I shall select my first instance from the records of the annual controversy which used to rage some ten or fifteen years ago, in sermons, newspapers, and magazines, immediately after every meeting of the British Association. A religious Dublin newspaper,—the "Statesman and Record,"—since extinct, took always an active part in these discussions on the anti-geological side, and boldly affirmed, as in a number now before me, that geology had the devil for its author. A learned correspondent of the paper, who was, however, somewhat more charitable, thought that at least thefactsof the science might be exempted from a condemnation so sweeping; nay, that, well interpreted, theymight be found decidedly opposed to at least the more mischievous deductions of the geologists; and in illustrating the point, we find him thus arguing, from certain appearances in the valley of the Nile, that the globe which we inhabit cannot possibly be more than six thousand years old.[42]"The valley of the Nile," says this writer, "is known to be covered with a bed of slime which the river has deposited in its periodical inundations, and which rests on a foundation of sand, like that of the adjacent desert. The French savans who accompanied Bonaparte in his Egyptian expedition made several experiments to ascertain the thickness and depth of this superincumbent bed. They dug about two hundred pits, and carefully measured the thickness in the transversal section of the valley, where the deposit had been free from obstacles, and had not been materially increased or lessened by local causes. They found the mean of all these measurements to be six and a half metres, or rather more than twenty feet. M. Gironde endeavored to determine the quantity of slime deposited in a century; and he found that the elevation of soil in that period was rather less than four inches and a half! Dividing the total thickness of the bed by the centenary elevation, he found the quotient 56.50; whence it followed that the inundations had commenced 5650 years before the year 1800, when the experiments were made,—a number which only differed 159 years from the Mosaic date. The difference is not very important, when it is considered that the most trifling error, whether in the measure of the entire superincumbent bed, or in the valuation of the quantity of slime deposited in a century, affects the final results. Notwithstanding this, the coincidence between the sacred historian and the computations of science is remarkable,and furnishes one proof more of the harmony existing between nature and revelation. An honest experimentalist was constrained to arrive at this conclusion at a period when the infidel school of our continental neighbors was in high feather. I am sorry to add, that the result of his own calculation had not that effect on the philosopher himself, or his free-thinking associates, which, for their own sakes, was desirable; but it is no less valuable to us on that account; for we know that an unwilling witness to the truth is worth a score of evidences already prejudiced in its favor."
Now, this is clear, distinct statement; and nothing can be more evident than that the theologian who makes it holds he is reasoning with conclusive effect in behalf of what may be termed the short chronology,—not in its legitimate connection with the recent introduction of the human species, but in its supposed bearing on the age of the earth. And in doing so he commits himself to the apparent positive fact, determined on what may be regarded as geologic data, that the river Nile has been flowing over its bed for about as many years as have elapsed, according to the Hebrew chronology adopted by Usher, since the creation of man, and no more. To the integrity of this inference he pledges himself, as an inference to which the infidel ought to have yielded, as conclusive in its bearing on the question of the earth's age, and as of singular value to the believer who sets himself to deal with the evidences of his faith. Now, without referring to the circumstance that the data on which the French savans under Napoleon founded have since been challenged by geologists, such as Lieutenant Newbold and Sir G. Wilkinson, who have carefully surveyed the rocks and soils of Egypt with the assistance of clearer light than existed at the commencement of the century, let us, for the argument's sake, holdthe inference to be quite as good as this theologian regards it. And see, we urge upon him, that you yourself do not suffer it to drop should you find that it commits you to the other side of the argument. Be at least as fair and honest as you say the infidels ought to have been. The six and a half metres of silt and slime,—representative, let us hold, of from five to six thousand years,—rest, you say, on "a foundation of sand like that of the adjacent desert." But have you ascertained on what the sand rests? I know nothing of that, replies the theologian; I had not even thought of that. But the geologist has thought of it, we reply; and has spent much time under the hot sun in ascertaining the point. For nearly three hundred miles,—from the inner boundaries of the delta to within a few hours' journey of the cataracts,—the silt and sand rest on what is known as the "marine" or nummulitic limestone,—a formation of great extent, for it runs into the Nubian desert on the one hand, and into the Libyan desert on the other; and which, though it abounds in the animalcules of the European chalk, is held to belong, in at least its upper beds, which are charged with nummulites, to the earlier Eocene. Over this marine limestone there rests a newer formation, of later Tertiary age, which contains the casts of sea shells, and whole forests of dicotyledonous trees, converted into a flint-like chert; and over all repose the sands and gravels of the desert. Underneath the silt of the river, then, and the sand of the desert, lie these two formations of the Tertiary division. The lower, which is of great thickness, must have been of slow formation. It is composed almost exclusively, in many parts, of microscopic animals, and abounds in others in fossil shells,—nautili, ostreadæ, turritella, and nummulites, with corals, sponges, the remains of crustacea, and the teeth of fishes. And between the period of its deposition and that of theformation which rests upon it the surface of what is now Egypt must have been elevated over the surface of the