and unsubmerged relics, is of vast geological antiquity. It was
certainly in existence, and had even undergone very considerable
erosion, before the Old Red Sandstone period, as is proved by the
fact that large tracts of the Old Red Sandstone formation are found
occupying hollows in its surface. Glenmore had already been excavated
when the conglomerates of the Old Red Sandstone began to be laid
down. Some of the low-lying maritime tracts of the Highland area in
Caithness, and the borders of the Moray Firth, are covered with the
sandstones of that age; and there is evidence to show that these
strata formerly extended over wide regions, from which they have since
been removed by erosion. The fact that the Old Red Sandstone deposits
still occupy such extensive areas in the north-east of the mainland,
and in Orkney, shows that the old table-land shelved away gradually
to north and east, and the same conclusion may be drawn, as we have
seen, from the direction followed by the main lines of the existing
drainage-system. We see, in short, in the table-land of the Highlands,
one of the oldest elevated regions of Europe--a region which has been
again and again submerged either in whole or in part, and covered with
the deposits of ancient seas and lakes, only to be re-elevated, time
after time, and thus to have those deposits in large measure swept away
from its surface by the long-continued action of running water and
other agents of denudation.
* * * * *
The Central Lowlands.--The belt of low-lying ground that separates the
Highlands from the Southern Uplands is, as we have seen, very well
defined. In many places the Uplands rise along its southern margin as
abruptly as the Highlands in the north. The southern margin coincides,
in fact, for a considerable distance (from Girvan to the base of the
Moorfoots) with a great fracture that runs in the same direction as the
bounding fracture or fault of the Highlands. The Central Lowlands may
be described, in a word, as a broad depression between two table-lands.
A glance at the map will show that the principal features of the
Lowlands have a north-easterly trend--the same trend, in fact, as the
bounding lines of the division. To this arrangement there are some
exceptions, the principal being the belt of hilly ground that extends
from the neighbourhood of Paisley, south-east through the borders of
Renfrewshire and Ayrshire, to the vicinity of Muirkirk. The major part
of the Lowlands is under 500 feet in height, but some considerable
portions exceed an elevation of 1000 feet, while here and there the
hills approach a height of 2000 feet--the two highest points (2352 and
2335 feet) being attained in Ben Cleugh, one of the Ochils, and in
Tinto. Probably the average elevation of the Lowland division does not
exceed 350 or 400 feet. Speaking generally, the belts of hilly ground,
and the more or less isolated prominences, are formed of more durable
rocks than are met with in the adjacent lower-lying tracts. Thus the
Sidlaws, the Ochil Hills, and the heights in Renfrewshire and Ayrshire,
are composed chiefly of more or less hard and tough volcanic rocks; and
when sandstones enter into the formation of a line of hills, as in the
Sidlaws, they generally owe their preservation to the presence of the
volcanic rocks with which they are associated. This is well illustrated
by the Lomond Hills in Fifeshire, the basal and larger portion of which
consists chiefly of somewhat soft sandstones, which have been protected
from erosion by an overlying sheet of hard basalt-rock. All the
isolated hills in the basin of the Forth are formed of knobs, bosses,
and sheets of various kinds of igneous rock, which are more durable
than the sandstones, shales, and other sedimentary strata by which they
are surrounded. Hence it is very evident that the configuration of the
Lowland tracts of Central Scotland is due to denudation. The softer
and more readily disintegrated rocks have been worn away to a greater
extent than the harder and less yielding masses.
Only in a few cases do the slopes of the hill-belts coincide with folds
of the strata. Thus, the northern flanks of the Sidlaws and the Ochils
slope towards the north-west, and this also is the general inclination
of the old lavas and other rocks of which those hills are composed.
The southern flanks of the same hill-belt slope in Fifeshire towards
the south-east--this being also the dip or inclination of the rocks.
