CHAPTER XIII.

Successors of the exterminated Tribes.--The Gap slowly filled.--Proof that the Vegetation of a Formation may long survive its Animal Tribes. Probable Cause.--Immensely extended Period during which Fishes were the Master-existences of our Planet.--Extreme Folly of an Infidel Objection illustrated by the Fact.--Singular Analogy between the History of Fishes as Individuals and as a Class.--Chemistry of the Lower Formation.--Principles on which the Fish-enclosing Nodules were probably formed.--Chemical Effect of Animal Matter in discharging the Color from Red Sandstone.--Origin of the prevailing tint to which the System owes its Name.--Successive Modes in which a Metal may exist.--The Pest orations of the Geologist void of Color.--Very different Appearance of the Ichthyolites of Cromarty and Moray.

The period of death passed, and over the innumerable dead there settled a soft, muddy sediment, that hid them from the light, bestowing upon them such burial as a November snow-storm bestows on the sere and blighted vegetation of the previous summer and autumn. For an unknown space of time, represented in the formation by a deposit about fifty feet in thickness, the waters of the depopulated area seem to have remained devoid of animal life. A few scales and plates then begin to appear. The fish that had existed outside the chasm seem to have gradually gained upon it, as their numbers increased, just as the European settlers of America have been gaining on the backwoods, and making themselves homes amid the burial-mounds of a race extinct for centuries. For a lengthened period, however, these finny settlers must have been comparatively few--mere squatters in the waste. In the beds of stratified clay in which their remains first occur, over what we may term the densely crowded platform of violent death, the explorer may labor for hours together without finding a single scale.

It is worthy of remark, however, that this upper bed abounds quite as much in the peculiar vegetable impressions of the formation as the lower platform itself. An abundance equally great occurs in some localities only a few inches over the line of the exterminating catastrophe. Thickets of exactly the same algæ, amid which the fish of the formation had sheltered when living, grew luxuriantly over their graves when dead. The agencies of destruction which annihilated the animal life of so extended an area, spared its vegetation; just as the identical forests that had waved over the semi-civilized aborigines of North America continued to wave over the more savage red men, their successors, long after the original race had been exterminated. The inference deducible from the fact, though sufficiently simple, seems in a geological point of view a not unimportant one. _The flora of a system may long survive its fauna; so that that may be but one formation, regarded with reference to plants, which may be two or more formations, regarded with reference to animals._ No instance of any such phenomenon occurs in the later geological periods. The changes in animal and vegetable life appear to have run parallel to each other from the times of the tertiary formations down to those of the coal; but in the earlier deposits the case must have been different. The animal organisms of the newer Silurian strata form essentially different groups from those of the Lower Old Red Sandstone, and both differ from those of the Cornstone divisions; and yet the greater portion of their vegetable remains seem the same. The stem-like impressions of the fucoid bed of the Upper Ludlow Rocks cannot be distinguished from those of the ichthyolite beds of Cromarty and Ross, nor these again from the impressions of the Arbroath pavement, or the Den of Balruddery. Nor is there much difficulty in conceiving how the vegetation of a formation should come to survive its animals. What is fraught with health to the existences of the vegetable kingdom, is in many instances a deadly poison to those of the animal. The grasses and water-lilies of the neighborhood of Naples flourish luxuriantly amid the carbonic acid gas which rests so densely over the pools and runnels out of which they spring, that the bird stoops to drink, and falls dead into the water. The lime that destroys the reptiles, fish, and insects of a thickly inhabited lake or stream, injures not a single flag or bulrush among the millions that line its edges. The two kingdoms exist under laws of life and death so essentially dissimilar, that it has become one of the common-places of poetry to indicate the blight and decline of the tribes of the one by the unwonted luxuriancy of the productions of the other. Otway tells us, in describing the horrors of the plague which almost depopulated London, that the "destroying angel stretched his arm" over the city,

"Till in th' untrodden streets unwholesome grass Grew of great stalk, and color gross, A melancholic poisonous green."

