Rosemarkie and its Scaurs--Kaes' Craig--A Jackdaw
Settlement--"Rosemarkie Kaes" and "Cromarty Cooties"--"The Danes,"
a Group of Excavations--At Home in Cromarty--The Boulder-clay of
Cromarty "begins to tell its story"--One of its marked Scenic
Peculiarities--Hints to Landscape Painters--"Samuel's Well"--A
Chain of Bogs geologically accounted for--Another Scenic
Peculiarity--"_Ha-has_ of Nature's digging"--The Author's earliest
Field of Hard Labor--Picturesque Cliff of Boulder-clay--Scratchings
on the Sandstone--Invariable Characteristic of true
Boulder-clay--Scratchings on Pebbles in the line of the longer
axis--Illustration from the Boulder-clay of Banff.
Rosemarkie, with its long narrow valley and its red abrupt _scaurs_,[14]
is chiefly interesting to the geologist for its vast beds of the
boulder-clay. I am acquainted with no other locality in the kingdom
where this deposit is hollowed into ravines so profound, or presents
precipices so imposing and lofty. The clay lies thickly over most part
of the Black Isle and the peninsula of Easter Ross,--both soft sandstone
districts,--bearing everywhere an obvious relation, as a deposit, to
both the form and the conditions of exposure of the existing land,--just
as the accumulated snow of a long-lying snow-storm, exposed to the
drifting wind, bears relation to the heights and hollows of the tracts
which it covers. On the higher eminences the clay forms a comparatively
thin stratum, and in not a few instances it has been wholly worn away;
while on the lower grounds, immediately over the old coast line, and in
the sides of hollow valleys,--exactly such places as we might expect to
see the snow occupying most deeply after a night of drift,--we find it
accumulated in vast beds of from eighty to an hundred feet in thickness.
One of these occurs in the opening of the narrow valley along which my
course this morning lay, and is known far and wide,--for it forms a
marked feature in the landscape, and harbors in its recesses a countless
multitude of jackdaws,--as the "Kaes' Craig of Rosemarkie." It presents
the appearance of a hill that had been cut sheer through the middle from
top to base, and exhibits in its abrupt front a broad red perpendicular
section of at least a hundred feet in height, barred transversely by
thin layers of sand, and scored vertically by the slow action of the
rains. Originally it must have stretched its vanished limb across the
opening like some huge snow-wreath accumulated athwart a frozen rivulet;
but the incessant sweep of the stream that runs through the valley has
long since amputated and carried it away; and so only half the hill now
remains. The Kaes' Craig resembles in form a lofty chalk cliff, square,
massy, abrupt, with no sloping fillet of vegetation bound across its
brow, but precipitous direct from the hill-top. The little ancient
village of Rosemarkie stretches away from its base on the opposite side
of the stream; and on its summit and along its sides, groups of
chattering jackdaws, each one of them as reflective and philosophic as
the individual immortalized by Cowper, look down high over the chimneys
into the streets. The clay presents here, more than in almost any other
locality with which I am acquainted, the character of a stratified
deposit; and the numerous bands of sand by which the cliff is
horizontally streaked from top to bottom we find hollowed, as we
approach, into a multitude of circular openings, like shot-holes in an
old tower, which form breeding-places for the daw and the sand-martin.
The biped inhabitants of the cliff are greatly more numerous than the
biped inhabitants of the quiet little hamlet below; and on Fortrose
fair-days, when, in virtue of an old feud, the Rosemarkie boys were wont
to engage in formidable bickers with the boys of Cromarty, I remember,
as one of the invading belligerents, that, in bandying names with them
in the fray, we delighted to bestow upon them, as their hereditary
sobriquet, given, of course, in allusion to their feathered neighbors,
the designation of the "_Rosemarkie kaes_." Cromarty, however, is
two-thirds surrounded by the waters of a frith abounding in sea-fowl;
and the little fellows of Rosemarkie, indignant at being classed with
their _kaes_, used to designate us with hearty emphasis, in turn, as the
"_Cromarty cooties_," _i.e._, coots.
A little higher up the valley, on the western side, there occurs in the
clay what may be termed a _group_ of excavations, composing a piece of
scenery ruinously broken and dreary, and that bears a specific character
of its own which scarce any other deposit could have exhibited. The
excavations are of considerable depth and extent,--hollows out of which
the materials of pyramids might have been taken. The precipitous sides
are fretted by jutting ridges and receding inflections, that present in
abundance their diversified alternations of light and shadow. The steep
descents form cycloid curves, that flatten at their bases, and over
which the ferruginous stratum of mould atop projects like a cornice.