The crest of the Ochils coincides, therefore, more or less closely,
with an anticlinal arch or fold of the strata. But when we follow the
axis of this arch towards the north-east into the Sidlaws, we find it
broken through by the Tay valley--the axial line running down through
the Carse of Gowrie to the north of Dundee. From the fact that many
similar anticlinal axes occur throughout the Lowlands, which yet give
rise to no corresponding features at the surface, we may conclude that
the partial preservation of the anticline of the Ochils and Sidlaws is
simply owing to the greater durability of the materials of which those
hills consist. Had the arch been composed of sandstones and shales it
would most probably have given rise to no such prominent features as
are now visible.
Another hilly belt, which at first sight appears to correspond roughly
to an anticlinal axis, is that broad tract of igneous rocks which
separates the Kilmarnock coal-field from the coal-fields of the Clyde
basin. But although the old lavas of that hilly tract slope north-east
and south-west, with the same general inclination as the surface, yet
examination shows that the hills do not form a true anticline. They
are built up of a great variety of ancient lavas and fragmental tuffs
or "ashes," which are inclined in many different directions. In short,
we have in those hills the degraded and sorely denuded fragments of an
ancient volcanic bank, formed by eruptions that began upon the bottom
of a shallow sea in early Carboniferous times, and subsequently became
sub-aërial. And there is evidence to show that after the eruptions
ceased the volcanic bank was slowly submerged, and eventually buried
beneath the accumulating sediments of later Carboniferous times.
The exposure of the ancient volcanic bank at the surface has been
accomplished by the denudation of the stratified masses which formerly
covered it, and its existence as a dominant elevation at the present
day is solely due to the fact that it is built up of more resistant
materials than occur in the adjacent low-lying areas. The Ochils and
the Sidlaws are of greater antiquity, but have a somewhat similar
history. Into this, however, it is not necessary to go.
The principal hills of the Lowlands form two interrupted belts,
extending north-east and south-west, one of them, which we may call the
Northern Heights, facing the Highlands, and the other, which may in
like manner be termed the Southern Heights, flanking the great Uplands
of the south. The former of these two belts is represented by the
Garvock Hills, lying between Stonehaven and the valley of the North
Esk; the Sidlaws, extending from the neighbourhood of Montrose to the
valley of the Tay at Perth; the Ochil Hills, stretching along the south
side of the Firth of Tay to the valley of the Forth at Bridge-of-Allan;
the Lennox Hills, ranging from the neighbourhood of Stirling to
Dumbarton; the Kilbarchan Hills, lying between Greenock and Ardrossan;
the Cumbrae Islands and the southern half of Arran; and the same line
of heights reappears in the south end of Kintyre. A well-marked hollow,
trough, or undulating plain of variable width, separates these Northern
Heights from the Highlands, and may be followed all the way from near
Stonehaven, through Strathmore, to Crieff and Auchterarder. Between the
valleys of the Earn and Teith this plain attains an abnormal height
(the Braes of Doune); but from the Teith, south-west by Flanders
Moss and the lower end of Loch Lomond to the Clyde at Helensburgh,
it resumes its characteristic features. It will be observed also
that a hollow separates the southern portion of Arran from the much
loftier northern or Highland area. The tract known as the Braes of
Doune, extending from Glen Artney south-east to Strath Allan, although
abutting upon the Highlands, is clearly marked off from that great
division by geological composition and structure, by elevation and
configuration. It is simply a less deeply eroded portion of the long
trough or hollow.
Passing now to the Southern Heights of the Lowlands, we find that these
form a still more interrupted belt than the Northern Heights, and that
they are less clearly separated by an intermediate depression from the
great Uplands which they flank. They begin in the north-east with the
isolated Garleton Hills, between which and the Lammermoors a narrow
low-lying trough or hollow appears. A considerable width of low ground
now intervenes before we reach the Pentland Hills, which are in like
manner separated from the Southern Uplands by a broad low-lying tract.
