THE only calcareous stratum in Rutherglen, is one that runs through a great part of the parish, and is a continuation of what, in this country, is called Cambuslang Marble. It is from a few inches, to two feet in thickness; and lies in a stratum of till, above the main coal. The ground is a darkish gray, ornamented with white bivalve shells; but sometimes it is reddish. Both varieties take a good polish, and are used in the Marble Manufacture at Glasgow. Pieces of this marble, and also of metallic limestone in Kilbride, are sometimes found in the earth, in a state of decomposition.
SPATUM (spar) forms a beautiful class of calcareous substances. The most plentiful is the rhomboidal; so called, because it breaks into fragments of a rhomboidal shape. It is commonly found in limestone strata; and frequently in iron-stone, and sometimes in whin. It is mostly semitransparent; but some of it is opaque, and of a reddish colour. Of the pyramidal spar the quarry at Philipshill affords a few specimens. In the fissures of a limestone stratum, near Jackton, is a considerable quantity of the prismatic spar. The crystals are hexehedral, and truncated: they adhere to a sparry incrustation formed on the stone; they are of different lengths, commonly about half an inch; and lie in all directions. In one specimen they adhere to the inside of a petrified bivalve-shell. Similar crystallizations are found in Lochrig quarry, near Stewarton, county of Ayr.
FIBROUS, or striated calcareous spar, is found a little above Kittochside. It is of a chalky appearance, and the stratum, or vein which it composes, is about an inch in thickness. The fibres are prismatic crystals, probably of six sides; are arranged like basaltic columns: they are pretty fine; in close, but not inseparable contact with each other; and make an oblique angle with the horizon, or particular direction in which the stratum, or vein lies. Specimens of this curious fossil are frequently found in till and stone marle, in the immediate neighbourhood of whin-stone rocks; and sometimes in fissures of the rocks themselves. The colour is often tinged with carnation, and not unfrequently with a faint blue. It is commonly of a silky, or silvery appearance, resembling some kinds of Gypsum.
CALCAREOUS Incrustations are found chiefly on limestone, sometimes on freestone, but seldom on roots or branches of trees.
STALACTITES, Isicles, or Dropstones, are found in the cavities of limestone, and large masses of petrifactions at Gillburnsynke. Their texture is chiefly lamellar, and their colour whitish, except when particles of iron communicate a reddish or yellowish tinge. Their shape is generally that of a perforated cone, or tube; but they are sometimes solid and variously branched.
STALAGMITES are formed in the bottom of cavities, chiefly where the dropstone is found. They are commonly of a roundish, or mammillary shape, and their colour, by reason of earthy and metallic mixtures, is not always the same.
TO calcareous earths belong Recent Petrifactions, of which there is a considerable variety in Kilbride. They consist of different genera of vegetables, as the Hypnum, Bryum, Marchantia, &c. belonging to the Cryptogamia class, which are petrified by water containing calcareous particles, and a certain proportion of fixed air. It is observable, that mosses are more susceptible of a thorough petrifaction, than any other kind of plants. The reason, by some, is supposed to be, “That mosses, &c. being destitute of congenial salt, readily admit into their pores adventitious ones, whilst the gramineous plants, being already furnished with it, will admit of no heterogeneous accession.”1 If this peculiarity is not owing to the particular construction, or texture of these plants, the true cause is, perhaps, yet to be discovered.
