[AJ]Different in one respect from the conglomerates of Arran. It abounds in rolled fragments of granite, whereas in those of Arran there occur no pebbles of this rock. Arran has now its granite in abundance; the northern locality has none; though, when the conglomerates of the Lower Old Red Sandstone were in the course of forming, the case was exactly the reverse.
[AJ]Different in one respect from the conglomerates of Arran. It abounds in rolled fragments of granite, whereas in those of Arran there occur no pebbles of this rock. Arran has now its granite in abundance; the northern locality has none; though, when the conglomerates of the Lower Old Red Sandstone were in the course of forming, the case was exactly the reverse.
The enormous depth of the Old Red Sandstone of England has been divided by Mr. Murchison into three members, or formations—the division adopted in hisElementsby Mr. Lyell, as quoted in an early chapter. These are, the lowest, or Tilestone formation, the middle, or Cornstone formation, and the uppermost, or Quartzose conglomerate formation. The terms are derived from mineralogical characters, and inadequate as designations, therefore, like that of the Old Red Sandstone itself, which, in many of its deposits, is notsandstone, and is notred. But they serve to express great natural divisions. Now the Tilestone member of England represents, as I have already stated, this Lower Old Red Sandstone formation of Scotland; but its extent of vertical development, compared with that of the other two members of the system, is strikingly different in the two countries. The Tilestones compose the least of the three divisions in England; their representative in Scotland forms by much thegreatest of the three; and there seems to be zoölogical as well as lithological evidence that its formation must have occupied no brief period.The same genera occur in its upper as in its lower beds, but the species appear to be different.I shall briefly state the evidence of this very curious fact.
The seat of Sir William Gordon Camming, of Altyre, is in the neighborhood of one of the Morayshire deposits discovered by Mr. Malcolmson; and for the greater part of the last two years Lady Gordon Gumming has been engaged in making a collection of its peculiar fossils, which already fills an entire apartment. The object of her Ladyship was the illustration of the Geology of the district, and all she sought in it on her own behalf was congenial employment for a singularly elegant and comprehensive mind. But her labors have rendered her a benefactor to science. Her collection was visited, shortly after the late meeting of the British Association in Glasgow, by Agassiz and Dr. Buckland; and great was the surprise and delight of the philosophers to find that the whole was new to Geology. All the species, amounting to eleven, and at least one of the genera, that of theGlyptolepis, were different from any Agassiz had ever seen or described before. The deposit so successfully explored by her Ladyship occurs high in the lower formation. Agassiz, shortly after, in comparing the collection of Dr. Traill (a collection formed at Orkney) with that of the writer, (a collection made at Cromarty,) was struck by the specific identity of the specimens. In the instances in which the genera agreed, he found that the species agreed also, though the ichthyolites of both differed specifically from the ichthyolites of Caithness, which occur chiefly in the upper beds of the formation, and from those also of Lady Cumming of Altyre, which occur, as I have said, at the top. And in examining into the cause, it wasfound that the two collections, though furnished by localities more than a hundred miles apart, were yet derived, if I may so express myself, from the same low platform, both alike representing the fossiliferous base of the system, and both removed but by a single stage from the great unfossiliferous conglomerate below. Thus there seem to be what may be termed two stories of being in this lower formation—stories in which the groups, though generically identical, are specifically dissimilar.[AK]
[AK]Since this period, however, several species identical with those of Cromarty have been found in the Morayshire deposits.
[AK]Since this period, however, several species identical with those of Cromarty have been found in the Morayshire deposits.
Upper Formations of the Old Red Sandstone.—Room, enough for each and to spare.—Middle, or Cornstone Formation.—TheCephalaspisits most characteristic Organism.—Description.—The Den of Balruddery richer in the Fossils of this middle Formation than any other Locality yet discovered.—Various Contemporaries of theCephalaspis.—Vegetable Impressions.—Gigantic Crustacean.—Seraphim.—Ichthyodorulites.—Sketch of the Geology of Forfarshire.—Its older Deposits of the Cornstone Formation.—The Quarries of Carmylie.—Their Vegetable and Animal Remains.—The Upper Formation.—Wide Extent of the Fauna and Flora of the earlier Formations.—Probable Cause.