sea, to be covered, in the course of ages, by great forests, which, ere the land assumed its present form and level, were submerged by another oscillation of the surface, and petrified amid beds of a siliceous sand at the bottom of the ocean. Nor is the underlying marine limestone by any means the oldest of the sedimentary rocks of Egypt. It rests on a sandstone of Permian or Triassic age; the sandstone rests, in turn, on the famous Breccia de Verde of Egypt; and the Breccia on a group of Azoic rocks, gneisses, quartzes, mica schists, and clay slates, that wrap round the granitic nucleus of Syene. The formations of Egypt constitute a well-determined part of that great series of systems which compose the upper portion of the earth's crust: its silt is by far the most inconsiderable of its deposits; and if five thousand six hundred and fifty years were exhausted in laying down layer after layer of the twenty feet which formitsaverage thickness, what enormous periods must we not demand in addition for the laying down of the forest formation, of the marine limestone formation, of the New Red Sandstone formation, of the Breccia de Verde formation, and, in short, for the some ten miles of fossiliferous rock of which those deposits form such definite, well-determined portions; besides the time necessary for the production of the enormously developed Azoic rocks which lie under all! The theologian, in this instance, instead of reasoning, as he himself supposed, in behalf of the short chronology, has been making out a very formidable case for the long one; and all that the geologist can have to urge upon him in the circumstances is simply that he should act as he holds the infidel ought to have done, and yield to the force of evidence. I may mention in the passing, that some of the most ancient buildings ofEgypt are formed of the Tertiary marine limestones of the country; the stones of the pyramids are charged with nummulites, known to the Arabs as "Pharaoh's beans;" and these organisms stand out in high relief on the weathered portions of the Great Sphinx. Some of the oldest things in the world in their relation to human history,—erections, many of which had survived the memory of their founders even in the days of Herodotus,—are formed of materials so modern in their relation to the geologic epochs, that they had no existence as rock until after the Palæozoic and Secondary ages had gone by. Not only the Carboniferous sandstone of the High Church and Parliament House of Edinburgh, but even the Oolitic (that is, Portland stone) of Somerset House and St. Paul's, are of an antiquity incalculably vast compared with the stone out of which the oldest of the pyramids were fashioned.
Fig. 116.Fig. 116.NUMMULITES LÆVIGATA.(Pharaoh's Beans.)
The second example which I shall adduce is one with which many of my auditors must be already familiar. The Falls of Niagara are gradually eating their way through an elevated tract of table-land, upwards towards Lake Erie, at the rate of about fifty yards in forty years; and it has been argued by Sir Charles Lyell, that as they are now seven miles distant from Queenston, where the elevation of theplateaux begins, they must have taken about ten thousand years to scoop out their present deep channel through that space.[43]Ten thousand years ago the Falls were, he infers, at Queenston; and the grounds on which he reasons are exactly those on which one would infer that a laborer who had cut a ditch two hundred yards long at the rate of ten yards per day, and was still at work without pause or intermission, had begun to cut it just twenty days previous. A reverend anti-geologist takes up Sir Charles;[44]and, after denouncing the calculation as "a stab at the Christian religion," seeing it involves the assertion that the "Falls were actually at Queenston four thousand years before the creation of the world according to Moses," he brings certain facts, adduced both by other writers and Sir Charles himself,to bear on the calculation, such as the fact that the deep trench through which the Niagara runs is much narrower in its lower than in its upper reaches, and that the river must have performed its work of excavation, when the breadth was less, at a greatly quicker rate than now. And thus the work of excavating the trench is brought fairly within six thousand years. Nor is the principle of the reasoning bad. In our illustration of the ditch excavated by the laborer we of course take it for granted that it is a ditch of the same depth and breadth throughout, and excavated in the same sort of soil; for if greatly narrower and shallower at one place than at another, or dug in a greatly softer mould, the rate of its excavation at different times might be very different indeed, and the general calculation widely erroneous, if based on the ratio of progress when it went on most slowly, taken as an average ratio for the whole. But the anti-geologist provokes only a smile when, in his triumph, he exultingly exclaims, "It is on grounds such as these that the most learned and voluminous among English geologists disputes the Mosaic history of the Creation and Deluge,—a strong proof that even men of argument on other subjects often reason in the most childish and ridiculous manner, and on grounds totally false, when they undertake to deny the truth of the Holy Scriptures." Now, it must be wholly unnecessary to remark here, that it is surely one thing to "undertake to deny the truth of the Holy Scriptures," and quite another and different thing to hold that the Niagara Falls may have been at Queenston ten thousand years ago; or further, that it seems not in the least wise to stake the truth of Revelation on any such issue. Let me request you, however, to observe, that in one important respect this writer resembles the former one. The former, ignorant of the various phenomena exhibited by the great deposits of Egypt, exhausted all his fivethousand six hundred years of available time in accounting for the formation of one of the least of them,—the silt of the Nile; and the latter, though he bids down Sir Charles some four thousand four hundred years or so in the one item of scooping out the bed of the St. Lawrence, at least expends the remainder of the ten thousand,—his five thousand six hundred years,—in that work of excavation alone, and leaves himself no further sums to set off against the various geologic processes that may have preceded it.
