Search just our sites by using our customised search engine
Unique Cottages | Electric Scotland's Classified Directory

Click here to get a Printer Friendly Page

First Impressions of England and its People
Chapter XII


Geological Coloring of the Landscape. — Close Proximity in this Neighborhood of the various Geologic Systems. — The Oolite ; its Medicinal Springs; how formed. — Cheltenham. — Strathpeffer. — The Saliferous System ; its Organic Remains and Foot-prints. — Record of Curious Passages in the History of the Earlier Reptiles. — Salt Deposits. — Theory. — The Abstraction of Salt from the Sea on a large Scale probably necessary to the continued Existence of its Denizens. — Lower New Red Sandstone. — Great Geologic Revolution. — Elevation of the Trap. — Hills of Clent; Era of the Elevation. — Coal Measures ; their three Forests in the Neighborhood of Wolverhampton. — Comparatively small Area of the Birmingham Coal-field. — Vast Coal-fields of the United States. — Berkeley’s Prophecy. — Old Red Sandstone. —Silurian System. — Blank.

Let us now raise from off the landscape another integument, — let us remove the boulder clays and gravels, as we formerly removed the vegetable mould, and lay the rock everywhere bare. There is no longer any lack of color in the prospect; it resembles, on the contrary, a map variously tinted by the geographer, to enable the eye to trace his several divisions, natural or arbitrary. The range of trap-hills which furnishes our peak of survey is of a deep olive-green; the New Red Sandstone that spreads out so widely around it, of a bright brick-red. There is a coal-field on either hand, — the barren field of the Forest of Wyre, and the singularly productive field of Dudley; and they both are irregularly checkered black, yellow, and gray. Beyond the Wyre field lies an immense district of a deep chocolate-red tint,— a huge development of the Old Red Sandstone. Still further beyond, we may discern in the distance a bluish-gray province of great extent, much broken 20 into hills, which consists of an at least equally huge development of the Silurian; while, rising over the red saliferous marls in an opposite direction, we may see a series of flat, low-lying rocks of the Oolitic system, passing from a pale neutral tint into a smoky brown and a light straw-yellow. In such close proximity are the geological systems in this part of the country, that the geologist who passes the night in Birmingham on the Lower New Red Sandstone, may go and take an early breakfast on the Silurian, the Old Red, the Carboniferous, the Saliferous, or the Oolitic systems, just as he inclines. Good sections, such as our northern sea-coasts furnish, are all that are wanting to render the locality one of the finest in the kingdom to the student of the stony science: but these he misses sadly; and he, alas! cannot deal with the stubborn integuments of the country in reality, as we are dealing with them so much at our ease in imagination, on one of the summits of the Clent Hills.

The integument that falls to be examined first in order, after the boulder drift and the gravels, is the Oolitic one; but it occupies merely a comer on the verge of the horizon, and need not engage us long. One remark regarding it, however, though rendered familiar to the geologic reader by the writings of Murchison and Mantell, I shall venture to repeat. We have seen how this central district of the kingdom has its storehouses of coal, iron, salt, lime, — liberal donations to the wants of the human animal, from the Carboniferous, Saliferous, and Silurian systems; and to these we must now add its inexhaustible deposits of medicine, — contributions to the general stock by the Oolitic system. Along the course of the Lias, medicinal springs abound; there is no other part of England where they rise so thickly, or of a quality that exerts a more powerful influence on the human frame. The mineral waters of Cheltenham, for instance, so celebrated for their virtues, are of the number; and the way in which they are elaborated in such vast quantities seems to be simply as follows: — They all rise in the Lias, — a formation abounding in sulphate of iron, lime, magnesia, lignite, and various bituminous matters; but they have their origin far beneath, in the saliferous marls of the Upper New Red, which the Lias overlies. In the inferior formation they are simply brine springs : but brine is a powerful solvent; passing through the Lias, it acts upon the sulphur and the iron; becomes, by means of the acid thus set free and incorporated with it, a more powerful solvent still operates upon the lime, upon the magnesia, upon the various lignites and bitumens; and at length rises to the surface, a brine-digested extract of Liasic minerals. The several springs yield various analyses, according to the various rocks of the upper formation which they pass through, — some containing more, some less lime, sulphur, iron, magnesia; but in all the dissolving menstruum is the same. And such, it would appear, is the mode in which Nature prepares her simples in this rich district, and keeps her medicine-chest ever full.

