CHAPTER VI.

[AB]Silurian System, part ii. p. 599.

[AC]In Russia, too, as shown by the recent discoveries of Murchison, the Old Red fishes of Caithness, and the Old Red shells of Devonshire, may be found lying embedded in the same strata.

[AD]Silurian System, part i. p. 183.

The vegetable remains of the formation are numerous, but obscure, consisting mostly of carbonaceous markings,such as might be formed by comminuted sea-weed. (SeePlate VII.) Some of the impressions fork into branches at acute angles, (see figs. 4, 5, and 6;) some affect a waved outline, (see figs. 7 and 8;) most of them, however, are straight and undivided. They lie in some places so thickly in layers as to give the stone in which they occur a slaty character. One of my specimens shows minute markings, somewhat resembling the bird-like eyes of the Stigmaria Ficoides of the Coal Measures;—the branches of another terminate in minute hooks, that remind one of the hooks of the young tendrils of the pea when they first begin to turn. (See fig. 3.) In yet another there are marks of the ligneous fibre; when examined by the glass, it resembles a bundle of horse-hairs lying stretched in parallel lines; and in this specimen alone have I found aught approaching to proof of a terrestrial origin. The deposition seems to have taken place far from land; and this lignite, if in reality such, had probably drifted far ere it at length became weightier than the supporting fluid, and sank.[AE]It is by no means rare to find fragments of wood that have been borne out to sea by the gulf stream from the shores of Mexico or the West Indian Islands, stranded on the rocky coasts of Orkney and Shetland.

[AE]The organism here referred to has been since slit by the lapidary, and the sections carefully examined. It proves to be unequivocally a true wood of the coniferous class. The following is the decision regarding it of Mr. William Nicol, of Edinburgh, confessedly one of our highest living authorities in that division of fossil botany which takes cognizance of the internal structure cf lignites, and decides from their anatomy their race and family:—

Edinburgh, 19th July, 1815.Dear Sir:—I have examined the structure of the fossil wood which you found in the Old Red Sandstone at Cromarty, and have no hesitation in stating, that the reticulated texture of the transverse sections, though somewhat compressed, clearly indicates a coniferous origin; but as there is not the slightest trace of a disk to be seen in the longitudinal sections parallel to the medullary rays, it is impossible to say whether it belongs to the Pine or Araucarian division. I am, &c.,William Nicol.

Edinburgh, 19th July, 1815.

Dear Sir:—I have examined the structure of the fossil wood which you found in the Old Red Sandstone at Cromarty, and have no hesitation in stating, that the reticulated texture of the transverse sections, though somewhat compressed, clearly indicates a coniferous origin; but as there is not the slightest trace of a disk to be seen in the longitudinal sections parallel to the medullary rays, it is impossible to say whether it belongs to the Pine or Araucarian division. I am, &c.,

William Nicol.

The dissimilarity which obtains between the fossils of the contemporary formations of this system in England and Scotland, is instructive. The group in the one consists mainly of molluscous animals; in the other, almost entirely of ichthyolites, and what seems to have been algæ. Other localities may present us with yet different groups of the same period—with the productions of its coasts, its lakes, and its rivers. At present, we are but beginning to know just a little of its littoral shells, and of the fish of its profounder depths. These last are surely curious subjects of inquiry. We cannot catechise our stony ichthyolites, as the necromantic lady of theArabian Nightsdid the colored fish of the lake, which had once been a city, when she touched their dead bodies with her wand, and they straightway raised their heads and replied to her queries. We would have many a question to ask them if we could—questions never to be solved. But even the contemplation of their remains is a powerful stimulant to thought. The wonders of Geology exercise every faculty of the mind—reason; memory, imagination; and though we cannot put our fossils to the question, it is something to be so aroused as to be made to put questions to one's self. I have referred to the consistency of style which obtained among these ancient fishes—the unity of character which marked every scale, plate, and fin of every various family, and which distinguished it from the rest; and who can doubt that the same shades of variety existed in their habits and their instincts? We speak of the infinity of Deity—of his inexhaustible variety of mind; but we speak of it until the idea becomes a piece of mere common-place in our mouths. It is well to bebrought to feel, if not to conceive of it—to be made to know that we ourselves are barren-minded, and that in Him "all fulness dwelleth." Succeeding creations, each with its myriads of existences, do not exhaust Him. He never repeats Himself. The curtain drops, at his command, over one scene of existence full of wisdom and beauty; it rises again, and all is glorious, wise, and beautiful as before, and all is new, Who can sum up the amount of wisdom whose record He has written in the rocks—wisdom exhibited in the succeeding creations of earth, ere man was, but which was exhibited surely not in vain? May we not say with Milton,—

Think not, though men were none,That heaven could want spectators, God want praise;Millions of spiritual creatures walked the earth,And these with ceaseless praise his works beheld?

It is well to return on the record, and to read in its unequivocal characters the lessons which it was intended to teach. Infidelity has often misinterpreted its meaning, but not the less on that account has it been inscribed for purposes alike wise and benevolent. Is it nothing to be taught, with a demonstrative evidence which the metaphysician cannot supply, that races are not eternal—that every family had its beginning, and that whole creations have come to an end?

The Lines of the Geographer rarely right Lines.—These last, however, always worth looking at when they occur.—Striking Instance in the Line of the Great Caledonian Valley.—Indicative of the Direction in which the Volcanic Agencies have operated.—Sections of the Old Red Sandstone furnished by the Granitic Eminences of the Line.—Illustration.—Lias of the Moray Frith.—Surmisings regarding its Original Extent.—These lead to an Exploratory Ramble.—Narrative.—Phenomena exhibited in the course of half an hour's Walk.—The little Bay.—Its Strata and their Organisms.