HithertoI have dwelt almost exclusively on the fossils of the Lower Old Red Sandstone, and the history of their discovery: I shall now ascend to the organisms of its higher platforms. The system in Scotland, as in the sister kingdom, has its middle and upper groups, and these are in no degree less curious than the inferior group already described, nor do they more resemble the existences of the present time. Does the reader remember the illustration of the pyramid employed in an early chapter—its three parallel bars, and the strange hieroglyphics of the middle bar? Let him now imagine another pyramid, inscribed with the remaining and later history of the system. We read, as before, from the base upwards, but find the broken and half-defaced characters of the second erection descending into the very soil, as in those obelisks of Egypt round which the sands of the desert have been accumulating for ages. Hence a hiatus in our history for future excavators to fill; and it contains many such blanks, every unfossiliferous bar in either pyramid representinga gap in the record. Three distinct formations the group undoubtedly contains—perhaps more; nor will the fact appear strange to the reader who remembers how numerous the formations are that lie over and under it, and that its vast depth of ten thousand feet equals that of the whole secondary system from top to bottom. Eight such formations as the Oolite, or ten such formations as the Chalk, could rest, the one over the other, in the space occupied by a group so enormous. To the evidence of its three distant formations, which is of a very simple character, I shall advert as I go along.
The central or Cornstone division of the system in England is characterized throughout its vast depth by a peculiar family of ichthyolites, which occur in none of the other divisions. I have already had occasion to refer to theCephalaspis. Four species of this fish have been discovered in the Cornstones of Hereford, Salop, Worcester, Monmouth, and Brecon;[AL]"and as they are always found," says Mr. Murchison, "in the same division of the Old Red System, they have become valuable auxiliaries in enabling the geologist to identify its subdivisions through England and Wales, and also to institute direct comparisons between the different strata of the Old Red Sandstone of England and Scotland." TheCephalaspisis one of the most curious ichthyolites of the system. (SeePlate X., fig. 1.) Has the reader ever seen a saddler's cutting knife?—a tool with a crescent-shaped blade, and the handle fixed transversely in the centre of its concave side. In general outline theCephalaspisresembled this tool—the crescent-shaped blade representing the head, the transverse handle the body. We have but to give thehandle an angular, instead of a rounded shape, and to press together the pointed horns of the crescent, till they incline towards each other, and the convex, or sharpened edge, is elongated into a semi-ellipse, cut in the line of its shortest diameter, in order to produce the complete form of theCephalaspis. The head, compared with the body, was of great size—comprising fully one third the creature's entire length. In the centre, and placed closely together, as in many of the flat fish, were the eyes. Some of the specimens show two dorsals, and an anal and caudal fin. The thin and angular body presents a jointed appearance, somewhat like that of a lobster or trilobite. Like the bodies of most of the ichthyolites of the system, it was covered with variously formed scales of bone; the creature's head was cased in strong plates of the same material, the whole upper side lying under one huge buckler—and hence the nameCephalaspis, or buckler-head. In proportion to its strength and size, it seems to have been amply furnished with weapons of defence. Such was the strength and massiveness of its covering, that its remains are found comparatively entire in arenaceous rocks impregnated with iron, in which few other fossils could have survived. Its various species, as they occur in the Welsh and English Cornstones, says Mr. Murchison, seem "not to have been suddenly killed and entombed, but to have been long exposed to submarine agencies, such as the attacks of animals, currents, concretionary action," &c.; and yet, "though much dismembered, the geologist has little difficulty in recognizing even the smallest portions of them." Nor does it seem to have been quite unfurnished with offensive weapons. The sword-fish, with its strong and pointed spear, has been known to perforate the oaken ribs of the firmest built vessels; and, poised and directed by its lesser fins, and impelled by itspowerful tail, it may be regarded either as an arrow or javelin flung with tremendous force, or as a knight speeding to the encounter with his lance in rest. Now there are missiles employed in Eastern warfare, which, instead of being pointed like the arrow or javelin, are edged somewhat like the crooked falchion or saddler's cutting-knife, and which are capable of being cast with such force, that they have been known to sever a horse's leg through the bone; and if the sword-fish may be properly compared to an arrow or javelin, the combative powers of theCephalaspismay be illustrated, it is probable, by a weapon of this kind—the head all around its elliptical margin presenting a sharp edge, like that of a cutting-knife, or falchion. Its impetus, however, must have been comparatively small, for its organs of motion were so: it was a bolt carefully fashioned, but a bolt cast from a feeble bow. But if weak in the assault, it must have been formidable when assailed. "The pointed horns of the crescent," said Agassiz to the writer, "seem to have served a similar purpose with the spear-like wings of thePterichthys,"—the sole difference consisting in the circumstance, that the spears of the one could be elevated or depressed at pleasure, whereas those of the other were ever fixed in the warlike attitude. And such was theCephalaspisof the Cornstones—not only the most characteristic, but in England and Wales almost the sole organism of the formation.