Let us trace the progress of a single pint of the water thus elaborated, from where it first alights on the spongy soil in a wintry shower, till where it sparkles in the glass in the pump-room at Cheltenham. It falls among the flat hills that sweep around the ancient city of Worcester, and straightway buries itself, all fresh and soft, in the folds of the Upper New Red Sandstone, where they incline gently to the east. It percolates, in its downward progress, along one of the unworkable seams of rock-salt that occur in the superior marls of the formation; and, as it pursues, furlong after furlong, its subterranean journey, savors more and more strongly of the company it keeps; becomes in succession hard, brackish, saline, briny; and then many fathoms below the level at which it had entered, escapes from the saliferous stratum, through a transverse fissure, into an inferior Liasic bed. And here it trickles, for many hundred yards, through a pyritiferous shale, on which its biting salts act so powerfully, that it becomes strongly tinctured by the iron oxide, and acidulated by the sulphur. And now it forces its upward way through the minute crevices of a dolomitic limestone, which its salts and acids serve partially to decompose; so that to its salt, iron and sulphur, it now adds its lime and its magnesia. And now it flows through beds of organic remains, animal and vegetable, — now through a stratum of belemnites, and now a layer of fish, — now beside a seam of lignite, and now along a vein of bitumen. Here it carries along with it a dilute infusion of what had been once the muscular tissue of a crocodile, and here the strainings of the bones of an ichthyosaurus. And now it comes gushing to the light in an upper Liasic stratum, considerably higher in the geologic scale than the saliferous sandstones into which it had at first sunk, but considerably lower with reference to the existing levels. And now take it and drink it off at once, without pause or breathing space. It is not palatable, and it smells villanously; but never did apothecary mix up a more curiously-compounded draught; and if it be not as salutary as it is elaborate, the faculty are sadly in error.

The underground history of the mineral springs of Great Britain would form an exceedingly curious chapter. I visited, a few weeks since, the springs at Strathpeffer, and explored, as carefully as rather imperfect sections and rather limited time permitted, the geology of the valley. The lower hills that rise around it are composed of the great conglomerate base of the Old Red Sandstone system. The denudation of ages has swept every trace of the superior strata from their sides and summits; but in the sheltered trough of the valley at least one of the overlying beds has escaped. We find laid at length along the hollow bottom, like a pancake in a platter, the lower ichthyolitic bed of the formation, so rich in other parts of the country in animal remains, but which exists in this locality as a gray brecciated rock, devoid of visible fossils, but so largely saturated with the organic matter into which they have been resolved, that, when struck by the hammer, the impalpable dust set loose affects very sensibly the organs of taste, and appeals scarce less strongly to those of smell than the swine-stones of England. And it is through this saturated bed that the mineral waters take their course. Even the upper springs of the valley, as they pass over it, contract, in a sensible degree, its peculiar taste and odor. The dweller on the sea-coast is struck, on entering the pump-room, by the familiarity of the powerful smell which fills the place. It is that of a muddy sea-bottom when uncovered by the ebb. He finds that, whatever else may have changed within the rock since the times of the Lower Old Red Sandstone, the scent of the ancient ooze of this system is exactly what it ever was; and he drinks the water, convinced, if a geologist, that if man did not come early enough in the day to breakfast on the fish of the Old Red, —Acantwdiens, Dipteriens, Coccostei, and Pterichthyes, — he has at least come quite in time enough to gulp down as medicine an infusion of their juices and their bones.

