CHAPTER V.
Trap-Dykes—"Cotton Apples"—Alternation of Lacustrine with Marine Remains—Analogy from the Beds of Esk—Aspect of the Island on its narrow Front—The Puffin—Ru-Stoir—Development of Old Red Sandstone—Striking Columnar character of Ru-Stoir—Discovery of Reptilian Remains—John Stewart's wonder at the Bones in the Stones—Description of the Bones—"Dragons, Gorgons, and Chimeras"—Exploration and Discovery pursued—The Midway Shieling—A Celtic Welcome—Return of the Yacht—"Array of Fossils new to Scotch Geology"—A Geologist's Toast—Hoffman and his Fossil.
We leave behind us the musical sand, and reach the point of the promontory which forms the northern extremity of the Bay of Laig. Wherever the beach has been swept bare, we see it floored with trap-dykes worn down to the level, but in most places accumulations of huge blocks of various composition cover it up, concealing the nature of the rock beneath. The long semi-circular wall of precipice which, sweeping inwards at the bottom of the bay, leaves to the inhabitants between its base and the beach their fertile meniscus of land, here abuts upon the coast. We see its dark forehead many hundred feet overhead, and the grassy platform beneath, now narrowed to a mere talus, sweeping upwards to its base from the shore,—steep, broken, lined thick with horizontal pathways, mottled over with ponderous masses of rock.
Among the blocks that load the beach, and render our onward progress difficult and laborious, we detect occasional fragments of an amygdaloidal basalt, charged with a white zeolite, consisting of crystals so extremely slender that the balls, with their light fibrous contents, remind us of cotton apples divested of the seeds. There occur, though more rarely, masses of a hard white sandstone, abounding in vegetable impressions, which, from their sculptured markings, recalled to memory the Sigillaria of the Coal Measures. Here and there, too, we find fragments of a calcareous stone, so largely charged with compressed shells, chiefly bivalves, that it may be regarded as a shell breccia. There occur, besides, slabs of fibrous limestone, exactly resembling the limestone of the ichthyolite beds of the Lower Old Red; and blocks of a hard gray stone, of silky lustre in the fresh fracture, thickly speckled with carbonaceous markings. These fragmentary masses,—all of them, at least, except the fibrous limestone, which occurs in mere plank-like bands,—represent distinct beds, of which this part of the island is composed, and which present their edges, like courses of ashlar in a building, in the splendid section that stretches from the tall brow of the precipice to the beach; though in the slopes of the talus, where the lower beds appear in but occasional protrusions and land-slips, we find some difficulty in tracing their order of succession.
Near the base of the slope, where the soil has been undermined and the rock laid bare by the waves, there occur beds of a bituminous black shale,—resembling the dark shales so common in the Coal Measures,—that seem to be of fresh water or estuary origin. Their fossils, though numerous, are ill preserved; but we detect in them scales and plates of fishes, at least two species of minute bivalves, one of which very much resembles a Cyclas; and in some of the fragments, shells of Cypris lie embedded in considerable abundance. After all that has been said and written by way of accounting for those alternations of lacustrine with marine remains, which are of such frequent occurrence in the various formations, secondary and tertiary, from the Coal Measures downwards, it does seem strange enough that the estuary, or fresh-water lake, should so often in the old geologic periods have changed places with the sea. It is comparatively easy to conceive that the inner Hebrides should have once existed as a broad ocean sound, bounded on one or either side by Oölitic islands, from which streams descended, sweeping with them, to the marine depths, productions, animal and vegetable, of the land. But it is less easy to conceive, that in that sound, the area covered by the ocean one year should have been covered by a fresh-water lake in perhaps the next, and then by the ocean again a few years after. And yet among the Oölitic deposits of the Hebrides evidence seems to exist that changes of this nature actually took place. I am not inclined to found much on the apparently fresh-water character of the bituminous shales of Eigg;—the embedded fossils are all too obscure to be admitted in evidence; but there can exist no doubt that fresh water, or at least estuary formations, do occur among the marine Oölites of the Hebrides. Sir R. Murchison, one of the most cautious, as he is certainly one of the most distinguished, of living geologists, found in a northern district of Skye, in 1826, a deposit containing Cyclas, Paludina, Neritina,—all shells of unequivocally fresh-water origin,—which must have been formed, he concludes, in either a lake or estuary. What had been sea at one period had been estuary or lake at another. In every case, however, in which these intercalated deposits are restricted to single strata of no great thickness, it is perhaps safer to refer their formation to the agency of temporary land-floods, than to that of violent changes of level, now elevating and now depressing the surface. There occur, for instance, among the marine Oölites of Brora,—the discovery of Mr. Robertson, of Inverugie,—two strata containing fresh-water fossils in abundance; but the one stratum is little more than an inch in thickness,—the other little more than a foot; and it seems considerably more probable, that such deposits should have owed their existence to extraordinary land-floods, like those which in 1829 devastated the province of Moray, and covered over whole miles of marine beach with the spoils of land and river, than that a sea-bottom should have been elevated for their production, into a fresh-water lake, and then let down into a sea-bottom again. We find it recorded in the "Shepherd's Calendar," that after the thaw which followed the great snow-storm of 1794, there were found on a part of the sands of the Solway Frith known as the Beds of Esk, where the tide disgorges much of what is thrown into it by the rivers, "one thousand eight hundred and forty sheep, nine black cattle, three horses, two men, one woman, forty-five dogs, and one hundred and eighty hares, beside a number of meaner animals." A similar storm in an earlier time, with a soft sea-bottom prepared to receive and retain its spoils, would have formed a fresh-water stratum intercalated in a marine deposit.