Thenatural boundaries of the geographer are rarely described by right lines. Whenever these occur, however, the geologist may look for something remarkable. There is one very striking example furnished by the north of Scotland. The reader, in consulting a map of the kingdom, will find that the edge of a ruler, laid athwart the country in a direction from south-west to north-east, touches the whole northern side of the great Caledonian Valley, with its long, straight line of lakes; and onwards, beyond the valley's termination at both ends, the whole northern side of Loch Eil and Loch Linnhe, and the whole of the abrupt and precipitous northern shores of the Moray Frith, to the extreme point of Tarbat Ness—a right line of considerably more than a hundred miles. Nor does the geography of the globe furnish a line better defined by natural marks. There is both rampart and fosse. On the one hand we have the rectilinear lochs and lakes, with an average profundity of depth more than equal to that of the German Ocean, and, added to these, the rectilinear lines of frith; on the other hand, with but few interruptions,there is an inclined wall of rock, which rises at a steep angle in the interior to nearly two thousand feet over the level of the Great Canal, and overhangs the sea towards its northern termination, in precipices of more than a hundred yards.[AF]

[AF]The valley of the Jordan, from the village of Laish to the southern extremity of the Dead Sea, furnishes another very remarkable instance of a geographical right line.

The direction of this rampart and fosse—this Roman wall of Scottish geological history—seems to have been that in which the volcanic agencies chiefly operated in upheaving the entire island from the abyss. The line survives as a sort of foot-track, hollowed by the frequent tread of earthquakes, to mark the course in which they journeyed. Like one of the great lines in a trigonometrical survey, it enables us, too, to describe the lesser lines, and to determine their average bearing.The volcanic agencies must have extended athwart the country from south-west to north-east.Mark in a map of the island—all the better if it be a geological one—the line in which most of our mountain ranges stretch across from the German Ocean to the Atlantic,—the line, too, in which our friths, lochs, and bays, on both the eastern and western coasts, and especially those of the latter, run into the interior. Mark, also, the line of the geological formations, where least broken by insulated groups of hills—the line, for instance, of the Old Red Sandstone belt, which flanks the southern base of the Grampians—the nearly parallel line of our Scottish Coal-field, in its course from sea to sea—the line of the Grauwacke, which forms so large a portion of the south of Scotland—the line of the English Coal-field, of the Lias, of the Oolite, of the Chalk—and how inthis process of diagonal lining, if I may so speak, the south-eastern portion of England comes to be cut off from the secondary formations altogether, and, but for the denudation of the valley of the Weald, would have exhibited only tertiary depositions. In all these lines, whether of mountains, lakes, friths, or formations, there is an approximation to parallelism with the line of the great Caledonian valley—proofs that the upheaving agency from beneath must have acted in this direction from some unknown cause, during all the immensely extended term of its operations, and along the entire length of the island. It is a fact not unworthy of remark, that the profound depths of Loch Ness undulated in strange sympathy with the reeling towers and crashing walls of Lisbon, during the great earthquake of 1755; and that the impulse, true to its ancient direction, sent the waves in huge furrows to the north-east and the south-west.

The north-eastern portion of this rectilinear wall or chain runs, for about thirty miles, through an Old Red Sandstone district. The materials which compose it are as unlike those of the plain out of which it arises, as the materials of a stone dike, running half-way into a field, are unlike the vegetable mould which forms the field's surface. The ridge itself is of a granitic texture—a true gneiss. At its base we find only conglomerates, sandstones, shales, and stratified clays, and these lying against it in very high angles. Hence the geological interest of this lower portion of the wall. As has been shrewdly remarked by Mr. Murchison,[AG]in one of his earlier papers, the gneiss seems to have been forced through the sandstone from beneath, in a solid, not a fluid form; and as the ridge a-top is a narrow one, and the sidesremarkably abrupt—an excellent wedge, both in consistency and form—instead of having acted on the surrounding depositions, as most of the south country traps have done that have merely issued from a vent, and overlaid the upper strata, it has torn up the entire formation from the very bottom. Imagine a large wedge forced from below through a sheet of thick ice on a river or pond. First the ice rises in an angle, that becomes sharper and higher as the wedge rises; then it cracks and opens, presenting its upturned edges on both sides, and through comes the wedge. And this is a very different process, be it observed, from what takes place when the ice merely cracks, and the water issues through the crack. In the one case there is a rent, and water diffused over the surface; in the other, there is the projecting wedge, flanked by the upturned edges of the ice; and these edges, of course, serve as indices to decide regarding the ice's thickness, and the various layers of which it is composed. Now, such are the phenomena exhibited by the wedge-like granitic ridge. The Lower Old Red Sandstone, tilted up against it on both sides, at an angle of about eighty, exhibits in some parts a section of well nigh two thousand feet, stretching from the lower conglomerate to the soft, unfossiliferous sandstone, which forms in Ross and Cromarty the upper beds of the formation. There is a mighty advantage to the geologist in this arrangement. When books are packed up in a deep box or chest, we have to raise the upper tier ere we can see the tier below, and this second tier ere we can arrive at a third, and so on to the bottom. But when well arranged on the shelves of a library, we have merely to run the eye along their lettered backs, and we can thus form an acquaintance with them at a glance, which in the other case would have cost us a good deal oftrouble. Now, in the neighborhood of this granitic wedge, or wall, the strata are arranged, not like books in a box,—such was their original position,—but like books on the shelves of a library. They have been unpacked and arranged by the uptilting agent; and the knowledge of them, which could only have been attained in their first circumstances by perforating them with a shaft of immense depth, may now be acquired simply by passing over their edges. A morning's saunter gives us what would have cost, but for the upheaving granite, the labor of a hundred miners for five years.