In this case, as in the other, let us grant, for the argument's sake, all the facts. Let us admit that the trench through which the St. Lawrence now flows has been cut by the river in somewhat less than six thousand years. But through what, let us ask, has it been cut? There can exist no doubt on the subject: it has been cut through an ancient graveyard of the Upper Silurian system, charged with the peculiar fossils characteristic of what are known as the Clinton and Niagara groups, and common, many of them, to the Upper Silurian of our own country and of the European continent.Leptæna depressaandPentamerus oblongus, two of the most frequent shells of the deposit, occur also in equal abundance in the Dudley and Caradoc formations of England; its prevailing encrinite,Ichthyocrinus lævis, is scarce distinguishable from an encrinite which I have often picked up in the quarries of the "Wren's Nest" (Ichthyocrinus pyriformis); while its prevailing trilobite,Phacops limulurus, seems to be but a transatlantic variety of our well knownAsaphus (Phacops) caudatus. Further, the sequence of the various formations both above and below the Niagara group, is shown with remarkable distinctness in that part of the world along the shores of the great lakes. They may be traced downward, on the one hand, along the Lower Silurian deposits, to the non-fossiliferous base on which the system rests, andupwards, on the other, through the Old Red Sandstone and the Carboniferous Limestone, to the workable Coal Measures. Both stratigraphically and palæontologically the place in the scale of the Niagara graveyard can be definitely determined; and a superficial deposit on the heights in its immediate neighborhood shows that the river did not begin its work of excavation among its long extinct shells, trilobites, and corals, until after not only the great Palæozoic, but also the Secondary and Tertiary divisions had been laid down, and the recent period ushered in. The superficial shells of the adjacent heights belong to the Pleistocene age, and show that in even that comparatively modern time the lower lands of Upper Canada were submerged beneath the level of the ocean, and that a series of deep seas, connected by broad sounds, occupied the place of the great lakes. Not until the last upheaval of the land was the river now known as the St. Lawrence called into existence, to begin its work of excavation; and ere that event took place, fully ten miles of fossiliferous rock had been deposited on the earth's surface, charged with the remains of many succeeding creations. The deposit through which the St. Lawrence is slowly mining its way is older than the river itself by the vast breadth of the four Tertiary periods, by that of all the Secondary ages,—Cretaceous, Oolitic, and Triassic,—by the periods, too, of the Permian system, of the Carboniferous system, of the Old Red system, and of the uppermost beds of the Upper Silurian system. But a simple illustration may better serve to show the true character of the conclusion urged here by the opponent of Sir Charles, than any such line of statement as that which I employ, however clear to the geologist. In the year 1817, Prince's Street, in Edinburgh, was opened up to the Calton Hill, and the Calton burying-ground cut through to the depth of many feet by the roadway. Let ussuppose that when the excavation has been carried a hundred yards into the cemetery, a geologist, finding the laborers cutting on the average about a yard per day, simply intimates as his opinion that the laborers have been a hundred days at work. "No," replies a controversialist on the anti-geological side; "for the first fifty yards, so soft was the subsoil, and so shallow the covering of mould, that the laborers must have cut at the rate of two yards a day; it has been merely for the last fifty yards that they have been excavating at the present slow rate: they cannot have been more than seventy-five days at work. I marvel exceedingly at the absurdity of geological reasoners:palpably the burying-ground of the Calton is only seventy-five days old." Now, such, in no exaggerated, but, on the contrary, greatly modified form, is the argument that would limit the age of the earth to the period during which the St. Lawrence has been scooping out a channel for itself, from Queenston to Niagara, through an ancient Silurian burying-ground. Both arguments alike confound the age of the ancient burying-grounds with the date of the modern excavations opened up through them; but in order to render the argument of my illustration equally absurd with the other, it would be not only necessary to infer that the Calton cemetery was only seventy-five days old, but also that the rock on which it rested was no older.
But enough of follies such as these! I had marked a good many other passages of similar character in the writings of the recent anti-geologists, and would have little difficulty in filling a volume with such; but it would be a useless, though mayhap curious work, and is much better exhibited by specimen than as a whole. A little folly is amusing, but much of it fatigues. There is a time coming, and now not very distant, when the vagaries of the anti-geologists will be as obsolete as those of the geographers ofSalamanca, or as those of the astronomers who upheld the orthodoxy of Ptolemy against Galileo and Newton; and when they will be regarded as a sort of curious fossils, very monstrous and bizarre, and altogether of an extinct type, but which had once not only life, but were formidable. It will then be seen by all what a noble vestibule the old geologic ages form to that human period in which moral responsibility first began upon earth, and a creature destined to immortality anticipated an eternal hereafter. There is always much of the mean and the little in the worlds which man creates for himself, and in the history which he gives them. Of all the abortions of the middle ages which have come down to us, I know not a more miserable one,—at once ludicrous and sad,—than that heavens and earth of CosmasIndicopleustes, the monk, which I illustrated by diagrams in my last lecture (Figs. 114,115). They are just such heavens and earth as a monk might have made, and made too at a sitting. The heavens, represented as a solid arch raised on tall walls, resemble, as a whole, the arch which figures in the middle of a freemason's apron, or, more homely still, the section of a wine cellar; while the earth lies beneath as a great plain or floor, with a huge hill in the distance, behind which the sun passes when it is night. And yet this scheme gave law to the world for more than six centuries, and lay like a nightmare on physical discovery, astronomic and geographical. The anti-geologists have been less mischievous, for they live in a more enlightened age; and we already see but the straggling remains of the body, and know that the time cannot be far distant when it will be as completely extinct as any of the old faunas. The great globe, ever revolving on itself, and journeying in space round the sun, in obedience to laws which it immortalized a Newton to discover and demonstrate, is an infinitely more sublime and noble object thanthe earth of Cosmas the monk, with its conical mountain and its crypt-like firmament; nor can I doubt that its history throughout the long geologic ages,—its strange story of successive creations, each placed in advance of that which had gone before, and its succeeding organisms, vegetable and animal, ranged according to their appearance in time, on principles which our profounder students of natural science have but of late determined,—will be found in an equal degree more worthy of its Divine Author than that which would huddle the whole into a few literal days, and convert the incalculably ancient universe which we inhabit into a hastily run-up erection of yesterday.