The work of deposition went on; a bed of pale yellow saliferous sandstone settled, tier over tier, on a bed of stratified clay, and was itself overlaid by another bed of stratified clay in turn. And this upper bed had also its organisms. The remains of its sea-weed still spread out thick and dark amid the foldings of the strata, and occasionally its clusters of detached scales. But the circumstances were less favorable to the preservation of entire ichthyolites than those under which the organisms of the lower platform were wrapped up in their stony coverings. The matrix, which is more micaceous than the other, seems to have been less conservative, and the waters were probably less still. The process went on. Age succeeded age, and one stratum covered up another. Generations lived, died, and were entombed in the ever-growing depositions. Succeeding generations pursued their instincts by myriads, happy in existence, over the surface which covered the broken and perishing remains of their predecessors, and then died and were entombed in turn, leaving a higher platform, and a similar destiny to the generations that succeeded. Whole races became extinct, through what process of destruction who can tell? Other races sprang into existence through that adorable power which One only can conceive, and One only can exert. An inexhaustible variety of design expatiated freely within the limits of the ancient type. The main conditions remained the same--the minor details were dissimilar. Vast periods passed; a class low in the scale still continued to furnish the master existences of creation; and so immensely extended was the term of its sovereignty, that a being of limited faculties, if such could have existed uncreated, and witnessed the whole, would have inferred that the power of the Creator had reached its extreme boundary, when fishes had been called into existence, and that our planet was destined to be the dwelling-place of no nobler inhabitants. If there be men dignified by the name of philosophers, who can hold that the present state of being, with all its moral evil, and all its physical suffering, is to be succeeded by no better and happier state, just because "all things have continued as they were" for some five or six thousand years, how much sounder and more conclusive would the inference have been which could have been based, as in the supposed case, on a period perhaps a hundred times more extended?

There exist wonderful analogies in nature between the geological history of the vertebrated animals as an order, and the individual history of every mammifer--between the history, too, of fish as a class, and that of every single fish. "It has been found by Tiedemann," says Mr. Lyell, "that the brain of the fœtus in the higher class of vertebrated animals assumes in succession the various forms which belong to fishes, reptiles, and birds, before it acquires those additions and modifications which are peculiar to the mammiferous tribes." "In examining the brain of the mammalia," says M. Serres, "at an early stage of life, you perceive the cerebral hemispheres consolidated, as in fish, in two vesicles isolated one from the other; at a later period you see them affect the configuration of the cerebral hemispheres of reptiles; still later, again, they present you with the forms of those of birds; and finally, at the era of birth, the permanent forms which the adult mammalia present." And such seems to have been the history of the vertebrata as an order, as certainly as that of the individual mammifer. The fish preceded the reptile in the order of creation, just as the crustacean had preceded the fish, and the annelid the crustacean. Again, though the fact be somewhat more obscure, the reptile seems to have preceded the bird. We find, however, unequivocal traces of the feathered tribes in well-marked foot-prints impressed on a sandstone in North America, at most not more modern than the Lias, but which is generally supposed to be of the same age with the New Red Sandstone of Germany and our own country. In the Oolite--at least one, perhaps two formations later--the bones of the two species of mammiferous quadrupeds have been found, apparently of the marsupial family; and these, says Mr. Lyell, afford the only example yet known of terrestrial mammalia in rocks of a date anterior to the older tertiary formations. The reptile seems to have preceded the bird, and the bird the mammiferous animal. Thus the fœtal history of the nervous system in the individual mammifer seems typical, in every stage of its progress, of the history of the grand division at the head of which the mammifer stands. Agassiz, at the late meeting of the British Association in Glasgow, mentioned an analogous fact. After describing the one-sided tail of the more ancient fish, especially the fish of the Old Red Sandstone,--the subjects of his illustration at the time,--he stated, as the result of a recent discovery, that the young of the salmon in their fœtal state exhibit the same unequally-sided condition of tail which characterizes those existences of the earlier ages of the world. The individual fish, just as it begins to exist, presents the identical appearances which were exhibited by the order when the order began to exist. Is there nothing wonderful in analogies such as these--analogies that point through the embryos of the present time to the womb of Nature, big with its multitudinous forms of being? Are they charged with no such nice evidence as a Butler would delight to contemplate, regarding that unique _style_ of Deity, if I may so express myself, which runs through all his works, whether we consider him as God of Nature, or Author of Revelation? In this style of type and symbol did He reveal himself of old to his chosen people; in this style of allegory and parable did He again address himself to them, when he sojourned among them on earth.

