Chapter 46

"He who, with pocket hammer, smites the edge Of luckless rock or prominent stone, disguised In weather stains, or crusted o'er by nature With her first growths--detaching by the stroke A chip or splinter, to resolve his doubts; And, with that ready answer satisfied, The substance classes by some barbarous name. And hurries on."--WORDSWORTH.

In the course of my two visits to Miss Dunbar, I had several opportunities of examining the sand-wastes of Culbin, and of registering some of the peculiarities which distinguish the arenaceous sub-aërial formation from the arenaceous sub-aqueous one. Of the present surface of the earth, considerably more than six millions of square miles are occupied in Africa and Asia alone by sandy deserts. With but the interruption of the narrow valley of the Nile, an enormous zone of arid sand, full nine hundred miles across, stretches from the eastern coast of Africa to within a few days' journey of the Chinese frontier: it is a belt that girdles nearly half the globe;--a vast "ocean," according to the Moors, "without water." The sandy deserts of the rainless districts of Chili are also of great extent: and there are few countries in even the higher latitudes that have not their tracts of arenaceous waste. These sandy tracts, so common in the present scene of things, could not, I argued, be restricted to the recent geologic periods. They must have existed, like all the commoner phenomena of nature, under every succeeding system in which the sun shone, and the winds blew, and ocean-beds were upheaved to the air and the light, and the waves threw upon the shore, from arenaceous sea-bottoms, their accumulations of light sand. And I was now employed in acquainting myself with the marks by which I might be able to distinguish sub-aërial from sub-aqueous formations, among the ever-recurring sandstone beds of the geologic deposits. I have spent, when thus engaged, very delightful hours amid the waste. In pursuing one's education, it is always very pleasant to get into those _forms_ that are not yet introduced into any school.

One of the peculiarities of the sub-aërial formation which I at this time detected struck me as curious. On approaching, among the sand-hills, an open level space, covered thickly over with water-rolled pebbles and gravel, I was surprised to see that, dry and hot as the day was elsewhere, the little open space seemed to have been subjected to a weighty dew or smart shower. The pebbles glistened bright in the sun, and bore the darkened hue of recent wet. On examination, however, I found that the rays were reflected, not from wetted, but from polished surfaces. The light grains of sand, dashed against the pebbles by the winds during a long series of years--grain after grain repeating its minute blow, where, mayhap, millions of grains had struck before--had at length given a resinous-looking, uneven polish to all their exposed portions, while the portions covered up retained the dull unglossy coat given them of old by the agencies of friction and water. I have not heard the peculiarity described as a characteristic of the arenaceous deserts; but though it seems to have escaped notice, it will, I doubt not, be found to obtain wherever there are sands for the winds to waft along, and hard pebbles against which the grains may be propelled. In examining, many years after, a few specimens of silicified wood brought from the Egyptian desert, I at once recognised on their flinty surfaces the resinous-like gloss of the pebbles of Culbin; nor can I doubt that, if geology has its sub-aërial formations of consolidated sand, they will be found characterized by their polished pebbles. I marked several other peculiarities of the formation. In some of the abrupter sections laid open by the winds, tufts of the bent-grass (_Arundo arenaria_--common here, as in all sandy wastes) that had been buried up where they grew, might be distinctly traced, each upright in itself, but rising tuft above tuft in the steep angle of the hillock which they had originally covered. And though, from their dark colour, relieved against the lighter hue of the sand, they reminded me of the carbonaceous markings of sandstone of the Coal Measures, I recognised at least _their arrangement_ as unique. It seems to be such an arrangement--sloping in the general line, but upright in each of the tufts--as could take place in only a sub-aërial formation. I observed further, that in frequent instances there occurred on the surface of the sand, around decaying tufts of the bent-grass, deeply-marked circles, as if drawn by a pair of compasses or a trainer--effects apparently of eddy winds whirling round, as on a pivot, the decayed plants; and yet further, that footprints, especially those of rabbits and birds, were not unfrequent in the waste. And as lines of stratification were, I found, distinctly preserved in the formation, I deemed it not improbable that, in cases in which high winds had arisen immediately after tracts of wet weather, and covered with sand, rapidly dried on the heights, the damp beds in the hollows, both the circular markings and the footprints might remain fixed in the strata, to tell of their origin. I found in several places, in chasms scooped out by a recent gale, pieces of the ancient soil laid bare, which had been covered up by the sand-flood nearly two centuries before. In one of the openings the marks of the ancient furrows were still discernible; in another, the thin stratum of ferruginous soil had apparently never been brought under the plough; and I found it charged with roots of the common brake (_Pteris aquilina_), in a perfect state of keeping, but black and brittle as coal. Beneath this layer of soil lay a thin deposit of the stratified gravel of what is now known as the later glacial period--the age of _osars_ and moraines; and beneath all--for the underlying Old Red Sandstone of the district is not exposed amid the level wastes of Culbin--rested the boulder clay, the memorial of a time of submergence, when Scotland sat low in the sea as a wintry archipelago of islands, brushed by frequent icebergs, and when sub-arctic molluscs lived in her sounds and bays. A section of a few feet in vertical extent presented me with four distinct periods. There was, first, the period of the sand-flood, represented by the bar of pale-sand; then, secondly, the period of cultivation and human occupancy, represented by the dark plough-furrowed belt of hardened soil; thirdly, there was the gravel; and, fourthly, the clay. And that shallow section exhausted the historic ages, and more; for the double band of gravel and clay belonged palpably to the geologic ages, ere man had appeared on our planet. There had been found in the locality, only a few years previous to this time, a considerable number of stone arrow-heads--some of them only partially finished, and some of them marred in the making, as if some fletcher of the stone age had carried on his work on the spot; and all these memorials of a time long anterior to the first beginnings of history in the island were restricted to the stratum of hardened mould.