ON THE LESS KNOWN FOSSIL FLORAS OF SCOTLAND.[45]
PART I.
Scotlandhas its four fossil floras,—its flora of the Old Red Sandstone, its Carboniferous flora, its Oolitic flora, and that flora of apparently Tertiary age of which his Grace the Duke of Argyll found so interesting a fragment overflown by the thick basalt beds and trap tuffs of Mull. Of these, the only one adequately known to the geologist is the gorgeous flora of the Coal Measures,—probably the richest, in at least individual plants, which the world has yet seen. The others are all but wholly unknown; and the Association may be the more disposed to tolerate the comparative meagreness of the few brief remarks which I purpose making on two of their number,—the floras of the Old Red Sandstone and the Oolite,—from the consideration that that meagreness is only too truly representative of the present state of our knowledge regarding them; and that if my descriptions be scanty and inadequate, it is only because the facts are still few. How much of the lost mayyet be recovered I know not; but the circumstance that two great floras,—remote predecessors of the existing one,—which once covered with their continuous mantle of green the dry land of what is now Scotland, should be represented by but a few coniferous fossils, a few cycadaceous fronds, a few ferns and club mosses, must serve to show what mere fragments of the past history of our country we have yet been able to recover from the rocks, and how very much in the work of exploration and discovery still remains for us to do. We stand on the further edge of the great floras of by-past creations, and have gathered but a few handfuls of faded leaves, a few broken branches, a few decayed cones.
The Silurian deposits of our country have not yet furnished us with any unequivocal traces of a terrestrial vegetation. Professor Nicol of Aberdeen, on subjecting to the microscope the ashes of a Silurian anthracite which occurs in Peeblesshire, detected in it minute tubular fibres, which seem, he says, to indicate a higher class of vegetation than the algæ; but these may have belonged to a marine vegetation notwithstanding. I detected some years ago, in the Trilobite-bearing schists of Girvan, associated with graptolites of the Lower Silurian type, a vegetable organism somewhat resembling the leaf of one of the pond weeds,—an order of plants, some of whose species, such as Zostera, find their proper habitats in salt water. I have placed beside this specimen a fragment of the same graptolite-bearing rock, across which I have pasted part of a leaf ofZostera marina, the only plant of our Scottish seas which is furnished with true roots, bears real flowers inclosed in herbaceous spathes, and produces a well formed farinaceous seed. It will be seen, that in the few points of comparison which can be instituted between forms so exceedingly simple, the ancient very closely resembles the recent organism.It is not impossible, therefore, that the Silurian vegetable may have belonged to some tribe of plants allied to Zostera; and if so, we can easily conceive how the Silurian anthracite of our country may be altogether of marine origin, and may yet exhibit in its microscopic tubular fibres vestiges of a vegetation higher than the algæ.
Fig. 117.Fig. 117.a,SILURIAN ORGANISM.b,GRAPTOLITE.c,PORTION OF THE LEAF OF ZOSTERA MARINA.
[It were well, in dealing with the very ancient floras, in which equivocal forms occur that might have belonged to either the land or the sea, to keep in view those curious plants of the present time, the habitats of which are decidedly marine, but which are marked by many of the peculiarities of the seed-bearing plants of the land. The superiority of Zostera to the common sea weeds of our coasts appears to have struck in the north of Scotland eyes very little practised in such matters, and seems to have given rise, in consequence, to a popular myth.Zostera marinaabounds on a series of sand banks, partiallyuncovered by the larger stream tides, which lie directly opposite the town of Cromarty, near the spot pointed out by tradition as the site of an earlier town, which was swept away some two or three hundred years ago by the encroachments of the sea. And these banks, with their thick covering of green Zostera, used to be pointed out by the fishermen of the place, in my younger days, as themeadowsof the old town, still bearing their original coverings of vegetation,—a vegetation altered no doubt by the "sea change" that had come over it, but still essentially the same, it was said, as that which had smiled around the old burgh, and not at all akin to the brown kelp or tangle that every storm from the boisterous north-east heaps along the shore. It was virtually affirmed that the luxuriant terrestrial grasses of ancient Cromarty had made a virtue of necessity in their altered circumstances; and that, settling down into grasses of the sea, they remained to testify that an ancient Cromarty there hadonce been.Zostera marina, like most plants of the land, ripens its seeds towards the close of autumn; and I have seen a smart night's frost at this season, when coincident with a stream tide that laid bare the beds, nip its seed-bearing stems by thousands; and have found them strewed along the beach a few days after, with all their grass-like spikes fully developed, and their grain-like seeds charged with a farinaceous substance, which one would scarce expect to find developed in the sea. In the higher reaches of the Cromarty Firth, the Zostera beds, which are of great extent, are much frequented, during the more protracted frosts of a severe winter, by wild geese and swans, that dig up and feed upon the saccharine roots of the plant. The Zostera of the warmer latitudes attain to a larger size than those of our Scottish seas. "A southern species," says Loudon, "Zostera oceanica, has leaves a foot long and an inchbroad. It is used as a thatch, which is said to last a century; bleaches white with exposure; and furnishes the rush-like material from which the envelops of Italian liquor flasks are prepared." The simple rectilinear venation of ribbon-like fronds, usually much broken, that occurs in the Lower Old Red Sandstone, has often reminded me of that exhibited by this exotic species of Zostera.]