[AL]Cephalaspis Lewisii,C. Lloydii,C. Lyellii, andC. rostratus.
[AL]Cephalaspis Lewisii,C. Lloydii,C. Lyellii, andC. rostratus.
Now of this curious ichthyolite we find no trace among the fossils of the Lower Old Red Sandstone. It occurs neither in Orkney nor Cromarty, Caithness nor Gamrie, Nairnshire nor the inferior ichthyolite beds of Moray. Neither in England nor in Scotland is it to be found in the Tilestone formation, or its equivalent. It is common, however, in the Old Red Sandstone of Forfarshire; and it occurs at Balruddery,in the Gray Sandstones which form on both sides the Tay, where the Tilestone formation seems wanting, the apparent base of the system. It is exclusively a medal of the middle empire.
In the last-mentioned locality, in a beautifully wooded dell, known as the Den of Balruddery, theCephalaspisis found associated with an entire group of other fossils, the recent discovery of Mr. Webster, the proprietor, who, with a zeal through which geological knowledge promises to be materially extended, and at an expense of much labor, has made a collection of all the organisms of the Den yet discovered. These the writer had the pleasure of examining in the company of Mr. Murchison and Dr. Buckland: he was afterwards present when they were examined by Agassiz; and not a single organism of the group could be identified on either occasion, by any member of the party, with those of the lower or upper formations. Even the genera are dissimilar. The fossils of the Lias scarce differ more from those of the Coal Measures, than the fossils of the Middle Old Red Sandstone from the fossils of the formations that rest over and under them. Each formation has its distinct group—a fact so important to the geologist, that he may feel an interest in its further verification through the decision of yet another high authority. The superior Old Red Sandstones of Scotland were first ascertained to be fossiliferous by Professor Fleming, of King's College, Aberdeen,[AM]confessedly one of the firstnaturalists of the age, and who, to his minute acquaintance with existing forms of being, adds an acquaintance scarcely less minute with those forms of primeval life that no longer exist. He it was who first discovered, in the Upper Old Red Sandstones of Fifeshire, the large scales and plates of that strikingly characteristic ichthyolite of the higher formation, now known as theHoloptychius—of which more anon; and, unquestionably, no one acquainted with his writings, or the character of his mind, can doubt that he examined carefully.