We strip off the Liasic integument, “ as ye peel the fig when its fruit i6 freshand it is with the Upper New Red formation, on which the Lias rests, — its saliferous marls and vast beds of rock-salt, — that we have now to deal. There occurs among the superior strata of the formation a bed of variously-colored sandstone, of little depth, but great horizontal extent, remarkable for containing, what in England at least is comparatively rare in the New Red, organic remains. We find it 20*' chiefly characterized by an inequilateral bivalve, not larger than a small pea, which conchologists term the Posidonomya; and by the teeth and ichthyodorulites of fishes: on the surface, too, of some of its ripple-marked slabs, curious records lie inscribed of the doings of the earlier reptiles. On one large slab in the Warwick Museum, figured by Sir Roderick Murchison, we may see the footprints of some betailed batrachian, that went waddling along, greatly at its leisure, several hundred thousand years ago, like the sheep of the nursery rhyme, “trailing its tail behind it.” There is a double track of footprints on the flag, — those of the right and left feet: in the middle, between the two, lies the long groove formed by the tail, — a groove continuous, but slightly zig-zagged, to indicate the waddle. The creature half-way in its course lay down to rest, having apparently not much to do, and its abdomen formed a slight hollow in the sand beneath. In again rising to its feet, it sprawled a little; and the hinder part of its body, in getting into motion, fretted the portion of the surface that furnished the main fulcrum of the movement, into two wave-like curves. The marks on another slab of the same formation compose such a notice of the doings of one of the earlier che-lonians as a provincial editor would set into type for his newspaper, were the reptile My Lord Somebody, his patron. The chelonian journeyed adown a moist sandy slope, furrowed by ripple-markings, apparently to a watering-place. He travelled leisurely, as became a reptile of consequence, set down his full weight each step he took, and left a deep-marked track in double line behind him. And yet, were his nerves less strong, he might have bestirred himself; for the southern heavens were dark with tempest at the time, and a thunderous-like shower, scarce a mile away, threatened to wet him to the skin. On it came: and the large round drops, driven aslant by a gale from the south, struck into the sand like small shot, at an angle of sixty. How the traveller fared on the occasion has not transpired; but clear and palpable it is that he must have been a firm fellow, and that the heavy globular drops made a much less marked impression on the sand consolidated by his tread, than when they fell elsewhere on the incoherent surface around him. Such are two of the curious old-world stories recorded on this upper bed of New Red Sandstone; and there are many more of the same class. A lower bed of light-colored stone occupies the base of the saliferous system, forming its pavement, and separating it from the inferior New Red. And this bed has also its organisms, chiefly vegetable,—flabelliform palm-leaves, — narrow, slender spikes, resembling those of the grasses,— and a peculiarly formed ear-like cone or catkin, termed the echinostachys. And these constitute some of the earliest remains known to the geologist of a flora specifically different from that of the Coal, Measures. Interposed between this pavement and the fossiliferous sandstone band above, there occurs a vast thickness of saliferous marls, interstratified with those enormous beds of rock-salt, continuous over wide areas, in which all the salt-mines of England have been excavated, and which now forces upon us, a second time, the problem of the saliferous deposits. The wind-bound ship-master, detained in port long after the specified day of sailing, takes instruments in the hands of a legal official, and, “ protesting against the weather,” frees himself from all risk of prosecution from passenger or supercargo. I have already, in like manner, entered my protest against the difficulties which environ this subject; and shall now launch into it, shielded by the document against the responsibility of failure, or the odium consequent on entering a wrong port.

If in the existing state of things we seek for phenomena similar in kind, to those which produced the Coal Measures, we shall not be disappointed; but we shall be greatly disappointed if we seek for phenomena not only similar in kind, but also equal in power. An American swamp or a Scotch morass gives us but the equivalent of a single thin seam of coal; a submarine peat-moss, based on a layer of vegetable mould, and topped by a bed of sea-sand, the equivalent merely of a single thin seam, resting on an earthy shale, and overlaid by a shelly sandstone. Swamp, morass, submerged peat-moss, nay, even if we add to these some river delta, which, like that of the Mississippi, receives the spoils of a wide forest-covered continent, are but slender representatives of even our Scottish coalfield, with its three hundred and eighty-seven successive beds, of which eighty-four are seams of coal. We must be content, in our illustrations drawn from the present scene of things, with phenomena similar in kind, without looking for aught corresponding in extent. Even had we now the Carboniferous vegetation, the stiff and rigid earth, grown old, would not exhibit the ever-recurring sinkings, with occasional risings, of surface, which buried the lower beds of the Carboniferous system full four thousand feet beneath its upper deposits. Now, in dealing with the Saliferous system, let us content ourselves, as in dealing with the Coal Measures, with simply illustrating the foregone phenomena by phenomena of the existing state of things apparently similar in kind, though palpably dissimilar in extent and degree. Let us take for granted, as we do in the case of the Carboniferous period, a comparatively flexible state of the earth’s crust, — frequent sinkings of the surface, with occasional risings and progressive depositions of matter, that keep pace with the general subsidence. And let us then refer to some of the salt formations of the present time, as illustrative of the way in which, amid greatly more active energies of nature, vastly more enormous deposits of this mineral came to be formed; just as our writers on the Coal Measures refer, on a similar understanding, to existing swamps and mosses.

