FOSSILS, comprehending according to Mineralogists, all unorganized bodies under the surface of the earth, are divided into Native, and Adventitious. The former include those bodies that were never organized: the latter such as one belonged to the animal or vegetable kingdom, and which retain some of their organized properties, but have now lost their organization.
NATIVE fossils, or minerals, comprehend Earths, Inflammables, Salts, Metals. Under some one or other of these divisions, Adventitious fossils, when chemically considered, are also included: but from the remains of their once organized structure, they are generally arranged in a class by themselves.
THE native earths comprehend the Argillaceous, Calcareous, Siliceous, Ponderous, and Magnesian. These earths are seldom, in a state of nature, found without mixture: but the kind that predominates fixes, in general, the character.
OF all the Earths, in Rutherglen and Kilbride, the Argillaceous is found in greatest plenty. Soft clay, or potter’s clay, abounds in many places, but on where, perhaps, in so fine a state as at Shawfield, where it is used for making bricks. The small quantity of sand in its composition, renders it not the most proper for that manufacture. This clay, for many yards in depth, is disposed in layers, or thin strata, from ⅟₁₂ to ½ of an inch in thickness; and which, owing to a small quantity of mud between them, are easily separable from one another. In the clay are great numbers of small concretions, vulgarly called Cam-stones, from half an inch, to an inch and a half in diameter. They lie in a horizontal position: all of them are oblate, and generally of an oblong figure, but some of them are pretty round; and not unfrequently three or four adhere to each other; in which case their figure is extremely irregular; but commonly they are shaped like buttons, and are composed of horizontal layers. They are not so hard but they may be scraped with a knife. When put into the fire they burst in pieces with a great explosion. They readily absorb water, but do not, with it, fall down into clay. Nitrous acid acts upon them very powerfully, and decomposes them into an impalpable powder: the solution, however, by the addition of the vitriolic acid, deposites a considerable quantity of Selenite: the clay in which they are imbedded is not affected by the acid. They become harder, and of a black colour, by torrefaction; but are not attracted by the magnet They are easily reduced, by the blow-pipe, to a black glass. In several specimens which I have examined, I could observe no nucleus round which they might have been formed. It is evident from certain inequalities on their surfaces, that they did not acquire their shape by attrition, but must have been concreted, probably by means of calcar, in the place where now found. They break with rough surfaces, and are harsh to the touch.
A bluish coloured pipe-clay is found near Limekilns. It was for some time used in the pipe-manufacture at Glasgow; but, owing to the expence of carriage, it is now neglected.
INDURATED clays abound in both parishes. The most plentiful is the Schistus or Till.1 It generally splits into lamellæ, and is of a grayish or blackish colour. It contains the following varieties: 1. Till, of an uniform and compact texture; smooth to the touch, and, by exposure to the air, falls down into a soft clay. It is of a blackish gray colour, and retains vegetable impressions, afterwards to be described. 2. Fire-clay, found between strata of coal, at Torrance and Stonelaw. It readily breaks, in various directions, into small pieces of no determined shape: the surfaces are uneven, and harsh to the touch: it is of a dusky colour, and does not readily fall down into clay. It is full of streaks and blotches, which seem to be the remains of grasses and reeds; but their original characters are so much effaced, as not to be easily distinguished. 3. Till, replete with Shells, Entrochi, and other spoils of the ocean. It is of a grayish colour, and, by exposure to the air, is readily decomposed. It is found above iron-stone, lime and coal. 4. Inflammable schistus. This kind is hard and black; burns, for a short time, with a clear flame, and is reduced to hard and white ashes. Found in the neighbourhood of coal. 5. Till, hard, black and slaty: is not decomposed by the air, nor kindled into a flame by heat. Found in various situations. 6. The most uncommon variety of till, in this country, is one that, by the miners, is called Maggy. It is incumbent on a coarse iron-stone, or doggar, at Mauchlanhole, and Torrance; and is generally found in the shape of cones, as pl. XX. fig. 8. These cones are of a dirty black colour, and are composed of concentric lamellæ, of various thickness, and which may be separated from one another, exhibiting surfaces adorned with small, but irregular undulations. The apices of the cones, which are of various dimensions, rest upon the stone, and the bases are lost in the surrounding till. They are softest at the base; but gradually increase in hardness towards the apex. The whole, however, is, in general, very hard. This curious fossil contains, along with clay, a considerable proportion of iron and lime, and, perhaps, some other substance which so-operates in the formation of its peculiar figure.
