Still feel the breeze down Ettrick break,
Although it chill my withered cheek;
Still lay my head by Teviot stone,
Though there forgotten and alone.”
And so human life will glide away, a new epoch will come, and the development of man’s immortal being will be accomplished in the new and brighter earth that is to arise.
We here close our review, over Scottish ground, of the earliest lessons to which we have access of the mineral structure of our globe. All the primary, palæozoic, and older class of the secondary rocks, are largely developed, leading us, indeed, a very little way into the inner chambers of the earth, but back through periods of time into the records of its history, for which the science itself furnishes no real standard of measurement. Vast, inconceivable cycles pass before the imagination, and fascinate the speculatist, while the sober inquirer pauses, doubts—nay, startles—at such remote undefined annals of creation. The legends and chronicles of Scotland are old indeed; but give geologists their own way, and what an antiquity would they assign to the mountains, valleys, and rivers of ancient Caledon! And yet, true it is, no rocks on the face of the earth can claim a deeper origin, an earlier arrangement, a more ancient ascent above the waters, than those whose nature and position we have so cursorily described.
Leaving for the present the question as to Time, geology has this advantage, in facilitating an acquaintance with its principles, that its lessons are as general as they are particular. Go where you will the record is before you, so that, generally speaking, what is observed of its subject in one district or country, or even continent, has its counterpart in some other place near or remote. The rocks of Scotland are all on the great scale, not solitary and individual specimens, but wide-spread formations along the face of the country. With scarcely a single exception, every class of rocks described in our course stretches from sea to sea over the island. The structure of Scotland is peculiar in this, that the bearing and the strike of the various strata, are correspondent and continuous. Hence the parallelism of the great straths and valleys. The principal rivers are observant of the same law. The several formations, from the primary crystalline to the coal and upper sandstones, have a common axis of elevation from nearly E. N. E. to W. S. W., partaking more of an equatorial than of a meridional direction. The porphyries and chains of the older traps maintain a similar direction. The greenstones and basalts, polygonal and jointed, or otherwise, are for the most part to be found within the area of the coal measures, or rising along the out-crop of the basins. Hence a description of any one locality will generally, in respect of the same series of rocks, be found applicable to another. The student may indifferently begin his researches as his convenience or sojourn for the time may direct. And whether it be the granite on the coasts of Aberdeen or of Arran—the schists of Glenisla or the Mull of Cantire—the silurian of St. Abb’s Head or Portpatrick—the devonian of Stonehaven or Girvan—the porphyries of Dundee or Largs—the shales and limestones of St. Andrews, Glasgow, or Ayr—the columnar basalts of Earlsferry, Orrock, Campsie, or Staffa—the lesson throughout will be one and the same, either as respects the mineral texture or the geological position of the rocks examined. A section, therefore, commencing at Ben Nevis and terminating at Kirkcudbright on the Solway, would present the very same series in all the main phenomena of superposition, structure, dislocation, and fossil remains, as the section adopted from Ben-Mac-Dhui to the Cheviots. Granite, gneiss, quartz rock, mica schist, and clay slate, underlie the old red sandstone which traverses the upper district of Stirlingshire. The traps of the Campsie Hills have thrown up, and form the boundary of the great coal-basin, of which Glasgow constitutes the center, and within whose area and suburbs are exhibited all the most striking features of the basalt and greenstone family—the elevation at the Necropolis beautifully showing the effects of their intrusion, and the induration of the sedimentary deposits. On the south, the coal metals are again succeeded by the old red sandstone and the porphyries, which in their turn are replaced by the silurian or graywacke rocks of the border counties. The section throughout is of the most varied and instructive character, diversified by the grandest mountain scenery, the loveliest of the Scottish lakes, and a development of the arts and sciences over inexhaustible coal and iron treasures which has rendered the name of the western metropolis illustrious among the cities of the world.
Should the geologist desire to extend his researches along the western coast and among the islands, he will experience an additional interest, arising chiefly from the numerous junctions of the different formations or sets of rocks which the constant erosion of the Atlantic has everywhere exposed to view. Gigantic isolated portions of granite or syenite, bared all around, are to be seen on every headland. The twistings and flexures of gneiss and the schists are frequent and remarkable. Columnar basalt, similar to Staffa, fringes the base of every islet and promontory; and from appearances like these, he will invariably infer the presence of the carboniferous deposits, which, in small detached patches are of common occurrence. Here, likewise, are to be found the lias and oolites, in marginal stripes on several of the islands, easily distinguished by their characteristic fossils, and giving unequivocal indications of a far greater extension, and continuity with the main land, ere the inroads of the sea had broken up and parted so much of the aboriginal structure of the district. The vi et sæpe cadendo of geological agency—the convulsions of subterranean forces, and the destroying powers of water—are exhibited in all their grandeur, where, in the face of cliffs exposed to their foundations, the hardest rocks may be observed yielding to every wave, and the whole inner machinery of granitic and basaltic dykes which upheaved them from their basis traced in their most varying forms and complicity. Out of the Ægean a finer group of islands is nowhere to be threaded—some scarcely raised above sea-level—some towering into the clouds, as in the lofty peaks of Mull, Jura, and Rum, with an altitude almost equal to their length—most of them glorying in names soft and euphonious as the choicest of classic Greece—and yet, all fragmentary and disrupted, as if but yesterday shivered by the thunder cloud. Skye exhibits an epitome not of the islands only, but nearly of our whole British geology, in which there is every variety of trap, combined with the primary series—coal, white sandstone, and limestone—the lias and oolites of secondary formation—and mountains 3,300 feet in height, composed of Labrador feldspar and hypersthene, whose crystals in the dark composite mass rival in structure, if not in beauty, the stalactitic concretions of the Spar Cave itself. Rocks, too, are here, of metamorphic texture, to which a Macculloch did not venture to assign a name or position in his list. And the serrated jagged pinnacles of the Coolin ridge, with the black Coruisk inclosed as in a crater, who will attempt to describe—unlike to everything else in bleak, naked, precipitous grandeur! The poet of the Isles has sketched the picture—
“Such are the scenes, where savage grandeur wakes
An awful thrill that softens into sighs;