[AG]SeeTransactions of the London Geological Societyfor 1828, p. 354.

By far the greater portion of the life of the writer was spent within less than half an hour's walk of one of these upturned edges. I have described the granitic rock, with reference to the disturbance it has occasioned as a wedge forced from below, and with reference to its rectilinear position in the sandstone district which it traverses, as a stone wall running half-way into a field. It may communicate a still corrector and livelier idea to think of it as a row of wedges, such as one sometimes sees in a quarry when the workmen are engaged in cutting out from the mass some immense block, intended to form a stately column or huge architrave. The eminences, like the wedges, are separated; in some places the sandstone lies between—in others there occur huge chasms filled by the sea. The Friths of Cromarty and Beauly, for instance, and the Bay of Munlochy, open into the interior between these wedge-like eminences;—the well-known Sutors of Cromarty represent two of the wedges; and it was the section furnished by the Southern Sutor that lay so immediately in the writer's neighborhood. The line of the Cromarty Frith forms an angle of about thirty-five degrees with that of the granitic line of wedge-like hills whichit bisects; and hence the peculiar shape of that tongue of land which forms the lower portion of the Black Isle, and which, washed by the Moray Frith on the one side, and by the Frith of Cromarty on the other, has its apex occupied by the Southern Sutor. Imagine a lofty promontory somewhat resembling a huge spear thrust horizontally into the sea—a ponderous mass of granitic gneiss, of about a mile in length, forming the head, and a rectilinear line of the Old Red Sandstone, more than ten miles in length, forming the shaft; and such is the appearance which this tongue of land presents, when viewed from its north-western boundary, the Cromarty Frith. When viewed from the Moray Frith,—its south-western boundary,—we see the same granitic spear-head, but find the line of the shaft knobbed by the other granitic eminences of the chain.

Now on this tongue of land I first broke ground as a geologist. The quarry described in my introductory chapter, as that in which my notice was first attracted by the ripple markings, opens on the Cromarty Frith side of this huge spear-shaft; the quarry to which I removed immediately after, and beside which I found the fossils of the Lias, opens on its Moray Frith side. The uptilted section of sandstone occurs on both sides, where the shaft joins to the granitic spear-head, but the Lias I found on the Moray Frith side alone. It studs the coast in detached patches, sorely worn by the incessant lashings of the Frith; and each patch bears an evident relation, in the place it occupies, to a corresponding knob or wedge in the granitic line. The Northern Sutor, as has been just said, is one of these knobs or wedges. It has its accompanying patch of Lias upheaved at its base, and lying unconformably, not only to its granitic strata, but also to its subordinate sandstones. The Southern Sutor, another of these knobs,has also its accompanying patch of Lias, which, though lying beyond the fall of the tide, strews the beach, after every storm from the east, with its shales and its fossils. The hill of Eathie is yet another knob of the series, and it, too, has its Lias patch. The granitic wedges have not only uptilted the sandstone, but they have also upheaved the superincumbent Lias, which, but for their agency, would have remained buried under the waters of the Frith, and its ever accumulating banks of sand and gravel. I had remarked at an early period the correspondence of the granitic knobs with the Lias patches, and striven to realize the original place and position of the latter ere the disturbing agent had upcast them to the light. What, I have asked, was the extent of this comparatively modern formation in this part of the world, ere the line of wedges were forced through from below? A wedge struck through the ice of a pond towards the centre breaks its continuity, and we find the ice on both sides the wedge; whereas, when struck through at the pond edge, it merely raises the ice from the bank, and we find it, in consequence, on but one side the wedge. Whether, have I often inquired, w T ere the granitic wedges of this line forced through the Lias at one of its edges, or at a comparatively central point? and about ten years ago I set myself to ascertain whether I could not solve the question. The Southern Sutor is a wedge open to examination on both its sides;—the Moray Frith washes it upon one side, the Cromarty Frith on the other. Was the Lias to be found on both its sides? If so, the wedge must have been forcedthroughthe formation, not merelybesideit. It occurs, as I have said, on the Moray Frith side of the wedge; and I resolved, on carefully exploring the Frith of Cromarty, to try whether it did not occur on that side too.