The chemistry of the formation seems scarce inferior in interest to its zoology; but the chemist had still much to do for Geology, and the processes are but imperfectly known. There is no field in which more laurels await the philosophical chemist than the geological one. I have said that all the calcareous nodules of the ichthyolite beds seem to have had originally their nucleus of organic matter. In nine cases out of ten the organism can be distinctly traced; and in the tenth there is almost always something to indicate where it lay--an elliptical patch of black, or an oblong spot, from which the prevailing color of the stone has been discharged, and a lighter hue substituted. Is the reader acquainted with Mr. Pepys's accidental experiment, as related by Mr. Lyell, and recorded in the first volume of the _Geological Transactions?_ It affords an interesting proof that animal matter, in a state of putrefaction, proves a powerful agent in the decomposition of mineral substances held in solution, and of their consequent precipitation. An earthen pitcher, containing several quarts of sulphate of iron, had been suffered to remain undisturbed and unexamined in a corner of Mr. Pepys's laboratory for about a twelvemonth. Some luckless mice had meanwhile fallen into it, and been drowned; and when it at length came to be examined, an oily scum, and a yellow, sulphureous powder, mixed with hairs, were seen floating on the top, and the bones of the mice discovered lying at the bottom; and it was found, that over the decaying bodies the mineral components of the fluid had been separated and precipitated in a dark-colored sediment, consisting of grains of pyrites and of sulphur, of copperas in its green and crystalline form, and of black oxide of iron. The animal and mineral matters had mutually acted upon one another; and the metallic sulphate, deprived of its oxygen in the process, had thus cast down its ingredients. It would seem that over the putrefying bodies of the fish of the Lower Old Red Sandstone the water had deposited, in like manner, the lime with which it was charged; and hence the calcareous nodules in which we find their remains enclosed. The form of the nodule almost invariably agrees with that of the ichthyolite within; it is a coffin in the ancient Egyptian style. Was the ichthyolite twisted half round in the contorted attitude of violent death? the nodule has also its twist. Did it retain its natural posture? the nodule presents the corresponding spindle form. Was it broken up, and the outline destroyed? the nodule is flattened and shapeless. In almost every instance the form of the organism seems to have regulated that of the stone. We may trace, in many of these concretionary masses, the operations of three distinct principles, all of which must have been in activity at one and the same time. They are wrapped concentrically each round its organism: they split readily in the line of the enclosing stratum, and are marked by its alternating rectilinear bars of lighter and darker color; and they are radiated from the centre to the circumference. Their concentric condition shows the chemical influences of the decaying animal matter; their fissile character and parallel layers of color indicate the general deposition which was taking place at the time; and their radiated structure testifies to that law of crystalline attraction, through which, by a wonderful masonry, the invisible but well-cut atoms build up their cubes, their rhombs, their hexagons, and their pyramids, and are at once the architects and the materials of the structure which they rear.

Another and very different chemical effect of organic matter may be remarked in the darker colored arenaceous deposits of the formation, and occasionally in the stratified clays and nodules of the ichthyolite bed. In a print-work, the whole web is frequently thrown into the vat and dyed of one color; but there afterwards comes a discharging process: some chemical mixture is dropped on the fabric; the dye disappears wherever the mixture touches; and in leaves, and sprigs, and patches, according to the printer's pattern, the cloth assumes its original white. Now the colored deposits of the Old Red Sandstone have, in like manner, been subjected to a discharging process. The dye has disappeared in oblong or circular patches of various sizes, from the eighth of an inch to a foot in diameter; the original white has taken its place; and so thickly are these speckles grouped in some of the darker-tinted beds, that the surfaces, where washed by the sea, present the appearance of sheets of calico. The discharging agent was organic matter; the uncolored patches are no mere surface films, for, when cut at right angles, their depth is found to correspond with their breadth, the circle is a sphere, the ellipsis forms the section of an egg-shaped body, and in the centre of each we generally find traces of the organism in whose decay it originated. I have repeatedly found single scales, in the ichthyolite beds, surrounded by uncolored spheres about the size of musket bullets. It is well for the young geologist carefully to mark such appearances--to trace them through the various instances in which the organism may be recognized and identified, to those in which its last vestiges have disappeared. They are the hatchments of the geological world, and indicate that life once existed where all other record of it has perished.[BC]