[AM]The Upper Old Red Sandstones of Moray were ascertained to be fossiliferous at nearly the same time by Mr. Martin, of the Anderson Institution, Elgin. There is a mouldering conglomerate precipice termed theScat-Craig, about four miles to the south of the town, more abundant in remains than perhaps any of the other deposits of the formation yet discovered; and in this precipice Mr. Martin first commenced his labors in the lied Sandstone of the district, and found it a mine of wonders. It is a place of singular interest—a rock of sepulchres; and its teeth, scales, and single bones occur in a state of great entireness; though, ere the deposit was formed, the various ichthyolites whose remains it contains seem to have been broken up, and their fragments scattered. Accumulations of larger and smaller pebbles alternate in the strata; and the bulkier bones and teeth are found invariably among the bulkier pebbles, thus showing that they were operated upon by the same laws of motion which operated on the inorganic contents of the deposit. At a considerably later period the fossils of the upper group were detected in the precipitous and romantic banks of the Findhorn, by Dr. Malcolmson, of Madras, when prosecuting his discoveries of the organisms of the lower formation. He found them, also, though in less abundance, in a splendid section exhibited in the Burn of Lethen, a rivulet of Moray, and yet again in the neighborhood of Altyre. The Rev. Mr. Gordon, of Birnie, and Mr. Robertson, of Inverugie, have been also discoverers in the district. To the geological labors of Mr. Patrick Duff, of Elgin, in the same field, I have already had occasion incidentally to refer. The patient inquiries of this gentleman have been prosecuted for years in all the formations of the province, from the Weald of Linksfield, with its peculiar lacustrine remains—lignites, minute fresh-water shells, and the teeth, spines, and vertebræ of fish and saurians—down to the base of the Old Red Sandstone, with itsCoccostei,Dipteri, andPterichthyes. His acquaintance with the organisms of theScat-Craigis at once more extensive and minute than that of, perhaps, any other geologist; and his collection of them very valuable, representing, as it does, a formation of much interest, still little known. Mr. Duff is at present engaged on a volume descriptive of the Geology of the province of Moray, a district extensively explored of late years, and abundant in its distinct groups of organisms, but of which general readers have still much to learn; and from no one could they learn more regarding it than from Mr. Duff. It is still only a few months since the Upper Old Red Sandstones of the southern districts of Scotland were found to be fossiliferous; and the writer is chiefly indebted for his acquaintance with their organisms to a tradesman of Berwickshire, Mr. William Stevenson, of Dunse, who, on perusing some of the geological articles which appeared in the Witness newspaper during the course of the last autumn, sent him a parcel of fossils disinterred from out the deep belt of Red Sandstone which leans to the south in that locality, against the grauwacke of the Lammermuirs. Mr. Stevenson had recently discovered them, he stated, near Preston-haugh, about two miles north of Dunse, in a fine section of alternating Sandstone and conglomerate strata that lie unconformably on the grauwacke. They consist of scales and occipital plates of theHoloptychius, with the remains of a bulky, but very imperfectly preserved ichthyodorulite; and the coarse, arenaceous matrices which surround them seem identical with the red gritty Sandstones of the Findhorn and theScat-Craig,
[AM]The Upper Old Red Sandstones of Moray were ascertained to be fossiliferous at nearly the same time by Mr. Martin, of the Anderson Institution, Elgin. There is a mouldering conglomerate precipice termed theScat-Craig, about four miles to the south of the town, more abundant in remains than perhaps any of the other deposits of the formation yet discovered; and in this precipice Mr. Martin first commenced his labors in the lied Sandstone of the district, and found it a mine of wonders. It is a place of singular interest—a rock of sepulchres; and its teeth, scales, and single bones occur in a state of great entireness; though, ere the deposit was formed, the various ichthyolites whose remains it contains seem to have been broken up, and their fragments scattered. Accumulations of larger and smaller pebbles alternate in the strata; and the bulkier bones and teeth are found invariably among the bulkier pebbles, thus showing that they were operated upon by the same laws of motion which operated on the inorganic contents of the deposit. At a considerably