We are told by Major Harris, in his “Highlands of Ethiopia,” that when on his journey, he reached, with his party, near the Abyssinian frontier, a desert valley, occupied by a salt lake, the Bahr Assal, which forms a prolongation of the Gulf of Tadjura. A broad bar of lava had cut off its waters from those of the gulf; and, fed by no rivers, and exposed in a burning climate to the unmitigated rays of the sun, intensified by reflection from hot rocky mountains, they had shrunk into “an elliptical basin, seven miles in its transverse axis, half-filled with smooth water of the deepest cerulean hue, and half with a solid sheet of glittering, snow-white salt, the offspring of evaporation.” Here, at least, was one extensive bed of salt in the forming; nor is it difficult to conceive how: the work of evaporation completed, and the entire lake rendered a white, solid mass, some general sinking of the surface continued, till the waves of the outer gulf toppled for a time over the lava bar, and then, succeeded, as such sinkings so often were during the Carboniferous period, by a slight elevatory movement, might give to it a second supply of brine with which to double its thickness. We find no lava bars in the saliferous sandstone ; but sand-bars raised by the surf on a flat arenaceous coast during a slow and equable sinking of the surface, would meet the emergencies of our theory less clumsily, and better. Let us conceive, then, along a range of flat coast extending from the northern parts of Lancashire to the Bristol Channel, a chain of lagoons, some of lesser, some of larger extent, and separated from the main sea by sand spits or bars raised by the surf; let us suppose the climate to be at least as warm as that on the African shore of the Ked Sea, in which the salt of the Bahr Assal is forming ; let us imagine a subsidence of the land going on so exceedingly slow and gradual as to be counterbalanced by the deposition of earthy matter taking place in the sea on the one hand, — by the crystallization of the salt in the lagoons, fed by occasional supplies of salt water, on the other, — and by the rise of the bar, ever operated upon by the surf, in the line between. A paroxysm of sudden subsidence would, of course, bring the formation of the salt-bed to a close, and cover it up with a stratum of sand or marl; a slight elevatory movement succeeding the paroxysm would have the effect of rendering the superimposed stratum the foundation of a second lagoon and second bed of salt. According as the periods between the elevatory movements and the paroxysms of subsidence were long or short, the beds of salt would be thick or thin. Among the five beds that occur at Stoke Prior, in the vicinity of Droitwich, there is one more than thirty feet in depth, and one not more than six inches. According as the duration of the term of submergence was extended or brief, would be the thickness or thinness of the bars by which the salt-beds were separated. At Stoke Prior, one of these separating bars falls short of three feet, while another somewhat exceeds twenty-four. As the lagoons chanced to be well or ill protected from the introduction of extraneous matter, the salt which formed in them would be pure or impure. One of the Stoke Prior beds contains full twenty-five per cent, of reddish marl, while another is so unmixed with earthy matter that it might be used, without any previous refining preparation, for the purpose of the fish-curer. And thus deposition after deposition would take place, and, as in the Coal Measures, subsidence succeed subsidence, until the entire Saliferous system would come to be formed. It has been started as an objection to the lagoon theory, that the salt-beds contain no organic remains, which, it is held, they would have done had they owed their origin to sea-water. I am, however, not sure that the objection is particularly strong. Let us remember that the organisms of the entire system in England are but few and ill preserved, and that the marls which alternate with the salt have failed to preserve ’organisms at all; while the shells of the superior band occur but as mere casts in an incoherent clay. Let us further remember what takes place in the upper pots and hollows of our rocky shores, when, at the height of a stream-tide, they receive their fill of sea-water mingled with sea-wrack, and are then left during the neaps to present their festering contents undisturbed and undiluted to the influence of the sun. Their waters assume a turbid blue color and a strong fetid odor, and become in this state so powerful a dissolvent, that a few warm days converts the wrack which they contain into an impalpable mud. Further, it may be deemed a fact worthy of consideration, as at least not hostile to the sea-water theory, that the rock-salt of England contains, like the bilge-water of these tide-forsaken pots, a considerable admixture of iodine, — a substance which enters largely into the composition of the sponges and marine algae.