[Footnote BC: Some of the clay-slates of the primary formations abound in these circular, uncolored patches, bearing in their centres, like the patches of the Old Red Sandstone, half obliterated nuclei of black. Were they, too, once fossiliferous? and do these blank erasures remain to testify to the fact? I find the organic origin of the patches in the Old Red Sandstone remarked by Professor Fleming as early as the year 1830, and the remark reiterated by Dr. Anderson, of Newburgh, in nearly the same words, but with no acknowledgment, ten years later. The following is the minute and singularly faithful description of the Professor:--

"On the surface of the strata in the lower beds, circular spots, nearly a foot in diameter, may be readily perceived by their pale yellow colors, contrasted with the dark red of the surrounding rock. These spots, however, are not, as may at first be supposed, mere superficial films, but derive their circular form from a colored sphere to which they belong. This sphere is not to be distinguished from the rest of the bed by any difference in mechanical structure, but merely by the absence of much of that oxide of iron with which the other portion of the mass is charged. The circumference of this colored sphere is usually well defined; and at its centre may always be observed matter of a darker color, in some cases disposed in concentric layers, in others of calcareous and crystalline matter, the remains probably of some vegetable or animal organism, the decomposition of which exercised a limited influence on the coloring matter of the surrounding rock. In some cases I have observed these spheres slightly compressed at opposite sides, in a direction parallel with the plane of stratification--the result, without doubt, of the subsidence or contraction of the mass, after the central matter or nucleus had ceased to exercise its influence."--(_Cheek's Edinburgh Journal_, Feb. 1831, p. 82.)]

It is the part of the chemist to tell us by what peculiar action of the organic matter the dye was discharged in these spots and patches. But how was the dye itself procured? From what source was the immense amount of iron derived, which gives to nearly five sixths of the Old Red Sandstone the characteristic color to which it owes its name? An examination of its lowest member, the great conglomerate, suggests a solution of the query. I have adverted to the large proportion of red-colored pebbles which this member contains, and, among the rest, to a red granitic gneiss, which must have been exposed over wide areas at the time of its deposition, and which, after the lapse of a period which extended from at least the times of the Lower Old Red to those of the Upper Oolite, was again thrust upwards to the surface, to form the rectilinear chain of precipitous eminences to which the hills of Cromarty and of Nigg belong. This rock is now almost the sole representative, in the north of Scotland, of the ancient rocks whence the materials of the Old Red Sandstone were derived. It abounds in hæmatic iron ore, diffused as a component of the stone throughout the entire mass, and which also occurs in it in ponderous insulated blocks of great richness, and in thin, thread-like veins. When ground down, it forms a deep red pigment, undistinguishable in tint from the prevailing color of the sandstone, and which leaves a stain so difficult to be effaced, that shepherds employ it in some parts of the Highlands for marking their sheep. Every rawer fragment of the rock bears its hæmatic tinge; and were the whole ground by some mechanical process into sand, and again consolidated, the produce of the experiment would be undoubtedly a deep red sandstone. In an upper member of the lower formation--that immediately over the ichthyolite beds--different materials seem to have been employed. A white, quartzy sand and a pale-colored clay form the chief ingredients; and though the ochry-tinted coloring matter be also iron, it is iron existing in a different condition, and in a more diluted form. The oxide deposited by the chalybeate springs which pass through the lower members of the formation, would give to white sand a tinge exactly resembling the tint borne by this upper member.

