[CHAPTER XII.]
The two Aspects in which. Matter can be viewed; Space and Time.—Geological History of the Earlier Periods.—The Cambrian System,—Its Annelids.—The Silurian System.—Its Corals, Encrinites, Molluscs, and Trilobites.—Its Fish.—These of a high Order, and called into Existence apparently by Myriads.—Opening Scene in the History of the Old Red Sandstone a Scene of Tempest.—Represented by the Great Conglomerate.—Red a prevailing Color among the Ancient Rocks contained in this Deposit.—Amazing Abundance of Animal Life.—Exemplified by a Scene in the Herring Fishery.—Platform of Death.—Probable Cause of the Catastrophe which rendered it such.
"There are only two different aspects," says Dr. Thomas Brown, "in which matter can be viewed. We may consider it simply as it exists, in space, or as it exists in time. As it exists in space we inquire into its composition, or, in other words, endeavor to discover what are the elementary bodies that coexist in the space which it occupies; as it exists in time, we inquire into its susceptibilities or its powers, or, in other words, endeavor to trace all the various changes which have already passed over it, or of which it may yet become the subject."
Hitherto I have very much restricted myself to the consideration of the Old Red Sandstone as it exists in space—to the consideration of it as we now find it. I shall now attempt presenting it to the reader as it existed in time—during the succeeding periods of its formation, and when its existences lived and moved as the denizens of primeval oceans. It is one thing to describe the appearance of a forsaken and desert country, with its wide wastes of unprofitable sand, its broken citadels and temples, its solitary battle-plains, and its gloomy streets of caverned and lonely sepulchres; and quite another to record its history during its days of smiling fields, populous cities, busy trade, and monarchical splendor. We pass from the dead to the living—from the cemetery, with its high piles of mummies and its vast heaps of bones, to the ancient city, full of life and animation in all its streets and dwellings.
Two great geological periods have already come to their close; and the floor of a widely-spread ocean, to which we can affix no limits, and of whose shores or their inhabitants nothing is yet known, is occupied to the depth of many thousand feet by the remains of bygone existences. Of late, the geologist has learned from Murchison to distinguish the rocks of these two periods—the lower as those of the Cambrian, the upper as those of the Silurian group. The lower—representative of the first glimmering twilight of being—of a dawn so feeble that it may seem doubtful whether in reality the gloom had lightened—must still be regarded as a period of uncertainty. Its ripple-marked sandstones, and its half coherent accumulations of dark-colored strata, which decompose into mud, show that every one of its many plains must have formed in succession an upper surface of the bottom of the sea; but it remains for future discoverers to determine regarding the shapes of life that burrowed in its ooze, or careered through the incumbent waters. In one locality it would seem as if a few worms had crawled to the surface, and left their involved and tortuous folds doubtfully impressed on the stone. Some of them resemble miniature cables, carelessly coiled; others, furnished with what seem numerous legs, remind us of the existing Nereidina of our sandy shores—those red-blooded, many-legged worms, resembling elongated centipedes, that wriggle with such activity among the mingled mud and water, as we turn over the stones under which they had sheltered. Were creatures such as these the lords of this lower ocean? Did they enter first on the stage, in that great drama of being in which poets and philosophers, monarchs and mighty conquerors, were afterwards to mingle as actors? Does the reader remember that story in the Arabian Nights, in which the battle of the magicians is described? At an early stage of the combat a little worm creeps over the pavement; at its close two terrible dragons contend in an atmosphere of fire. But even the worms of the Cambrian System can scarce be regarded as established. The evidence respecting their place and their nature must still be held as involved in some such degree of doubt as attaches to the researches of the antiquary, when engaged in tracing what their remains much resemble—the involved sculpturings of some Runic obelisk, weathered by the storms of a thousand winters. There is less of doubt, however, regarding the existences of the upper group of rocks—the Silurian.
