CHAPTER IV.THE WEALDEN FORMATION.

CHAPTER IV.THE WEALDEN FORMATION.

The Wealden formation is more local than any of the deposits we have yet considered. The term has a particular reference to the district features of Kent, Surrey, Sussex, and Hampshire, known as theWolds, from the Germanwald, signifying a wood or forest: and as the geological position of the group is in immediatesuperiorconnection with the oolites, andinferiorto the chalk, the character and history of the Wealden fall to be given in this place. The Specton clay of Yorkshire, displayed along the cliffs adjoining Filey Bay, is considered to belong to the same series as thegaultor blue and gray marls of Cambridge, Kent and Sussex; but it contains some characteristic indications of the Kimmeridge clay, and, therefore, we should expect that, in Yorkshire, these two strata are not separated as in the south of England.

I.Nature and Extent of the Deposit.The Wealden is a fresh water or estuary formation, as is clearly established by its fossils as well as by its lithology. The group consists of layers of clay, sand, shale, with subordinate beds of limestone, grit, and friable sandstone. The Hastings sands, Tilgate Forest beds, Tunbridge Wells deposits, and the Ashburn lignite shales and ferruginous sands, are all constituents of the series. The Dover Railway traverses the formation between Red Hill and Ashford: the branch leading to Tunbridge Wells affords excellent sections of the clay and sands. Thus occupying, in an irregular triangular form, the south-east of England, the wealden again emerges in the principality of Hanover, and other places in the north of Germany: continuing in the same course, it is again found on the British shores, occurring at Linksfield, near Elgin.

It would not be easy to restore, in imagination, the surrounding aspect of the superficial area now occupied by patches of the wealden formation. Take your station on the Peak of Derby, or Shotover Hill, or the heights of Ivanhoe—not so perilous adventure as that of the heroine of the tale on the battlements of Malvoisin—and you overlook a vast extent of vale and woodland, all then one broad expanse of water. This inland sea filled the whole intermediate district traced above, studded, in all probability, with islands, and fringed with shallows and rich arborescent headlands. Sharks prowled and darted in every direction; pterodactyles may be descried looming along the waste; while in terror or in joy, the plesiosaurus reared aloft his far-stretching neck, and then withdrew into his fenny retreats. The saurians, with their strong muscular jaws, are actively engaged, each according to his kind, by the shores or in the waters; while over the busy scene, the fierce-weltering ichthyosaurus looks in wild amazement, his large eyes leaping in their sockets, and spreading dismay among the tenants of the deep, as even now, when a kite enters a thorny brake, or pursues his stealthy flight over the meadows and green fields of timid nestling bird.

Nor would the land animals be less actively employed in maintaining the laws of their creation. No skeletons of birds have yet been detected; but their foot-prints, we have seen, are numerous. These clouds of insects, and other brilliant objects that flit with such rapidity across the sky, have all been stirred, and are leaping they know not whither, for the tread of a monster’s feet is heard through the forest, mailed in plated horn thicker than Ajax’s shield, and, pursued by another, presses and plunges onward in reckless haste. Imagine the many encounters during a single season between one set of the terrestrials only, the saurians; of the class, there are the remains of the megalosaurus, the great saurian—of the geosaurus, the land saurian—of the hylæosaurus, the forest saurian—of the teleosaurus, the perfect saurian,—all fitted with jaws and teeth, most cruelly bent on mischief, and restrained by no brotherly sympathies when accident or bold defiance bring them in the way of each other. The fell onslaughts of generous man, tribe against tribe, clan to clan, nation to nation, for some inconceivable nothing or unintended provocation, recordedwithin the brief historical epoch, may reconcile one to a picture of the irrationals similarly engaged, and throughout periods of time sufficient for the deposition of the entire oolitic series, before which the rule of earthly dynasties shrinks into utter insignificance.

These depositions accomplished, and successive races entombed within them, there is evidence that the floor of the ocean was raised above the waters, and that central Europe presented, all around, a breast of high land. There are various intercalations, in the series of marine and terrestrial deposits as well as of fresh and salt water fossils. Violent internal convulsions prevailed throughout the period, and the animals were all of a kind to care little for the war of the elements. Meanwhile a fresh water formation is completed in many places a thousand feet in thickness, and consisting of a series of beds; not continuous all round the shores of the oolitic detritus, but confined to a few localities, and characterized everywhere by its own group of organisms. This is the wealden formation. And the question arises, How this series of fresh water clays, and sands, and grits, was produced at a time when the sea prevailed so universally over the whole of continental Europe, and the eastern division of Great Britain? The solution is simpler than at first sight might appear, when viewed in connection with the existing distribution of all our great primary formations. The extent of dry land was such as to furnish watershed for numerous rivers. The mountains supplied the detrital matter. This was brought to the river’s mouth, where it formed deltas; or spread out on the floor of estuaries, where it received the few marine fossils which are found in the formation. Cast your eye along the geological map of western Europe, and—in the mountains of Wales, the silurian district of the north-west of France, the primary rocks of the tributaries of the Elbe, the Hartz mountains, and the gneiss and granites of Sutherland and Caithness—we have all the materials and requisites that are necessary for the silting process of the wealden, its accumulation, and geographical distribution as referred to in its range and extent.