Fig. 118.Fig. 118.FUCOID.
Fig. 119.Fig. 119.FUCOIDS.
Associated with the earliest ichthyic remains of the Old Red Sandstone, we find vegetable organisms in such abundance, that they communicate often a fissile character to the stone in which they occur. But, existing as mere carbonaceous markings, their state of keeping is usually so bad, that they tell us little else than that the antiquely-formedfishes of this remote period swam over sea bottoms darkened by forests of algæ. The prevailing plant was one furnished with a long, smooth stem, which, though it threw off, in the alternate order, numerous branches at least half as stout as itself, preserved its thickness for considerable distances without diminution,—a common fucoidal characteristic. We find its remains mixed in the rock, though sparingly, with those of a rough-edged plant, knobbed somewhat like the thong-like receptacles ofHimanthalia lorea, which also threw off branches like the other, but diminished more rapidly. A greatly more minute vegetable organism of the same beds, characterized by its bifid partings, which strike off at angles of about sixty, somewhat resembles the small-fronded variety ofDictyota dichotoma, save that the slim terminations of the frond are usually bent into little hooks, like the tendrils of the pea just as their points begin to turn. Another rather rare plant of the period, existing as a broad, irregularly cleft frond, somewhat resembling that of a modernCutleriaorNitophyllum, betrays at once, in its outline and general appearance, its marine origin; as does also an equally rare contemporary, which, judging from its appearance, seems to have been a true fucus. It exists in the rock as if simply drawn in Indian ink; for it exhibits no structure, though, as in some of the ferns of theCoal Measures, what were once the curls of its leaflets continue to exist as sensible hollows on the surface. It broadens and divides atop into three or four lobes, and these, in turn, broaden and divide into minor lobes, double or ternate, and usually rounded at their terminations. In general appearance the plant not a little resembles those specimens ofFucus vesiculosuswhich we find existing in a diminutive form, and divested of both the receptacles and the air vessels, at the mouth of rivers. Of two other kinds of plants I have seen only confused masses, in which the individuals were so crowded together, and withal so fragmentary and broken, that their separate forms could not be traced. In the one the general appearance was such as might be produced by compressed and tangled masses ofChorda filium, in which the linear and even tubular character of the plant could be determined, but not its continuous, cord-like aspect; in the other, the fragments seemed well nigh as slim as hairs, and the appearance was such as might be produced by branches of that common ectocarpus,E. littoralis, which may be seen on our rocky coasts roughening at low water the stems of laminaria. When highly magnified, a mesial groove might be detected running along each of the hair-like lines. With these marine plants we occasionally find large rectilinear stems, resolved into a true coal, but retaining no organic character by which to distinguish them. As I have seen some of these more than three inches in diameter, and, though existing as mere fragments, several feet in length, they must, if they were also plants of the sea, have exceeded in size our largest laminaria.[46]And such are thefew vegetable organisms, of apparently aquatic origin, which I have hitherto succeeded in detecting in the Lower Old Red Sandstone of Scotland.[47]Their individual numbers, however, must have been very great, though, from the destructible character of their tissues, their forms have perished in the stone. The immensely developed flagstones of Caithness seem to owe their dark color to organic matter mainly of vegetable origin. So strongly bituminous, indeed, are some of the beds of dingier tint, that they flame in the fire like slates steeped in oil.
Fig. 120.Fig. 120.
The remains of a terrestrial vegetation in this deposit are greatly scantier than those of its marine plants; but they must be regarded as possessing a peculiar interest, as, with the exception of the spore cases of the Ludlow rocks, the oldest of their class, in at least the British islands, whose true place in the scale can be satisfactorily established. In the flagstones of Orkney there occurs, though very rarely, a minute vegetable organism, which I have elsewhere described as having much the appearance of one of oursmaller ferns, such as the maidenhair-spleenwort, or dwarf moonwort. It consists of a minute stem, partially covered by what seems to be a small sheath or hollow bract, and bifurcates into two fronds or pinnæ, fringed by from ten to twelve leaflets, that nearly impinge on each other, and somewhat resemble in their mode of arrangement the leaflets of one of our commonest Aspleniums,—Asplenium trichomanes. One of our highest authorities, however, in such matters (Professor Balfour of Edinburgh) questions whether this organism be in reality a fern, and describes it from the specimen on the table, in the Palæontological chapter of his admirable Class Book, simply as "a remarkable pinnate frond." (Fig. 13, p. 56.) We find it associated with the remains of a terrestrial plant allied to lepidodendron, and which in size and general appearance not a little resembles one of our commonest club mosses,—Lycopodium clavatum.