The passage of metals from lower to higher formations, and from one combination to another, constitutes surely a highly interesting subject of inquiry. The transmission of iron in a chemical form, through chalybeate springs, from deposits in which it had been diffused in a form merely mechanical, is of itself curious; but how much more so its passage and subsequent accumulation, as in bog-iron and the iron of the Coal Measures, through the agency of vegetation! How strange, if the steel axe of the woodman should have once formed part of an ancient forest!--if, after first existing as a solid mass in a primary rock, it should next have come to be diffused as a red pigment in a transition conglomerate--then as a brown oxide in a chalybeate spring--then as a yellowish ochre in a secondary sandstone--then as a component part in the stems and twigs of a thick forest of arboraceous plants--then again as an iron carbonate, slowly accumulating at the bottom of a morass of the Coal Measures--then as a layer of indurated bands and nodules of brown ore, underlying a seam of coal--and then, finally, that it should have been dug out, and smelted, and fashioned, and employed for the purpose of handicraft, and yet occupy, even at this stage, merely a middle place between the transmigrations which have passed, and the changes which are yet to come. Crystals of galena sometimes occur in the nodular limestones of the Old Red Sandstone; but I am afraid the chemist would find it difficult to fix their probable genealogy.

In at least one respect, every geological history must of necessity be unsatisfactory; and, ere I pass to the history of the two upper formations of the system, the reader must permit me to remind him of it. There have been individuals, it has been said, who, though they could see clearly the forms of objects, wanted, through some strange organic defect, the faculty of perceiving their distinguishing colors, however well marked these might be. The petals of the rose have appeared to them of the same sombre hue with its stalk; and they have regarded the ripe scarlet cherry as undistinguishable in tint from the green leaves under which it hung. The face of nature to such men must have for ever rested under a cloud; and a cloud of similar character hangs over the pictorial restorations of the geologist. The history of this and the last chapter is a mere profile drawn in black, an outline without color--in short, such a chronicle of past ages as might be reconstructed, in the lack of other and ampler materials, from tombstones and charnel-houses. I have had to draw the portrait from the skeleton. My specimens show the general form of the creatures I attempt to describe, and not a few of their more marked peculiarities; but many of the nicer elegancies are wanting; and the "complexion to which they have come" leaves no trace by which to discover the complexion they originally bore. And yet color is a mighty matter to the ichthyologist. The "fins and shining scales," "the waved coats, dropt with gold," the rainbow dyes of beauty of the watery tribes, are connected often with more than mere external character. It is a curious and interesting fact, that the hues of splendor in which they are bedecked are, in some instances, as intimately associated with their instincts--with their feelings, if I may so speak--as the blush which suffuses the human countenance is associated with the sense of shame, or its tint of ashy paleness or of sallow with emotions of rage, or feelings of a panic terror. Pain and triumph have each their index of color among the mute inhabitants of our seas and rivers. Poets themselves have bewailed the utter inadequacy of words to describe the varying tints and shades of beauty with which the agonies of death dye the scales of the dolphin, and how every various pang calls up a various suffusion of splendor.[BD] Even the common stickleback of our ponds and ditches can put on its colors to picture its emotions. There is, it seems, a mighty amount of ambition, and a vast deal of fighting sheerly for conquests' sake, among the myriads of this pygmy little fish which inhabit our smaller streams; and no sooner does an individual succeed in expelling his weaker companions from some eighteen inches or two feet of territory, than straight way the exultation of conquest converts the faded and freckled olive of his back and sides into a glow of crimson and bright green. Nature furnishes him with a regal robe for the occasion. Immediately on his deposition, however,--and events of this kind are even more common under than out of the water,--his gay colors disappear, and he sinks into his original and native ugliness.[BE]

[Footnote BD: The description of Falconer must be familiar to every reader, but I cannot resist quoting it. It shows how minutely the sailor poet must have observed. Byron tells us how

"Parting day Dies like the dolphin, whom each pang imbues With a new color, as it gasps away, The last still loveliest, till--tis gone, and all is gray."