later period the fossils of the upper group were detected in the precipitous and romantic banks of the Findhorn, by Dr. Malcolmson, of Madras, when prosecuting his discoveries of the organisms of the lower formation. He found them, also, though in less abundance, in a splendid section exhibited in the Burn of Lethen, a rivulet of Moray, and yet again in the neighborhood of Altyre. The Rev. Mr. Gordon, of Birnie, and Mr. Robertson, of Inverugie, have been also discoverers in the district. To the geological labors of Mr. Patrick Duff, of Elgin, in the same field, I have already had occasion incidentally to refer. The patient inquiries of this gentleman have been prosecuted for years in all the formations of the province, from the Weald of Linksfield, with its peculiar lacustrine remains—lignites, minute fresh-water shells, and the teeth, spines, and vertebræ of fish and saurians—down to the base of the Old Red Sandstone, with itsCoccostei,Dipteri, andPterichthyes. His acquaintance with the organisms of theScat-Craigis at once more extensive and minute than that of, perhaps, any other geologist; and his collection of them very valuable, representing, as it does, a formation of much interest, still little known. Mr. Duff is at present engaged on a volume descriptive of the Geology of the province of Moray, a district extensively explored of late years, and abundant in its distinct groups of organisms, but of which general readers have still much to learn; and from no one could they learn more regarding it than from Mr. Duff. It is still only a few months since the Upper Old Red Sandstones of the southern districts of Scotland were found to be fossiliferous; and the writer is chiefly indebted for his acquaintance with their organisms to a tradesman of Berwickshire, Mr. William Stevenson, of Dunse, who, on perusing some of the geological articles which appeared in the Witness newspaper during the course of the last autumn, sent him a parcel of fossils disinterred from out the deep belt of Red Sandstone which leans to the south in that locality, against the grauwacke of the Lammermuirs. Mr. Stevenson had recently discovered them, he stated, near Preston-haugh, about two miles north of Dunse, in a fine section of alternating Sandstone and conglomerate strata that lie unconformably on the grauwacke. They consist of scales and occipital plates of theHoloptychius, with the remains of a bulky, but very imperfectly preserved ichthyodorulite; and the coarse, arenaceous matrices which surround them seem identical with the red gritty Sandstones of the Findhorn and theScat-Craig,
Now, a few years since, I had the pleasure of introducing Professor Fleming to the Organisms of the Lower Old Red Sandstone, as they occur in the neighborhood of Cromarty; and, notwithstanding his extensive acquaintance with the upper fossils of the system, he found himself, among the lower, in an entirely new field. His knowledge of the one group served but to show him how very different it was from the other. With the organisms of the lower he minutely acquainted himself; he collected specimens from Gamrie,Caithness, and Cromarty, and studied their peculiarities; and yet, on being introduced last year to the discoveries of Mr. Webster at Balruddery, he found his acquaintance with both the upper and lower groups stand him in but the same stead that his first acquired knowledge of the upper group had stood him a few years before. He agreed with Agassiz in pronouncing the group at Balruddery essentially a new group. Add to this evidence the well weighed testimony of Mr. Murchison regarding the three formations which the Old Red Sandstone contains in England, where the entire system is found continuous, the Cornstone overlying the Tilestone, and the Quartzose conglomerate the Cornstone; take into account the fact that, there, each formation has its characteristic fossil, identical with some characteristic fossil of the corresponding formation of Scotland—that the Tilestones of the one, and the lower group of the other, have theirDipterusin common—that the Cornstones of the one, and the middle group of the other, have theirCephalaspisin common—that the Quartzose conglomerate of the one, and the upper group of the other, have theirHoloptychiusin common; and then say whether the proofs of distinct succeeding formations can be more surely established. If, however, the reader still entertain a doubt, let him consult the singularly instructive section of the entire system, from the Carboniferous Limestone to the Upper Silurian, given by Mr. Murchison, in hisSilurian System, (Part II., Plate XXXI., fig. 1,) and he will find the doubt vanish. But to return to the fossils of the Cornstone group.