The continuity of the coasts of France and England is herein supposed, and, upon geological data, this is a matter of far simpler inference than the framing even of a political constitution that will stand a decade of the years of our fleeting pilgrimage. Thevision of Plato’s Atlantis in the great ocean becomes in the geologist’s creed a reality, who believes that a vast continent must have existed on our south and west, all now sunk and whelmed in the deep abyss. A chain of islands would just indicate the positions of the Alps, the Pyrenees, the Carpathians, and the Caucasian ranges, all then overlooking central and eastern Europe, not yet elevated above the waves. “At this period,” says Professor Ansted, “it is most probable that no great east and west subterranean movement had acted on the part of the earth’s crust now above the water in the northern hemisphere, and possibly the first intimation of such a disturbing force, may be traced, though faintly, in the existence of a considerable estuary, in which our wealden beds were deposited. From the condition of the upper Portland beds, we find, that, just at the close of the oolitic period, there were very numerous changes of level induced over a small area in the south-east of England, then, most likely, not far from the coast line of a large continent.”

It may seem to many presumptuous, and beyond all the usual latitude of exaggerated description to attempt to dwell thus minutely on physical arrangements, and a vegetable and animal economy, so remote and beyond the sphere of observation. Remarkable enough that our great healing springs of Bath, Cheltenham, Leamington, Tunbridge, and Harwich, are all situated among, or have their origin in, the series of deposits we have been considering. But the judgment, more than the fancy, is employed in studying the geography of the ancient world, in looking out from the heights around, and trying again to unite the waters and the dry land, to recall the vanishing traces of former sea-marks, and from the disinterred remains of the remarkable races that inhabited the island, and swarmed around its coasts, to contemplate the ways and doings of

“That Eternal Mind,Who built the spacious universe, and deckedEach part so richly with whate’er pertainsTo life, to health, to pleasure.”

“That Eternal Mind,Who built the spacious universe, and deckedEach part so richly with whate’er pertainsTo life, to health, to pleasure.”

“That Eternal Mind,Who built the spacious universe, and deckedEach part so richly with whate’er pertainsTo life, to health, to pleasure.”

“That Eternal Mind,

Who built the spacious universe, and decked

Each part so richly with whate’er pertains

To life, to health, to pleasure.”

And these three blessings all are striving to maintain, to restore, or to acquire. Life, health, pleasure—these are the great stimulants to all human exertion, and how best to promote them oughtto be the aim of human study. The suite of rocks which compose the carboniferous system is one clearly of pre-arrangement, and designed for man’s use. The strata, now beneath us, as undeniably evince a like beneficent purpose. The treasures of saline rock, gypseous marls, iron sands, and pyritous clays, may be mysterious all, in their origin: but their uses and their ends, human wants and frailties have long since established. The cravings of appetite satisfied, every creature has an instinct, which unerringly leads it to seek a remedy against injury and disease; and a provision for the one equally with the other, has been made by Him who notices the sparrow in his fall, and careth for the ravens of the desert. Slow of apprehension the mind, that cannot discern in the strata under review, a striking instance of foresight, a gift of benevolent wisdom, recesses long since stored with medicaments and restoratives for human frailties; and, though no angel now is there to trouble the waters, a kind Providence has designed them, and a good heart will use them, as tokens of its love.

II.The Organic Remainsare chiefly of a fluviatile and terrestrial character. The beds in which they occur were deposited in the channel, or delta, of a river of great breadth, and demonstrate the existence of a large extent of neighboring country. These beds range from Hastings into Dorsetshire, but are not found to the north of the Thames. In Portland and the Isle of Wight they likewise exist with all their peculiar organisms in the greatest abundance. In the latter locality, the wealden beds form the cliffs between Atherfield Point and Compton Bay; they also overhang the Bay of Sandown. The Purbeck beds and sands are well displayed at Durdle Cove, Warbarrow, and Swanage Bays; and in the Vale of Wardour the same strata are developed. In every one of these beautiful, picturesque, accessible, and very limited districts, you have congregated specimens of the fauna and flora of rivers, groves, forests, and plains, which have no longer a place on the terraqueous globe. Compared with the living or extinct races they constitute a chapter in natural history nowhere else to be seen or studied.