MOST of the schistus contains a quantity of Mica, and a little sand, but not much Allum.
THE Rough-hill, and the adjacent banks, are composed of indurated clay, which breaks in all directions, and serves as a cement to a vast number of small stones which it envelopes. These stones, although argillaceous, are considerably harder than the cementitious matter; and most of them readily split into thin pieces. They are all rounded by attrition; lie in all directions, as if thrown together in the greatest disorder; and are of different colours and consistencies. This rock exhibits an excellent specimen of what may be called an argillaceous Breccia.
THE chief component part of the Osmund stone, found at Burnhouse, Rawhead, and several places in Kilbride, seems to be clay. This remarkable stone, which is universally known all over the country, is of various colours; as gray, brown, whitish, &c. It is generally so soft, when lately quarried, that it may be cut with a chisel; but afterwards becomes much harder. It breaks in all directions; the surfaces are unequal, and harsh to the touch. It readily absorbs water, and, if recently heated in the fire, the absorption is attended with a hissing noise. The acids do not affect it: nor are the brownish coloured kinds destitute of iron, in its calciform state. The osmund stands a very great heat, without being rent or melted; for which reason it is used for ovens, furnaces, &c. where a strong and constant heat is necessary. But when used for paving ovens, care must be taken to have it all of the same kind: for if one stone is more dense than another, the bread will be unequally fired. For want of this precaution several ovens have been rendered useless, and the stone held in disrepute. In some specimens a great variety of small stones of different substances, colours and shapes are closely cemented together. The greatest part of the osmund, when burnt, assumes a darker colour, and loses three per Cent. of its weight, but afterwards regains it, by absorbing moisture from the atmosphere. Some of it is considerably porous, and almost semivitrified: in this case it has, when struck, a strong and clear sound: the pores, in some specimens, are pretty large.
THE osmund is found in large masses in the form of rocks, and in some places it has the appearance of stratification. In many places, as at Kilmalcolm, it is found below whin-stone, with hardly any other kind of substance intervening. The pores and crevices are, in some specimens, filled with siliceous, and in others, with calcareous spar, and sometimes with Zeolite. A white Steatites, afterwards to be mentioned, is lodged in the crevices of this stone: and, in the parish of Eaglesham, a great quantity of the ponderous spar is interspersed in it. Not unfrequently these two substances are beautifully intermixed: and, in many specimens, large fragments of osmund are imbedded, or insulated in the barytes. It is probable that the osmund is a volcanic production.
A small specimen of what appears to be a vitreous volcanic production, is all of the kind I have met with in this country. It was found in the Eldrig not far from a rock of osmund. The colour is a dull green. When broken the fractures were glossy, conchoidal and smooth, but contained a great number of minute specks, shaped like the point of a dart. It is not transparent, and does not emit fire with steel. In appearance it pretty much resembles what is vulgarly called bastard Jasper, found plentifully in a hill called Dumfuen, in the Island of Arran.
ZEOLITE2 is found, although sparingly, in Kilbride. The most rare is a variety in which the fibres are of a white colour, extremely fine, having the appearance of cotton wool, and lying loosely across each other, without any regular order. It is found in the pores, or bladder-holes of whin-stone. The compact crystallized Zeolite, in which the fibres diverge from a point, is found in different kinds of stones. The colour is commonly white, but metallic mixtures give it various tinges. It is found at Blackburnmill, Browncastle, and the Piel.
STEATITES,3 or Soap clays, are arranged, by some authors, among argillaceous fossils; by others among magnesian earths. The finest, perhaps, in Britain is found a little above Rawhead. It is considerably heavy; greasy to the touch; free from sand and metallic mixtures; and of a beautiful white colour. When tried by Mr. Young, in the Delf Manufacture at Glasgow, it produced Porcelain, equal, if not superior in fineness, to ware made of the best materials in Europe. It makes an excellent paste for Crayons, and may be wrought up with the most delicate colours. It is found in small quantities in the crevices, and pores of an osmund rock. This valuable fossil, upon proper search, may, probably, be found in considerable plenty.
