Directly in the gorge of the ravine, where we may see the partially wooded banks receding as they ascend from the base to the centre, and then bellying over from the centre to the summit, there is a fine chalybeate spring, surmounted by a dome of hewn stone. It was discovered by the miners when in quest of the mineral which they did not and could not discover, and forms one of the finest specimens of a true Artesian well which I have any where seen. They had bored to a considerable depth, when, on withdrawing the kind of auger used for the purpose, a bolt of water, which occupied the whole diameter of the bore, came rushing after, like the jet of a fountain, and the work was prosecuted no further; for, as steam-engines were not yet invented, no pit could have been wrought with so large a stream issuing into it; and as the volume was evidently restricted by the size of the bore, it was impossible to say how much greater a stream the source might have supplied. The spring still continues to flow towards the sea, between its double row of cresses, at the rate of about a hogshead per minute—a rate considerably diminished, it is said, from its earlier volume, by some obstruction in the bore. The waters are not strongly tinctured—a consequence, perhaps, of their great abundance; but we may see every pebble and stock in their course enveloped by a ferruginous coagulum, resembling burnt sienna, that has probably been disengaged from the dark red sandstone below, which is known to owe its color to the oxide of iron. A Greek poet would probably have described the incident as the birth of the Naiad; in the north, however, which, in an earlier age, had also its Naiads, though, like the fish of the Old Red Sandstone, they have long since become extinct, the recollection of it is merely preserved by tradition, as a curious, though by no means poetical fact, and by the name of the well, which is still known as the well of the coal-heugh—the old Scotch name for a coal-pit. Calderwood tells us, in his description of a violent tempest which burst out immediately as his persecutor, James VI., breathed his last, that in Scotland the sea rose high upon the land, and that many "coal-heughs were drowned."
There is no science whose value can be adequately estimated by economists and utilitarians of the lower order. Its true quantities cannot be represented by arithmetical figures or monetary tables; for its effects on mind must be as surely taken into account as its operations on matter, and what it has accomplished for the human intellect as certainly as what it has done for the comforts of society or the interests of commerce. Who can attach a marketable value to the discoveries of Newton? I need hardly refer to the often-quoted remark of Johnson; the beauty of the language in which it is couched has rendered patent to all the truth which it conveys. "Whatever withdraws us from the power of the senses," says the moralist—"whatever makes the past, the distant, or the future, predominate over the present, advances us in the dignity of thinking beings." And Geology, in a peculiar manner, supplies to the intellect an exercise of this ennobling character. But it has, also, its cash value. The time and money squandered in Great Britain alone in searching for coal in districts where the well-informed geologist could have at once pronounced the search hopeless, would much more than cover the expense at which geological research has been prosecuted throughout the world. There are few districts in Britain occupied by the secondary deposits, in which, at one time or another, the attempt has not been made. It has been the occasion of enormous expenditure in the south of England among the newer formations, where the coal, if it at all occurs, (for we occasionally meet with wide gaps in the scale,) must be buried at an unapproachable depth. It led in Scotland—in the northern county of Sutherland—to an unprofitable working for many years of a sulphureous lignite of the inferior Oolite, far above the true Coal Measures. The attempt I have just been describing was made in a locality as far beneath them. There is the scene of another and more modern attempt in the same district, on the shores of the Moray Frith, in a detached patch of Lias, where a fossilized wood would no doubt be found in considerable abundance, but no continuous vein even of lignite. And it is related by Dr. Anderson, of Newburgh, that a fruitless and expensive search after coal has lately been instituted in the Old Red Sandstone beds which traverse Strathearn and the Carse of Gowrie, in the belief that they belong not to the Old, but to the New Red Sandstone—a formation which has been successfully perforated in prosecuting a similar search in various parts of England. All these instances—and there are hundreds such—show the economic importance of the study of fossils. The Oolite has its veins of apparent coal on the coast of Yorkshire, and its still more amply developed veins—one of them nearly four feet in thickness—on the eastern coast of Sutherlandshire; the Lias has its coniferous fossils in great abundance, some of them converted into a lignite which can scarce be distinguished from a true coal; and the bituminous masses of the Lower Old Red, and its carbonaceous markings, appear identical, to an unpractised eye, with the impressions on the carboniferous sandstones, and the bituminous masses which they, too, are occasionally found to enclose. Nor does the mineralogical character of its middle beds differ in many cases from that of the lower members of the New Red Sandstone. I have seen the older rock in the north of Scotland as strongly saliferous as any of the newer sandstones, of well nigh as bright a brick-red tint, of as friable and mouldering a texture, and variegated as thickly with its specks and streaks of green and buff-color. But in all these instances there are strongly characterized groups of fossils, which, like the landmarks of the navigator, or the findings of his quadrant, establish the true place of the formations to which they belong. Like the patches of leather, of scarlet, and of blue, which mark the line attached to the deep-sea lead, they show the various depths at which we arrive. The Earls of Sutherland set themselves to establish a coal-work among the chambered univalves of the Oolite, and a vast abundance of its peculiar bivalves. The coal-borers who perforated the Lias near Cromarty passed every day to and from their work over one of the richest deposits of animal remains in the kingdom—a deposit full of the most characteristic fossils; and drove their auger through a thousand belemnites and ammonites of the upper and inferior Lias, and through gryphites and ichthyodorulites innumerable. The sandstones of Strathearn and the Carse of Gowrie yield their plates and scales of the Holoptychius, the most abundant fossil of the Upper Old Red; and the shale of the little dell in which the first Earl of Cromarty set his miners to work, contains, as I have said, plates of the Coccosteus and scales of the Osteolepis—fossils found only in the Lower Old Red. Nature, in all these localities, furnished the index, but men lacked the skill necessary to decipher it.[AU] I may mention that, independently of their well-marked organisms, there is a simple test through which the lignites of the newer formations may be distinguished from the true coal of the carboniferous system. Coal, though ground into an impalpable powder, retains its deep black color, and may be used as a black pigment; lignite, on the contrary, when fully levigated, assumes a reddish, or, rather, umbry hue.
