EXTRANEOUS, or Adventitious Fossils are such as originally were organized bodies. They are arranged into two classes. The one comprehends the fossil remains of animals and vegetables, that were natives of the land: the other, those of the sea. Both are subdivided into subordinate Orders, Genera, Species and Varieties, founded on characters established in Zoology and Botany. The parishes of Rutherglen and Kilbride contain a greater variety, in both classes, than, perhaps, any other bounds of equal extent in the world.
PETRIFIED PRODUCTIONS OF THE LAND.
THE most extensive order of terrene productions consists of Vegetable Impressions. They are chiefly found in argillaceous strata, above coal, in Rutherglen. Many thousands of them are contained in a solid foot of till; and make their appearance on the surfaces of the lamellæ, into which it may be subdivided. They are also found in strata of sand-stone; and likewise in pieces of iron-stone, interspersed in the till. They are thrown together in the utmost disorder; only they lie flat, in a horizontal direction. From several circumstances it appears, that they did not grow where now found; but were carried by water from their native soil, and deposited among sand or mud, now converted into stone or till.
SUCH a vast quantity of mud, containing many millions of vegetables, must have been collected in a deep and large bay, where the smallest particle of argilla, or mica, had sufficient time to subside. The depth of water, in which they were suspended, must have been very great. Any calculation, instituted upon phenomena, coming within the reach of our experience, may be very erroneous. In our enquiries into such subjects, great allowances must be made for the different states of the earth, at different periods. We cannot, perhaps, form an adequate idea of the state of the upper strata of the earth, soon after it emerged out of the chaotic waters, or the universal deluge. A local inundation might, for ought we know, have then produced effects, of which the recent phenomena of the world can give us no examples. We should, therefore, proceed with great caution, in drawing comparisons between the ancient and present state of the globe: and the theories we presume to make of the formation of the earth, and many of its pristine phenomena, should be proposed with the utmost dissidence.
THE vegetable impressions, found in Rutherglen and Kilbride, are mostly of plants belonging to the Cryptogamia class; the order of Filices; and genera which are the indigena of woods, glens and marshes. The specimens are mostly in fragments. Some of the species are not now natives of Europe: and others have never, any where in the world, been discovered in a recent state. Their characters will best appear by the annexed plates, in which the natural size of the impressions is, in general, preserved.
FIG. I. pl. X. seems to be an Arundo, or Bamboo of India. Fig. 2. is distorted and swollen, owing to a wound, at a, which it had received in a recent state. Some specimens of the Bamboo, found in free-stone, at the east quarry of Rutherglen, retain their original shape: but most of them are a little depressed. Some are of a brownish colour. Whether fig. 3. is a variety of the above is uncertain; the striæ are exceedingly minute and regular. Fig. 4. appears to be an Equisetum, of which fig. 5. is a joint, with the leaves spread out. That fig. 6. is a plant of the same genus does not admit of a doubt. Fig. 7. and 8. may be roots of plants, or mutilated skeletons of some of the Ferns. i never heard of them being discovered any where but at Stonelaw. Whether fig. I. pl. XI. is of the Bamboo kind is not certain: if it is, the diameter must have been very large. It is sometimes found on coal, in which case the surface is extremely smooth. the characters of fig. 2. are not so perfect, as to ascertain the particular genus to which it belongs. Fig. 3. is probably a fragment of what Lhwyd (Lithoph. Brit. No. 186.) calls Lithopteris fæmina Glocestrensis, Trichomanis pinnulis longioribus. This variety is very rare. Fig. 4. is, by Lhwyd, called Lithosmunda minor; sive Osmunda mineralis pinnulis brevioribus, densius dispositis. Some of the single leaves, or pinnulæ, many of which are found separately, are two inches in length, and of a proportionable breadth. Fig. 5. from its habit, seems to be the Osmunda spicant. That fig. I. pl. XII. is an Asplenium is highly probable. Fig. 2. is a plant, probably yet unknown, in a recent state. Fig. 3. seems to be what Lhwyd calls Rubeola. It bears a distant resemblance to the Asperula odorata. The Equisetum, fig. 4. is very distinct: it seems, however, to be different from fig. 4. pl. X. That fig. 5. pl. XII. belongs to the Ferns, is very probable. Certainty with respect to some of the species of these impressions cannot be obtained, till we are better acquainted with exotic plants, of the Cryptogamia class. The varieties above-mentioned are not equally plenty. Fig. 4. 6. 7. pl. X. and all the figures in pl. XII. are scarce.
THE strata of coal, in both parishes, frequently retain many fragments of branches of trees, in a charred state. They lie blended together in the utmost confusion; and many of them retain distinct traces of the concentric lamellæ which originally composed the ligneous part of the wood. Many of the specimens are replete with pyrites. These once organized remains afford a strong proof, that vegetable substances were originally concerned in the formation of coal. This circumstance alone, however, is not conclusive; for several specimens of charred wood have been found in free-stone, where there was no appearance of coal accompanying the wood. I have found some specimens of charred wood, retaining its original structure, imbedded in whin-stone, as in the rock of Dumbarton. Examples of this are very rare.