OF the Calcareous class of earth, Kilbride contains a very great quantity. Limestone bears the greatest proportion of any other kind. It is found at Jackton, Hermyres, Limekilns, &c. &c. The strata are generally from 3 to 7 feet in thickness: they lie below different substances, as mould, clay and till. In some places their surfaces, when uncovered, are entire and smooth; in others, as at Hermyres, they are rent into wide perpendicular fissures, almost the whole depth of the stratum. These rents, which observe no regular direction, are extremely rough in their surfaces, and gradually diminish in their wideness, as they descend into the stone, and are commonly found near the extremity of the stratum. The roughness is occasioned by shells, and other marine productions, with which the stone is replete. There is something in the construction, or composition, of these exuviæ, that withstands the corroding substance that acts upon the limestone, and wastes it away, Owing to this, these once organized remains of the ocean preserve their shape, whilst the matter in which they were originally imbedded, and to which they now but slightly adhere, is worn away. the stone, at the upper edge of these fissures, is not unfrequently branched out, like irregularly shaped horns, of about half a yard in length, and two or three inches in thickness.
THE original cause of these fractures in limestone is not, perhaps, easy to ascertain. Similar effects have been produced by a transition from heat to cold; from a state of fluidity, by a solvent, to a state of dryness, by evaporation; or by some powerful pressure from beneath, by which a stratum has been raised from a horizontal, to an oblique or circular direction.
TWO strata, or, in the language of workmen, two posts of limestone are found in most of the quarries in Kilbride. They are divided from one another by a stratum of till, about 3 feet in thickness. Below the under post is commonly a stratum of coarse limestone flag, not worth burning. It is chiefly composed of sand and clay, combined with a little lime.
LIMESTONE strata are found at various depths: from 1 to 50 feet. When they are deeper than 24, or 30, the working of the stone is reckoned unprofitable.
BESIDES the regular strata, a great number of detached pieces, called Stammerers, are, in many places of the parish, found imbedded in clay. They are from an inch, to 3 or 4 feet in thickness; but of no regular shape. The most of them are, by attrition, rounded on the corners. They are not all of the same texture, quality or colour. Many of them differ considerably from any stratum of limestone, as yet discovered in the parish. Some of them, being very good, are carefully preserved by the workmen; whilst others are so bad that they are not worth collecting.
OF all the varieties of limestone in the parish, the grayish coloured is by far the most common. A stratum of a white colour, and close fine texture is wrought at Jackton. Limestone, containing a considerable proportion of iron, which gives it a red colour, is found in the lands of East-Milton. It is little valued. All the varieties contain extraneous fossils, which, in some places, are so numerous, that, except a little cement by which they are combined, they compose the whole substance of the stone. Some kinds admit of a polish, equal almost to the finest marble. Their beauty is set off to advantage, by the shells, entrochi, madrepores, &c. with which they are replete.
LIME from Kilbride is in high repute both for manure and building. It generally takes a strong band: and some of it, especially what is produced at Hermyres, has this peculiar quality, that, when properly mixed, and wrought warm, as the workmen express themselves, it very readily takes a firm band in water. For this reason it is used in building bridges.
NO lime that comes to Glasgow, if we except the Netherwood lime, belonging to Mr. Glassford, is in so great estimation for house-plaster, as lime from Kilbride. But care must be taken in preparing it. If wrought new, that is, soon after stacking, it frequently rises in blisters. These are produced by what the workmen call particles in the plaster. These particles, when examined, are found to be either small pieces of cinders, or coal, that have got among the plaster; or small fragments of shells, corralloides, &c. which have not been thoroughly decomposed during the stacking of the lime. There seems to be something in the construction, or composition of these crystallized substances, that prevents them from falling down into powder, so readily as the rest of the stone. Afterwards, however, they swell, by absorbing moisture from the air, and thereby occasion the blisters above-mentioned. This is entirely prevented by properly souring the lime before it is wrought into plaster.4
BESIDES a tendency to rise in blisters, the lime from Hermyres has been found to lose its hardness and consistency, and to fall down into powder, after it had been for some time on the wall. A considerable quantity of moisture seems necessary to make this uncommon lime retain it solidity. Owing to this quality, however, it may in some cases be preferable to most other kinds of lime. Its peculiarities are probably owing to a considerable quantity of selenite and manganese, that appear to be in the stone.