The characteristic fossil of this deposit, theCephalaspis, occurs in considerable abundance in Forfarshire, and in a much more entire state than in the Cornstones of England and Wales. The rocks to which it belongs are also developed,though more sparingly, in the northern extremity of Fife, in a line parallel to the southern shores of the Tay. But of all the localities yet known, the Den of Balruddery is that in which the peculiar organisms of the formation may be studied with best effect. The oryctology of the Cornstones of England seems restricted to four species of theCephalaspis. In Fife, all the organisms of the formation yet discovered are exclusively vegetable—darkened impressions of stems like those of the inferior ichthyolite beds, confusedly mixed with what seem slender and pointed leaflets drawn in black, and numerous circular forms, which have been deemed the remains of the seed-vessels of some unknown sub-aerial plant. "These last occur," says Professor Fleming, the original discoverer, "in the form of circular flat patches, not equalling an inch in diameter, and composed of numerous smaller contiguous circular pieces;" thetout ensembleresembling "what might be expected to result from a compressed berry, such as the bramble or the rasp." In Forfarshire, the remains of theCephalaspisare found associated with impressions of a different character, though equally obscure—impressions of polished surfaces carved into seeming scales; but in Balruddery alone are the vegetable impressions of the one locality, and the scaly impressions of the other, together with the characteristic ichthyolites of England and Forfarshire, found associated with numerous fossils besides, many of them obscure, but all of them of interest, and all of them new to Geology.
One of the strangest organisms of the formation is a fossil lobster, of such huge proportions, that one of the average sized lobsters, common in our markets, might stretch its entire length across the continuous tail-flap in which the creature terminated. And it is a marked characteristic of the fossil, that the terminal flap should be continuous; in all theexisting varieties with which I am acquainted, it is divided into angular sections. The claws nearly resembled those of the common lobster; their outline is similar; there is the same hawk-bill curvature outside, and the inner sides of the pincers are armed with similar teeth-like tubercles. The immense shield which covered the upper part of the creature's body is more angular than in the existing varieties, and resembles, both in form and size, one of those lozenge-shaped shields worn by knights of the middle ages on gala days, rather for ornament than use, and on which the herald still inscribes the armorial bearing of ladies who bear title in their own right. As shown in some of the larger specimens, the length of this gigantic crustacean must have exceeded four feet. Its shelly armor was delicately fretted with the forms of circular or elliptical scales. On all the many plates of which it was composed we see these described by gracefully waved lines, and rising apparently from under one another, row beyond row. They were, however, as much the mere semblance of scales as those relieved by the sculptor on the corslet of a warrior's effigy on a Gothic tomb—mere sculpturings on the surface of the shell. This peculiarity may be regarded as throwing light on the hitherto doubtful impressions of the sandstone of Forfarshire—impressions, as has been said, of smooth surfaces carved into seeming scales. They occur as impressions merely, the sandstone retaining no more of the original substance of the organism than the impressed wax does of the substance of the seal; and the workmen in the quarries in which they occur, finding form without body, and struck by the resemblance which the delicately waved scales bear to the sculptured markings on the wings of cherubs—of all subjects of the chisel the most common—fancifully termed themSeraphim. They have turned out, as was anticipated,to be the detached plates of some such crustacean as the lobster of Balruddery.
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 theSeraphimof 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.
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. (SeePlate 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 hisBridgewater Treatise, and Lyell, in hisElements, 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 Gothiccast of its roddings, those of theDiplacanthusof the Lower Old Red Sandstone described in pages 125 and 126 of the present volume, and figured inPlate 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 theRadiata; 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, stratifiedclay, 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 abona fideframe—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 grounddown 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 hammerthrough 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 ofriband-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. (SeePlate 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 thempuddock 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.
The animal remains, though less numerous, are more interesting. They are identical with those of the Den of Balruddery. I saw, in the possession of the superintendent of the quarries, a well-preserved head of theCephalaspisLyellii. The crescent-shaped horns were wanting, and the outline a little obscure; but the eyes were better marked than in almost any other specimen I have yet seen, and the circular star-like tubercles which roughen the large occipital buckler, to which the creature owes its name, were tolerably well defined. I was shown the head of another individual of the same species in the centre of a large slab, and nothing could be more entire than the outline. The osseous plate still retained the original brownish-white hue of the bone, and its radiated porous texture; and the sharp crescent-shaped horns were as sharply defined as during the lifetime of the strangely organized creature which they had defended. In both specimens the thin angular body was wanting. Like almost all the other fish of the Old Red Sandstone, the bony skeleton of theCephalaspiswas external—as much so as the shell of the crab or lobster: it presented at all points an armor of bone, as complete as if it had been carved by the ivory-turner out of a solid block; while the internal skeleton, which in every instance has disappeared, seems to have been composed of cartilage. I have compared its general appearance to a saddler's cutting-knife;—I should, perhaps, have said a saddler's cutting-knife divested of the wooden handle—the broad, bony head representing the blade, and the thin angular body the iron stem usually fixed in the wood. No existence of the present creation at all resembles theCephalaspis. Were we introduced to the living creatures which now inhabit the oceans and rivers of Mars and Venus, we could find nothing among them more strange in appearance, or more unlike our living acquaintances of the friths and streams, than theCephalaspidesof Carmylie.