Between neighboring excavations there stand up dividing walls, tall and
thin as those of our city buildings, and in some cases broken at their
upper edges into rows of sharp pinnacles or inaccessible turf-coped
turrets; while at the bottom of the hollows, washed by the runnels
which, in the slow lapse of years, have been the architects of the
whole, we find cairn-like accumulations of water-rolled stones,--the
disengaged pebbles and boulders of the deposit. The boulders and pebbles
project also from the steep sides, at all heights and of all sizes,
like the primary masses inclosed in our ancient conglomerates, when
exhibited in wave-worn precipices,--forcing upon the mind the conclusion
that the boulder-clay is itself but an unconsolidated conglomerate of
the later periods, which occupies nearly the same relative position to
the existing vegetable mould, with all its recent productions, that the
great conglomerate of the Old Red Sandstone occupies in relation to the
lower ichthyolite beds of that system, with their numerous extinct
organisms. But its buried stones are fretted with hieroglyphic
inscriptions, in the form of strange scratchings and polishings,
grooves, ridges, and furrows,--always associated with the
boulder-clays,--which those of the more ancient conglomerates want, and
which, though difficult to read, seem at length to be yielding up the
story which they record. Of this, however, more anon. Viewed by
moonlight, when the pale red of the clay where the beam falls direct is
relieved by the intense shadows, these excavations of the valley of
Rosemarkie form scenes of strange and ghostly wildness: the projecting,
buttress-like angles,--the broken walls,--the curved inflections,--the
pointed pinnacles,--the turrets, with their masses of projecting
coping,--the utter lack of vegetation, save where the heath and the
furze rustle far above,--all combine to form assemblages of dreary
ruins, amid which, in the solitude of night, one almost expects to see
spirits walk. These excavations have been designated, from time
immemorial, by the neighboring town's-people, as "the Danes;" but
whether the name be, as is most probable, merely a corruption of an
appropriate enough Saxon word, "the dens," or derived, as a vague
tradition is said to testify, from the ages of Danish invasion, it is
not quite the part of the geologist to determine. It may be worth
mentioning, however, from its bearing on the point, that there are two
excavations in the boulder-clay near Cromarty, one of which has been
long known by the name of "the Morial's Den," while the other, greatly
smaller in size, rejoices in the double diminutive of "the Little
Dennie." For an hour or so the Danes proved agreeable though somewhat
silent companions; and then, climbing the opposite side of the valley, I
gained the high road, and, walking on to Cromarty, found myself once
more among "the old familiar faces."
In a few days the storm blew by; and as the prolonged rains had cleared
out the deep ravines of the district, and given to the boulder-clay in
which they are scooped a freshness in its section analogous to fresh
fracture in rocks of harder consistency, I availed myself of the
facilities afforded me in consequence, for exploring it once more. It
has long constituted one of the hardest of the many riddles with which
our Scottish deposits exercise the patience and ingenuity of the
geologist. I remember a time when, after passing a day under its barren
_scaurs_, or hid in its precipitous ravines, I used to feel in the
evening as if I had been travelling under the cloud of night, and had
seen nothing. It was a morose and taciturn companion, and had no
speculation in it. I might stand in front of its curved precipices, red,
yellow or gray, according to the prevailing average color of the rocks
on which it rests, and mark their water-rolled boulders, of all
qualities and sizes, sticking out in bold relief from the surface, like
the rock-like protuberances that roughen the rustic basements of the
architect, from the line of the wall; but I had no _open sesame_ to form
vistas through them into the recesses of the past. I saw merely the
stiff pastry matrix of which they are composed, and the inclosed
pebbles. But the boulder-clay has of late become more sociable; and,
though with much hesitancy and irresolution, like old Mr. Spectator on
the first formal opening of his mouth,--a consequence, doubtless, in
both cases of previous habits of silence long indulged,--it begins to
tell its story. And a most curious story it is.
The morning was clear, but just a little chill; and a soft covering of
snow, that had fallen during the storm on the flat summit of Ben-Wevis,
and showed its extreme tenuity by the paleness of its tint of watery
blue, was still distinctly visible at the distance of full twenty miles.