The depth of this group, as estimated by Mr. Murchison, is equal to double the height of our highest Scottish mountains; and four distinct platforms of being range in it, the one over the other, like stories in a building. Life abounded on all these platforms, and in shapes the most wonderful. The peculiar encrinites of the group rose in miniature forests, and spread forth their sentient petals by millions and tens of millions amid the waters; vast ridges of corals peopled by their innumerable builders,—numbers without number,—rose high amid the shallows; the chambered shells had become abundant—the simpler testacea still more so; extinct forms of the graptolite, or sea-pen, existed by myriads; and the formation had a class of creatures in advance of the many-legged annelids of the other. It had its numerous family of trilobites,—crustaceans nearly as high in the scale as the common crab,—creatures with crescent-shaped heads, and jointed bodies, and wonderfully constructed eyes, which, like the eyes of the bee and the butterfly, had the cornea cut into facets resembling those of a multiplying glass. Is the reader acquainted with the form of the common Chiton of our shores—the little boat-shaped shell-fish, that adheres to stones and rocks like the limpet, but which differs from every variety of limpet, inbearing as its covering a jointed, not a continuous shell? Suppose a chiton with two of its terminal joints cut away, and a single plate of much the same shape and size, but with two eyes near the centre, substituted instead, and the animal, in form at least, would be no longer a chiton, but a trilobite. There are appearances, too, which lead to the inference that the habits of the two families, though representing different orders of being, may not have been very unlike. The chiton attaches itself to the rock by a muscular sucker or foot, which, extending vent rally along its entire length, resembles that of the slug or the snail, and enables it to crawl like them, but still more slowly, by a succession of adhesions. The locomotive powers of the trilobite seem to have been little superior to those of the chiton. If furnished with legs at all, it must have been with soft rudimentary membranaceous legs, little fitted for walking with; and it seems quite as probable, from the peculiarly shaped under margin of its shell, formed, like that of the chiton, for adhering to flat surfaces, that, like the slug and the snail, it was unfurnished with legs of any kind, and crept on the abdomen. The vast conglomerations of trilobites for which the Silurian rocks are remarkable, are regarded as further evidence of a sedentary condition, Like Ostreæ, Chitones, and other sedentary animals, they seemed to have adhered together in vast clusters, trilobite over trilobite, in the hollows of submarine precipices, or on the flat, muddy bottom below. And such were the master existences of three of the four Silurian platforms, and of the greater part of the fourth, if, indeed, we may not regard the chambered molluscs, their contemporaries,—creatures with their arms clustered round their heads, and with a nervous system composed of a mere knotted cord,—as equally high in the scale. We rise to the topmost layers of the system,—to an upper gallery of its highest platform,—and find nature mightily in advance.
Another and superior order of existences had sprung into being at the fiat of the Creator—creatures with the brain lodged in the head, and the spinal cord enclosed in a vertebrated column. In the period of the Upper Silurian, fish properly so called, and of very perfect organization, had become denizens of the watery element, and had taken precedence of the crustacean, as, at a period long previous, the crustacean had taken precedence of the annelid. In what form do these, the most ancient beings of their class, appear? As cartilaginous fishes of the higher order. Some of them were furnished with bony palates, and squat, firmly-based teeth, well adapted for crushing the stone-cased zoöphytes and shells of the period, fragments of which occur in their fœcal remains; some with teeth that, like those of the fossil sharks of the later formations, resemble lines of miniature pyramids, larger and smaller alternating; some with teeth sharp, thin, and so deeply serrated that every individual tooth resembles a row of poniards set upright against the walls of an armory; and these last, says Agassiz, furnished with weapons so murderous, must have been the pirates of the period. Some had their fins guarded with long spines, hooked like the beak of an eagle; some with spines of straighter and more slender form, and ribbed and furrowed longitudinally like columns; some were shielded by an armor of bony points; and some thickly covered with glistening scales. If many ages must have passed ere fishes appeared, there was assuredly no time required to elevate their lower into their higher families. Judging, too, from this ancient deposit, they seem to have been introduced, not by individuals and pairs, but by whole myriads.
"Forthwith, the sounds and seas, each creek and bay,
With fry innumerable swarmed; and shoals
Of fish, that with their fins and shining scales
Glide under the green wave in plumps and sculls,
Banked the mid sea."
The fish-bed of the Upper Ludlow Rock abounds more in osseous remains than an ancient burying-ground. The stratum, over wide areas, seems an almost continuous layer of matted bones, jaws, teeth, spines, scales, palatal plates, and shagreen-like prickles, all massed together, and converted into a substance of so deep and shining a jet color, that the bed, when "first discovered, conveyed the impression," says Mr. Murchison, "that it enclosed a triturated heap of black beetles." And such are the remains of what seem to have been the first existing vertebrata. Thus, ere our history begins, the existences of two great systems, the Cambrian and the Silurian, had passed into extinction, with the exception of what seem a few connecting links, exclusively molluscs, that are found in England to pass from the higher beds of the Ludlow rocks into the Lower or Tilestone beds of the Old Red Sandstone.[AZ] The exuviæ of at least four platforms of being lay entombed furlong below furlong, amid the gray, mouldering mudstones, the harder arenaceous beds, the consolidated clays, and the concretionary limestones, that underlay the ancient ocean of the Lower Old Red. The earth had already become a vast sepulchre, to a depth beneath the bed of the sea equal to at least twice the height of Ben Nevis over its surface.
[AZ] "Upwards of eight hundred extinct species of animals have been described as belonging to the earliest, or Protozoic and Silurian period, and of these only about one hundred are found also in the overlying Devonian series; while but fifteen are common to the whole Palæozoic period, and not one extends beyond it."—(M. de Verneuil and Count D'Archiac, quoted by Mr. D. T. Ansted. 1844.)