I observed, besides, in the quarry, remains of the hugecrustacean of Balruddery. The plates of theCephalaspisretain the color of the original bone; the plates of the crustacean, on the contrary, are of a deep red tint, which contrasts strongly with the cold gray of the stone. They remind one, both in shape and hue, of pieces of ancient iron armor, fretted into semi-elliptical scales, and red with rust. I saw with one of the workmen what seemed to have been the continuous tail-flap of an individual of very considerable size. It seemed curiously puckered where it had joined to the body, much in the manner that a gown or Highlander's kilt is puckered where it joins to the waistband; and the outline of the whole plate was marked by what I may venture to term architectural elegance. The mathematician could have described it with his ruler and compasses. The superintendent pointed out to me another plate in a slab dressed for a piece of common pavement. It was a regularly formed parallelogram, and had obviously composed one of the jointed plates which had covered the creature's body. I could not so easily assign its place to yet a third plate in the possession of the Rev. Mr. Wilson, of Carmylie. It is colored, like the others, and like them, too, fretted into minute scales, but the form is exactly that of a heart—not such a heart as the anatomist would draw, but such a heart, rather, as we see at times on valentines of the humbler order, or on the ace of hearts in a pack of cards. Possibly enough it may have been the breastplate of this antique crustacean of the Cornstones. The spawn of our common blue lobster is composed of spherical black grains, of nearly the size of mustard-seed. It struck me as not very improbable that the reticulated markings of the flagstones of Carmylie may have been produced by the minute eggs of this fossil crustacean, covered up by some hastily deposited layer of mingled mud and sand, and forced into thepolygonal form by pressing against each other, and by the weight from above.
The gray fissile bed in which these organisms occur was perforated to its base on two several occasions, and in different parts of the quarries—in one instance, merely to ascertain its depth; in the other, in the course of excavating a tunnel. In the one case it was found to rest on a bed of trap, which seemed to have insinuated itself among the strata with as little disturbance, and which lay nearly as conformably to them as the greenstone bed of Salisbury Crags does to the alternating sandstones and clays which both underlie and overtop it. In the other instance the excavators arrived at a red, aluminous sandstone, veined by a purplish-colored oxide of iron. The upper strata of the quarry are overlaid by a thick bed of grayish-red conglomerate.
Leaving behind us the quarries of Carmylie, we descend the hill-side, and rise in the system as we lower our level and advance upon the sea. For a very considerable distance we find the rock covered up by a deep-red diluvial clay, largely charged with water-worn boulders, chiefly of the older primary rocks, and of the sandstone underneath. The soil on the higher grounds is moory and barren—a consequence, in great part, of a hard, ferruginous pan, which interposes like a paved floor between the diluvium and the upper mould, and which prevents the roots of the vegetation from striking downwards into the tenacious subsoil. From its impervious character, too, it has the effect of rendering the surface a bog for one half the year, and an arid, sun-baked waste for the other. It seems not improbable that the heaths which must have grown and decayed on these heights for many ages, may have been main agents in the formation of this pavement of barrenness. Of all plants, they are said to contain most iron.According to Fourcroy, a full twelfth part of the weight of oak, when dried, is owing to the presence of this almost universally diffused metal; and the proportion in our common heaths is still larger. It seems easy to conceive how that, as generation after generation withered on these heights, and were slowly resolved into a little mossy dust, the minute metallic particles which they had contained would be carried downwards by the rains through the lighter stratum of soil, till, reaching the impermeable platform of tenacious clay beneath, they would gradually accumulate there, and at length bind its upper layer, as is the nature of ferruginous oxide, into a continuous stony crust. Bog iron, and the clay ironstone, so abundant in the Coal Measures, and so extensively employed in our iron-works, seem to have owed their accumulation in layers and nodules to a somewhat similar process, through the agency of vegetation. But I digress.
