The Old Red Sandstone; or, New Walks in an Old Field

by Hugh Miller

The ability displayed by Cuvier in restoring, from a few broken fragments of bone, the skeleton of the entire animal to which the fragments had belonged, astonished the world He had learned to interpret signs as incomprehensible to every one else as the mysterious handwriting on the wall had been to the courtiers of Belshazzar. The condyle of a jaw became in his hands a key to the character of the original possessor; and in a few mouldering vertebræ, or in the dilapidated bones of a fore-arm or a foot, he could read a curious history of habits and instincts. In common with several gentlemen of Edinburgh, all men known to science, I was as much struck with the skill displayed by Agassiz in piecing together the fragments of the huge crustacean of Balruddery, and in demonstrating its nature as such. The numerous specimens of Mr. Webster were opened out before us. On a previous morning I had examined them, as I have said, in the company of Mr. Murchison and Dr. Buckland; they had been seen also by Lord Greenock, Dr. Traill, and Mr. Charles M'Laren; and their fragments of new and undescribed fishes had been at once recognized with reference to at least their class. But the collection contained organisms of a different kind, which seemed inexplicable to all—forms of various design, but so regularly mathematical in their outlines that they might be all described by a ruler and a pair of compasses, and yet the whole were covered by seeming scales. There were the fragments of scaly rhombs, of scaly crescents, of scaly circles, with scaly parallelograms attached to them, and of several other regular compound figures besides. Mr. Murchison, familiar with the older fossils, remarked the close resemblance of the seeming scales to those of the Seraphim of Forfarshire, but deferred the whole to the judgment of Agassiz; no one else hazarded a conjecture. Agassiz glanced over the collection. One specimen especially caught his attention—an elegantly symmetrical one. It seemed a combination of the parallelogram and the crescent: there were pointed horns at each end; but the convex and concave lines of the opposite sides passed into almost parallel right lines towards the centre. His eye brightened as he contemplated it. "I will tell you," he said, turning to the company—"I will tell you what these are—the remains of a huge lobster." He arranged the specimens in the group before him with as much apparent ease as I have seen a young girl arranging the pieces of ivory or mother-of-pearl in an Indian puzzle. A few broken pieces completed the lozenge-shaped shield; two detached specimens, placed on its opposite sides, furnished the claws; two or three semi-rings, with serrated edges, composed the jointed body; the compound figure, which but a minute before had so strongly attracted his attention, furnished the terminal flap; and there lay the huge lobster before us, palpable to all. There is homage due to supereminent genius, which nature spontaneously pays when there are no low feelings of envy or jealousy to interfere with her operations; and the reader may well believe that it was willingly rendered on this occasion to the genius of Agassiz.

PLATE IX.

The terminal flap of this gigantic crustacean was, as I have said, continuous. The creature, however, seems to have had contemporaries of the same family, whose construction in the divisions of the flap resembled more the lobsters of the present day; and the reader may see in the subjoined print the representation of a very characteristic fragment of an animal of this commoner type, from the Middle Sandstones of Forfarshire. (See [Plate IX.], fig. 1.) It is a terminal flap—one of several divisions—curiously fretted by scale-like markings, and bearing on its lower edge a fringe, cut into angular points, somewhat in the style of the Vandyke edgings of a ruff or the lacings of a dead-dress. It may be remarked, in passing, that our commoner lobsters bear, on the corresponding edge, fringes of strong, reddish-colored hair. The form altogether, from its wing-like appearance, its feathery markings, and its angular points, will suggest to the reader the origin of the name given it by the Forfarshire workmen. With another such flap spreading out in the contrary direction, and a periwigged head between them, we would have one of the sandstone cherubs of our country churchyards complete.