With this object I set out on an exploratory excursion, on adelightful morning of August, 1830. The tide was falling; it had already reached the line of half ebb; and from the Southern Sutor to the low, long promontory on which the town of Cromarty is built, there extended a broad belt of mingled sand-banks and pools, accumulations of boulders, and shingle, and large tracts darkened with algæ. I passed direct by a grassy pathway to the Sutor, the granitic spear-head of a late illustration,—and turned, when I reached the curved and contorted gneiss, to trace through the broad belt left by the retiring waters, and in a line parallel to what I have described as the shaft of the huge spear, the beds and strata of the Old Red Sandstone in their ascending succession. I first crossed the conglomerate base of the system, here little more than a hundred feet in thickness. The ceaseless dash of the waves, which smooth most other rocks, has a contrary effect on this bed, except in a few localities, where its arenaceous cement of base is much indurated. Under both the Northern and Southern Sutors the softer cement yields to the incessant action, while the harder pebbles stand out in bold relief; so that, wherever it presents a mural front to the breakers, we are reminded, by its appearance, of the artificial rock work of the architect. It roughens as the rocks around it polish. Quitting the conglomerate, I next passed over a thick bed of coarse reel and yellow sandstone, with here and there a few pebbles sticking from its surface, and here and there a stratum of finer-grained fissile sandstone inserted between the rougher strata: I then crossed over a strata of an impure grayish limestone, and a slaty clay, abounding, as I long afterwards ascertained, in ichthyolites and vegetable remains. There are minute veins in the limestone (apparently cracks filled up) of a jet black bituminous substance, resembling anthracite; the stratified clayis mottled by layers of semi-aluminous, semi-calcareous nodules, arranged like layers of flint in the upper Chalk. These nodules, when cut up and polished, present very agreeable combinations of color; there is generally an outer ring of reddish brown, an inner ring of pale yellow, and a central patch of red, and the whole is prettily veined with dark-colored carbonate of lime.[AH]Passing onwards and upwards in the line of the strata, I next crossed over a series of alternate beds of coarse sandstone and stratified clay, and then lost sight of the rock altogether, in a wide waste of shingle and boulder-stones, resting on a dark blue argillaceous diluvium, sometimes employed in that part of the country, from its tenacious and impermeable character, for lining ponds and dams, and as mortar for the foundations of low-lying houses, exposed in wet weather to the sudden rise of water. The numerous boulders of this tract have their story to tell, and it is a curious one. The Southern Sutor, with its multitudinous fragments of gneiss, torn from its sides by the sea, or loosened by the action of frosts and storms, and rolled down its precipices, is only a few hundred yards away;—its base, where these lie thickest, has been swept by tempests, chiefly from the east, for thousands and thousands of years; and the direct effect of these tempests, regarded as transporting agents, would have been to strew this stony tract with those detached fragments. The same billow that sends its long roll from the German Ocean to sweep the base of the Sutor, and to leap up against its precipices to the height of eighty and a hundred feet, breaks in foam, only a minute after, over this stony tract;which has, in consequence, its sprinkling of fragments of gneiss, transported by an agency so obvious. But for every one such fragment which it bears, we find at least ten boulders that have been borne for forty and fifty miles in the opposite direction from the interior of the country—a direction in which no transporting agency now exists. The tempests of thousands of years have conveyed for but a few hundred yards not more than a tithe of the materials of this tract; nine tenths of the whole have been conveyed by an older agency over spaces of forty and fifty miles. How immensely more powerful, then, or how immensely protracted in its operation, must that older agency have been!

[AH]A concretionary limestone of the Old Red system in England, variegated with purple and green, was at one time wrought as a marble.—Silurian System, Part i. p. 176.

I passed onwards, and reached a little bay, or, rather, angular indentation of the coast, in the neighborhood of the town. It was laid bare by the tide, this morning, far beyond its outer opening; and the huge, table-like boulder, which occupies nearly its centre, and to which, in a former chapter, I have had occasion to refer, held but a middle place between the still darkened flood-line that ran high along the beach, and the brown line of ebb that bristled far below with forests of the rough-stemmed tangle. This little bay, or inflection of the coast, serves as a sort of natural wear in detaining floating drift-weed, and is often found piled, after violent storms from the east, with accumulations, many yards in extent, and several feet in depth, of kelp and tangle, mixed with zoöphytes and mollusca, and the remains of fish killed among the shallows by the tempest. Early in the last century, a large body of herrings, pursued by whales and porpoises, were stranded in it, to the amount of several hundred barrels; and it is said that salt and cask failed the packers when but comparatively a small portion of the shoal were cured, and that by much the greatest part of them were carriedaway by the neighboring farmers for manure. Ever since the formation of the present coast-line, this natural wear has been arresting, tide after tide, its heaps of organic matter, but the circumstances favorable to their preservation have been wanting: they ferment and decay when driven high on the beach; and the next spring-tide, accompanied by a gale from the west, sweeps every vestige of them away; and so, after the lapse of many centuries, we find no other organisms among the rounded pebbles that form the beach of this little bay, than merely a few broken shells, and occasionally a mouldering fish-bone. Thus very barren formations may belong to periods singularly rich in organic existences. When what is now the little bay was the bottom of a profound ocean, and far from any shore, the circumstances for the preservation of its organisms must have been much more favorable. In no locality in the Old Red Sandstone with which I am acquainted have such beautifully preserved fossils been found. But I anticipate.

In the middle of the little bay, and throughout the greater part of its area, I found the rock exposed—a circumstance which I had marked many years before, when a mere boy, without afterwards recurring to it as one of interest. But I had now learned to look at rocks with another eye; and the thought which first suggested itself to me regarding the rock of the little bay was, that I had found the especial object of my search—the Lias. The appearances are in some respects not dissimilar. The Lias of the north of Scotland is represented in some localities by dark-colored, unctuous clays, in others by grayish black sandstones, that look like indurated mud, and in others by beds of black fissile shale, alternating with bands of coarse, impure limestone, and studded between the bands with limestone nodules of richerquality and finer grain. The rock laid bare in the little bay is a stratified clay, of a gray color tinged with olive, and occurring in beds separated by indurated bands of gray, micaceous sandstone. They also abound in calcareous nodules. The dip of the strata, too, is very different from that of the beds which lean against the gneiss of the Sutor. Instead of an angle of eighty, it presents an angle of less than eight. The rocks of the little bay must have lain beyond the disturbing, uptilting influence of the granitic wedge. So thickly are the nodules spread over the surface of some of the beds, that they reminded me of floats of broken ice on the windward side of a lake after a few days' thaw, when the edges of the fragments are smoothed and rounded, and they press upon one another, so as to cover, except in the angular interstices, the entire surface.

