The argillaceous deposit of Blackpots occupies, in the form of a green swelling bank, a promontory rather soft than bold in its contour, that projects far into the sea, and forms, when tipped with its slim column of smoke from the tile-kiln, a pleasing feature in the landscape. I had set it down on the previous day, when it first caught my eye from the lofty cliffs of Gamrie-head, at the distance of some ten or twelve miles, as different in character from all the other features of the prospect. The country generally is moulded on a framework of primary rock, and presents headlands of hard, sharp outline, to the attrition of the waves; whereas this single headland in the midst,—soft-lined, undulatory, and plump,—seems suited to remind one of Burns's young Kirk Alloway beauty disporting amid the thin old ladies that joined with her in the dance. And it is a greatly younger beauty than the Cambrian and mica-schist protuberances that encroach on the sea on either side of it. The sheds and kilns of a tile-work occupy the flat terminal point of the promontory; and as the clay is valuable, in this tile-draining age, for the facility with which it can be moulded into pipe-tiles (a purpose which the ordinary clays of the north of Scotland, composed chiefly of re-formations of the Old Red Sandstone, are what is technically termed too short to serve), it is gradually retreating inland before the persevering spade and mattock of the laborer. The deposit has already been drawn out into many hundred miles of cylindrical pipes, and is destined to be drawn out into many thousands more,—such being one of the strange metamorphoses effected in the geologic formations, now that that curious animal the Bimana has come upon the stage; and at length it will have no existence in the country, save as an immense system of veins and arteries underlying the vegetable mould. Will these veins and arteries, I marvel, form, in their turn, the fossils of another period, when a higher platform than that into which they have been laid will be occupied to the full by plants and animals specifically different from those of the present scene of things,—the existences of a happier and more finished creation? My business to-day, however, was with the fossils which the deposit now contains,—not with those which it may ultimately form.
The Blackpots clay is of a dark-bluish or greenish-gray color, and so adhesive, that I now felt, when walking among it, after the softening rains of the previous night and morning, as if I had got into a bed of bird-lime. It is thinly charged with rolled pebbles, septaria, and pieces of a bituminous shale, containing broken Belemnites, and sorely-flattened Ammonites, that exist as thin films of a white chalky lime. The pebbles, like those of the boulder-clay of the northern side of the Moray Frith, are chiefly of the primary rocks and older sandstones, and were probably in the neighborhood, in their present rolled form, long ere the re-formation of the inclosing mass; while the shale and the septaria are, as shown by their fossils, decidedly Liasic. I detected among the conchifers a well-marked species of our northern Lias, figured by Sowerby from Eathie specimens,—the Plagiostoma concentrica; and among the Cephalopoda, though considerably broken, the Belemnite elongatus and Belemnite lanceolata, with the Ammonite Kœnigi (mutabilis),—all Eathie shells. I, besides, found in the bank a piece of a peculiar-looking quartzose sandstone, traversed by hard jaspedeous veins of a brownish-gray color, which I have never found, in Scotland at least, save associated with the Lias of our north-eastern coasts. Further, my attention was directed by Dr. Emslie to a fine Lignite in his collection, which had once formed some eighteen inches or two feet of the trunk of a straight slender pine,—probably the Pinites Eiggensis,—in which, as in most woods of the Lias and Oölite, the annual rings are as strongly marked as in the existing firs or larches of our hill-sides.[11] The Blackpots deposit is evidently a re-formation of a Liasic patch, identical, both in mineralogical character and in its organic remains, with the lower beds of the Eathie Lias; while the fragments of shale which it contains belong chiefly to an upper Liasic bed. So rich is the dark-colored tenacious argil of the Inferior Lias of Eathie, that the geologist who walks over it when it is still moist with the receding tide would do well to look to his footing;—the mixture of soap and grease spread by the ship-carpenter on his launch-slips, to facilitate the progress of his vessel seawards, is not more treacherous to the tread: while the Upper Liasic deposit which rests over it is composed of a dark slaty shale, largely charged with bitumen. And of a Liasic deposit of this compound character, consisting in larger part of an inferior argillaceous bed, and in lesser part of a superior one of dark shale, the tile-clay of Blackpots has been formed.
