frequent ague-fits and earth-waves; and, after some mightier earthquake had billowed the landscape, dashing together the crests of tall trees and gigantic shrubs, there would be a roar, as of many waters, heard from the distant outskirts of the scene, and one long wall of breakers seen stretching along the line where earth and sky meet,-stretching inwards and travelling onwards with yet louder and louder roar,-Calamite and Ulodendron, Sigillaria and Tree-fern, disappearing amid the foam,-until at length all would be submerged, and only here and there a few Araucarian tops seen over a sea without visible shore. Such was the character, and such were the revolutions, of the land of the Carboniferous era,—a land that seems to have been called into being less for the sake of its own existence than for that of the existences of the future.

LECTURE SIXTH.

Remote Antiquity of the Old Red Sandstone-Suggestive of the vast Tracts of Time with which the Geologist has to deal-Its great Depth and Extent in Scotland and England-Peculiarity of its Scenery-Reflection on first discovering the Outline of a Fragment of the Asterolepis traced on one of its Rocks-Consists of Three Distinct Formations-Their Vegetable Organisms-The Caithness Flagstones: how formed-The Fauna of the Old Red Sandstone-The Pterichthys of the Upper or Newest Formation-The Cephalaspis of the Lower Formation -The Middle Formation the most abundant in Organic Remains-Destruction of Animal Life in the Formation sudden and violent-The Asterolepis and Coccosteus--The Silurian the Oldest of the Geologic Systems-That in which Animal and Vegetable Life had their earliest beginnings-The Theologians and Geologists on the Antiquity of the Globe-Extent of the Silurian System in Scotland-The Classic Scenery of the Country situated on it-Comparatively Poor in Animal and Vegetable Organisms-The Unfossiliferous Primary Rocks of Scotland-Its Highland Scenery formed of them-Description of GlencoeOther Highland Scenery glanced at-Probable Depth of the Primary Stratified Rocks of Scotland-How deposited-Speculations of Philosophers regarding the Processes to which the Earth owes its present Form-The Author's Views on the subject.

I INCIDENTALLY mentioned, when describing the Oolitic productions of our country, that the shrubs and trees of this Secondary period grew, on what is now the east coast of Sutherland, in a soil which rested over rocks of Old Red Sandstone, and was composed mainly, like that of the county of Caithness in the present day, of the broken débris of this ancient system. We detect fragments of the Old Red flagstones still fast jammed among the petrified roots of old Oolitic trees; we find their water-rolled pebbles existing as a breccia, mixed up with the bones of huge Oolitic reptiles and the shells of extinct Oolitic molluscs; we even find some of its rounded masses incrusted over with the corals of the Oolite: the masses had existed in that

remote age of the world as the same grey indurated blocks of stone that we find them now; and busy Madreporites, -Isastræa and Thamnastræa,-whose species have long since perished, built up their stony cells on the solid. foundations which the masses furnished. Nay, within the close compressed folds of these flagstones lay their many various fossils, glittering scale, and sharp spine, and cerebral buckler, in exactly the same state of keeping as now; and had there been a geologist to take hammer in hand in that Oolitic period, when the spikes of the Pinites Eiggensis were green upon the living tree, and the Equisetum columnare waved its tall head to the breeze, he would have found in these stones the organisms of a time that would have seemed as remote then as it does in the present late age of the world. We may well apply to this incalculably ancient Old Red system what Wordsworth says of his old Cumberland beggar,—

'Him from my childhood have I known; and then

He was so old, he seems not older now.'

This glimpse, through the medium of the high antiquity of the Oolite, of an antiquity vastly higher still,-that of the Old Red Sandstone,-may well impress us with the enormous extent of those tracts in time with which the geological historian is called on to deal. There are some of the lesser planets that seem to the naked eye quite as distant as many of those fixed stars whose parallax the astronomer has failed to ascertain; but when they come into a state of juxtaposition, and the moveless star is seen dimly through the atmosphere of the moving planet, we are taught how enormous must be those tracts of space which intervene between them, and keep them apart. And it is thus with the periods of the geologist. Even the comparatively near are so distant, that the remote seem scarce more so; but the dead and stony antiquity of one system, seen as if through the living nature of another, enables us, in at least

some degree, to appreciate the vastness of those cycles by which they were separated. It is further interesting, too, thus to find one antiquity curiously inlaid, as it were, in another. We feel as if, amid the ancient relics of a Pompeii or a Herculaneum, we had stumbled on the cabinet of some Roman antiquary, filled with bronze and granite memorials of the first Pharaohs, or of the old hunter king who founded Nineveh ;-things that in times which we now deem ancient had been treasured up as already grown venerably old.

The Old Red Sandstone underlies the Coal Measures, and is, in Scotland at least, still more largely developed than these, both in depth and lateral extent. In Caithness and Orkney, one of the three great formations of which it consists has attained to a thickness that equals the height of our highest hills over the sea.1 The depth of the entire system in England has been estimated by Sir Roderick Murchison at ten thousand feet; and as these ten thousand feet include three formations so distinct in their groups of animal life that not a species of fish has been found common to both higher and lower, it must represent in the history of the globe an enormously protracted period of time.

The scenery of the Old Red Sandstone we find much affected to the south of the Grampians, like that of the Coal Measures, by the presence of the trap rocks; but in the north, where there is no trap, it bears a character decidedly its own. It is remarkable for rectilinear ridges elongated for miles, that, when they occur in semi-Highland districts, where the primary rocks have been heaved into wave-like hills, or ascend into boldly-contoured mountains, constitute a feature noticeable for the contrast which it forms to all the other features of the scene. In approaching the eastern coast

1 The Caithness flagstones and their ichthyolites constitute, according to Sir R. Murchison, the central portion of the Old Red group. — W. S. S.

of Caithness from the south, the voyager first sees a mountain country, the land piled up stern and high,-the undulations bold and abrupt. He is looking on the Highlands of Sutherlandshire. All at once, however, the aspect of the landscape changes;—the broken and wavy line suddenly descends to a comparatively low level, and, wholly altering its character, stretches away to the north, straight as a tightened cord, or as if described by a ruler. Caithness thus seen in profile reminds one of a long thin proboscis, or mesmerized arm, stretched stiffly out from the Highlands to the distant Orkneys. In sailing upwards along the Moray Firth, the line which defines seawards the plain of Easter Ross from the Hill of Nigg to the low rocky promontory of Tarbat, topped by its lighthouse, presents nearly the same rectilinear character. Another long straight line which meets the eye on entering the bay of Cromarty stretches westwards from the hill of granitic gneiss immediately over the town, and runs for many miles into the interior along the bleak ridge of the Black Isle. Yet another rectilinear line may be seen running on the south side of the Moray Firth, from beyond the Moor of Culloden, which it includes, to the eastern end of Loch Ness. And in all these instances the rectilinear ridges are composed of Old Red Sandstone. On some localities on the seaboard of the country the system is much traversed by firths and bays, and what in Caithness and Orkney are termed goes,―narrow inlets in the line of faults, along which the waves find straight passage far into the interior. From the Hill of Nigg, the centre of an Old Red Sandstone district, the eye at once commands three noble firths, all scooped out of the deposit, the Firth of Cromarty, the Dornoch Firth, and the upper reaches of the Moray Firth. It commands, too, what is scarce less a feature of the Old Red system,—the rich corn-bearing plains of Moray and of Easter Ross; and from the union which the prospect exhibits of two elements