Single masses of salt, like those of Cordova, might come to be elaborated by a greatly more simple process. The Mediterranean is not an intertropical sea ; but what, notwithstanding, would be the probable result, were it to be cut off from the Atlantic by some such bar of rock as severed the Bahr AssaL from the Gulf of Tadjura ? There is no other inland sea that, in proportion to its extent of surface, receives such scanty contributions of river water; and, to supply the waste of evaporation from its million of square miles of surface, its deep throat is continually gulping up the waters of the Atlantic at the rate of many thousand tons hourly. A powerful current flows incessantly inwards through the Straits of Gibraltar, and yet the level within is not more than maintained. Were the Atlantic excluded, the inland sea would of course gradually dry up, until its area had so considerably lessened that its rivers would be of themselves sufficient to counterbalance its waste of surface; and were its rivers wanting, as might well be the case had it a Desert of Sahara on its northern, as on its southern side, even its profounder depths of more than a thousand fathoms would in time evaporate, and but enormous beds of salt remain behind. It seems not improbable, that the loose arenaceous materials of the New Red Sandstone may have existed, ere they formed an ocean bottom, as the incoherent sands of some geologic Sahara that encircled the inland seas and lagoons of this system, and that a consequent lack of rivers may have operated influentially in the formation of the salt. By the way, may not this process of separating huge deposits of this mineral from the sea, — a process which has been going on, we find, in every formation, from the Onondaga salt group of the Upper Silurian, as developed in the United States of America, down to the recent salt-lakes of the Asiatic basin, — be a provision in nature for preserving to the ocean its proper degree of density and saturation ? In the natural course of things, the sea would necessarily be growing salter and heavier. The waves wash out of every shore, and receive from every river, minute supplies of salt, which evaporation has scarce any tendency to dissipate, and which, in the lapse of ages, would be necessarily accumulating in the waters, till the delicate gills and branchiae of the various inmates, formed with reference to a rarer medium, would labor amid the dense and briny fluid, and their bodies, heretofore of a gravity exactly proportioned to that of their element, but now grown too light for it, would float helplessly atop. True, the salt seems in every instance to have been abstracted and locked up by accident; but then the recurrence of the accident in every geologic formation demonstrates it to be one of those on which the adept in the doctrine of chances might safely calculate. It seems an accident of the fixed class on which Goldsmith bases his well-known reflection in the “Vicar of Wakefield.” “To what a fortuitous concurrence,” he remarks, “do we not owe every pleasure and convenience of our lives! How many seeming accidents must unite before we can be clothed or fed! The peasant must be disposed to labor, the shower must fall, the wind fill the merchant’s sail, or numbers must want the usual supply.”

And now we strip off the thick saliferous integument of the Upper New Red, with all its marls, rock-salts and sandstones, and lay bare the lower formation. Within at least the range of our prospect, we shall find in it few marks of organic existence, arid these few doubtful and indistinct. Some of the red incoherent sandstones which form its base contain carbonaceous markings, but of a character too obscure to be interpreted; and we may occasionally detect in the calcareous conglomerate above — its upper member — shells and encrinital stems; but they occur in merely the enclosed fragments, and belong to the older rocks. And yet there attaches no little geologic interest to this barren formation: it marks the era of a great change. The rugged conglomerate, which rises so high along the flanks of the hill on which we stand, represents in this locality the Magnesian Limestone, — the formation with which the long-derived and darkly-antique Palaeozoic systems end, and on whose upper platform the first of the Secondary systems begins. A strange shifting of scenes took place on that rough stratum at our feet; but it would seem as if the theatre had been darkened when the alterative process was going on. The lamps burnt low, and concealed the machinery of the stage. In the long course of geologic history there have been many medals struck, — many previous to the time of this revolution, and many after it; but none records the nature of the revolution itself; nor is there geology enough in the world to fill up the gap. It yawns in the middle of the forum, and no one has dared to fling even a plausible conjecture into it. Up till the deposition of that Magnesian stratum had taken place, all the fish of which we possess specimens sufficiently well-preserved to indicate the fact were characterized by the heterocercal tail, — the vertebral column was prolonged into the upper lobe of the caudal fin ;1 but with that stratum the peculiarity ceased, and fishes with the homocercal tail of our common osseous varieties took their place. In that Magnesian formation, too, just ere the occurrence of the revolution, we find the first trace of reptiles. The long drama of the Palaeozoic period, with all its distinct acts, ended with the dethronement of the huge sauroid fish,—for untold ages the master existence of creation; and the new-born reptile reigned in its stead. We find, too, numerous well-known types of shells, familiar in the older rocks, appearing in this formation for the last time. So far as is yet known, the Magnesian Limestone contains the last-created species of Producta, and the last-created Spirifer. We ascertain that these shells continued to exist up till the breaking out of this great geologic revolution, and that then, like some of the extinct French noblesse cut short by the guillotine, they disappear forevermore. And now, raising from off the landscape this curious integument, and setting it aside, as Signor Sarti removes to a side-table one of the bits of his figure, — a piece of the external skin, mayhap, thickened by its adipose lining or a well-compacted sheet of muscle and sinew, — we lay bare the coal-fields, and the range of trappean eminences that broke them up as with wedges, just as their upper strata had been consolidated, and they had received their first thin covering of the Lower New Red.