There occur among the other organisms of Balruddery numerous ichthyodorulites—fin-spines, such as those to which I have called the attention of the reader in describing the thorny-finned fish of the lower formation. But the ichthyodorulites of Balruddery differ essentially from those of Caithness, Moray, and Cromarty. These last are described on both sides, in every instance, by either straight, or slightly curved lines; whereas one of the describing lines in a Balruddery variety is broken by projecting prickles, that resemble sharp, hooked teeth set in a jaw, or, rather, the entire ichthyodorulite resembles the sprig of a wild rose-bush, bearing its peculiar aquiline shaped thorns on one of its sides. Buckland, in his Bridgewater Treatise, and Lyell, in his Elements, refer to this peculiarity of structure in ichthyodorulites of the latter formations. The hooks are invariably ranged on the concave or posterior edge of the spine, and were employed, it is supposed, in elevating the fin. Another ichthyodorulite of the formation resembles, in the Gothic cast of its roddings, those of the Diplacanthus of the Lower Old Red Sandstone described in pages 125 and 126 of the present volume, and figured in [Plate VIII.], fig. 2, except that it was proportionally stouter, and traversed at its base by lines running counter to the striæ that furrow it longitudinally. Of the other organisms of Balruddery I cannot pretend to speak with any degree of certainty. Some of them seem to have belonged to the Radiata; some are of so doubtful a character that it can scarce be determined whether they took their place among the forms of the vegetable or animal kingdoms. One organism in particular, which was at first deemed the jointed stem of some plant resembling a calamite of the Coal Measures, was found by Agassiz to be the slender limb of a crustacean. A minute description of this interesting deposit, with illustrative prints, would be of importance to science: it would serve to fill a gap in the scale. The geological pathway, which leads upwards to the present time from those ancient formations in which organic existence first began, has been the work of well nigh as many hands as some of our longer railroads: each contractor has taken his part; very extended parts have fallen to the share of some, and admirably have they executed them; but the pathway is not yet complete, and the completion of a highly curious portion of it awaits the further labors of Mr. Webster, of Balruddery.

A considerable portion of the rocks of this middle formation in Scotland are of a bluish-gray color: in Balruddery, they resemble the mudstones of the Silurian System; they form at Carmylie the fissile, bluish-gray pavement, so well known in commerce as the pavement of Arbroath; they occur as a hard, micaceous building-stone in some parts of Fifeshire; in others they exist as beds of friable, stratified clay, that dissolve into unctuous masses where washed by the sea. In England, the formation consists, throughout its entire depth, of beds of red and green marl, with alternating beds of the nodular limestones, to which it owes its name, and with here and there an interposing band of indurated sandstone.

The Cornstone formation is more extensively developed in Forfarshire than in any other district in Scotland; and from this circumstance the result of the writer's observations regarding it, during the course of a recent visit, may be of some little interest to the reader. About two thirds the entire area of this county is composed of Old Red Sandstone. It forms a portion of that great belt of the system which, extending across the island from the German Ocean to the Frith of Clyde, represents the southern bar of the huge sandstone frame in which the Highlands of Scotland is set. The Grampians run along its inner edge—composing part of the primary nucleus which the frame encloses: the Sidlaw Hills run through its centre in a line nearly parallel to these, and separated from them by Strathmore, the great valley of Angus. The valley and the hills thus form, if I may so express myself, the mouldings of the frame—mouldings somewhat resembling the semi-recta of the architect. There is first, reckoning from the mountains downwards, an immense concave curve—the valley; then an immense convex one—the hills; and then a half curve bounded by the sea. The illustration may further serve to show the present condition of the formation: it is a frame much worn by denudation, and—just as in a bona fide frame—it is the higher mouldings that have suffered most. Layer after layer has been worn down on the ridges, exactly as on a raised moulding we may see the gold leaf, the red pigment, and the whiting, all ground down to the wood; while in the hollow moulding beside it, on the contrary, the gilt is still fresh and entire. We find in the hollows the superior layers of the frame still overlying the inferior ones, and on the heights the inferior ones laid bare. To descend in the system, therefore, we have to climb a hill—to rise in it, we have to descend into a valley. We find the lowest beds of the system any where yet discovered in the county on the moory heights of Carmylie; its newer deposits may be found on the sea-shore, beside the limeworks of Hedderwick, and in the central hollows of Strathmore.