At their southern extremity, however, the Pentlands merge more or less
gradually into a somewhat broken and interrupted group of hills which
abut abruptly on the Southern Uplands, in the same manner as the
Braes of Doune abut upon the slate hills of the Highland borders. In
this region the greatest heights reached are in Tinto (2335 feet), and
Cairntable (1844 feet), and, at the same time, the hills broaden out
towards north-west, where they are continued by the belt of volcanic
rocks already described as extending between the coal-fields of the
Clyde and Kilmarnock. Although the Southern Heights abut so closely
upon the Uplands lying to the south, there is no difficulty in drawing
a firm line of demarcation between the two areas--geologically and
physically they are readily distinguished. No one with any eye for
form, no matter how ignorant he may be of geology, can fail to see
how strongly contrasted are such hills as Tinto and Cairntable with
those of the Uplands, which they face. The Southern Heights are again
interrupted towards the south-east by the valleys of the Ayr and the
Doon, but they reappear in the hills that extend from the Heads of Ayr
to the valley of the Girvan.
Betwixt the Northern and Southern Heights spread the broad Lowland
tracts that drain towards the Forth, together with the lower reaches
of the Clyde valley, and the wide moors that form the water-parting
between that river and the estuary of the Forth. The hills that occur
within this inner region of the Central Lowlands are usually more or
less isolated, and are invariably formed by outcrops of igneous rock.
Their outline and general aspect vary according to the geological
character of the rocks of which they are composed--some forming more
or less prominent escarpments like those of the Bathgate Hills and the
heights behind Burntisland and Kinghorn, others showing a soft rounded
contour like the Saline Hills in the west of Fifeshire. Of the same
general character as this inner Lowland region is the similar tract
watered by the Irvine, the Ayr, and the Doon. This tract, as we have
seen, is separated from the larger inner region lying to the east by
the volcanic hills that extend from the Southern Heights north-west
into Renfrewshire.
The largest rivers that traverse the Central Lowlands take their rise,
as might be expected, in the mountainous table-lands to the north and
south. Of these the principal are the North and South Esks, the Tay
and the Isla, the Earn, and the Forth, all of which, with numerous
tributaries, descend from the Highlands. And it will be observed
that they have breached the line of the Northern Heights in three
places--namely, in the neighbourhood of Montrose, Perth, and Stirling.
The only streams of importance coming north from the Southern Uplands
are the Clyde and the Doon, both of which in like manner have broken
through the Southern Heights. Now, just as the main water-flows of
the Highlands indicate the average slope of the ancient land-surface
before it was trenched and furrowed by the innumerable valleys that
now intersect it, so the direction followed by the greater rivers that
traverse the Lowlands mark out the primeval slopes of that area. One
sees at a glance, then, that the present configuration of this latter
division has been brought about by the erosive action of the principal
rivers and their countless affluents, aided by the sub-aërial agents
generally--rain, frost, ice, etc. The hills rise above the average
level of the ground, not because they have been ridged up from below,
but simply owing to the more durable nature of their component rocks.
That the Northern and Southern Heights are breached only shows that the
low grounds, now separating those heights from the adjacent Highlands
and Southern Uplands, formerly stood at a higher level, and so allowed
the rivers to make their way more or less directly to the sea. Thus,
for example, the long trough of Strathmore has been excavated out of
sandstones, the upper surface of which once reached a much greater
height, and sloped outwards from the Highlands across what is now the
ridge of the Sidlaw Hills. Here then, in the Central Lowlands, as in
the Highlands, true mountain- or hill-ranges are absent. But if we
are permitted to term any well-marked line or belt of high ground a
"range," then the Northern and Southern Heights of the Lowlands are
better entitled to be so designated than any series of mountains in the
Highlands.
* * * * *
The Southern Uplands.--The northern margin of this wide division having
already been defined, we may now proceed to examine the distribution
of its mountain-masses. Before doing so, however, it may be as well
to point out that considerable tracts in Tweeddale, Teviotdale, and
Liddesdale, together with the Cheviot Hills, do not properly belong
to the Southern Uplands. In fact, the Cheviots bear the same relation
to those Uplands as the Northern Heights do to the Highlands. Like
them they are separated by a broad hollow from the Uplands, which they
face--a hollow that reaches its greatest extent in Tweeddale, and
rapidly wedges out to south-west, where the Cheviots abut abruptly
on the Uplands. Even where this abrupt contact takes place, however,
the different configuration of the two regions would enable any
geologist to separate the one set of mountains from the other. But for
geographical purposes we may conveniently disregard these geological
contrasts, and include within the Southern Uplands all the area lying
between the Central Lowlands and the English Border.