I must, I find, employ, though with considerable modifications, an illustration which I have used at least once before. Here is a small shallow pond, covered over with a thick cake of ice, and with a line of boulders rising in its centre. There have been two frosts and an intervening thaw. Just as the first frost set in, the boulder tops lay under the surface, and the earlier-formed crust of ice stretched over them; but, as frequently happens when the temperature sinks suddenly below the freezing point, a great shrinking of the water took place : the ice, unsupported from beneath, leaned for a little while on the boulders, and then giving way on both sides, half-way between their summits and the shore, and, as a direct consequence, cracking also directly over them, the summits came through, and the ice-sheets lay reclining in masses against them, broken by faults, and shivered by transverse cutting's. At this stage, however, the thaw came on, and encircled with a shallow ring of water, that rose over the depressed surface, the central patch of shivered ice, and the boulders in the midst; and then the second frost set in, and the shallow liquefied ring became a solid. Now, let us mark the phenomena exhibited. There, first, in the centre of the pond, rises the line of boulders. There is an isolated area all around them, — a formation of the earlier frost, much broken by faults; and these radiate from the stones rudely and irregularly, but still, on the whole, distinctly enough to indicate the boulder-line as a producing cause of the fracturing and dislocation. And then, around this broken and disjointed area, we find an encircling formation of the later frost, — the solidified ring, — in which there are no faults or cuttings, but in which all is undisturbed and entire. Our geological model is now complete; that row of boulders represents the chain of Trap and Silurian hills which runs along the Dudley coal-field, and whose elevation from below has so broken up the formation with long lines of radiating faults and transverse fractures. The fractured, insulated area of the ice of the first frost represents the coal-field itself; the unbroken enveloping ring of the second, the surrounding New Red Sandstone.

Now, there are several points worthy of notice in this model. Observe, first, that we can ascertain with great certainty, relatively at least, at what period the dislocations and fracturings of the central area took place. They occurred at the close, or not long after the close, of the first ice formation, and not later; for had they taken place during the time of the second ice formation, it also would have been broken up, whereas we find it entire. Observe, next, that under the shallow solidified ring of the second frost we may naturally expect to find existing, as a nether stratum, a prolongation of the shattered ice of the first.

And founding on exactly this simple principle, the New Red Sandstone of this part of the country, i. e. the unfractured ice of the second frost, has been lately pierced through, to get at the Coal Measures, i. e. the fractured ice of the first; and very valuable though deeply-seated seams of coal have repaid the boldness of the search, and confirmed the justness of the reasoning. Observe, further, that this broken condition of the coalfield, if its surface were bared in the style we have dared to uncover it from our hill-top, as Asmodeus uncovered the houses of Madrid, would present, viewed from above, a very striking appearance. Of the twelve panes in the window opposite to which I write, by far the most conspicuous is the pane through the centre of which an unlucky urchin sent yesterday a stone. There is a little hole in the middle, from which some fifteen or twenty bright rays proceed, star-like, to every part of the astragal frame. The ray-like cracks of the coal-field are, of course, wholly obscured by the diluvium and the vegetable mould. A shower of snow — to return to our first illustration — has covered up, with a continuous veil, central boulders, flawed area, and encircling ring, reducing them all to one aspect of blank uniformity; and we can but dip down upon the cracks and flaws, here the point of a finger, there the end of a stick; and so, after many soundings have thus been taken, piece out a plan of the whole. It would seem as if, in at least one of the planets to which we point the telescope, there is no such enveloping integument; and the starred and fractured surface remains exposed and naked, like that of the ice of the pond ere the snow-shower came on. Those who have enjoyed the luxury of hearing Professor Nichol, of Glasgow, lecture on the lunar phenomena, must remember his graphic description of the numerous ray-like lines, palpable as the cracks in a damaged pane, that radiate in every direction, some of them extending for hundreds of miles, from all the larger craters of the moon.