Rounding the promontory, we lose sight of the Bay of Laig, and find the narrow front of the island that now presents itself exhibiting the appearance of a huge bastion. The green talus slopes upwards, as its basement, for full three hundred feet; and a noble wall of perpendicular rock, that towers over and beyond for at least four hundred feet more, forms the rampart. Save towards the sea, the view is of but limited extent; we see it restricted, on the landward side, to the bold face of the bastion; and in a narrow and broken dell that runs nearly parallel to the shore for a few hundred yards between the top of the talus and the base of the rampart,—a true covered way,—we see but the rampart alone. But the dizzy front of black basalt, dark as night, save where a broad belt of light-colored sandstone traverses it in an angular direction, like a white sash thrown across a funeral robe,—the fantastic peaks and turrets in which the rock terminates atop,—the masses of broken ruins, roughened with moss and lichen, that have fallen from above, and lie scattered at its base,—the extreme loneliness of the place, for we have left behind us every trace of the human family,—and the expanse of solitary sea which it commands,—all conspire to render the scene a profoundly imposing one. It is one of those scenes in which a man feels that he is little, and that nature is great. There is no precipice in the island in which the puffin so delights to build as among the dark pinnacles overhead, or around which the silence is so frequently broken by the harsh scream of the eagle. The sun had got far adown the sky ere we had reached the covered way at the base of the rock. All lay dark below; and the red light atop, half absorbed by the dingy hues of the stone, shone with a gleam so faint and melancholy, that it served but to deepen the effect of the shadows.
The puffin, a comparatively rare bird in the inner Hebrides, builds, I was told, in great numbers in the continuous line of precipice which, after sweeping for a full mile round the Bay of Laig, forms the pinnacled rampart here, and then, turning another angle of the island, runs on parallel to the coast for about six miles more. In former times the puffin furnished the islanders, as in St. Kilda, with a staple article of food, in those hungry months of summer in which the stores of the old crop had begun to fail, and the new crop had not yet ripened; and the people of Eigg, taught by their necessities, were bold cragsmen. But men do not peril life and limb for the mere sake of a meal, save when they cannot help it; and the introduction of the potato has done much to put out the practice of climbing for the bird, except among a few young lads, who find excitement enough in the work to pursue it for its own sake, as an amusement. I found among the islanders what was said to be a piece of the natural history of the puffin, sufficiently apocryphal to remind one of the famous passage in the history of the barnacle, which traced the lineage of the bird to one of the pedunculated cirripedes, and the lineage of the cirripede to a log of wood. The puffin feeds its young, say the islanders, on an oily scum of the sea, which renders it such an unwieldy mass of fat, that about the time when it should be beginning to fly, it becomes unable to get out of its hole. The parent bird, not in the least puzzled, however, treats the case medicinally, and,—like mothers of another two-legged genus, who, when their daughters get over stout, put them through a course of reducing acids to bring them down,—feeds it on sorrel leaves for several days together, till, like a boxer under training, it gets thinned to the proper weight, and becomes able, not only to get out of its cell, but also to employ its wings.
We pass through the hollow, and, reaching the farther edge of the bastion, towards the east, see a new range of prospect opening before us. There is first a long unbroken wall of precipice,—a continuation of the tall rampart overhead,—relieved along its irregular upper line by the blue sky. We mark the talus widening at its base, and expanding, as on the shores of the Bay of Laig, into an irregular grassy platform, that, sinking midway into a ditch-like hollow, rises again towards the sea, and presents to the waves a perpendicular precipice of redstone. The sinking sun shone brightly this evening; and the warm hues of the precipice, which bears the name of Ru-Stoir,—the Red Head,—strikingly contrasted with the pale and dark tints of the alternating basalts and sandstones in the taller cliff behind. The ditch-like hollow, which seems to indicate the line of a fault, cuts off this red headland from all the other rocks of the island, from which it appears to differ as considerably in texture as in hue. It consists mainly of thick beds of a pale red stone, which M'Culloch regarded as a trap, and which, intercalated with here and there a thin band of shale, and presenting not a few of the mineralogical appearances of what geologists of the school of the late Mr. Cunningham term Primary Old Red Sandstone, in some cases has been laid down as a deposit of Old Red proper, abutting in the line of a fault on the neighboring Oölites and basalts. In the geological map which I carried with me,—not one of high authority however,—I found it actually colored as a patch of this ancient system. The Old Red Sandstone is largely developed in the neighboring island of Rum, in the line of which the Ru-Stoir seems to have a more direct bearing than any of the other deposits of Eigg; and yet the conclusion regarding this red headland merely adds one proof more to the many furnished already, of the inadequacy of mineralogical testimony, when taken in evidence regarding the eras of the geologist. The hard red beds of Ru-Stoir belong, as I was fortunate enough this evening to ascertain, not to the ages of the Coccosteus and Pterichthys, but to the far later ages of the Plesiosaurus and the fossil crocodile. I found them associated with more reptilian remains, of a character more unequivocal than have been yet exhibited by any other deposit in Scotland.
