If you have taken up your abode for the night at classic Rugby, at sporting Melton-mowbray, or among the academic bowers of Oxford, there are objects all around, in every hill-side, ravine, or railway section, to fill you at once with admiration and astonishment. Go, inquire of that rock. It is the lias limestone; beyond it, and at no great distance, lies the oolite; and there, in the immediate vicinity of both, you have the Stonesfield slate. We invite you to examine any one of these common-place looking stones; and not in Gulliver, not in the history of the Knight of La Mancha, not in all the Mysteries of Udolpho, not in the Romance of the Forest whose harmonious periods so charmed our youth, will you find anything to compare with the marvels therein to be disclosed. The machinery of a tale may require the aid of giants and genii, but here is “truth without fiction,” more startling, marvelous, and so beyond the bounds of nature as now felt and seen, that the most daring fancy is utterly outstripped in its loftiest flights into the regions of the ideal. The series of beds which constitute the mineral features of this extensive district contains the full development of the reptilian type to which we were introduced in the last chapter. Animals there are in these rocks, with forms and features, so fantastic, and apparently disproportioned, that the tales of the most unscrupulous traveler would suffer in comparison. And in truth, there is no page in the book of nature—none, certainly, in all the works of man—so fraught with wonders, or remarkable for stirring incident, as the epoch of animal life whose history is there inscribed.
I. The Nature of the Rocks. The oolitic or Jurassic system, like that of the new red sandstone, comprises the subdivisions of two well-marked natural groups, in which the lias or lower series is included. In point of geographical range, the oolite formation is extensively distributed over the surface of the globe; in mineral character it is varied in every possible degree of texture and composition; in geognostic arrangement there are intercalations, without end, of marine and terrestrial detritus; the organic remains are in the greatest profusion, both as to diversity of type and increase of new creations; and, locally, such has been the appreciation of its various members, that there is scarcely a town or parish in the south-eastern part of England, that has not received from or given habitations and name to, some one of its numerous subdivisions.
Resting upon the triassic formation, there are bands of lias shales, limestones, sandy and ferruginous strata, and upper shales, including nodular concretions and beds of limestone. This series is distributed over the counties of York, Northampton, Somerset, and Dorset. The next are the lower oolites, which comprise an extensive series of calcareous, concretionary sands and sandstones, limestone, thin seams of coal and ligneous clays, and the Cornbrash limestone, which in many localities is a mere aggregation of shells and other marine exuviæ. The Stonesfield slate, the Forest marble, and the Fuller’s earth beds, are included in the group, ranging along the Yorkshire coast, through Northampton, Oxford, and Gloucester shires; and in Scotland we have their equivalents in the Brora coal and oolitic limestone of Sutherlandshire, Skye, and the adjacent islands. The middle oolite succeeds, which includes the Oxford clay, the Kelloway rock, and the coral-rag, all more or less distinguished by their profusion and peculiarity of fossils, chiefly shells, echini, and corals. The whole formation terminates in two well known deposits, the Kimmeridge clay and Portland oolite, with its bands of green and red sands, layers of chert and drift-wood. This group prevails in Oxfordshire, Berks, Wilts, Bucks, and the Isle of Portland; the matrix of fossilized reptilia, fishes, and cycadeous plants.
The term Oolite or roestone, as applied to the whole of the groups enumerated above, is derived from the resemblance between the small rounded grains of which the limestones are generally composed, and the roe of a fish. The Jura mountains, which divide France from Switzerland, consist mainly of these deposits, and hence Jurassic—the Terrains Jurrassiques of continental geologists. The word lias is simply a corruption of liers (layers), and has from time immemorial been applied to the rocks of this group. Their relation and order of superposition are fully brought out along the sections of the Great Western Railway from London to Bath. The Birmingham line from Derby by Rugby to the metropolis intersects nearly every member of the series, until they are covered about Wallingford by the chalk.