If there are no mountains in the Highlands so grouped and arranged as
to be properly termed "ranges," this is not less true of the Southern
Uplands. Perhaps it is the appearance which those Uplands present when
viewed from the Central Lowlands that first suggested the notion that
they were ranges. They seem to rise like a wall out of the low grounds
at their base, and extend far as eye can reach in an approximately
straight line. It seems more probable, however, that our earlier
cartographers merely meant, by their conventional hill-shading, to mark
out definitely the water-partings. But to do so in this manner now,
when the large contour maps of the Ordnance Survey may be in any one's
hands, is inexcusable. A study of those maps, or, better still, a visit
to the tops of a few of the dominant points in the area under review,
will effectually dispel the idea that the Southern Uplands consist of a
series of ridges zigzagging across the country. Like the Highlands, the
area of the Southern Uplands is simply an old table-land, furrowed into
ravine and valley by the operation of the various agents of erosion.
Beginning our survey of these Uplands in the east, we encounter
first the Lammermoor Hills--a broad undulating plateau--the highest
elevations of which do not reach 2000 feet. West of this come the
Moorfoot Hills and the high grounds lying between the Gala and the
Tweed--a tract which averages a somewhat higher elevation--two points
exceeding 2000 feet in height. The next group of mountains we meet
is that of the Moffat Hills, in which head a number of important
rivers--the Tweed, the Yarrow, the Ettrick, and the Annan. Many points
in this region exceed 2000 feet, others approach 2500 feet; and some
reach nearly 3000 feet, such as Broad Law (2754 feet), and Dollar
Law (2680 feet). In the south-west comes the group of the Lowthers,
with dominant elevations of more than 2000 feet. Then follow the
mountain-masses in which the Nith, the Ken, the Cree, the Doon, and
the Girvan take their rise, many of the heights exceeding 2000 feet,
and a number reaching and even passing 2500 feet, the dominant point
being reached in the noble mountain-mass of the Merrick (2764 feet).
In the extreme south-west the Uplands terminate in a broad undulating
plateau, of which the highest point is but little over 1000 feet. All
the mountain-groups now referred to are massed along the northern
borders of the Southern Uplands. In the south-west the general surface
falls more or less gradually away towards the Solway--the 500 feet
contour line being reached at fifteen miles, upon an average, from
the sea-coast. In the extreme north-east the high grounds descend in
like manner into the rich low grounds of the Merse. Between these low
grounds and Annandale, however, the Uplands merge, as it were, into the
broad elevated moory tract that extends south-east, to unite with the
Cheviots--a belt of hills rising along the English Border to heights of
1964 feet (Peel Fell), and 2676 feet (the Cheviot).
The general configuration of the main mass of the Southern
Uplands--that is to say, the mountain-groups extending along the
northern portion of the area under review, from Loch Ryan to the coast
between Dunbar and St. Abb's Head--is somewhat tame and monotonous. The
mountains are flat-topped elevations, with broad, rounded shoulders
and smooth grassy slopes. Standing on the summits of the Higher hills,
one seems to be in the midst of a wide, gently undulating plain, the
surface of which is not broken by the appearance of any isolated peaks
or eminences. Struggling across the bogs and peat-mosses that cover
so many of those flat-topped mountains, the wanderer ever and anon
suddenly finds himself on the brink of a deep green dale. He discovers,
in short, that he is traversing an elevated undulating table-land,
intersected by narrow and broad trench-like valleys that radiate
outwards in all directions from the dominant bosses and swellings of
the plateau. The mountains, therefore, are merely broad ridges and
banks separating contiguous valleys; in a word, they are, like the
mountains of the Highlands, monuments of erosion, which do not run in
linear directions, but form irregular groups and masses.