[AU] There occurs in Mr. Murchison's Silurian System a singularly amusing account of one of the most unfortunate of all coal-boring enterprises; the unlucky projector, a Welsh farmer, having set himself to dig for coal in the lowest member of the system, at least six formations beneath the only one at which the object of his search could have been found. Mr. Murchison thus relates the story:—
"At Tin-y-coed I found a credulous farmer ruining himself in excavating a horizontal gallery in search of coal, an ignorant miner being his engineer. The case may serve as a striking example of the coal-boring mania in districts which cannot by possibility contain that mineral; and a few words concerning it may, therefore, prove a salutary warning to those who speculate for coal in the Silurian Rocks. The farmhouse of Tin-y-coed is situated on the sloping sides of a hill of trap, which throw off, upon its north-western flank, thin beds of black grauwacke shale, dipping to the west-north-west at a high angle. The color of the shale, and of the water that flowed down its sides, the pyritous veins, and other vulgar symptoms of coal-bearing strata, had long convinced the farmer that he possessed a large hidden mass of coal, and, unfortunately, a small fragment of real anthracite was discovered, which burnt like the best coal. Miners were sent for, and operations commenced. To sink a shaft was impracticable, both from the want of means, and the large volume of water. A slightly inclined gallery was therefore commenced, the mouth of which was opened at the bottom of the hill, on the side of the little brook which waters the dell. I have already stated that, in many cases, where the intrusive trap throws off the shale, the latter preserves its natural and unaltered condition to within a certain distance of the trap; and so it was at Tin-y-coed, for the level proceeded for 155 feet with little or no obstacle. Mounds of soft black shale attested the rapid progress of the adventurers, when suddenly they came to a 'change of metal.' They were now approaching the nucleus of the little ridge; and the rock they encountered was, as the men informed me, 'as hard as iron,' viz., of lydianized schist, precisely analogous to that which is exposed naturally in ravines where all the phenomena are laid bare. The deluded people, however, endeavored to penetrate the hardened mass, but the vast expense of blasting it put a stop to the undertaking, not, however, without a thorough conviction on the part of the farmer, that, could he but have got through that hard stuff, he would most surely have been well recompensed, for it was just thereabouts that they began to find 'small veins of coal.' It has been before shown, that portions of anthracite are not unfrequent in the altered shale, where it is in contact with the intrusive rock. And the occurrence of the smallest portion of anthracite is always sufficient to lead the Radnorshire farmer to suppose that he is very near 'El Dorado.' Amid all their failures, I never met with an individual who was really disheartened; a frequent exclamation being, 'O, if our squires were only men of spirit, we should have as fine coal as any in the world!'"—(Silurian System, Part I., p. 328.)