I set myself carefully to examine. The first nodule I laid open contained a bituminous looking mass, in which I could trace a few pointed bones and a few minute scales. The next abounded in rhomboidal and finely enamelled scales, of much larger size and more distinct character. I wrought on with the eagerness of a discoverer entering for the first time in aterra incognitaof wonders. Almost every fragment of clay, every splinter of sandstone, every limestone nodule, contained its organism—scales, spines, plates, bones, entire fish; but not one organism of the Lias could I find—no ammonites, no belemnites, no gryphites, no shells of any kind: the vegetable impressions were entirely different; and not a single scale, plate, or ichthyodorulite could I identify with those of the newer formation. I had got into a different world, and among the remains of a different creation; but where was its proper place in the scale? The beds of the little bay are encircled by thick accumulations of diluviumand debris, nor could I trace their relation to a single known rock. I was struck, as I well might, by the utter strangeness of the forms—the oar-like arms of thePterichthysand its tortoise-like plates—the strange, buckler-looking head of theCoccosteus, which, I suppose, might possibly be the back of a small tortoise, though the tubercles reminded me rather of the skin of the shark—the polished scales and plates of theOsteolepis—the spined and scaled fins of theCheiracanthus—above all, the one-sided tail of at least eight out of the ten or twelve varieties of fossil which the deposit contained. All together excited and astonished me. But some time elapsed ere I learned to distinguish the nicer generic differences of the various organisms of the formation. I found fragments of thePterichthyson this morning; but I date its discovery, in relation to the mind of the discoverer, more than a twelvemonth later.[AI]I confounded theCheiracanthus, too, with its single-spined, membranous dorsal, withDiplacanthusichthyolite, furnished with two such dorsals; and theDiplopteruswith theOsteolepis. Still, however, I saw enough toexhilarate and interest: I wrought on till the advancing tide came splashing over the nodules, and a powerful August sun had risen towards the middle sky; and were I to sum up all my happier hours, the hour would not be forgotten in which I sat down on a rounded boulder of granite, by the edge of the sea, when the last bed was covered, and spread out on the beach before me the spoils of the morning.

[AI]I find, by some notes, which had escaped my notice when drawing up for theWitnessnewspaper the sketches now expanded into a volume, that in the year 1834 I furnished the collection of a geological friend, the Rev. John Swanson, minister of the parish of Small Isles, in the Outer Hebrides, with a well-marked specimen of thePterichthys Milleri. The circumstance pleasingly reminds me of the first of all my early acquaintance, who learned to deem the time not idly squandered that was spent in exploring the wonders of bygone creations. Does the minister of Small Isles still remember the boy who led him in quest of petrifactions—himself a little boy at the time—to a deep, solitary cave on the Moray Frith, where they lingered amidst stalactites and mosses till the wild sea had surrounded them unmarked, barring all chance of retreat, and the dark night came on?

Further Discoveries of the Ichthyolite Beds.—Found in one Locality under a Bed of Peat.—Discovered in another beneath an ancient Burying-ground.—In a third underlying the Lias Formation.—In a fourth overtopped by a still older Sandstone Deposit.—Difficulties in ascertaining the true Place of a newly-discovered Formation.—Caution against drawing too hasty Inferences from the mere circumstance of Neighborhood.—The Writer receives his first Assistance from without.—Geological Appendixof the Messrs. Anderson, of Inverness.—Further Assistance from the Researches of Agassiz.—Suggestions.—Dr. John Malcolmson.—His Extensive Discoveries in Moray.—He submits to Agassiz a Drawing of thePterichthys.—Place of the Ichthyolites in the Scale at length determined.—Two distinct Platforms of Being in the Formation to which they belong.

I commencedforming a small collection, and set myself carefully to examine the neighboring rocks for organisms of a similar character. The eye becomes practised in such researches, and my labors were soon repaid. Directly above the little bay there is a corn-field, and beyond the field a wood of forest trees; and in this wood, in the bottom of a water-course, scooped out of the rock through a bed of peat, I found the stratified clay charged with scales. A few hundred yards farther to the west there is a deep, wooded ravine cut through a thick bed of red diluvial clay. The top of the bank directly above is occupied by the ruins of an ancient chapel, and a group of moss-grown tombstones; and in the gorge of this ravine, underlying the little field of graves by about sixty feet, I discovered a still more ancient place of sepulture—that of the ichthyolites. I explored every bank,rock, and ravine on the northern or Cromarty Frith side of the tongue of land, with its terminal point of granitic gneiss, to which I have had such frequent occasion to refer, and then turned to explore the southern, or Moray Frith side, in the rectilinear line of the great valley. And here I was successful on a larger scale. A range of lofty sandstone cliffs, hollowed by the sea, extends for a distance of about two miles between two of the granitic knobs or wedges of the line—the Southern Sutor and the hill of Eathie. And along well nigh the entire length of this range of cliffs, I succeeded in tracing a continuous ichthyolite bed, abounding in remains, and lying far below the Lias, and unconformable to it. I pursued my researches, and in the sides of a romantic precipitous dell, through which the Burn of Eathie—a small, mossy stream—finds its way to the Moray Frith, I again discovered the fish-beds running deep into the interior of the country, with immense strata of a pale yellow sandstone resting over them, and strata of a chocolate red lying below. But their place in the geological scale was still to fix.