The rocks that enter into the formation of this portion of the Southern
Uplands have much the same character throughout. Consequently there
is less variety of contour and colour than in the Highlands. The
hills are not only flatter atop, but are much smoother in outline,
there being a general absence of those beetling crags and precipices
which are so common in the Highland regions. Now and again, however,
the mountains assume a rougher aspect. This is especially the case
with those of Carrick and Galloway, amongst which we encounter a
wildness and grandeur which are in striking contrast to the gentle
pastoral character of the Lowthers and similar tracts extending along
the northern and higher parts of the Southern Uplands. Descending to
details, the geologist can observe also modifications of contour even
among those monotonous rounded hills. Such modifications are due to
differences in the character of the component rocks, but they are
rarely so striking as the modifications that arise from the same cause
in the Highlands. To the trained eye, however, they are sufficiently
manifest, and upon a geologically coloured map, which shows the
various belts of rock that traverse the Uplands from south-west to
north-east, it will be found that the mountains occurring within
each of those separate belts have certain distinctive features. Such
features, however, cannot be depicted upon a small orographical map.
The separation of those mountains into distinct ranges, by reference
to their physical aspect, is even less possible here than in the
Highlands. Now and again, bands of certain rocks, which are of a
more durable character than the other strata in their neighbourhood,
give rise to pronounced ridges and banks, while hollows and valleys
occasionally coincide more or less closely with the outcrops of the
more readily eroded strata; but such features are mere minor details
in the general configuration of the country. The courses of brooks
and streams may have been frequently determined by the nature and
arrangement of the rocks, but the general slope of the Uplands and the
direction of the main lines of water-flow are at right angles to the
trend of the strata, and cannot therefore have been determined in that
way. The strata generally are inclined at high angles--they occur, in
short, as a series of great anticlinal arches and synclinal curves, but
the tops of the grand folds have been planed off, and the axes of the
synclinal troughs, so far from coinciding with valleys, very often run
along the tops of the highest hills. The foldings and plications do
not, in a word, produce any corresponding undulations of the surface.
Mention has been made of the elevated moory tracts that serve to
connect the Cheviots with the loftier Uplands lying to north-west.
The configuration of these moors is tamer even than that of the
regions just described, but the same general form prevails from
the neighbourhood of the Moffat Hills to the head-waters of the
Teviot. There, however, other varieties of rock appear, and produce
corresponding changes in the aspect of the high grounds. Not a few of
the hills in this district stand out prominently. They are more or less
pyramidal and conical in shape, being built up of sandstones often
crowned atop with a capping of some crystalline igneous rock, such as
basalt. The Maiden Paps, Leap Hill, Needs Law, and others are examples.
The heights draining towards Liddesdale and lower reaches of Eskdale,
composed chiefly of sandstones, with here and there intercalated
sheets of harder igneous rock, frequently show escarpments and
terraced outlines, but have a general undulating contour; and similar
features are characteristic of the sandstone mountains that form the
south-west portion of the Cheviots. Towards the north-east, however,
the sandstones give place to various igneous rocks, so that the hills
in the north-east section of the Cheviots differ very much in aspect
and configuration from those at the other extremity of the belt. They
have a more varied and broken outline, closely resembling many parts of
the Ochils and other portions of the Northern and Southern Heights of
the Central Lowlands.
The low-lying tracts of Roxburghshire and the Merse, in like manner,
present features which are common to the inner region of the Central
Lowlands. Occasional ridges of hills rise above the general level of
the land, as at Smailholm and Stitchell to the north of Kelso, while
isolated knolls and prominences--some bald and abrupt, others smooth
and rounded--help to diversify the surface. Bonchester Hill, Rubers
Law, the Dunian, Penielheugh, Minto Hills, and the Eildons may be
mentioned as examples. All of these are of igneous origin, some being
mere caps of basalt resting upon a foundation of sandstone, while
others are the stumps of isolated volcanoes.
In the maritime tracts of Galloway the low grounds repeat, on a smaller
scale, the configuration of the lofty Uplands behind, for they are
composed of the same kinds of rock. Their most remarkable feature is
the heavy mountain-mass of Criffel, rising near the mouth of the Nith
to a height of 1800 feet.