Thus of eight genera of plants in the wealden, there areonly four common to it and the oolites, but not a single species. Of the hundreds of zoophytes in the older formation, not one occurs in the newer. Twenty genera of insects existed in the period of the wealden, one only of which is prolonged from the antecedent period of oolitic life; one new genus of Crustacean (the Cypris), and five species; while the conchifera have little in common, save the mytilus and unio, and both of which, generically, have been transmitted from the carboniferous era. The fishes of the wealden consist of seven genera, of which only one is new, the Sphenonchus. The reptilians amount to eleven genera, three of which present remains in the oolitic group, Cetiosaurus, Chelonia, and Megalosaurus—same species in both. The Cetiosaurus belongs to the whale race of animals, and it is singular to find the tribe exhibiting the same stupidity, or hardihood it may be, in forsaking, then as now, their briny element, and seeking a grave in the clays and sands of fresh water shoals! The Hylæosaurus and Iguanodon were both found in the Tilgate Forest beds, but have been noticed under the fauna of the oolite series, as probably living in the age of, as they approach so closely in structure and size to, the reptilian types of the deposit; frequenting the woods and pastures, while their mighty cotemporaries were following their instincts in the seas and lakes of the district.

It would thus appear that the close of the oolitic period of the earth’s history resembles the close of the carboniferous period, in the sudden transition from an exuberant to a remarkably barren display of vegetable fossils. In the comparative scantiness of the sauroid family of fishes, by which the outgoing of the coal era is likewise distinguished, we may fancy another point of analogy in the diminution of the monstrous reptilians that appears to have taken place after this series of deposits. May it be inferred that these two periods enjoyed a higher degree of temperature than has prevailed, either before or since, generally over the earth’s surface, and more certainly in these northern latitudes? Interred among the strata of both lie the remains of races, vegetable and animal, which have perished: and what we describe by kindred names are confined to climes and regions basking near the equator, and enlightened by other constellations. Then the alternating deposits of clay, lime, ironstone, coal, salt, gypsum, speak oflakes and estuaries, rolling rivers and high lands no longer existing in these parts. A few leaves of their annals are inscribed with forms of grotesque life, and stirring activities, which are there to attest the majesty of their revolutions. Geology, in little more than twenty years, has made the discovery, collected the facts, arranged and systematized the knowledge of the character and habits of the successive generations whose domain, whether of land or water, was so different from ours, and now all passed away.

A higher temperature, from central heat, will not explain these facts, for that should have prevailed more in the devonian, and still more in the silurian periods,—and of this we have no evidence. Appearances would rather support an opposite conclusion. The sweep of the comet again, resorted to upon occasions, may have destroyed, but could not maintain, such a state of things. A change of the polar axis, of the most inconsiderable extent, is demonstrated to be highly improbable, or almost impossible. And now, in the unwearied march of science, often baffled but never cast down, it has been announced as the probable solution of all the changes of the past,the progression of the whole solar system, whereby the earth, and all the sister planets, are dragged through infinite space, and brought successively within the sphere of new constellations—now in a hotter and now in a milder efflux of ether—combining its own with a more general movement in a universal whirl—and thus constantly subjected, in all its parts, to ever-varying external influences! This, at least, is the ingenious theory of M. Poisson, which, he thinks, will account for the central heat of the globe, dipped for a time into a burning atmosphere, and cooling off more rapidly on the surface, and will give a no less plausible explanation as to the extent and frequency of change effected on the surface. Geology and astronomy become, when viewed in this light, correlative sciences, and impart an illustrative interest to the researches of each other. The lofty flights of the one are brought down, as it were, to more earthly things; while the geologist, on the other hand, is lifted from his miry pit and downward studies, to meditate on the “sweet influences and bands” that harmonize and link all the planets in their orbits, and rejoices to see his own earth taking part in the eternal music of thespheres. He is pleased to believe, according to the view of the astronomer, that this ball of stone and clay enjoys at times a vitality all over, which warms and cherishes into life natant forms, and creeping things, and flying dragons, whose development of powers could not have been sustained, on so great a scale, in the lower and less favored regions.

But while the cause may be adequate to the effect—and in the approximation to the truth there is a feeling of satisfaction, an elevation of vision and elasticity of thought, as

“Rays divine dart round the globe,”

“Rays divine dart round the globe,”

“Rays divine dart round the globe,”

“Rays divine dart round the globe,”

—still the speculation referred to belongs rather to the poetry than to the philosophy of science, influencing the imagination more than the judgment, and trenching on relations that lie beyond the field of legitimate research.

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