cleavage, while the fracture of others is conchoidal. Round the nodules the slate bends like wood round a knot. A well-defined stratum of the character described appears in Easdale and occupies such a position as to justify a division of the slate deposit into an upper and a lower seam, as represented in the section. The slates of Easdale are much affected by what the quarriers call "cuts" (gearraidhean). These are joints which intersect the strata in a vertical direction. Some are found to extend from the surface to the greatest depth reached, while others pass through a few beds only. The greater number, however, appear to be confined to one stratum. Where the rock is thus divided into lengths of a few feet it is more easily quarried; for, although at the cuts it does not seem to have ever been completely separated, it parts readily in much the same way as a sheet of glass does after it has been run over by the glazier's diamond.

"Faults in the rock are called 'skews' by the quarriers, and not infrequently they are filled with clay, caused by the attrition of the surfaces in the process of displacement. They are very injurious, and render the rock coarse and friable in their immediate neighbourhood."

Mr. Whyte, who was called by James Nicol, Professor of Natural History in Aberdeen University, "the intelligent overseer of the Easdale quarries," was born at Bunawe in 1800, and came to Easdale in 1824, as Quarry wright. His general intelligence and steadiness soon gained for him the position of quarry manager, a post he held for over thirty years. He was an excellent mechanic, in the early thirties, for instance, he devised and constructed a small pleasure boat propelled by an Archimedean screw: the boat was used for many years to ferry himself to and fro across the channel. An acute observer of natural phenomena, he became a passable geologist, and his remarks upon the rock features of the Easdale slate-beds are worth preserving as the first succinct and correct appreciation of the geological characteristics of this interesting island; much clearer, for instance, than the lengthy description of Easdale given by Dr. MacCulloch in his Geology of the Western Isles: indeed the learned doctor seems to have had an imperfect knowledge of this particular rock, and it is doubtful whether he had a clear notion of the difference between slaty cleavage and stratification. Mr. Whyte left Easdale in 1863, became manager for the Earl of Mansfield of Logiealmond Slate Quarries, and died at Methven in Perthshire in 1885.

Reference has already been made to the numerous trap dykes which intrude here and there among the slate. One series runs between the seams, and it might appear that these sheets of igneous rock were contemporaneous with the slate formation, at any rate they do not affect the quality of the adjacent rock very much; but when these dykes cross the beds they render the rock unworkable for many feet on each side, not only from what one may call a contact metamorphism, but from mechanical disruption of the strata. These latter dykes are the bane of slate-quarrying, and have on many occasions caused the abandonment of what otherwise would have been valuable workings.

Interposed occasionally between the strata are seams of dark limestone banded with quartz or calcite. A vein of this material may be seen on the shores of Cuan Sound; it is folded into three large arches; these have been denuded of overlying rock and make a pretty picture.

A large detached tower of rock, capped with the remains of a prehistoric fort, rises from the old beach near its southern termination. It is known as "Caisteal Muici". Dr. Christison, in his work upon the "Early Fortifications in Scotland", describes this hill-fort fully, and the description is aided by very striking drawings. The rock is about 60 feet high, quite unapproachable on three sides, with a narrow steep slope of debris on the fourth by which access was obtained to the fort. The walls, still in parts about 8 feet high, are built on the edge of the steep sides, while a lower work protects the approach.

There are about fifty forts of a similar nature in Lorn, and of that number sixteen are in Netherlorn. They are variously called hill-forts, Danish forts, or duns. Sometimes, on account of the circular or oval forms in which they are invariably built, they are called "curvilinear forts." The popular belief is that they were watch-towers guarding the coast and announcing by fire-signals the approach of an invader; but more than likely they were the abode of predatory chiefs, each with his crew of piratical followers. The sites usually selected were, a rocky eminence precipitous on three sides, a promontory jutting into the sea, or the rounded top or pinnacle of a hill. Their defensive strength was entirely due to the nature of the site, as the buildings generally were of a miserable description. The use of flanking towers, bastions, or outworks was evidently unknown; indeed, few of the later Highland castles possess these, and active defence would be almost as dangerous as the attack. At the most they gave the inmates protection against a sudden assault. Another of these ancient fortalices is situated at the extreme north end of the "raised beach"; it is known as Dun Aorain. It was a building of much greater strength and magnitude than Caisteal Muici. Erected upon a bottle-shaped peninsula, the neck of land being strongly fortified, it guarded the mouth of the Caolas at Easdale, a channel which in olden times would usually have been selected for smaller boats, journeying north and south, to avoid the heavy seas which are seldom absent off Easdale.

The north-west or "back" of Sell presents a magnificent series of sheer precipices and deep cavernous gullies, the resting-place of the raven and the abode of numerous flights of wild pigeon. These precipices flank the huge mass of trap rock which constitutes Dunmore Hill, the highest part of the island. This cap of trap covers the slate, which, disappearing below it at Easdale, reappears at Ardencaple on the north. On the little patches of beach left here and there embaying the land along this rugged shore are to be found outliers of red sandstone, dipping north-west, the last vestiges of that rock on the island. Curious pinnacles and stacs present themselves J one of these, the " Bishop of Lorn," has, when viewed from the sea, a remarkable resemblance to a bishop, habited in his vestments, in the attitude of prayer.