I had next to determine whether aught remained to indicate the period of its re-formation. The tile-works at the point of the promontory rest on a bed of shell-sand, composed exclusively, like the sand so abundant on the western coast of Scotland, of fragments of existing shells. These, however, are so fresh and firm, that, though the stratum which they form seems to underlie the clay at its edges, I cannot regard them as older than the most modern of our ancient sea-margins. They formed, in all probability, in the days of the old coast line, a white shelly beach, under such a precipitous front of the dark clay as argillaceous deposits almost always present to the undermining wear of the waves. On the recession of the sea, however, to its present line, the abrupt, steep front, loosened by the frosts and washed by the rains, would of course gradually moulder down over them into a slope; and there would thus be communicated to the shelly stratum, at least at its edges, an underlying character. The true period of the re-formation of the deposit was, I can have no doubt, that of the boulder-clay. I observed that the septaria and larger masses of shale which the bed contains, bear, on roughly-polished surfaces, in the line of their larger axes, the mysterious groovings and scratchings of this period,—marks which I have never yet known to fail in their chronological evidence. It may be mentioned, too, simply as a fact, though one of less value than the other, that the deposit occurs in its larger development exactly where, in the average, the boulder-clays also are most largely developed,—a little over that line where the waves for so many ages charged against the coast, ere the last upheaval of the land or the recession of the sea sent them back to their present margin. There had probably existed to the west or north-west of the deposit, perhaps in the middle of the open bay formed by the promontory on which it rests,—for the small proportion of other than Liasic materials which it contains serves to show that it could be derived from no great distance,—an outlier of the Lower Lias. The icebergs of the cold glacial period, propelled along the submerged land by some arctic current, or caught up by the gulf-stream, gradually grated it down, as a mason's laborer grates down the surface of the sandstone slab which he is engaged in polishing; and the comminuted debris, borne eastwards by the current, was cast down here. It has been stated that no Liasic remains have been found in the boulder-clays of Scotland. They are certainly rare in the boulder-clays of the northern shores of the Moray Frith; for there the nearest Lias, bearing in a western direction from the clay, is that of Applecross, on the other side of the island; and the materials of the boulder-deposits of the north have invariably been derived in the line, westerly in its general bearing, of the grooves and scratches of the iceberg era. But on the southern shore of the frith, where that westerly line passed athwart the Liasic beds of our eastern coast, organisms of the Lias are comparatively common in the boulder-clays; and here, at Blackpots, we find an extensive deposit of the same period formed of Liasic materials almost exclusively. Fragments of still more modern rocks occur in the boulder-clays of Caithness. My friend Mr. Robert Dick, of Thurso, to whose persevering labors and interesting discoveries in the Old Red Sandstone of his locality I have had frequent occasion to refer, has detected in a blue boulder-clay, scooped into precipitous banks by the river Thorsa, fragments both of chalk-flints and a characteristic conglomerate of the Oölite. He has, besides, found it mottled from top to bottom, a full hundred feet over the sea-level, and about two miles inland, with comminuted fragments of existing shells. But of this more anon.
CHAPTER III.
From Blackpots to Portsoy—Character of the Coast—Burn of Boyne—Fever Phantoms—Graphic Granite—Maupertuis and the Runic Inscription—Explanation of the quo modo of Graphic Granite—Portsoy Inn—Serpentine Beds—Portsoy Serpentine unrivalled for small ornaments—Description of it—Significance of the term serpentine—Elizabeth Bond and her "Letters"—From Portsoy to Cullen—Attritive Power of the Ocean illustrated—The Equinoctial—From Cullen to Fochabers—The Old Red again—The old Pensioner—Fochabers—Mr. Joss, the learned Mail-guard—The Editor a sort of Coach-guard—On the Coach to Elgin—Geology of Banffshire—Irregular paging of the Geologic Leaves—Geologic Map of the County like Joseph's Coat—Striking Illustration.