There are not a few interesting appearances in this Dudley coal-field. Its seams, like those of every other coal-field yet known, have been formed under very various conditions : some of them must have been deposits of vegetable matter washed by rivers into seas or lakes; some of them seem to have formed in marshy hollows, like our existing peat-mosses, or, if we must seek out analogies from somewhat warmer climates than those in which peat is elaborated, like the Dismal Swamp of the United States; and some evidently covered as great forests the sites which they now occupy as coal-seams. There is a colliery about a mile and a half to the south of Wolverhampton, where an outcrop of what is termed the bottom coal is wrought in the open air. The surface, in consequence, has been bared of the debris and diluvium, and in one corner the upper plane of a thin seam of coal exposed for about a quarter of an acre. It is found to present exactly the appearance of a moor on which a full-grown fir wood had been cut down a few months before, and only the stumps left behind. Stump rises beside stump, to the number of seventy-three in all: the thickly-diverging roots strike out on every side into what had been once vegetable mould, but which now exists as an indurated, brownish-colored shale. Many trunks, sorely flattened, lie recumbent on the coal, some of them full thirty feet in length, while some of the larger stumps measure rather more than two feet in diameter. There lie thick around, stigmaria, lepido-dendra, calamites, and fragments of ulodendra; and yet, with all the assistance which these lent, the seam of coal formed by this ancient forest does not exceed five inches in thickness. It must have required no little vegetable matter to consolidate into the mineral which supplies us, year after year, with our winter fuel; the coal which loads a single large collier would, when it existed as wood, have built many large colliers. Not a few of the stumps in this area are evidently water-worn; and there have been found immediately over them scales of Megalichthys, and the shells of an Unio, somewhat resembling in form the common pearl muscle of our rivers, but considerably smaller. The prostrate forest had been submerged, and molluscs lived and fishes swam over it. It is further worthy of notice, that this upper forest is underlaid, at the depth of a few feet, by a second forest, in which the stumps lie as thickly, and are of as great a size, as in the first; and that this second forest is underlaid, in turn, by the remains of yet a third. We find three full-grown forests closely packed up in a depth of not more than twelve feet.

Once more, ere we wrap up this Carboniferous integument of the landscape, and lay bare the Old Red Sandstone, let us mark to how small a coal-field central England has, for so many years, owed its flourishing trade. Its area, as I have already had occasion to remark, scarcely equals that of one of our larger Scottish lakes ; and yet how many thousand steam-engines has it set in motion, — how many railway trains has it propelled across the country, — how many thousand wagonloads of salt has it elaborated from the brine, — how many million tons of iron has it furnished, raised to the surface, smelted, and hammered ! It has made Birmingham a great city, — the first iron depot of Europe ; and filled the country with crowded towns and busy villages. And if one small field has done so much, what may we not expect from those vast basins, laid down by Lyell in the geological map of the United States, prefixed to his recent singularly interesting work of travels? When glancing, for the first time, over the three huge coalfields of the States, each surrounded by its ring of Old Red Sandstone, like patches of mineral bitumen floating in their clay-tinged pools, I called to mind the prophecy of Berkeley, and thought I could at length see, what Berkeley could not, the scheme of its fulfilment. The metaphysical bishop marked the westward course of empire : he saw Persia resigning the sceptre to Macedonia, and Macedonia yielding it, in turn, to Rome, and to those western nations of Europe that abut on the Atlantic. And at a time when North America was still covered with the primeval forests, he anticipated an age in which that country would occupy as preeminent a place among the nations as had been occupied in other ages by Assyria or Rome. Its enormous coal-fields — equal in extent, some of them, to all England, and whose dark seams, exposed to the light for miles, inlay the landscape as with ebony, and impart to it its most striking peculiarity of feature — seem destined to form no mean element in its greatness. If a patch containing but a few square miles has done so much for central England, what may not fields containing many hundred square leagues do for the United States?

“Westward the course of empire takes its way;
The four first acts already past,
A fifth shall close the drama with the day:
Time’s noblest offspring is the last.”