From Ardencaple Point, known in Gaelic as Rudha na Garbhairde (the promontory of the rough heights), a good view of the "Toad of Lorn" (Losgann Lathurnach) may be had. Surveyed from a distance, this curious rock feature appears like a huge frog in a state of watchful repose. It requires little imagination to detect the protuberant eyes and elongated mouth of the "toad ugly and venomous." The island of Seil is separated from the mainland by Clachan Sound, which to the south widens into a broader expanse of water known as Ardmaddie Loch; while the narrow passage of Cuan (Gaelic cumhan, narrow) divides it from the islands of Luing and Torsa.

A true idea of these ocean channels can only be got by boating upon them. At every bend of their sinuous course entertaining and unexpected views are disclosed. Entering Clachan Sound from the north with ebb tide, we are astonished to find a rapid current bearing us along between banks green to the water's edge, and delightfully wooded with ash and birch. High precipices close us in on each side, and were it not for the presence of the long streaming tangle (Laminaria) below, we might consider ourselves far from the open sea, borne along by the current of a great river. To aid in the deception we suddenly discover in Front of us a large gracefully arched bridge, through which we get a glimpse of a broad lake--Ardmaddie Loch--embosomed in diversified shores; wooded cliffs surmounted by heath-covered rolling uplands on the one side, and the green, fertile shores of Seil on the other.

Clachan Bridge is a single arch of masonry, with a span of 70 feet, and 40 feet above the bed of the channel. It was completed in 1792, from plans by the famous Telford. Vessels of 40 tons burthen may pass through this channel with high tides.

For about a mile south of the bridge the channel remains tortuous. Just at that point where it broadens into the loch there is a narrow deep bay or cul-de-sac. Here, in 1835, a huge whale (probably Balaena australias) was killed. The animal having failed to force a passage through the sound, in attempting to turn ran into the creek. The whale measured 78 feet from snout to tail, the lower jaw was 21 feet long, while the flukes measured 18 feet from tip to tip. In August 1837 a school of one hundred and ninety-two Pilot whales (Globiocephalus melas) was captured about the same spot: the largest was 26 feet long.

Further down the loch, on the east, we meet with a remarkable dyke of basalt, forming a huge wall 50 feet high and about 5 feet broad, passing from a precipitous rock of schist, right across the old sea-beach for about 100 yards towards the Ardmaddie ferry-pier: the precipice is known as Creag Giullain (Giullan, a little boy--a term of endearment). During the Seven Years' War, Major John MacLachlan, the Laird of Kilchoan, served in the American campaigns against the French. While doing outpost duty he was captured by Indians. The savages bound his arms, placed him upon the back of his horse Giullan, tied his hair to a, tree, and left him to await a painful death, when the horse should move away. However, the fond and docile animal, obedient to its master's entreaties, remained still, until the Major in some way or another tore himself from the tree. MacLachlan made his way to safety, but was afterwards quite bald, hence he was called in his later days "A' Major maol" (the bald major). He took Giullan home to Kilchoan. Some years later he rented Ardmaddie House and grounds. Giullan was allowed to stray at will over the best pastures, had no work to do, and no one was allowed to interfere with him. As the horse grew old and blind he became a nuisance to the neighbouring crofters and cottars, and to get rid of him with an easy conscience, avoiding blame, they devised the following plan. Tying to the horse's neck a short pole, from the end of which a wisp of fresh hay dangled in front of the animal's nose, they set him straight for the precipice; the horse followed the wisp, with the foregone result that Giullan strayed accidentally over the rock which has since borne his name.

Between many of the islands the channel is very narrow; indeed, it would seem as if some mighty convulsion of nature had thrown what was a long promontory of land into a number of disjointed fragments. Through these straits rush currents of enormous volume and great velocity, on whose surface large bossy ebullitions and deep whirlpools alternate, speeding past as they are while powerful eddies on each side permit the passage at all states of the tide. The boatmen take advantage of these lateral currents to gain a vantage-ground whereby they can traverse the main current safely.

The stream which flows through the Sound of Cuan attains a maximum velocity of 9 miles an hour with spring tides. As it emerges from the gut (Beul a chuain) and encounters borne along by the main stream; each side permit the passage at all the resistance of the body of waters outside a great heaving and rippling is caused, which is further accentuated by the presence of a long submerged reef or spit extending the greater part of the distance across the mouth. With a strong gale of wind against tide the commotion is very great. At such times, the bleak coast, the fiercely turbulent sea with its huge breakers tossed hither and thither shedding spray and spindrift afar, the whistling of the wind up the narrows, and the sullen roar of the stream as it forces its way persistently to the sea, combine to make the scene vividly impressive.

"Full of great rooms and small the palace stood,
All various, each a perfect whole,
From living Nature, fit for every mood
And change of my still soul.

"One show'd an iron coast and angry waves,
You seem'd to hear them climb and fall
And roar rock-thwarted under bellowing caves,
Beneath the windy wall."

-TENNYSON, The Palace of Art.


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