I had seen enough to convince me that they form a continuous convex stratum in the sandstone spear-shaft, covering it saddle-wise from side to side, dipping towards the Moray Frith on the south, and to the Cromarty Frith on the north—that, as in abona fidespear-shaft, the annual ring or layer of growth of one season is overlaid by the annual rings of succeeding seasons, and underlaid by those of preceding ones; so this huge semi-ring of fossiliferous clays and limestones had its underlying semi-ring of Red Sandstone, and its overlying semi-rings of yellow, of red, and of gray sandstone. I knew, besides, that beneath there was a semi-ring of conglomerate, the base of the system; and that, for more than two hundred yards upwards, ring followed ring in unbrokensuccession—now sandstone, now limestone, now stratified clay. But though intimately acquainted with these lower rocks for more than a hundred fathoms from their base upwards, and with the upper rocks on both sides the ichthyolitic bed for more than a hundred feet, there was an intervening hiatus, whose extent at this period I found it impossible to ascertain. And hence my uncertainty regarding the place of the ichthyolites, seeing that whole formations might be represented by the occurring gap. On the Moray Frith side, where the sections are of huge extent, a doubtful repeat in the strata at one point of junction, and an abrupt fault at another, cuts off the upper series of beds to which the organisms belong, from the lower to which the great conglomerate belongs. On the Cromarty Frith side the sections are mere detached patches, obscured at every point by diluvium and soil; and, in conceiving of the whole as a continuous line, with the Lias a-top and the granite group at the bottom, I was ever reminded of those coast-lines of the ancient geographers, where a few uncertain dots, a few deeper markings, and here and there a blank space or two, showed the blended results of conjecture and discovery—whether they give aTerra Incognita Australiato the one hemisphere, or a North-Western passage to the other. The ichthyolites in a section so doubtful might be regarded as belonging to either the Old or the New Red Sandstone—to the Coal Measures, or to the Mountain Limestone. All was uncertainty.

One remark in the passing: it may teach the young geologist to be cautious in his inferences, and illustrate, besides, those gaps which occur in the geological scale. I had now discovered the ichthyolite beds in five different localities; in one of these—the first discovered—there is no overlying stratum; it seems as if the bed formed the top of the formation:in all the others the overlying stratum is different, and belongs to distant and widely separated ages. We cut in one locality through a peat moss—part of the ruins, perhaps, of one of those forests which covered, about the commencement of the Christian era, well nigh the entire surface of the island, and sheltered the naked inhabitants from the legions of Agricola. We find, as we dig, huge trunks of oak and elm, cones of the Scotch fir, handfuls of hazel-nuts, and bones and horns of the roe and the red deer. The writer, when a boy, found among the peat the horn of a gigantic elk. And, forming the bottom of this recent deposit, andlying conformably to it, we find the ichthyolite beds, with their antique organisms. The remains of oak and elm leaves, and of the spikes and cones of the pine, lie within half a foot of the remains of theCoccosteusandDiplopterus. We dig in another locality through an ancient burying-ground; we pass through a superior stratum of skulls and coffins, and an inferior stratum, barren in organic remains, and then arrive at the stratified clays, with their ichthyolites. In a third locality we find these in junction with the Lias, and underlying its lignites, ammonites, and belemnites, just as we see them underlying, in the other two, the human bones and the peat moss. And in yet a fourth locality we see them overlaid by immense arenaceous beds, that belong evidently, as their mineralogical character testifies, to either the Old or the New Red Sandstone. The convulsions and revolutions of the geological world, like those of the political, are sad confounders of place and station, and bring into close fellowship the high and the low; nor is it safe in either world,—such have been the effects of the disturbing agencies,—to judge of ancient relations by existing neighborhoods, or of original situations by present places of occupancy. "Misery," says Shakspeare, "makesstrange bedfellows." The changes and convulsions of the geological world have made strange bedfellows too. I have seen fossils of the Upper Lias and of the Lower Old Red Sandstone washed together by the same wave, out of what might be taken, on a cursory survey, for the same bed, and then mingled with recent shells, algæ, branches of trees, and fragments of wrecks on the same sea-beach.

Years passed, and in 1834 I received my first assistance from without, through the kindness of the Messrs. Anderson, of Inverness, who this year published their Guide to theHighlands and Islands of Scotland—a work which has never received half its due measure of praise. It contains, in a condensed and very pleasing form, the accumulated gleanings, for half a lifetime, of two very superior men, skilled in science, and of highly cultivated taste and literary ability; whose remarks, from their intimate acquaintance with every foot-breadth of country which they describe, invariably exhibit that freshness of actual observation, recorded on the spot, which Gray regarded as "worth whole cart-loads of recollection." But what chiefly interested me in their work was its dissertative appendices—admirable digests of the Natural History, Antiquities, and Geology of the country. The appendix devoted to Geology, consisting of fifty closely printed pages,—abridged in part from the highest geological authorities, and in much greater part the result of original observation,—contains, beyond comparison, the completest description of the rocks, fossils, and formations of the Northern and Western Highlands, which has yet been given to the public in a popular form. I perused it with intense interest, and learned from it, for the first time, of the fossil fishes of Caithness and Gamrie.

There was almost nothing known, at the period, of theoryctology of the older rocks—little, indeed, of that of the Old Red Sandstone, in its proper character as such; and with no such guiding clew as has since been furnished by Agassiz, and the later researches of Mr. Murchison, the writer of the appendix had recorded as his ultimate conclusion, that "the middle schistoze system of Caithness, containing the fossil fish, was intermediate in geological character and position between the Old and New Red Sandstone formations." The ichthyolites of Gamrie he described as resembling those of Caithness; and I at once recognized, in his minute descriptions of both, the fossil fish of Cromarty. The mineralogical accompaniments, too, seemed nearly the same. In Caithness, the animal remains are mixed up in some places with a black bituminous matter like tar. I had but lately found among the beds of the little bay a mass of soft adhesive bitumen, hermetically sealed up in the limestone, which, when broken open, reminded me, from the powerful odor it cast, and which filled for several days the room in which I kept it, of the old Gaulish mummy of which we find so minute account in the Natural History of Goldsmith. The nodules which enclosed the organisms at Gamrie were described as of a sub-crystalline, radiating, fibrous structure. So much was this the case with some of the nodules at Cromarty, that they had often reminded me, when freshly broken, though composed of pure carbonate of lime, of masses of asbestos. The scales and bones of the Caithness ichthyolites were blended, it was stated, with the fragments of a "supposed tortoise nearly allied to trionyx;" one of the ichthyolites, aDipterus, was characterized by large scales, a double dorsal, and a one-sided tail; the entire lack of shells and zoöphytes was remarked, and the abundance of obscure vegetable impressions. In short, had the accomplished writer of the appendix been briefly describing the bedsat Cromarty, instead of those of Caithness and Gamrie, he might have employed the same terms, and remarked the same circumstances—the striated nodules, the mineral tar, the vegetable impressions, the absence of shells and zoöphytes, the large-scaled, and double-finned ichthyolites—the peculiarities of which applied equally to theDipterusandDiplopterus—and the supposed tortoise, in which I once recognized theCoccosteus. It was much to know, that this doubtful formation—for as doubtful I still regarded it—was of such considerable extent, and occurred in localities so widely separated. I corresponded with the courteous author of the appendix, at that time General Secretary to the Northern Institution for the Promotion of Science and Literature, and Conservator of its Museum; and, forwarding to him duplicates of some of my better specimens, had, as I had anticipated, the generic identity of the Cromarty ichthyolites with those of Caithness and Gamrie fully confirmed.