I carried on my researches in this--what I may term the chronological--direction, in connexion with the old-coast line, which, as I have already said, is finely developed in the neighbourhood of Cromarty on both sides of the Firth, and represented along the precipices of the Sutors by its line of deep caves, into which the sea never now enters. And it, too, pressed upon me the fact of the amazing antiquity of the globe. I found that the caves hollowed by the surf--when the sea stood from fifteen to five-and-twenty feet above its present level, or, as I should perhaps rather say, when the land sat that much lower--were deeper, on the average, by about one-third, than those caves of the present coast-line that are still in the course of being hollowed by the waves. And yet the waves have been breaking against the present coast-line during the whole of the historic period. The ancient wall of Antoninus, which stretched between the Firths of Forth and Clyde, was built at its terminations with reference to the existing levels; and ere Caesar landed in Britain, St. Michael's Mount was connected with the mainland, as now, by a narrow neck of beach laid bare by the ebb, across which, according to Diodorus Siculus, the Cornish miners used to drive, at low water, their carts laden with tin. If the sea has stood for two thousand six hundred years against the present coast-line--and no geologist would fix his estimate of the term lower--then must it have stood against the old line, ere it could have excavated caves one-third deeper than the modern ones, three thousand nine hundred years. And both sums united more than exhaust the Hebrew chronology. Yet what a mere beginning of geologic history does not the epoch of the old coast-line form! It is but a starting-point from the recent period. Not a single shell seems to have become extinct during the last six thousand years. The organisms which I found deeply embedded in the soil beneath the old coast-line were exactly those which still live in our seas; and I have been since told by Mr. Smith of Jordanhill, one of our highest authorities on the subject, that he detected only three shells of the period with which he was not familiar as existing forms, and that he subsequently met with all three, in his dredging expeditions, still alive. The six thousand years of human history form but a portion of the geologic day that is passing over us: they do not extend into the _yesterday_ of the globe, far less touch the myriads of ages spread out beyond. Dr. Chalmers had taught, more than a quarter of a century previous to this time, that the Scriptures do not fix the antiquity of the earth. "If they fix anything," he said, "it is only the antiquity of the human species." The Doctor, though not practically a geologist at the time, had shrewdly weighed both the evidence adduced and the scientific character of the men who adduced it, and arrived at a conclusion, in consequence, which may now be safely regarded as the final one. I, on the other hand, who knew comparatively little about the standing of the geologists, or the weight which ought to attach to their testimony, based my findings regarding the vast antiquity of the earth on exactly the data on which they had founded theirs; and the more my acquaintance with the geologic deposits has since extended, the firmer have my convictions on the subject become, and the more pressing and inevitable have I felt the ever-growing demand for longer and yet longer periods for their formation. As certainly as the sun is the centre of our system, must our earth have revolved around it for millions of years. An American theologian, the author of a little book entitled the "Epoch of Creation," in doing me the honour of referring to my convictions on this subject, states, that I "betray indubitable tokens of being spell-bound to the extent of infatuation, by the foregone conclusion of" my "theory concerning the high antiquity of the earth, and the succession of animal and vegetable creations." He adds further, in an eloquent sentence, a page and a half long, that had I first studied and credited my Bible, I would have failed to believe in successive creations and the geologic chronology. I trust, however, I may say I did first study and believe my Bible. But such is the structure of the human mind, that, save when blinded by passion or warped by prejudice, it must yield an involuntary consent to the force of evidence; and I can now no more refuse believing, in opposition to respectable theologians such as Mr. Granville Penn, Professor Moses Stuart, and Mr. Eleazar Lord, that the earth is of an antiquity incalculably vast, than I can refuse believing, in opposition to still more respectable theologians, such as St. Augustine, Lactantius, and Turretine, that it has antipodes, and moves round the sun. And further, of this, men such as the Messrs. Penn, Stuart, and Lord may rest assured, that what I believe in this matter now, all theologians, even the weakest, will be content to believe fifty years hence.