[48]It sendsout its branches in exactly the same style,—some short and simple, others branched like the parent stem,—in an arrangement approximately alternate; and is everywhere covered, stem and branch, by thickly set scale-like leaflets, that, suddenly narrowing, terminate in exceedingly slim points. It has, however, proportionally a stouter stem than Lycopodium; its leaves, when seen in profile, seem more rectilinear and thin; and none of its branches yet found bear the fructiferous stalk or spike. Its resemblance, however, to this commonest of the Lycopodia,—a plant that may be gathered by handfuls on the moors by which the flagstones are covered,—is close enough to suggest a new reading of the familiar adage on the meeting of extremes. Between the times of this ancient fossil,—one of the oldest of land plants yet known,—and those of the existing club moss that now scatters its light spores by millions over the dead and blackened remains of its remote predecessor, many creations must have intervened, and many a prodigy of the vegetable world appeared, especially in the earlier and middle periods,—Sigillaria, Favularia, Knorria, and Ulodendron,—that have had no representatives in the floras of latter times; and yet here, flanking the immense scale at both its ends, do we find plants of so nearly the same form and type, that it demands a careful survey to distinguish their points of difference. Here, for instance, to illustrate the fact, is there a specimen ofLycopodium clavatum, from one of these Caithness moors, that agrees branch for branch, and both in the disposition of its scales and in general outline, with the specimen in the stone. What seems to be an early representative of the Calamites occurs in the same beds. Some of thespecimens are of large size,—at least from nine inches to a foot in circumference,—and retain their thickness, though existing as fragments several feet in length, with but little diminution throughout. They resembled the interior casts of Calamites in being longitudinally furrowed; but the furrows are flatter, and are themselves minutely striated lengthwise by lines as fine as hairs; and, instead of presenting any appearance of joints, there run diagonally across the stems, interrupted and very irregular lines of knobs. These I find referred to by Dr. Joseph Hooker, in describing a set of massive but ill preserved remains of the same organism detected in South Ness quarry, near Lerwick, by the Hon. Mr. Tuffnell, as taking, in two of the specimens, "the appearance of transverse knobs and bars (mayhap spirally arranged) that cross the striæ obliquely. But though the knobs," he adds, "may perhaps indicate a peculiar character of the plants, they have more probably been caused by pressure during silicification." As, however, they also occur in the best preserved fragment of the plant which I have yet seen,—a Thurso specimen which I owe to my friend Mr. Dick,—I deem it best to regard them, provisionally at least, as one of the characteristics of the plant. I may mention, that while I disinterred one of my specimens from the Thurso flagstones, where it occurred among remains of Dipterus and Asterolepis, I derived another specimen from the great overlying formation of pale Red Sandstone to which the lofty hills of Hoy and the tall mural precipices of Dunnet Head belong; and that this plant is the only organism which has yet been found in this uppermost member of the Lower Old Red, to at least the north of the Moray Firth. Another apparently terrestrial organism of the lower formation, of, however, rare occurrence, very much resembles a sheathing bract or spathe. It is of considerable size,—from four to six inchesin length, by from two to three inches in breadth,—of a broadly elliptical and yet somewhat lanceolate form, deeply but irregularly corrugated, the rugæ exhibiting a tendency to converge towards both its lower and upper terminations, and with, in some instances, what seems to be the fragment of a second spathe springing from its base. Another and much smaller vegetable organism of the same beds presents the form of a spathe-enveloped bud or unblown flower wrapped up in its calyx; but all the specimens which I have yet seen are too obscure to admit of certain determination. I may here mention, that curious markings, which have been regarded as impressions made by vegetables that had themselves disappeared, have been detected during the last twelvemonth in a quarry of the Lower Old Red Sandstone near Huntly, by the Rev. Mr. Mackay of Rhynie. They are very curious and very puzzling; but though some of the specimens present the appearance of a continuous midrib, that throws off, with a certain degree of regularity, apparent leaflets, I am inclined to regard them rather as lying within the province of the ichnologist than of the fossil botanist. They bear the same sort of resemblance to a long, thickly-leaved frond, like that of the "hard fern," that the cast of a many-legged annelid does to a club moss; and I was struck, on my first walk along the Portobello beach, after examining a specimen kindly sent me by Mr. Mackay, to see how nearly the tract of a small shore crab (Carcinus Mænas) along the wet sand resembled them, in exhibiting what seemed to be an obscure midrib fringed with leaflets.
But the genuine vegetable organism of the formation, indicative of the highest rank of any yet found in it, is a true wood of the cone-bearing order. I laid open the nodule which contains this specimen, in one of the ichthyolite beds of Cromarty, rather more than eighteen yearsago; but though I described it, in the first edition of my little work on the Old Red Sandstone, in 1841, as exhibiting the woody fibre, it was not until 1845 that, with the assistance of the optical lapidary, I subjected its structure to the test of the microscope. It turned out, as I had anticipated, to be the portion of a tree; and on my submitting the prepared specimen to one of our highest authorities,—the late Mr. William Nicol,—he at once decided that the "reticulated texture of the transverse section, though somewhat compressed, clearly indicated a coniferous origin." I may add, that this most ancient of Scottish lignites presents several peculiarities of structure. Like some of the Araucarians of the warmer latitudes, it exhibits no lines of yearly growth; its medullary rays are slender, and comparatively inconspicuous; and the discs which mottle the sides of its sap-chambers, when viewed in the longitudinal section, are exceedingly minute, and are ranged, so far as can be judged in their imperfect state of keeping, in the alternate order peculiar to the Araucarians. On what perished land of the early Palæozoic ages did this venerably antique tree cast root and flourish, when the extinct genera Pterichthys and Coccosteus were enjoying life by millions in the surrounding seas, long ere the flora or fauna of the Coal Measures had begun to be?