My narrative is, I am afraid, becoming tedious; but it embodies somewhat more than the mere history of a sort of Robinson Crusoe in Geology, cut off for years from all intercourse with his kind. It contains, also, the history of a formation in its connection with science; and the reader will, I trust, bear with me for a few pages more. Seasons passed; and I received new light from the researches of Agassiz, which, if it did not show me my way more clearly, rendered it at least more interesting, by associating with it one of those wonderful truths, stranger that fictions, which rise ever and anon from the profounder depths of science, and whose use, in their connection with the human intellect, seems to be to stimulate the faculties. I have often had occasion to refer to the one-sided condition of tail characteristic of the ichthyolites of the Old Red Sandstone. Itcharacterizes, says Agassiz, the fish of all the more ancient formations. At one certain point in the descending scale Nature entirely alters her plan in the formation of the tail. All the ichthyolites above are fashioned after one particular type—all below after another and different type. The bibliographer can tell at what periods in the history of letters one character ceased to be employed and another came into use. Black letter, for instance, in our own country, was scarce ever resorted to for purposes of general literature after the reign of James VI.; and in manuscript writing the Italian hand superseded the Saxon about the close of the seventeenth century. Now, is it not truly wonderful to find an analogous change of character in that pictorial history of the past which Geology furnishes? From the first appearance of vertebrated existences to the middle beds of the New Red Sandstone,—a space including the Upper Ludlow rocks, the Old Red Sandstone in all its members, the Mountain Limestone, with the Limestone of Burdie House, the Coal Measures, the Lower New Red, and the Magnesian Limestone,—we find only the ancient or unequally lobed type of tail. In all the formations above, including the Lias, the Oolite, Middle, Upper, and Lower, the Wealden, the Green-Sand, the Chalk, and the Tertiary, we find only the equally-lobed condition of tail. And it is more than probable, that, with the tail, the character of the skeleton also changed; that the more ancient type characterized, throughout, the semi-cartilaginous order of fishes, just as the more modern type characterizes the osseous fishes; and that the upper line of the Magnesian Limestone marks the period at which the order became extinct. Conjecture lacks footing in grappling with a revolution so extensive and so wonderful. Shall I venture to throw out a suggestion on the subject, in connection with anothersuggestion which has emanated from one of the first of living geologists? Fish, of all existing creatures, seem the most capable of sustaining high degrees of heat, and are to be found in some of the hot springs of Continental Europe, where it is supposed scarce any other animal could live. Now, all the fish of the ancient type are thickly covered by a defensive armor of bone, arranged in plates, bars, or scales, or all the three modes together, as in theOsteolepisand one half its contemporaries. The one-sided tail is united invariably to a strong cuirass. And it has been suggested by Dr. Buckland, that this strong cuirass may have formed a sort of defence against the injurious effects of a highly heated surrounding medium. The suggestion is, of course, based purely on hypothesis. It may be stated, in direct connection with it, however, that in the Lias—the first richly fossiliferous formation overlying that in which the change occurred—we find, for the first time in the geological system, decided indications of a change of seasons. The foot-prints of winter are left impressed amid the lignites of the Cromarty Lias. In a specimen now before me, the alternations of summer heat and winter cold are as distinctly marked in the annual rings as in the pines or larches of our present forests; whereas in the earlier lignites, contemporary with ichthyolites of the ancient type, either no annual rings appear, or the markings, if present, are both faint and unfrequent.Just ere winter began to take its place among the seasons, the fish fitted for living in a highly heated medium disappeared:they were created to inhabit a thermal ocean, and died away as it cooled down. Fish of a similar type may now inhabit the seas of Venus, or even of Jupiter, which, from its enormous bulk, though greatly more distant from the sun than our earth, may still powerfully retain the internal heat.