What first strikes the eye, in approaching the Ru-Stoir from the west, is the columnar character of the stone. The precipices rise immediately over the sea, in rude colonnades of from thirty to fifty feet in height; single pillars, that have fallen from their places in the line, and exhibit a tenacity rare among the trap-rocks,—for they occur in unbroken lengths of from ten to twelve feet,—lie scattered below; and in several places where the waves have joined issue with the precipices in the line on which the base of the columns rest, and swept away the supporting foundation, the colonnades open into roomy caverns, that resound to the dash of the sea. Wherever the spray lashes, the pale red hue of the stone prevails, and the angles of the polygonal shafts are rounded; while higher up all is sharp-edged, and the unweathered surface is covered by a gray coat of lichens. The tenacity of the prostrate columns first drew my attention. The builder scant of materials would have experienced no difficulty in finding among them sufficient lintels for apertures from eight to twelve feet in width. I was next struck with the peculiar composition of the stone; it much rather resembles an altered sandstone, in at least the weathered specimens, than a trap, and yet there seemed nothing to indicate that it was an Old Red Sandstone. Its columnar structure bore evidence to the action of great heat; and its pale red color was exactly that which the Oölitic sandstones of the island, with their slight ochreous tinge, would assume in a common fire. And so I set myself to look for fossils. In the columnar stone itself I expected none, as none occur in vast beds of the unaltered sandstones, out of some one of which I supposed it might possibly have been formed; and none I found: but in a rolled block of altered shale of a much deeper red than the general mass, and much more resembling Old Red Sandstone, I succeeded in detecting several shells, identical with those of the deposit of blue clay described in a former chapter. There occurred in it the small univalve resembling a Trochus, together with the oblong bivalve, somewhat like a Tellina; and, spread thickly throughout the block, lay fragments of coprolitic matter, and the scales and teeth of fishes. Night was coming on, and the tide had risen on the beach; but I hammered lustily, and laid open in the dark red shale a vertebral joint, a rib, and a parallelogramical fragment of solid bone, none of which could have belonged to any fish. It was an interesting moment for the curtain to drop over the promontory of Ru-Stoir; I had thus already found in connection with it well nigh as many reptilian remains as had been found in all Scotland before,—for there could exist no doubt that the bones I laid open were such; and still more interesting discoveries promised to await the coming morning, and a less hasty survey. We found a hospitable meal awaiting us at a picturesque old two-story house, with, what is rare in the island, a clump of trees beside it, which rises on the northern angle of the Oölitic meniscus; and after our day's hard work in the fresh sea-air, we did ample justice to the viands. Dark night had long set in ere we reached our vessel.
Next day was Saturday; and it behooved my friend, the minister,—as scrupulously careful in his pulpit preparations for the islanders of Eigg as if his congregation were an Edinburgh one,—to remain on board, and study his discourse for the morrow. I found, however, no unmeet companion for my excursion in his trusty mate John Stewart. John had not very much English, and I had no Gaelic; but we contrived to understand one another wonderfully well; and ere evening I had taught him to be quite as expert in hunting dead crocodiles as myself. We reached the Ru-Stoir, and set hard to work with hammer and chisel. The fragments of red shale were strewed thickly along the shore for at least three quarters of a mile; wherever the red columnar rock appeared, there lay the shale, in water-worn blocks, more or less indurated; but the beach was covered over with shingle and detached masses of rock, and we could nowhere find it in situ. A winter storm powerful enough to wash the beach bare might do much to assist the explorer. There is a piece of shore on the eastern coast of Scotland, on which for years together I used to pick up nodular masses of lime containing fish of the Old Red Sandstone; but nowhere in the neighborhood could I find the ichthyolite bed in which they had originally formed. The storm of a single night swept the beach; and in the morning the ichthyolites lay revealed in situ under a stratum of shingle which I had a hundred times examined, but which, though scarce a foot in thickness, had concealed from me the ichthyolite bed for five twelvemonths together!