And now, stripping off the dark Coal Measures like a pall, we expose the chocolate-colored beds of the Old Red Sandstone. In our immediate neighborhood there is a hiatus in the geologic series, — the Carboniferous system rests on the Silurian ; but westwards, and on to the south-west, we may see the Old Red Sandstone stretching away in enormous development. As estimated by a practised eye, — that of Sir Roderick Murchison, — its entire thickness in this part of the country falls little short of ten thousand feet. Here, as everywhere else, it seems chiefly re .narkable for its strange forms of the vertebrate animals, exclusively fish. The Upper Old Red formation, so rich in Scotland in the remains of Holoptychius,

Bothriolepis, and their contemporaries, is comparatively barren in England. The middle formation, however, we find mottled with ichthyolitic fragments, representative of the two great orders of fish in which, at this early period, and for long ages after, all vertebrate existence was comprised. Fragments of the ichthyodorulites of Placoids are not unfrequent; and the occipital plates of the Ganoid Cephalaspides abound. The true fish seems to have overspread and taken full possession of the seas during the deposition of this system, as the Trilobite had taken possession of them in the preceding one. But we hasten on: the thick Old Red coils up and away, like a piece of old elastic parchment that had been acquiring for ages the set of the roll; and now the still more ancient Silurian system occupies the entire prospect. In this system the remains of the vertebrate animals first appear, — few and far between, and restricted, so far as is yet known, to its great upper division exclusively. We pass hurriedly downwards. The vertebrata vanish from creation. We have traced the dynasty to its first beginnings; and now an ignobler, though more ancient, race of kings occupy the throne. We have reached, in our explorations, the dynasty of the crustacea. In all creation, as it exists in this period of dusk antiquity, we see nothing that overtops the Trilobite, with his jointed mail of such exquisite workman-prints of this eldest of reptiles should be found so far in advance of what has been long deemed the vanguard of its order, — the thecodent Saurians of the Permian, — and this, too, in a system so carefully explored as the Coal Measures ; and yet the occurrence is not without a parallel in the geologic scheme. The mammal of the Stonesfield Slate stands as much alone, and still further in advance of its fellows. I do not find that I have anything to alter in my statement regarding the introduction of the fish. In Professor Silliman’s American Journal for January 1846, it is stated, that an ichthyodorulite had been just discovered in the Onondago Limestone of New York, and an imperfectly-preserved fish-bone in the Oris-kany Sandstone of the same state. There seems, however, to be no reason to conclude from their contemporary organisms, — chiefly shells and corals, which closely approximate to those of the Wenlock Limestone, — that either of them belonged to a more ancient fish than the ichthyodorulite described by Mr. Sedgwick, to which I have already had occasion to refer. It seems not unworthy of remark, that while among the fish of the Old Red Sandstone considerably more than three-fourths of the species, and greatly more than nineteen-twentieths of the individuals, are of the Ganoid order, all the fish of the Silurian system yet discovered are Pla-coids. [The statement here regarding the absence of fish in the Lower Silurian, which I retain in a second edition, as it may serve to indicate the onward march of geological science, was in accordance, only a few months ago, when the first edition of this work appeared, with what was known of the more ancient rocks and their fossils. But it also illustrates, like my statement respecting the reptiles of the Permian, the unsolid character of negative evidence, when made the basis of positive assertion. It is now determined that the Lower, like the Upper Silurian, has its fish. “Alas for one of my generalizations, founded on negative evidence, on which you build !5 ’ says Sir Roderick Murchison, in a communication which I owe to his kindness. c< The Lower Silurian is no longer to be viewed as an invertebrate period ; for the Onchus (species not yet decided) has been found in Llandeilo Flags, and in the Lower Silurian Rocks of Bala. In one respect I am gratified by the discovery ; for the form is so very like that of the Onchus Murchisoni of the Ludlow Rocks, that it is clear the Silurian system is one great natural-history series, as proved, indeed, by all its other organic remains.” — Second    ] ship, and his prominent eye of many facets, that so capriciously refuses to admit the light through more or less than just its four hundred and ten spherical lenses. The Cephalopoda, indeed, may have held with him a divided empire; but the Brachiopoda, the Pteropoda, the Gasteropoda, and the Ace-phala, must have been unresisting subjects, and all must have been implicit deference among the Crinoidea, the Pennularia, the Corals, and the Sponges. As we sink lower and lower, the mine of organic existence waxes unproductive and poor: a few shells now and then appear, a few graptolites, a few sponges. Anon we reach the outer limits of life: a void and formless desert stretches beyond, and dark night comes down upon the landscape.


Return to Book Index Page

 


This comment system requires you to be logged in through either a Disqus account or an account you already have with Google, Twitter, Facebook or Yahoo. In the event you don't have an account with any of these companies then you can create an account with Disqus. All comments are moderated so they won't display until the moderator has approved your comment.

comments powered by Disqus

Quantcast