I may be here permitted to mention, that in a little volume, written in reply to a widely known and very ingenious work on the Development hypothesis, I described and figured this unequivocally genuine lignite, in order to show that a true wood takes its place among the earliest terrestrial plants known to the geologist. I at the same time mentioned,—desirous, of course, that the facts of the question should be fairly stated, whatever their bearing,—that the nodule in which it occurred had been partially washed out of the fish bed in which I found it, by theaction of the surf; and my opponent, fixing on the circumstance, insinuated, in the answer with which he honored me, that it hadnotbelonged to the bed at all, but had been derived from some other formation of later date. He ought, however, to have taken into account my further statement, namely, that the same nodule which enclosed the lignite contained part of another fossil, the well marked scales ofDiplacanthus striatus, an ichthyolite restricted, like the Coccosteus (a specimen of which occurred in a neighboring nodule), to the Lower Old Red Sandstone exclusively. If there be any value whatever in palæontological evidence, this Cromarty lignite must have been deposited in a sea inhabited by the Coccosteus and Diplacanthus. It is demonstrable that, while yet in the recent state, a Diplacanthus lay down and died beside it; and the evidence in the case is unequivocally this, that in the oldest portion of the oldest terrestrial flora yet known, there occurs the fragment of a tree quite as high in the scale as the stately Norfolk Island pine, or the noble cedar of Lebanon.
[I have failed hitherto in finding any remains of terrestrial plant-covered surfaces in the Old Red Sandstone of Scotland, though decided traces of desiccated sub-ærial ones are not rare. Shallows and banks seem to have been numerous during the period of at least the Lower formation. The flagstones of Caithness and Orkney, and the argillaceous fish beds of Cromarty and Ross, not only abound in the ripple-marked surfaces of a shallow sea, but also in cracked and flawed planes that must have dried and split into polygonal partings in the air and the sun. The appearance of these in the neighborhood of the town of Thurso, about half a mile to the east of the river, is not a little curious. Bearing throughout the general dingy hue of the flagstones, they yet consist of alternating bedsof two distinct characters and qualities. The one kind, fissile, finely grained, and sharply ripple-marked, seems to have been deposited in shallow water; the other, not fissile, but, if I may so speak, felted together so as to yield with difficulty to the hammer in any direction, and traversed by polygonal partings, filled up usually by the substance of the overlying stratum, appears to have had a different origin. The state of keeping, too, in which the ichthyic remains of these alternating beds occur is always very different. The smaller and more delicately organized fishes are never found entire, save in the fissile, finely grained beds; in the others we detect only scattered fragments; and even these, unless they belonged to the robust Asterolepis or his congeners,—which, however, in these beds they usually do,—much broken. The polygonal partings seem to indicate that these toughly-felted beds, whose very style of weathering—rough, gnarled, fretted into globose protuberances and irregular hollows—shows that it had not been formed by quiet deposition, must have had their broad backs raised for a time above the surface of the water, to be desiccated in the hot sun. And the fragmentary state of the fossils which they contain seems to point, with the roughnesses of their weathered surfaces, to some peculiarity in their origin. The recollection which they awoke in my mind with each visit I paid them for three years together, may probably indicate what that origin was. I had a relation who died more than a quarter of a century ago, who passed many years in British Guiana, in the colony of Berbice, and whose graphic descriptions of that part of South America made a strong impression upon me when a boy, and still dwells in my memory. He was settled on a cotton plantation near the coast side; and so exceedingly flat was the surrounding country, that the house in which he dwelt, though nearly two miles distant from the shore, stood littlemore than five feet above its level. The soil consisted of a dark gray consolidated mud; and in looking seawards from the margin of the land, there was nothing to be seen, when the tide fell, save dreary mud flats whole miles in extent, with the line of blue water beyond stretching along the distant horizon. These mud flats were much frequented by birds of the wader family, that used to come and fish in the shallow pools for the small fry that had lingered behind when the tide fell; and my cousin, a keen sportsman in his day, has told me that he used to steal upon them in his mud shoes,—flat boards attached to the soles, like the snow shoes of the higher latitudes,—and enjoy rare sport in knocking down magnificent game, such as "the roseate spoonbill" and "gorgeous flamingo." There were times, however, when the mud shoe proved of no avail, and the flat expanse remained impassable for weeks,—
"A boggy syrtis, neither seaNor good dry land."
The coast,—directly impinged on by the drift current, and beaten by the long roll of waves which had first begun to rise under the impulsions of the trade winds on the African coast two thousand miles away,—was much exposed to tempests; and after every fresh storm from the east, a huge bank of mud used to come rolling in from the sea, three or four feet abreast, and remain wholly impassable until, during some two or three neap tides, its surface had been exposed to a tropical sun, and partially consolidated by the heat. And then the waste would become passable as before, and the chopped and broken surface, exposed to the ordinary action of the sea, and to gradual depositions during flood, would begin to be smoothed over, and the birds would find themselves no longer safe. Now, I am inclined to think that we have here the conditions necessaryto the formation of the Thurso deposits. Let us suppose, near where Thurso now stands, a wide tract of flat mud banks in a sea so shallow as to be laid dry at ebb for miles together. Let us further suppose periods of tranquil deposition or re-arrangement, during which one ripple-marked stratum is laid quietly down over another, and the fish, killed by accident, or left stranded by the evaporation of the little pools, are covered up, like the plants in a botanist's drying-book, in a state of complete entireness. Let us yet further suppose great mud banks driven by occasional tempests from the deeper water beyond, and so heaped up over these sedimentary beds as to be exposed during even the flood of neap tides to the desiccating influences of the atmosphere and the sun, until the surface has become hard as a sun-burned brick, and has chopped into polygonal partings, with wide rents between. And finally, let us suppose the whole in this state laid under water at the return of stream tides, and exposed to the ordinary sedimentary action. Does it not seem probable that the alternating beds in all their conditions would be given us by such a process? In the stratum represented by the mud bank, the stone would be of what I have termed afelted, not a fissile character; its organic remains would exist in a fragmentary and scattered state,—for, torn up from their places of original deposition, and rolled onwards in the storm-impelled mud, they could not fail to be broken up and dispersed; and further, they would be in large part those of bulky deep-sea fishes. And lastly, the surface of these beds would be polygonally cracked and flawed, and the wider cracks filled up by the substance of the overlying strata. And these overlying strata, on the other hand,—the result of a period of quiet deposition in shallow water,—would be regularly bedded, and their ichthyic remains, consisting mainly of small littoral fishes, would be preservedin a state of comparative entireness. For, however, such numerous repetitions of alternatelyfeltedand fissile ripple-marked strata as we find in the neighborhood of Thurso,—repetitions carried on for hundreds of feet in vertical extent,—we require yet another condition,—that condition of gradual subsidence in the general crust which can alone account for the fact so often pressed upon the geologist in exploring the Coal Measures, that in deposits thousands of feet in thickness, each stratum in succession had been laid down in a shallow sea.]
