Imperial gazeteer of Scotland, or, Dictionary of Scottish topography > Volume 1

INTEODUCTION.
" The newer secondary rocks have been but very sparingly observed in Scotland; yet it is
rather a curious fact, that the few patches which have been discovered, are superimposed
generally on the old red sandstone, and have not been seen reposing in their uninterrupted
order in the secondary series. Thus the lias shales, highly micaceous, and some of the upper
beds of the oolitic system, occur at the mouth of the Cromarty frith from Dunrobin-castle
to the Ord of Caithness, at Applecross and other points on the mainland, — and in the Western
Isles, on the borders of Mull, the south and east of Skye, and near the Cock of Arran, on a
small coal deposit. The equivalent of the fresh-water deposits of the wealds of Sussex,
geologically situate above the oolitic group, and below the chalk, is seen near Elgin in Moray,
and Loch-Staffin in Skye. In the central and southern divisions of Scotland, those newer
groups of rocks have not been detected.
" In tracing the geological features of the country in the ascending order of the groups,
and confining ourselves to the geographical divisions pointed out, we next come to the transi-
tion or greywacke system, now divided into two principal sections, — the lower or Cumbrian,
and the upper or Silurian. So far as is hitherto ascertained, the Silurian division is unknown
in Scotland; but the Cumbrian rocks, nearly destitute of organic remains, cover the principal
part of the great area of the south of Scotland. These greywacke strata stand at high angles
of from 60° to 90° from the horizon, and consist chiefly of coarse slaty strata, seldom divisible
into thin roofing slates, and often alternating with arenaceous and coarse conglomerates.
Amongst these strata limestone is seldom found; and when it is, the quality is inferior. In
the division of the island of which we now treat, coal and its accompaniments are known in
very few places. Coal is, however, worked at Canoby, and on the borders at the Carter-Fell.
The only other rock formation found in connection with the old transition group here (with
the exception of igneous rocks), is a red sandstone, ascertained, in some situations, to be the
old red, but in some other places considered to be the new red sandstone, particularly in
Dumfries-shire, where the surfaces of the slabs have curious impressions, supposed to be those
of the feet of a species of tortoise.
" In the central division of Scotland is placed the great coal basin ; but adhering to our
rule of marking the successive formations in the ascending order, we shall first treat of the
old red sandstone, the most ancient rock in this subdivision of the country. This rock abuts
against the line of the primary rocks, and stretches across the whole country, from the
German ocean to the Atlantic, pursuing a south-westerly and north-easterly direction. From
the northern line of division it stretches south to the frith of Tay, bearing through Dunning,
near Stirling, to Dumbarton, and thence through the Western Isles, Bute and Arran, and is
wrapped nearly round the extremity of the mainland at the Mull of Kintyre. The old red
sandstone thus forms a long, uninterrupted, and extensive fertile valley. In the north-western
part it rises into hills, in the sides of one of which, Uam Vor, are deep and hideous fissures,
the effect of some convulsion. It is more irregularly distributed on the southern boundary
of the middle division, commencing on the east about Dunbar, and stretching westerly on the
line of the transition range of Moorfoot and Lammermoor-hills beyond Middleton, where it is
interrupted by a range of trap, but is again found in the country round Lanark. This for-
mation appears to be of vast thickness, especially in the northern part of the division, and
may, it is supposed from recent observation, be divided into three portions, the lower, the
middle, and the upper beds. In what are considered the lower strata, the remains of fishes
have been found in a high state of preservation, and also large scales and other remnants of
a sauroid character, such as those of the holoptychus. The well-known Arbroath pavement
belongs to the old red sandstone series.
" The most important group in the central district is the coal formation, consisting of lime-
stone, ironstone, freestone, coal, and clays. Its extent from east to west is bounded only by
the extremities of the land. To the north it is cut off from the old red sandstone by a range
of trap hills, crossing the country from east to west. On the south it is bounded by the
greywacke and old red sandstone. Its breadth averages 40 miles ; and it is in length about
70. The mountain limestone forms generally the basis of this group; though it is frequently
found interstratified with other members of the series, and abounds with countless numbers
of organic remains. Below the mountain limestone, however, but belonging to the same
group, a bed of limestone is worked at Burdiehouse, near Edinburgh, in which the organic
remains differ essentially from those of that just named. These remains consist of many of
the plants which distinguish the coal formation; but it also includes the teeth, scales, and
other bones of fish, which partake of the reptile character, some of which must have been of