through soft materials, occupying a part of the ridge of which the Calton Hill and Dumbie Dykes are portions. The soft materials of this valley of St Leonard's were probably similar to those which have been exposed at the Royal Terrace, of which, indeed, they seem to be extensions, resting and covered by the trap; while it is to be particularly noticed that the valley becomes narrow, and terminates just where the harder beds of whinstone approximate.

The valley of the Hunter's Bog is still more instructive. It occupies a position between the whinstone of Salisbury Craigs on the west side, and the Raven's Craig and Dasses on the east, and has been scooped out of the comparatively soft materials of sandstone and clay, the remaining portions of which may yet be seen at the quarries on the west side. Like the valley on the east of St Leonards, it contracts where the hard rock of Salisbury Craigs approaches that of Arthur's Seat, but at its northern extremity it exhibits a peculiarity which establishes a resemblance to that of the Haymarket or the North Loch-it bifurcates, and the hard rock, with its slope in the direction of the valley, constituting the HAGGIS-NOW, has modified the excavating agency precisely in the same manner as the Castle Rock and the Calton Hill, indicating, at the same time, that the direction of the motion was south-westerly.

Behind the Dasses and the Lang-raw, which form the eastern margin of the Hunter's Bog, is the singular valley termed the DRY DAM, which takes its rise between the Nether Hill and the summit of Arthur's Seat, follows a course nearly parallel with the Hunter's Bog, and bifurcates at St Anthony's Chapel, where it terminates, after uniting with the south branch of the Hunter's Bog at the WELL. Towards the head of the DRY DAM there is another valley which opens upon Dunsappie, where we have the excavation and bifurcation analogous to the cases which have been already referred to, the softer materials having occupied the place of excavation.

On the Whinney Hill of Arthur's Seat there are tolerably distinct indications of what seem in their general character to resemble a river course. Running water in a channel has not

only a tendency, from lateral deflections, to form a zig-zag course, but also from vertical deflections to produce a succession of fords and pools or reaches. Traces of such reaches may be observed at Sampson's Grave and other places of the hill.*

Excavations such as Duddingstone Loch, Hunter's Bog, Dunsappie, and Lochend, point in a very obvious manner to this scooping power of deflected or resisted currents; although the formation of some of these hollows may be traced to different agencies, in as far as the retention of water is concerned. I may here observe, that in forming the new embankment at Dunsappie, traces of an earlier one were very distinct, so that an old compensation pond for the use of Holyrood House may now be hastily conceived as the site of an ancient lake. Lochend, Duddingstone, and the Meadows were probably converted into lochs by the unequal distribution of the superficial strata.

The whole phenomena which have thus been briefly noticed, appear to indicate, and not unequivocally, water moving over the surface in an easterly direction with great impetuosity. In order to account for this appearance, it has become fashionable of late, with a certain class of speculative geologists, to assume the submergence of our island in the ocean, at which time the current, then prevailing, is supposed to have formed the hollows to which we have been referring these oceanic currents having been assisted by huge icebergs exerting their crushing and abrading power. The elevation of the land is by such observers imagined to have taken place by sudden jerks or paroxysms, proofs of which are pointed out in certain levels or plains assumed to be sea margins, and in the occurrence of sea shells in what are termed raised beaches.

We are not in a position at this stage of the inquiry to enter on the discussion of the questions connected with this supposed submergence, and elevation, because, without an attentive ex

* Well-marked traces of river reaches occur in other districts, as in the serpentine rock to the east of the Buck of Cabrach, and in a more river-like course through a wood, on the east side of the gneiss rock of Tyrebagger, Aberdeenshire.