It is a curious circumstance, that the Old Red flagstones which lie along the southern flanks of the Grampians, and are represented by the gray stone known in commerce as the Arbroath Pavement, have not, so far as is yet known, an organism in common with the Old Red flagstones of the north. I at one time supposed that the rectilinear, smooth-stemmed fucoid, already described, occurred in both series, as the gray stones have also their smooth-stemmed, rectilinear, tape-like organism; but the points of resemblance were too few and simple to justify the conclusion that they were identical, and I have since ascertained that they were entirely different plants. The fucoid of the Caithness flagstones threw off, as I have shown, in the alternate order, numerous ribbon-like branches or fronds; whereas the ribbon-like fronds or branches of the Forfarshire plant rose by dozens from a common root, like the fronds of Zostera, and somewhat resembled a scourge of cords fastened to a handle. Contemporary with this organism of the gray flagstone formation, and thickly occupying the planes on which it rests, there occur fragments of twisted stems, some of them from three to four inches in diameter (though represented by but mere films of carbonaceous matter), and irregularly streaked, or ratherwrinkled, longitudinally, like the barkof some of our forest trees, though on a smaller scale. With these we find in considerable abundance irregularly-shaped patches, also of carbonaceous matter, reticulated into the semblance of polygonal, or, in some instances, egg-shaped meshes, and which remind one of pieces of ill woven lace. When first laid open, these meshes are filled each with a carbonaceous speck; and, from their supposed resemblance, in the aggregated form, to the eggs of the frog in their albuminous envelop, the quarriers term them "puddock [frog] spawn." The slabs in which they occur, thickly covered over with their vegetable impressions, did certainly remind me, when I first examined them some fifteen years ago, of the bottom of some stagnant ditch beside some decaying hedge, as it appears in middle spring, when paved with fragments of dead branches and withered grass, and mottled with its life-impregnated patches of the gelid substance regarding which a provincial poet tells his readers, in classical Scotch, that
"Puddock-spue is fu' o' e'en,An' every e'e 's a pu-head."[49]
Higher authorities than the quarriers,—among the rest, the late Dr. Mantell,—have been disposed to regard these polygonal markings as the fossilized spawn of ancient Batrachians; but there now seems to be evidence enough from which to conclude that they are the remains, not of the eggs of an animal, but of the seed of a plant. Such was the view taken many years ago by Dr. Fleming,—the original discoverer, let me add, of fossils both in those Upper and Middle Old Red Sandstone deposits that lie in Scotland to the south of the Grampians. "Theseorganisms," we find him saying, in a paper published in "Cheek's Edinburgh Journal" (1831), "occur in the form of circular flat patches, not equalling an inch in diameter, and composed of numerous smaller contiguous pieces. They are not unlike what might be expected to result from a compressed berry, such as the bramble or the rasp. As, however, they are found adjacent to the narrow leaves of gramineous [looking] vegetables, and chiefly in clay slate, originally lacustrine silt, it is probable that they constituted the conglobate panicles of extinct species of the genus Junicus or Sparzanium." From specimens subsequently found by Dr. Fleming, and on which he has erected his speciesParka decipiens, it seems evident that the nearly circular bodies (which in all the better preserved instances circumscribe the small polygonal ones) were set in receptacles somewhat resembling the receptacle or calyx of the strawberry or rasp. Judging from one of the specimens, this calyx appears to have consisted of five pieces, which united in a central stem, and were traversed by broad irregularly diverging striæ. And the spawn-like patches of Carmylie appear to be simply ill preserved specimens of this fruit, whatever its true character, in which the minute circular portions, divested of the receptacle and stem, had been throwninto irregular forms by the joint agency of pressure and decay. The great abundance of these organisms,—for so abundant are they, that visitors to the Carmylie quarries find they can carry away with them as many specimens as they please,—may be regarded as of itself indicative of a vegetable origin.[50]It is not in the least strange, however, that they should have been taken for patches of spawn. The large-grained spawn of fishes, such as the lump-fish, salmon, or sturgeon, might be readily enough mistaken, in even the recent state, for the detached spherical-seed vessels of fruit, such as the bramble-berry, the stone-bramble, or the rasp. "Hang it!" I once heard a countryman exclaim, on helping himself at table to a spoonful of Caviare, which he had mistaken for a sweet-meat, and instantly, according to Milton, "with sputtering noise rejected,"—"Hang it for nasty stuff!—I took it for bramble berry jam."