The sun, low in the sky,--for the hour was early,--cast its slant rays
athwart the prospect, giving to each nearer bank and hillock, and to the
more distant protuberances on the mountain-sides, those well-defined
accompaniments of shadow that serve by throwing the minor features of a
landscape upon the eye in bold relief, to impart to it an air of higher
finish and more careful filling up than it ever bears under a more
vertical light. I took the road which, leading westward from the town
towards Invergordon Ferry, skirts the Frith on the one hand, and runs
immediately under the noble escarpment of green bank formed by the old
coast line on the other. Fully two-thirds of the entire height of the
rampart here, which rises in all about a hundred feet over the
sea-level, is formed of the boulder-clay; and I am acquainted with no
locality in which the deposit presents more strongly, for at least the
first half mile, one of its marked scenic peculiarities. It is furrowed
vertically on the slope, as if by enormous flutings in the more antique
Doric style; and the ridges by which these are separated,--each from a
hundred to a hundred and fifty feet in length, and from five-and-twenty
to thirty feet in average height,--resemble those burial mounds with
which the sexton frets the churchyard turf; with this difference,
however, that they seem the burial mounds of giants, tall and bulky as
those that of old warred against the gods. They are striking enough to
have caught the eye of the children of the place, and are known among
them as the Giants' Graves. I could fain have taken their portrait in a
calotype this morning, as they lay against the green bank,--their feet
to the shore, and their heads on the top of the escarpment,--like
patients on a reclining bed, and strongly marked, each by its broad bar
of yellow light and of dark shadow, like the ebon and ivory buttresses
of the poet. This little vignette, I would have said to the landscape
painter, represents the boulder-clay, after its precipitous banks--worn
down, by the frosts and rains of centuries, into parallel runnels, that
gradually widened into these hollow grooves--had sunk into the angle of
inclination at which the disintegrating agents ceased to operate, and
the green sward covered all up. You must be studying these peculiarities
of aspect more than ever you studied them before. There is a time coming
when the connoisseur will as rigidly demand the specific character of
the various geologic rocks and deposits in your hills, _scaurs_, and
precipices, as he now demands specific character in your shrubs and
trees.
It is worthy the notice of the young geologist, who has just set himself
to study the various effects produced on the surface of a country by the
deposits which lie under it, that for about a quarter of a mile or so,
the base of the escarpment here is bordered by a line of bogs, that bear
in the driest weather their mantling of green. They are fed with a
perennial supply of water, by a range of deep-seated springs, that come
bursting out from under the boulder-clay; and one of their number, which
bears I know not why, the name of Samuel's Well, and yields its equable
flow at an equable temperature, summer and winter, into a stone trough
by the way-side, is not a little prized by the town's-people, and the
seamen that cast anchor in the opposite roadstead, for the lightness and
purity of its water. What is specially worthy of notice in the case is,
the very definite beginning and ending of the chain of bogs. All is dry
at the base of the escarpment, up to the point at which they commence;
and then all is equally dry at the point at which they terminate. And of
exactly the same extent,--beginning where the bogs begin, and ending
where they end,--we may trace an ancient stratum of pure sand,--of
considerable thickness, intercalated between the base of the clay and
the superior surface of the Old Red Sandstone. It is through this
permeable sand that the profoundly seated springs find their way to the
surface,--for the clay is impermeable; and where it comes in contact
with the rock on either side of the arenaceous stratum, the bogs cease.
The chain of green bogs is a consequence of the stratum of permeable
sand. I have in vain sought this ancient layer of sand,--decidedly of
the same era with the argillaceous bed which overlies it,--for aught
organic. A single shell, so unequivocally of the period of the
boulder-clay as to occur at the base of the deposit, would be worth, I
have said, whole drawerfuls of fossils furnished by the better-known
deposits. But I have since seen in abundance shells of the boulder-clay.
There is another scenic peculiarity of the clay, which the neighborhood
of Cromarty finely illustrates, and of which my walk this morning
furnished numerous striking instances. The Giants' Graves--to borrow
from the children of the place--occur on the steep slopes of the old
coast line, or in the sides of ravines, where the clay, as I have said,
had once presented a precipitous front, but had been gradually moulded,
under the attritive influences of the elements, into series of
alternating ridges and furrows, which, when they had flattened into the
proper angle, the green sward covered up from further waste. But the
deep dells and narrow ravines in which many ranges of these graves occur
are themselves peculiarities of the deposit. Wherever the boulder-clay
lies thick and continuous, as in the parish of Cromarty, on a sloping
table-land, every minute streamlet cuts its way to the solid rock at the
bottom, and runs through a deep dell, either softened into beauty by the
disintegrating process, or with all its precipices standing up raw and
abrupt over the stream. Four of these ravines, known as the "Old Chapel
Burn," the "Ladies' Walk," the "Morial's Den," and the "Red Burn," each
of them cutting the escarpment of the ancient coast line from top to
base, and winding far into the interior, occur in little more than a
mile's space; and they lie still more thickly farther to the west. These
dells of the boulder clay, in their lower windings,--for they become
shallower and tamer as they ascend, till they terminate in the uplands
in mere _drains_, such as a ditcher might excavate at the rate of a
shilling or two per yard,--are eminently picturesque. On those gentler
slopes where the vegetable mould has had time and space to accumulate,
we find not a few of the finest and tallest trees of the district. There
is a bosky luxuriance in their more sheltered hollows, well known to the
schoolboy what time the fern begins to pale its fronds, for their store
of hips, sloes, and brambles; and red over the foliage we may see, ever
and anon as we wend upwards, the abrupt frontage of some precipitous
_scaur_, suited to remind the geologist, from its square form and flat
breadth of surface, of the cliffs of the chalk. When viewed from the
sea, at the distance of a few miles, these ravines seem to divide the
sloping tracts in which they occur into large irregular fields, laid out
considerably more in accordance with the principles of the landscape
gardener than the stiffly squared rectilinear fields of the
agriculturist. They are _ha-has_ of Nature's digging; and their bottom
and sides in this part of the country we still find occupied in a few
cases--though in many more they have been ravaged by the wasteful
axe--by noble forest-_hedges_, tall enough to overtop, in at least their
middle reaches, the tracts of table-land which they divide.