I still pursued my inquiries, and received a valuable auxiliary in a gentleman from India, Dr. John Malcolmson, of Madras—a member of the London Geological Society, and a man of high scientific attainments and great general knowledge. Above all, I found him to possess, in a remarkable degree, that spirit of research, almost amounting to a passion, which invariably marks the superior man. He had spent month after month under the burning sun of India, amid fever marshes and tiger jungles, acquainting himself with the unexplored geological field which, only a few years ago, that vast continent presented, and in collecting fossils hitherto unnamed and undescribed. He had pursued his inquiries, too, along the coasts of the Red Sea, and far upwards on the banks of the Nile; and now, in returning for a time to his own country, he had brought with him the determination of knowing it thoroughly as a man of science and a geologist. I had the pleasure of first introducing him to the ichthyolites of the Lower Old Red Sandstone, by bringing him to my first-discovered bed, and laying open, by a blow of the hammer, a beautifulOsteolepis. He was much interested in the fossils of my little collection, and at once decided that the formation which contained them could be no representative of the Coal Measures. After ranging over the various beds on both sides the rectilinear ridge, and acquainting himself thoroughly with their organisms, he set out to explore the Lower Old Red Sandstones of Moray and Banff, hitherto deemed peculiarly barren, but whose character too much resembled that of the rocks which he had now ascertained to be so abundant in fossils, not to be held worthy of further examination. He explored the banks of the Spey, and found the ichthyolite beds extensively developed at Dipple, in the middle of an Old Red Sandstone district. He pursued hisresearches, and traced the formation in ravines and the beds of rivers, from the village of Buckie to near the field of Culloden; he found it exposed in the banks of the Nairn, in the ravines above Cawdor Castle, on the eastern side of the hill of Rait, at Clune, Lethen-bar, and in the vale of Rothes—and in every instance low in the Old Reel Sandstone. The formation hitherto deemed so barren in remains proved one of the richest of them all, if not in tribes and families, at least in individual fossils; and the reader may form some idea of the extent in which it has already been proved fossiliferous, when he remembers that the tract includes as its extremes Orkney, Gamrie, and the north-eastern gorge of the great Caledonian Valley. The ichthyolites were discovered in the latter locality in the quarry of Inches, three miles beyond Inverness, by Mr. George Anderson, the gentleman to whose geological attainments, as one of the authors of theGuide Book, I have lately had occasion to refer.

I had now corresponded for several years with a little circle of geological friends, and had described in my letters, and in some instances had attempted to figure in them, my newly-found fossils. A letter which I wrote early in 1838 to Dr. Malcolmson, then at Paris, and which contained a rude drawing of thePterichthys, was submitted to Agassiz, and the curiosity of the naturalist was excited. He examined the figure, rather, however, with interest than surprise, and read the accompanying description, not in the least inclined to scepticism by the singularity of its details. He had looked on too many wonders of a similar cast to believe that he had exhausted them, or to evince any astonishment that Geology should be found to contain one wonder more. Some months after, I sent a restored drawing of the same fossil to the Elgin Scientific Society. I must state, however, that the restorationwas by no means complete. The paddle-like arms were placed further below the shoulders than in any actual species; and I had transferred, by mistake, to the creature's upper side, some of the plates of theCoccosteus. Still the type was unequivocally that of thePterichthys. The secretary of the Society, Mr. Patrick Duff, an excellent geologist, to whose labors, in an upper formation of the Old Red Sandstone, I shall have afterwards occasion to refer, questioned, as he well might, some of the details of the figure, and we corresponded for several weeks regarding it, somewhat in the style of Jonathan Oldbuck and his antiquarian friend, who succeeded in settling the meaning of two whole words, in an antique inscription, in little more than two years. Most of the other members looked upon the entire drawing, so strange did the appearance seem, as embodying a fiction of the same class with those embodied in the pictured griffins and unicorns of mythologic Zoölogy; and, in amusing themselves with it, they bestowed on its betailed and bepaddled figure, as if in anticipation of Agassiz, the name of the draughtsman. Not many months after, however, abona fidePterichthysturned up in one of the newly discovered beds of Nairnshire, and the Association ceased to joke, and began to wonder. T merely mention the circumstance in connection with a right challenged, at the late meeting of the British Association at Glasgow, by a gentleman of Elgin, to be regarded as the original discoverer of thePterichthys. I am, of course, far from supposing that the discovery was not actually made, but regret that it should have been kept so close a secret at a time when it might have stood the other discoverer of the creature in such stead.

The exact place of the ichthyolites in the system was still to fix. I was spending a day, early in the winter of 1839,among the nearly vertical strata that lean against the Northern Sutor. The section there presented is washed by the tide for nearly three hundred yards from where it rests on the granitic gneiss; and each succeeding stratum in the ascending order may be as clearly traced as the alternate white and black squares in a marble pavement. First there is a bed of conglomerate two hundred and fifteen feet in thickness, "identical in structure," say Professor Sedgwick and Mr. Murchison, u with the older red conglomerates of Cumberland and the Island of Arran,[AJ]and which cannot be distinguished from those conglomerates which lean against the southern flank of the Grampians, and on which Dunnottar Castle is built. Immediately above the conglomerate there is a hundred and fourteen feet more of coarse sandstone strata, of a reddish yellow hue, with occasionally a few pebbles enclosed, and then twenty-seven feet additional of limestone and stratified clay. There are no breaks, no faults, no thinning out of strata—all the beds lie parallel, showing regular deposition. I had passed over the section twenty times before, and had carefully examined the limestone and the clay, but in vain. On this occasion, however, I was more fortunate. I struck off a fragment. It contained a vegetable impression of the same character with those of the ichthyolite beds; and after an hour's diligent search, I had turned out from the heart of the stratum plates and scales enough to fill a shelf in a museum—the helmet-like snoutof an Osteolepis, the thorn-like spine of aCheiracanthus, and aCoccosteuswell nigh entire. I had at length, after a search of nearly ten years, found the true place of the ichthyolite bed. The reader may smile, but I hope the smile will be a good-natured one; a simple pleasure may be not the less sincere on account of its simplicity; and "little things are great to little men." I passed over and over the strata, and found there could be no mistake. The place of the fossil fish in the scale is little more than a hundred feet above the top, and not much more than a hundred yards above the base of the great conglomerate; and there lie over it in this section about five hundred feet of soft, arenaceous stone, with here and there alternating bands of limestone and beds of clay studded with nodules—all belonging to the inferior Old Red Sandstone.

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