The most ancient beds in the county yet known belong, as unequivocally shown by their fossils, to but the middle formation of the system. They have been quarried for many years in the parish of Carmylie; and the quarries, as may be supposed, are very extensive, stretching along a moory hill-side for considerably more than a mile, and furnishing employment to from sixty to a hundred workmen. The eye is first caught, in approaching them, as we surmount a long, flat ridge, which shuts them out from the view of the distant sea, by what seems a line of miniature windmills, the sails flaring with red lead, and revolving with the lightest breeze at more than double the rate of the sails of ordinary mills. These are employed—a lesson probably borrowed from the Dutch—in draining the quarries, and throw up a very considerable body of water. The line of the excavations resembles a huge drain, with nearly perpendicular sides—a consequence of the regular and well-determined character of the joints with which the strata are bisected. The stone itself is a gray, close-grained fissile sandstone, of unequal hardness, and so very tough and coherent—qualities which it seems to owe in part to the vast abundance of mica which it contains—that it is quite possible to strike a small hammer through some of the larger flags, without shattering the edges of the perforation. Hence its value for various purposes which common sandstone is too brittle and incoherent to serve. It is extensively used in the neighborhood as a roofing slate; it is employed, too, in the making of water cisterns, grooved and jointed as if wrought out of wood, and for the tops of lobby and billiard tables. I have even seen snuff-boxes fashioned out of it, as a sort of mechanical feat by the workmen,—a purpose, however, which it seems to serve only indifferently well,—and single slabs of it cut into tolerably neat window frames for cottages. It is most extensively used, however, merely as a paving-stone for lobbies and lower floors, and the footways of streets. When first deposited, and when the creatures whose organic remains it still preserves careered over its numerous platforms, it seems to have existed as a fine, muddy sand, formed apparently of disintegrated grauwacke rocks, analogous in their mineral character to the similarly colored grauwacke of the Lammermuirs, or of primary slates ground down by attrition into mud, and mixed up with the pulverized fragments of schistose gneiss and mica schist.

I was first struck, on descending among the workmen, by the comparative abundance of the vegetable remains. In some parts of the quarries almost every layer of the strata is covered by carbonaceous markings—irregularly grooved stems, branching oat into boughs at acute angles, and that at the first glance seem the miniature semblances of the trunks of gnarled oaks and elms, blackened in a morass, and still retaining the rough bark, chapped into furrows: oblong, leaf-like impressions, too, and impressions of more slender form, that resemble the narrow, parallel edged leaves of the sea-grass weed. I observed, in particular, one large bunch of riband-like leaflets converging into a short stem, so that the whole resembled a scourge of cords; and I would fain have detached it from the rock, but it lay on a mouldering film of clay, and broke up with my first attempt to remove it. A stalk of sea-grass weed plucked up by the roots, and compressed in a herbarium, would present a somewhat similar appearance. Among the impressions there occur irregularly shaped patches, reticulated into the semblance of polygonal meshes. They remind one of pieces of ill-woven lace; for the meshes are unequal in size, and the polygons irregular. (See [Plate IX.], fig. 2.) When first laid open, every mesh is filled with a carbonaceous speck; and from their supposed resemblance to the eggs of the frog, the workmen term them puddock spawn. They are supposed by Mr. Lyell to form the remains of the eggs of some gasteropodous mollusc of the period. I saw one flagstone, in particular, so covered with these reticulated patches, and so abundant, besides, in vegetable impressions of both the irregularly furrowed and grass-weed-looking class, that I could compare it to only the bottom of a ditch beside a hedge, matted with withered grass, strewed with blackened twigs of the hawthorn, and mottled with detached masses of the eggs of the frog. All the larger vegetables are resolved into as pure a coal as the plants of the Coal Measures themselves—the kind of data, doubtless, on which unfortunate coal speculators have often earned disappointment at large expense. None of the vegetables themselves, however, in the least resemble those of the carboniferous period.