I passed, a little farther on, the quarry of Old Red Sandstone, with a
huge bank of boulder-clay resting over it, in which I first experienced
the evils of hard labor, and first set myself to lessen their weight by
becoming an observer of geological phenomena. It had been deserted
apparently for many years; and the debris of the clay partially covered
up, in a sloping talus, the frontage of rock beneath. Old Red Sandstone
and boulder-clay, a broad bar of each!--such was the compound problem
which the excavation propounded to me when I first plied the tool in
it,--a problem equally dark at the time in both its parts. I have since
got on a very little way with the Old Red portion of the task; but alas
for the boulder-clay portion of it! A bar of impenetrable shadow has
rested long and obstinately over the newer deposit; and I scarce know
whether the light which is at length beginning to play on its pebbly
front be that of the sun or of a delusive meteor. But courage, patient
hearts! the boulder-clay will one day yield up _its_ secret too. Still
further on by a few hundred yards, I could have again found use for the
calotype, in transferring to paper the likeness of a protuberant
picturesque cliff, which, like the Giants' Graves, could have belonged,
of all our Scotch deposits, to only the boulder-clay. It stands out, on
the steep acclivity of a furze-covered bank, abrupt as a precipice of
solid rock, and yet seamed by the rain into numerous divergent channels,
with pyramidal peaks between; and, combining the perpendicularity of a
true cliff with the water-scooped furrows of a yielding clay, it
presents a peculiarity of aspect which strikes, by its grotesqueness,
eyes little accustomed to detect the picturesque in landscape. I
remember standing to gaze upon it when a mere child; and the fisher
children of the neighboring town still tell that "_it has been
prophesied_" it will one day fall, "and kill a man and a horse on the
road below,"--a legend which shows it must have attracted _their_ notice
too.
I selected as the special scene of exploration this morning, a deep
ravine of the boulder-clay, which had been recently deepened still more
by the waters of a mill-pond, that had burst during a thunder-shower,
and, after scooping out for themselves a bed in the clay some twelve or
fifteen feet deep, where there had been formerly merely a shallow drain,
had then tumbled into the ravine, and bared it to the rock. The
sandstones of the district, soft and not very durable, show the
scratched and polished surfaces but indifferently well, and, when
exposed to the weather, soon lose them; but in the bottom of the runnel
by which the ravine is swept I found them exceedingly well marked,--the
polish as decided as the soft red stone could receive, and the lines of
scratching running in their general bearing due east and west, at nearly
right angles with the course of the stream. Wherever the rock had been
laid bare during the last few months, _there_ were the markings;
wherever it had been laid bare for a few twelvemonths, they were gone. I
next marked a circumstance which has now for several years been
attracting my attention, and which I have found an invariable
characteristic of the true boulder-clay. Not only do the rocks on which
the deposit rests bear the scratched and polished surfaces, but in every
instance the fragments of stone which it incloses bear the scratchings
also, if from their character capable of receiving and retaining such
markings, and neither of too coarse a grain nor of too hard a quality.
If of limestone, or of a coherent shale, or of a close, finely-grained
sandstone, or of a yielding trap, they are scratched and
polished,--invariably on one, most commonly on both their sides; and it
is a noticeable circumstance, that the lines of the scratchings occur,
in at least nine cases out of every ten, in the lines of their longer
axes. When decidedly oblong or spindle-shaped, the scratchings run
lengthwise, preserving in most cases, on the under and upper sides, when
both surfaces are scratched, a parallelism singularly exact; whereas,
when of a broader form, so that the length and breadth nearly
approximate,--though the lines generally find out the longer axis, and
run in that direction,--they are less exact in their parallelism, and
are occasionally traversed by cross furrows. Of such certain occurrence
is this longitudinal lining on the softer and finer-grained pebbles of
the boulder-clay, that I have come to regard it as that special
characteristic of the deposit on which I can most surely rely for
purposes of identification. I am never quite certain of the boulder-clay
when I do not detect it, nor doubtful of the true character of the
deposit when I do. When examining, for instance, the accumulation of
broken Liasic materials in the neighborhood of Banff, I made it my first
care to ascertain whether the bank inclosed fragments of stone or shale
bearing the longitudinal markings; and felt satisfied, on finding that
it did, that I had discovered the period of its re-formation.