EXOTIC Pines exhibit another class of impressions. They may be divided into two kinds: such as are superficial only; and such as retain, at least in part, the original shape of the tree. The varieties they contain, however, are not numerous. Fig. 4. pl. XIII. is on a level surface, in an argillaceous free-stone. The specimen was, in 1789, found in the bed of Calder water, near Torrance. Other specimens of chequered impressions, found at the same place, are considerably larger than in this draught. Fig. 6. is on till found, ann. 1790, in the iron-stone mines, in the lands of Basket.1 It is on a concave surface, with a convex one corresponding to it. The original bark, between the two surfaces, is converted into a coally substance. Fig. I. is perhaps of the same species, but of a much younger plant. The configurations are on a level surface, and are amongst the smallest I have seen. What renders the specimen a great curiosity is the remains of the leaves, lying on each side, as had they been pressed down by a superincumbent weight. Specimens with this peculiarity are extremely rare; two or three are all I have seen, and I know not if they have been discovered any where else. The impressions are on inflammable till, found above coal, at Stonelaw, ann. 1792. The till contains great numbers of bivalve shells, of the kind delineated fig. 4. pl. XVI. On the same piece of till is the impression fig. 3. pl. XIII. It is of a larger plant than the other, and the denticulations occasioned by the bases of the leaves are distinctly seen. Of this kind several specimens, on iron-stone, coal, till and free-stone, are found in many places of Scotland. The surfaces are sometimes level, but more frequently concave. One specimen of the impression fig. 5. is all of the kind I have discovered. It is of a level surface, on iron-stone, found ann. 1788, near Mauchlan-hole. Specimens of figured stones, having rows of holes, in an oblique direction, are not unfrequent in Kilbride. The holes are not of the same depth nor wideness. Each of them commonly contains a small column, mostly of the shape and size of the draught fig. 7. These pillars are generally hollow, and regularly punctured on the top. They adhere to the stone at their bases, and are from ½ to ⅙ of an inch in length. In some specimens the surface of the stone, between the rows of holes, is ornamented with the rugosities, &c. of the external surface of the vegetable, from which the impression was made. These curious stones are of excellent iron-stone: they are turned out along with coal, and are mostly found in the bed of Calder water, near Torrance. Externally they are of an irregular and rugged shape, having no appearance of any organized figure; but when broken, the impressions are found in the middle of them.
THE most common impression of what is supposed to be the Pine, is the kind delineated fig. 2. The specimens are chiefly on free-stone, and sometimes on coal, or till. They are ornamented with small protuberances, running obliquely round the trunk or branch. The more perfect specimens are likewise adorned with small furrows, among the protuberances, as in the figure. This particular structure is not uncommon with many species of plants. When on free-stone the original shape of the branch is preserved entire; only the internal structure of the ligneous part is destroyed, the whole being converted into a solid mass of stone; excepting what is thought to have been the pith, which is distinguishable, and often separable from the rest. It is seldom found in the middle. The specimens are of various sizes, from 2 feet, to 2 inches in diameter; and sometimes 8, or 10 feet in length. They are seldom or never branched; and lie chiefly in a slanting, but sometimes in a horizontal direction. Not unfrequently they penetrate the thickness of the rock, and spread themselves alongst the upper surface of a stratum of coal, or other substance that may be below it. Of this we have some beautiful examples in Glen-Garvel, in the parish of Kilsyth. These impressions abound in coal counties; and are, in many places, not improperly known by the name of Coal-Stalk. This term, however, is, in Campsie, Baldernock and some other places, ascribed to a recent vegetable root, that penetrates a considerable way in the earth; and, in some few instances, even through the crevices of the free-stone itself. The shrub to which it belonged must have been cut down, when clearing the ground for cultivation. That this root, therefore, springs out of the coal, and vegetates on the top, is unquestionably a vulgar error.
AMONG the coal, near Torrance, is found a very curious species of an exotic plant. Instead of the protuberances, mentioned above, it is covered with oblique rows of spines, about half and inch in length, and ⅛ in thickness, at the base: they are drawn out to a sharp point, and lie flat on the stone. Most of them are fractured; owing apparently to some violent pressure: the fractures, in some instances, are near the base, in others near the point. The specimens are of excellent iron-stone, and mostly retain evident marks of the pith; but are totally destitute of the internal structure of the wood. They are frequently branched, the branches going off at an angle, considerably acute: and are not opposite; but whether sparse or alternate, is not known. The specimens are commonly no longer than 5, or 6 inches; and are from 3, to 1 in diameter: those retaining the spines entire are very rare.
OF all the varieties of petrified wood, in these bounds, the most perfect is one found among the coal at Stonelaw. Most of the specimens are of the size of the draught fig. 6. pl. XII. The bark, which is regularly denticulated by a kind of sharp pointed papillæ, appears to have been cut, or broken asunder, on the one side; and to have contracted itself backward, as we sometimes see examples in the bark of living plants. Owing to this disruption the fibrous, or vascular structure of the ligneous part if exhibited. When viewed on the side, at a, it appears to be striated: but when viewed on the end, at b, a great number of pores are seen. These pores are filled with white Selenite, which is set off to advantage by their being inclosed in a very black, stoney substance, containing a considerable proportion of lime. From the structure this petrifaction would appear to belong to the Cane, rather than to the Pine. None of the specimens are branched, or jointed: they are not found in great plenty.
IMPRESSIONS of the bark of what seems to have been the Oak, Elm, &c. are sometimes, though sparingly, found in free-stone.