I parted from Dr. Emslie, and walked on along the shore to Portsoy,—for three-fourths of the way over the prevailing grauwacke of the county, and for the remaining fourth over mica schist, primary limestone, hornblende slate, granitic and quartz veins, and the various other kindred rocks of a primary district. The day was still gloomy and gray, and ill suited to improve homely scenery; nor is this portion of the Banff coast nearly so striking as that which I had travelled over the day before. It has, however, its spots of a redeeming character,—rocky recesses on the shore, half-beach, half-sward, rich in wild-flowers and shells,—where one could saunter in a calm sunny morning, with one's bairns about one, very delightfully; and the interior is here and there agreeably undulated by diluvial hillocks, that, when the sun falls low in the evening, must chequer the landscape with many a pleasing alternation of light and shadow. The Burn of Boyne,—which separates, about two miles from Portsoy, a grauwacke from a mica-schist district,—with its bare, open valley, its steep limestone banks, and its gray, melancholy castle, long since roofless and windowless, and surrounded by a few stunted trees, bears a deserted and solitary shagginess about it, that struck me as wildly agreeable. It is such a valley as one might expect to meet a ghost in, in some still, dewy evening, as gloamin was darkening into uncertainty the outlines of the ancient ruin, and the newly-kindled stars looked down upon the stream.
It so happened, however, that my only story connected with either ruin or valley was as little a ghost story as might be. I remember that, when lying ill of fever on one occasion,—indisposed enough to see apparition after apparition flitting across the bed-curtains, like the figures of a magic lantern posting along the darkened wall, and yet self-possessed enough to know that they were but mere pictures in the eye, and to watch them as they rose,—I set myself to determine whether they were in any degree amenable to the will, or connected by the ordinary associative links of the metaphysician. Fixing my mind on a certain object, I strove to call it up in the character, not of an image of the conceptive faculty, but of a fever-vision on the retina. The image which I pictured to myself was that of a death's head, yellow and grim, and lighted up, as if from within, amid the darkness of a burial vault. But the death's head obstinately refused to rise. I had no control, I found, over the fever imagery. And the picture that rose instead, uncalled and unexpected, was that of a coal-fire burning brightly in a grate, with a huge tea-kettle steaming cheerily over it.
In traversing the bare height which, rising on the western side of the valley of the Boyne, owes its comparatively bold relief in the landscape to the firmness of the primary rock which composes it, I picked up a piece of graphic granite, bearing its inlaid characters of dark quartz on a ground of cream-colored feldspar. This variety, however, though occasionally found in rolled boulders in the neighborhood of Portsoy, is not the graphic granite for which the locality is famous, and which occurs in a vein in the mica schist of the eminence I was now traversing, about a mile to the east of the town. The prevailing ground of the granite of the vein is a flesh-colored feldspar; and the thickly-marked quartzose characters with which it is set, greatly smaller and paler than in the cream-colored stone, bear less the antique Hebraic look, and would scarce deceive even the most credulous antiquary. Antiquarians, however, have been sometimes deceived by weathered specimens of this graphic rock, in which the characters were of considerable size, and restricted to thin veins, covering the surface of a schistose groundwork. Maupertuis, during his famous journey to Lapland, undertaken in 1737, to establish, from actual measurement, that the degrees of latitude are longer towards the pole than at the equator, and which demonstrated, of consequence, the true figure of the earth, travelled thirty leagues out of his way, through a wild country covered with snow, to examine an ancient monument, of which, he says, "the Fins and Laplanders frequently spoke, as containing in its inscription the knowledge of everything of which they were ignorant." He found it on the side of a mountain, buried in snow; and ascertained, after kindling a great fire around it, in order to lay it bare, that it was a stone of irregular form, composed of various layers of unequal hardness, and that the characters, which were rather more than an inch in length, were written on "a layer of a species of flint," chiefly in two lines, with a few scattered signs beneath, while the rest of the mass was composed of a rock more soft and foliated. Graphic granite, it may be mentioned, generally occurs, not in masses, but in veins and layers. The inscription had been described in a previously published dissertation of immense erudition, as Runic; but a Runic scholar of the party found he could make nothing of it. The philosopher himself was struck by the frequent repetition of characters of nearly the same form on the stone; but he was ingenious enough to get over the difficulty, by remembering that in our notation, after the Arabic manner, characters shaped exactly alike may be very frequently repeated,—nay, as in some of the lines of the Lapland inscription, may succeed each other, as in the sums I. II. III. IIII. or X. XX. XXX.,—and yet very distinct and definite ideas attach to them all. Still, however, he could not, he says, venture on authoritatively deciding whether the inscription was a work of man or a sport of nature. He stood between his two conclusions, like our Edinburgh antiquarians between the two fossil Maries of Gueldres; and, richer in eloquence than most of the philosophers his contemporaries, was quite prepared, in his uncertainty, to give gilded mounting and a purple pall to both.