THESE petrifactions are chiefly found at Gillburnsynke, Mauchlanhole, and Pateshall, on the banks of Calder: and on the south bank of Kittoch, a little below Burnbrae. They were, in 1787, in great perfection at Pateshall.2 A large space was covered with moss, which, on the surface, retained a beautiful verdure, but about an inch or two below, exhibited the various degrees of petrifaction, from the slightest adhesion of the calcareous matter, till the vegetable was thoroughly replete with it. The whole was, at the depth of about 6 inches, a mass of stoney hardness. The stem and branches of the same plant, although in perfect vegetation near the top, could be traced a considerable way downward. The petrifaction is not of that kind which consists of an incrustation only, but the whole of the plant is replete with the petrifying substance. Whilst this curious operation of nature was going on, and inviting the diligent investigators of the works of God, to this pleasant, though retired spot; the impending bank gave way, and buried the petrifactions under huge masses of stone, with the earth and shrubs that were above the rock. Instead of affording an agreeable retirement, where many of the genuine beauties of nature were to be seen, the place now exhibits a scene of wild desolation. Sixty or seventy years will, perhaps, be insufficient for producing a group of petrified mosses, equal to the former. From every appearance it is evident, that Gillburnsynke, a considerable number of years ago, underwent a fate in some respects similar. On the face of the rock over which the petrifying water runs, and which is about 30 feet high, large masses of petrifactions had, in a long series of years, been formed. But the weight had, at length, accumulated to such a degree, that they brought away part of the rock to which they adhered, and fell into the glen below, where they now lie. This operation of nature is, on the face of the rock, again going forwards, and large pieces of petrified mosses are now making their appearance.
THE existence of the Sulphate of Lime, is evident from specimens of beautifully radiated crystals of Selenite, that are sparingly found in Lawrieston quarry.3 They consist of about 20 or 30 radii, diverging from a center containing a small piece of pyrites, like a pin-head. These radii are transparent, of different lengths, commonly about ⅛ of an inch; and the thickness of a horse-hair in breadth. They are as broad and gross at the extremity as at any other part. These radiated, and superficial crystallizations, are formed on the surfaces of a blackish coloured till, of pyritaceous clay, incumbent on limestone.
THE Barytes, or ponderous spar, has, in small quantities, been found in a quarry near Nook. Probably a vast quantity of that matrix metalli exists in the Eldrig, and the neighbouring hills. It makes its appearance in great plenty, and in various forms and situations, in an adjacent glen. Some specimens are semitransparent; others opaque. Its hexahedral crystals, in the form of thin plates, are likewise found here: they are sometimes confusedly arranged in the shape of a crest, or cock’s comb, from the bigness of a hazel nut, to several inches in diameter. The spar is, in some few specimens, ornamented with rock-crystals. Some of them are hexahedral prisms, terminated at each end by a pyramid of the same number of sides. In some the pyramids are joined base to base: others consist of a single pyramid only. Some of them are nearly an inch in length, and ¼ in thickness; and others are not much larger than the point of a pin, and appear on the surface of the spar like minute granulations. All of them make a deep scratch on glass. Considerable numbers are enveloped in the barytes, and lie in all directions: and in some specimens, pieces of the barytes are enveloped in clusters of crystals. Not unfrequently a congeries of barytical crystals is found united with a broad plate of rock crystal; an irregular stratum of which runs through part of the rock. Detached, and sharply angulated, pieces of osmund stone are frequently found wholly inclosed in the barytes: and pieces of the barytes, in like manner, inclosed or insulated in the osmund. These varieties lay a foundation upon which a theorist might build not a few conjectures.
SILICEOUS substances are not unfrequent in Rutherglen and Kilbride. Quartzy nodules, or chuckie-stones, as they are vulgarly called, are very common, and are of various colours. The Quartz is also found in small veins running through whin-stone, and sometimes micaceous schistus.
WHIN-STONE affords, in this country, a considerable variety of the saxa silicea. The Scottish term whin is frequently, in common language, made use of to express any thing that is hard, sharp and prickly. According to this meaning the whin-stone signifies one, the fragments of which have sharp and prickly corners. The word taken in this peculiar sense, is equally significant with any name, as yet given to this class of stones, from the Greek, German, or English languages.