The rock appears in the course of the Elliot, a few hundred yards above the pastoral village of Arbirlot. We find it uptilted on a mass of claystone amygdaloid, that has here raised its broad back to the surface amid the middle shales and sandstones of the system. The stream runs over the intruded mass; and where the latter terminates, and the sandstones lean against it, the waters leap from the harder to the softer rock, immediately beside the quiet parish burying-ground, in a cascade of some eight or ten feet. From this point, for a full mile downwards, we find an almost continuous section of the sandstone—stratum leaning against stratum—in an angle of about thirty. The portion of the system thus exhibited must amount to many hundred yards in vertical extent; but as I could discover no data by which to determine regarding the space which may intervene between its lowest stratum and the still lower beds of Carmylie, I couldform no guess respecting the thickness of the whole. In a bed of shale, about a quarter of a mile below the village, I detected several of the vegetable impressions of Carmylie, especially those of the grass-weed looking class, and an imperfectly preserved organism resembling the parallelogramical scale of aCephalaspis. The same plants and animals seem to have existed on this high platform as on the Carmylie platform far beneath.
A little farther down the course of the stream, and in the immediate neighborhood of the old weather-worn tower of the Ouchterlonies, there occurs what seems a break in the strata. The newer sandstones seem to rest unconformably on the older sandstones which they overlie. The evening on which I explored the course of the Elliot was drizzly and unpleasant, and the stream swollen by a day of continuous rain, and so I could not examine so minutely as in other circumstances I would have done, or as was necessary to establish the fact. In since turning over theElementsof Lyell, however, I find, in his section of Forfarshire, that a newer deposit of nearly horizontal strata of sandstone and conglomerate lies unconformably, in the neighborhood of the sea, on the older sandstones of the district; and the appearances observed near the old tower mark, it is probable, one of the points of junction—a point of junction also, if I may be so bold as venture the suggestion, of the formation of theHoloptychius nobilissimuswith the formation of theCephalaspis—of the quartzose conglomerate with the Cornstones. In my hurried survey, however, I could find none of the scales or plates of the newer ichthyolite in this upper deposit, though the numerous spherical markings of white, with their centrical points of darker color, show that at one time the organisms of these upper beds must have been very abundant.
We pass to the upper formation of the system. Over the belt of mingled gray and red there occurs in the pyramid a second deep belt of red conglomerate and variegated sandstone, with a band of lime a-top, and over the band a thick belt of yellow sandstone, with which the system terminates.[AN]Thus the second pyramid consists mineralogically, like the first, of three great divisions, or bands; its two upper belts belonging, like the three belts of the other, to but one formation—the formation known in England as the Quartzose Conglomerate. It is largely developed in Scotland. We find it spread over extensive areas in Moray, Fife, Roxburgh, and Berwick shires. In England, it is comparatively barren in fossils; the only animal organic remains yet detected in it being a single scale of theHoloptychiusfound by Mr. Murchison; and though it contains vegetable organisms in more abundance, so imperfectly are they preserved, that little else can be ascertained regarding them than that they were landplants, but not identical with the plants of the Coal Measures. In Scotland, the formation is richly fossiliferous, and the remains belong chiefly to the animal kingdom. It is richly fossiliferous, too, in Russia, where it was discovered by Mr. Murchison, during the summer of last year, spread over areas many thousand square miles in extent. And there, as in Scotland, theHoloptychiusseems its most characteristic fossil.