Sometimes a chance incident taught me an interesting geological lesson. At the close of the year 1830, a tremendous hurricane from the south and west, unequalled in the north of Scotland, from at least the time of the great hurricane of Christmas 1806, blew down in a single hour four thousand full-grown trees on the Hill of Cromarty. The vast gaps and avenues which it opened in the wood above could be seen from the town; and no sooner had it begun to take off than I set out for the scene of its ravages. I had previously witnessed, from a sheltered hollow of the old coast-line, the extraordinary appearance of the sea. It would seem as if the very violence of the wind had kept down the waves. It brushed off their tops as they were rising, and swept along the spray in one dense cloud, white as driving snow, that rose high into the air as it receded from the shore, and blotted out along the horizon the line between sky and water. As I approached the wood, I met two poor little girls of from eight to ten years, coming running and crying along the road in a paroxysm of consternation; but, gathering heart on seeing me, they stood to tell that when the storm was at its worst they were in the midst of the falling trees. Setting out for the Hill on the first rising of the wind, in the expectation of a rich harvest of withered boughs, they had reached one of its most exposed ridges just as the gale had attained to its extreme height, and the trees began to crash down around them. Their little tear-bestained countenances still continued to show how extreme the agony of their terror had been. They would run, they said, for a few paces in one direction, until some huge pine would come roaring down, and block up their path; when, turning with a shriek, they would run for a few paces in another; and then, terrified by a similar interruption, again strike off in a third. At length, after passing nearly an hour in the extremest peril, and in at least all the fear which the circumstances justified, they succeeded in making their way unhurt to the outer skirts of the wood. Bewick would have found in the incident the subject of a vignette that would have told its own story. In getting into the thick of the trees, I was struck by the extraordinary character of the scene presented. In some places, greatly more than half their number lay stretched upon the ground. On the more exposed prominences of the Hill, scarce a tree was left standing for acres together: they covered the slopes; tree stretched over tree like tiles on a roof, with here and there some shattered trunk whose top had been blown off, and carried by the hurricane some fifteen or twenty yards away, leaning in sad ruin over its fallen comrades. What, however, formed the most striking, because less expected, parts of the scene, were the tall walls of turf that stood up everywhere among the fallen trees, like the ruins of dismantled cottages. The granitic gneiss of the Hill is covered by a thick deposit of the red boulder clay of the district, and the clay, in turn, by a thin layer of vegetable mould, interlaced in every direction by the tree roots, which, arrested in their downward progress by the stiff clay, are restricted to the upper layer. And, save where here and there I found some tree snapped across in the midst, or divested of its top, all the others had yielded at the line between the boulder clay and the soil, and had torn up, as they fell, vast walls of the felted turf, from fifteen to twenty feet in length, by from ten to twelve feet in height. There were quite enough of these walls standing up among the prostrate trees, to have formed a score of the eastern Sultan's ruined villages; and they imparted to the