I have said that the waters of the well of the coal-heugh are chalybeate—a probable consequence of their infiltration through the iron oxides of the superior beds of the formation, and their subsequent passage through the deep red strata of the inferior bed. There could be very curious chapters written on mineral springs, in their connection with the formations through which they pass. Smollett's masterpiece, honest old Matthew Bramble, became thoroughly disgusted with the Bath waters on discovering that they filtered through an ancient burying-ground belonging to the Abbey, and that much of their peculiar taste and odor might probably be owing to the "rotten bones and mouldering carcasses" through which they were strained. Some of the springs of the Old Red Sandstone have also the churchyard taste, but the bones and carcasses through which they strain are much older than those of the Abbey burying-ground at Bath. The bitumen of the strongly impregnated rocks and clay-beds of this formation, like the bitumen of the still more strongly impregnated limestones and shales of the Lias, seems to have had rather an animal than vegetable origin. The shales of the Eathie Lias burn like turf soaked in oil, and yet they hardly contain one per cent, of vegetable matter. In a single cubic inch, however, I have counted about eighty molluscous organisms, mostly ammonites, and minute striated scallops; and the mass, when struck with the hammer, still yields the heavy odor of animal matter in a state of decay. The lower fish-beds of the Old Red are, in some localities, scarcely less bituminous. The fossil scales and plates, which they enclose, burn at the candle; they contain small cavities filled with a strongly scented, semi-fluid bitumen, as adhesive as tar, and as inflammable; and for many square miles together the bed is composed almost exclusively of a dark-colored, semi-calcareous, semi-aluminous schist, scarcely less fetid, from the great quantity of this substance which it contains, than the swine-stones of England. Its vegetable remains bear but a small proportion to its animal organisms; and from huge accumulations of these last decomposing amid the mud of a still sea, little disturbed by tempests or currents, and then suddenly interred by some widely spread catastrophe, to ferment and consolidate under vast beds of sand and conglomerate, the bitumen[AV] seems to have been elaborated. These bituminous schists, largely charged with sulphuret of iron, run far into the interior, along the flanks of the gigantic Ben Nevis, and through the exquisitely pastoral valley of Strathpeffer. The higher hills which rise over the valley are formed mostly of the great conglomerate—Knockferril, with its vitrified fort—the wooded and precipitous ridge over Brahan—and the middle eminences of the gigantic mountain on the north; but the bottom and the lower slopes of the valley are occupied by the bituminous and sulphureous schists of the fish-bed, and in these, largely impregnated with the peculiar ingredients of the formation, the famous medicinal springs of the Strath have their rise. They contain, as shown by chemical analysis, the sulphates of soda, of lime, of magnesia, common salt, and, above all, sulphuretted hydrogen gas—elements which masses of sea-mud, charged with animal matter, would yield as readily to the chemist as the medicinal springs of Strathpeffer. Is it not a curious reflection, that the commercial greatness of Britain, in the present day, should be closely connected with the towering and thickly spread forests of arboraceous ferns and gigantic reeds—vegetables of strange form and uncouth names—which flourished and decayed on its surface, age after age, during the vastly extended term of the carboniferous period, ere the mountains were yet upheaved, and when there was as yet no man to till the ground? Is it not a reflection equally curious, that the invalids of the present summer should be drinking health, amid the recesses of Strathpeffer, from the still more ancient mineral and animal debris of the lower ocean of the Old Red Sandstone, strangely elaborated for vast but unreckoned periods in the bowels of the earth? The fact may remind us of one of the specifics of a now obsolete school of medicine, which flourished in this country about two centuries ago, and which included in its materia medica portions of the human frame. Among these was the flesh of Egyptian mummies, impregnated with the embalming drugs—the dried muscles and sinews of human creatures who had walked in the streets of Thebes or of Luxor three thousand years ago.
[AV] "In the slaty schists of Seefeld, in the Tyrol," say Messrs. Sedgwick and Murchison, "there is such an abundance of a similar bitumen, that it is largely extracted for medicinal purposes."—(Geol. Trans. for 1829, p. 134.)
The commoner mineral springs of the formation, as might be anticipated, from the very general diffusion of the oxide to which it owes its color, are chalybeate. There are districts in Easter-Ross and the Black Isle in which the traveller scarcely sees a runnel by the way-side that is not half choked up by its fox-colored coagulum of oxide. Two of the most strongly impregnated chalybeates with which I am acquainted gush out of a sandstone bed, a few yards apart, among the woods of Tarbat House, on the northern shore of the Frith of Cromarty. They splash among the pebbles with a half-gurgling, half-tinkling sound, in a solitary but not unpleasing recess, darkened by alders and willows; and their waters, after uniting in the same runnel, form a little, melancholy looking lochan, matted over with weeds, and edged with flags and rushes, and which swarms in early summer with the young of the frog in its tadpole state, and in the after months with the black water-beetle and the newt. The circumstance is a somewhat curious one, as the presence of iron as an oxide has been held so unfavorable to both animal and vegetable life, that the supposed poverty of the Old Red Sandstone in fossil remains has been attributed to its almost universal diffusion at the period the deposition was taking place. Were the system as poor as has been alleged, however, it might be questioned, on the strength of a fact such as this, whether the iron militated so much against the living existences of the formation, as against the preservation of their remains when dead.