amination of the materials occurring on the surface, and their modes of distribution, inquiries too frequently executed in a careless manner, the imagination is very apt to mislead the judgment. But when we shall have instituted such inquiries into the superficial strata of the neighbourhood, the examination of such notions will not be otherwise than a pleasing and easy task. In the mean time, the character of the valleys of abrasion, the hard abrupt rocks facing the west, and the soft protected matter on the lee side, constituting what Sir James Hall termed the craig and tail, warrant us in disregarding the agency of oceanic currents. The tides of the sea act on all sides of a protuberance or island, on account of ripple action, even although the flood and ebb movements may differ in intensity. The Bass, the May, and Inchkeith exhibit no craig and tail appearances, nor is there a trace of such a character in the islands situate in the most rapid of our tideways-the Pentland Firth. If the Castle, the Calton, and Arthur's Seat had ever experienced the fate of the aborigines, and been "beaten, bobbed, and thumped," whether by tidal waves and currents, or icebergs vast, even granting that there was little wind in those days to generate destructive ripple waves, no appearance of a lee side would have been traceable, equalling in magnitude and distinctness the phenomena which have been indicated. If we call to our assistence the Gulf stream, it will not furnish us with analogous phenomena, as the Hebrides, the Orkneys, and Zetland abundantly testify.

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CHAPTER III.

Remains of Abrasion-Effects of Floods-Examples of Rubbed and Scratched Surfaces Deceptive Appearances-Crumpled Surfaces-Fissures and Flaws.

IN the last chapter the conclusion was arrived at, that water had passed over the surface of the district with great velocity, and in an easterly direction, probably at successive intervals, plowing up the soft materials of the rocks, and removing them, modifying by abrasion the harder portions, and thus giving to the valleys and hills their peculiar configuration. Currents on a smaller scale and acting suddenly have frequently taken place, although their peculiar effects have too seldom been recorded in sufficient detail. The following cases, however, may serve as a guide to our further inquiries into a series of phenomena of the most interesting kind.

Sir James Hall, by whom this department of Natural Science was most successfully introduced and illustrated upwards of forty years ago, has put on record that "a country house (in a neighbouring county to Berwick) situated on the slope of a hill, was assailed by a sudden torrent of water, produced by the sudden bursting of a thunder-storm on the hill above. The impetuosity of the stream was such, that it forced its way through the under storey of the house, carrying along with it quantities of sand and gravel and stones of considerable bulk. Happening to be on the spot a few weeks after the accident took place, I observed that every stone, as it passed through the house, had left a rut or scratch behind it upon the flags over which it passed." (Trans. Royal Soc. Edin .vol. vii. p. 128.)

Mr Smith of Jordan Hill, who has laboured zealously and successfully in this department of petralogy, has stated-"At

Greenock in 1834, I witnessed the effects of an inundation, caused by the breaking down of the head of a reservoir, in which upwards of thirty lives were destroyed. In its track to the sea, it exhibited all the phenomena of diluvial action. The streets and walls were marked with furrows; masses of stone, and even of cast iron, were mixed up with clay and gravel, without regard to their gravity; whilst within the houses everything was covered with a thick layer of fine silt, exactly as in the diluvial caves." (Wern. Mem. vol. viii. p. 65.)

Mr David Milne Home of Milnegraden, to whose important labours we have already referred, says,-" In the Tower Burn near Dunglass, there was lately a railway debacle, owing to the breaking down of a high embankment by water accumulating behind it. The torrent carried down with it large quantities of earth and stones; in the course of the passage of which, innumerable scratches and ruts were produced on the solid rock and on large blocks of stone lying in the channel of the burn. I have procured one of the hardest of these blocks, composed of greywacke, which was scratched and rutted on this occasion. It will be found to have on its upper surface at least fifty striæ, all more or less parallel, and some of them of considerable depth. It is deposited in the Museum of the Society. The direction of the striæ on this and other blocks, I found to be coincident with what had been the course of the torrent which passed over them. The striæ thus produced are the more remarkable that they were not on a surface of solid rock, but on a block or boulder capable of yielding to an impulse." (Parallel Roads of Lochaber, p. 42.)

The facts which we have now referred to seem naturally to suggest the question, Do the rocks, by their rubbed and scratched surfaces, furnish proof that a torrent of water has passed over them, carrying sand and stones in its career; and do these dressed surfaces indicate the direction in which the current flowed? Should satisfactory answers be obtained to these inquiries, and coincident with the conclusion already reached, from the consideration of the direction of the valleys and the shape of the hills, we shall be in a condition prepared