THE whin-stone is various in its hardness, colour, &c. in proportion to the silex, and extraneous mixtures, which it contains. The kind that mostly prevails in Kilbride, is what is commonly called rotten whin, because, when exposed to the weather, it cracks and falls down into small pieces, and is reduced to clay, or mud. Of this kind many hills in Scotland are composed. They generally, however, contain great numbers of roundish pieces of hard whin-stone that resist the action of heat, air and water. They are generally inclosed within concentric lamellæ of rotten whin, that are easily decomposed. These balls contain a great quantity of quartz, feld spar, and schorl, and freely emit fire with steel, which the rest of the rock very sparingly does. They are from 1, to 6 or 8 feet in diameter. No stones in the country afford better materials for making roads: but owing to their great hardness, they are commonly neglected; whilst the more easily procured rotten whin is preferred, and thereby the roads are greatly hurt.
TO this class of stones may be added the Basaltes, of which the estate of Cathkin,4 a little above Rutherglen, affords a beautiful specimen. A Colonade, consisting of 164 pillars were, by workmen procuring materials for a turnpike road, brought into view. They are about 30 feet high, and a foot and a half in diameter. They are mostly five-sided, but the sides are not equal. A thin dissepimentum, some parts of which are ochreous, and others argillaceous, separates them from one another. Not a few specimens of it are very hard, approaching to a vitreous and metallic texture whilst others are loose, and friable between the fingers. Itis generally of a reddish colour, and becomes darker and magnetic by torrefaction. Some of it is porous, having some of the cavities filled with a sooty-like substance, among which are found transparent rock-crystals, of hexahedral pyramids. In the columns, the transverse subdivisions are very imperfect: in some instances they exhibit a convex, and a corresponding concave surface. the basaltic stone is considerably brittle; does not emit fire with steel; is not acted upon by acids; and is generally of a darkish gray colour. It affects the magnetic needle, a proof that it is not destitute of iron. After being heated in the fire it becomes darker in the colour and grows so hard as to strike fire with steel. The flame of a blow-pipe readily melts it into a black glass. The columns, some of which are a little curved, incline to the south, at an angle of about 75 degrees. In the west side of the rock, the pillars gradually coalesce into one another, at their bases, till they become a solid mass.5
CATHKIN hills are not altogether destitute of Petrosilex and Rock Crystal. The finest Jasper I have met with is of their production. The ground, which is a faint yellow, is beautifully striped and blotched with a blood red. The fractures present surfaces of a fine polish.
GRIT, Cos arenarea, sand-stone, or free-stone, is, in great abundance, in those parts of both parishes where coal is found. This useful fossil admits of several varieties, according to the colour, shape and size of the particles of sand, and the cement by which they are combined. The colour, in general, is white, grayish, or inclining to brown. The stone, in the west quarry of Rutherglen, is beautifully blotched with red spots, of various diameters. Their colour proceeds from small nodules of argillaceous iron-ore which are imbedded in the stone, and are so soft as to be scraped with the nail. They commonly contain particles of mica. these nodules must have been interspersed in the sand, before it was hardened into stone; and strongly indicate, that a considerable quantity of this kind of ore exists in Cathkin hills, near the bottom of which the quarry lies. The east quarry of Rutherglen contains a white free-stone, of an excellent quality. It is, in Glasgow, highly valued for building.
ARGILLACEOUS grit, having the sand combined by means of a clayey cement, is very plenty in Kilbride. It lies in strata, and readily splits into flags, or thin layers. From a stratum of this kind, in the Gill6 near Bogton, excellent grind-stones have been taken. When the cement is siliceous the stone is generally very hard, and difficult to cut. Some of this kind is found above coal; and often composes a great part of the dykes, or troubles, which derange the regular strata. It is commonly white, and emits fire copiously with steel. To the siliceous class belongs a stratum of mill-stone grit, at Polliskin-glen, above Torrance, from which mill-stones have been procured. With the cement is combined a small quantity of iron, which, after the stone has been long exposed to the air, makes its appearance in the form of ochre. Grit, of which the cement is mostly calcar, abounds in the neighbourhood of Limekilns, and Edwardshall. It contains fragments of shells, entrochi, and other marine productions. It splits in thin layers, and is used for hearth-stones, dykes, &c.
ALONG with the free-stone, may be mentioned the Breccia quartzosa, detached pieces of which are found both in Rutherglen and Kilbride.