When one looks at these innumerable bands of rock, and the great diversity of earthy matter of which they are composed, the mind becomes utterly overwhelmed by the rapidity and vastness of the changes which, during this epoch, occurred upon the surface of the globe. A turbid, and often agitated, condition of the waters in which they were deposited is very clearly indicated. The animals of the period were manifestly of a class peculiarly adapted to the impregnated element, the slimy banks, and shallows which prevailed. The flora was abundant, of a kind, and produced in circumstances, favorable for the formation of a lignite coal. The spasmodic action which prevailed after the deposition of the carboniferous beds had not entirely subsided at the Permian period. The change was of too violent a kind to have been brought about without great internal, as well as external, commotion. We find, accordingly, in most districts, that the rocks of this class are upturned and disrupted. The detritus of the new red sandstone and magnesian limestone, thereby occasioned, would go to form new land during the submergence of such portions of the surface as were retained beneath the waters. The oscillations were numerous and frequent, corresponding with the aggregate of beds which compose the system; while the quality and arrangement of the sediment point to changes and alterations in sea-levels, river courses, land boundaries, estuaries, the size and distribution of the basins into which the alluvia were transported. The geographic extent, combined with the frequently insulated position of the oolitic series, clearly demonstrates a vast alteration in the bed of the ocean, as well as in the ridges and elevations which gave diversity to the land. The oolites, in fact, constitute vast calcareous reefs, raised upon the inverted strata of the older formations, which formed the cliffs and headlands of a sea swarming with lizards and crocodilians, and over whose thick umbrageous banks roamed the flying pterodactyle, watching or perhaps escaping from, the singular saurians that reposed in the thickets beneath. The substitution of the pyritous clays for the saliferous marls; the dark argillaceous oolites and blue mottled lias for the yellow crystalline dolomite, is in harmony and keeping with the plants and animals which now, for the first time, sprang into existence.
II. The Organic Remains are very abundant, and in both plants and animals there are various new kinds. Of the former are the cycadeæ, allied to the existing pine-apple; also the lilaceæ, and some other undescribed genera. With regard to animals, this has been emphatically called “the age of reptiles,” along with which there are new families of fishes, crustacea, mollusca, and corals. The warm-blooded animals now for the first time appear, of which there are two genera, the Amphitherium and Phascolotherium, found in the Stonesfield slate near Oxford, and considered, by analogy of structure, to be allied to the marsupials that inhabit the Australian continent. The same interesting locality has furnished two new genera of insects, the Prionus Ooliticus and Coccinella Wittsii; in the lias, of different places, eleven genera and species have been discovered, but of which only wings and fragments have been obtained. A perfect specimen of this order has recently been found, by the Rev. P. B. Brodie, in the upper lias, near Cheltenham, resembling the genus diplax; but so shattered in the head, that its precise character cannot be determined. The reptilians supply alike new terrestrial and marine tortoises and turtles—lizards, whose arms and legs were provided with a filmy membrane, like bats, to enable them to fly—amphibious saurians, and water saurians unlike anything now in existence.
Contrast this catalogue with the few organic remains to be met with in the preceding period, and ask what called such a newly-inhabited world into being? The face of nature, so remarkably elaborated out of the waste and decay of these old stony materials, is moving all over with life—replenished, so far as yet discovered, with seventy-five generic and specific forms of new vegetation—a hundred and ten new forms of hard-working corallines—seven hundred and thirteen genera and species of the shelly tribes, from the simplest to the most complicated of the chambered orders—a hundred and sixty distinct races of fishes, placoids and ganoids—three varieties of the most strangely constructed mammalian quadrupeds, with thirteen kinds of insects to titillate and keep them in action—and all this array of organic life moving side by side with forty families of gigantic reptiles, herbivorous and carnivorous, creeping, swimming, and flying! The wonders of art have nothing to compare with this. The structure of a blade of grass will not suffer an atheist to live. During the six thousand years of man’s existence, one new living thing, of any order or type, has not been called into being. Astronomy is daily adding to her achievements, and penetrating farther among the systems of the universe; but the nebular theory of creation is gone, and the new-world germs will not expand at its fanciful bidding. Geology nobly bears testimony in every page to the rule of one supreme intelligent Creator—an exuberance of life and forms which announces the authoritative interposition of Him
“Whose word leaps forth at once to its effect;
Who calls for things that are not—and they come.”
And the mandate goes forth, in that awful simplicity of Omnipotence, which learning cannot mystify nor ignorance overlook.