Falconer, in anticipating, reversed the simile. The huge animal, struck by the "unerring barb" of Rodmond, has been drawn on board, and

"On deck he struggles with convulsive pain; But while his heart the fatal javelin thrills, And flitting life escapes in sanguine rills, What radiant changes strike the astonished sight! What glowing hues of mingled shade and light! Not equal beauties gild the lucid West With parting beams o'er all profusely drest; Not lovelier colors paint the vernal dawn, When Orient dews impearl the enamelled lawn; Than from his sides in bright suffusion flow, That now with gold empyreal seem to glow; Now in pellucid sapphires meet the view, And emulate the soft celestial hue; Now beam a flaming crimson on the eye, And now assume the purple's deeper dye. But here description clouds each shining ray-- What terms of art can Nature's powers display?" ]

[Footnote BE: "In the _Magazine of Natural History_" says Captain Brown, in one of his notes to White's _Sellorne_, "we have a curious account of the pugnacious propensities of these little animals. 'Having at various times,' says a correspondent, 'kept these little fish during the spring and part of the summer months, and paid close attention to their habits. I am enabled from my own experience to vouch for the facts I am about to relate. I have frequently kept them in a deal tub, about three feet two inches wide, and about two feet deep. When they are put in for some time, probably a day or two, they swim about in a shoal, apparently exploring their new habitation. Suddenly one will take possession of the tub, or, as it will sometimes happen, the bottom, and will instantly commence an attack upon his companions; and if any of them venture to oppose his sway, a regular and most furious battle ensues. They swim round and round each other with the greatest rapidity, biting, (their mouths being well furnished with teeth,) and endeavoring to pierce each other with their lateral spines, which, on this occasion, are projected. I have witnessed a battle of this sort which lasted several minutes before either would give way; and when one does submit, imagination can hardly conceive the vindictive fury of the conqueror, who, in the most persevering and unrelenting way, chases his rival from one part of the tub to another, until fairly exhausted with fatigue. From this period an interesting change takes place in the conqueror, who, from being a speckled and greenish-looking fish, assumes the most beautiful colors; the belly and lower jaws becoming a deep crimson, and the back sometimes a cream color, but generally a fine green, and the whole appearance full of animation and spirit. I have occasionally known three or four parts of the tub taken possession of by these little tyrants, who guard their territories with the strictest vigilance, and the slightest invasion brings on invariably a battle. A strange alteration immediately takes place in the defeated party: his gallant bearing forsakes him, his gay colors fade away, he becomes again speckled and ugly, and he hides his disgrace among his peaceable companions.'"]

But of color, as I have said, though thus important, the ichthyologist can learn almost nothing from Geology. The perfect restoration of even a Cuvier are blank outlines. We just know by a wonderful accident that the Siberian elephant was red. A very few of the original tints still remain among the fossils of our north country Lias. The ammonite, when struck fresh from the surrounding lime, reflects the prismatic colors, as of old; a huge Modiola still retains its tinge of tawny and yellow; and the fossilized wood of the formation preserves a shade of the native tint, though darkened into brown. But there is considerably less of color in the fossils of the Old Red Sandstone. I have caught, and barely caught, in some of the newly disinterred specimens, the faint and evanescent reflection of a tinge of pearl; and were I acquainted with my own collection only, imagination, borrowing from the prevailing color, would be apt to people the ancient oceans, in which its forms existed, with swarthy races exclusively. But a view of the Altyre fossils would correct the impression. They are enclosed, like those of Cromarty, in nodules of an argillaceous limestone. The color, however, from the presence of iron, and the absence of bitumen, is different. It presents a mixture of gray, of pink, and of brown; and on this ground the fossil is spread out in strongly contrasted masses of white and dark red, of blue, and of purple. Where the exuviæ lie thickest, the white appears tinged with delicate blue--the bone is but little changed. Where they are spread out more thinly, the iron has pervaded them, and the purple and deep red prevail. Thus the same ichthyolite presents, in some specimens, a body of white and plum-blue attached to fins of deep red, and with detached scales of red and of purple lying scattered around it. I need hardly add, however, that all this variety of coloring is, like the unvaried black of the Cromarty specimens, the result, merely, of a curious chemistry.