"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
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.
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
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."
The Palace of Art.