have wandered for hours,' says Hugh Miller, 'amid the sand-wastes of this ruined barony, and seen only a few stunted bushes of broom, and a few scattered tufts of withered bent, occupying, amid utter barrenness, the place of what, in the middle of the seventeenth century, had been the richest fields of the rich province of Moray.'1 The coast of Aberdeenshire is varied with wide stretches of drifting sands. One of these extends for several miles on both sides of Rattray Head, and another runs for some fifteen miles from near Slains to Aberdeen. Many a fair field has disappeared under the dunes, as these march inland. The parish of Forvie,' says Pennant, 'is now entirely overwhelmed with sand except two farms. It was in 1600 all arable land, now covered with shifting sands, like the deserts of Arabia, and no vestiges remain of any buildings except a small fragment of a church."2 The wide Tents Muir, between the bay of St. Andrews and the mouth of the Tay, presents a remarkably good example of the parallelism of the suc cessive sand-ridges with the line of the coast.

On the west side of the country many tracts of dunes also occur. They are particularly abundant in the southern half of the Hebrides, where the Atlantic breezes have built up an almost continuous strip of sandy ridges along the western coasts of Bernera and North and South Uist. Again, on the west sides of the islands of Coll and Tiree, and in Macrihanish Bay, Cantire, similar accumulations may be seen. Even in the comparatively sheltered basin of the Clyde, examples occur not less extensive than those of more open parts of the coast-line. The margin of Ayrshire, for fully fifteen miles between Stevenston and Ayr, is fringed with dunes, where the same melancholy tale of devastation is 1 Sketch-Book of Popular Geology, p. 13. 2 First Tour, p. 144.

told. Fifteen years ago, to the east of Stevenston, I saw a roadway deeply buried under the loose drifting sand, and only traceable by the tops of the blackened decaying hedgerow on either side of it. The Wigtonshire shores are likewise mottled with dunes.

In connection with the subject of the blown-sand accumulations of the Scottish coast-line, I may refer to the remarkably interesting archæological discoveries which in recent years have been made in them. From those of Wigton and Culbin, in particular, thousands of objects have been recovered, ranging in antiquity from the Stone Age up to the reign of Queen Victoria. The constant shifting of the sand makes it continually cover up the present surface and expose old ones, so that objects of vastly different age may be buried almost side by side in the same deposit.

The mere mechanical force of the wind upon the surface of the land is probably nowhere in Britain so sensibly felt as among the bare and exposed Orkney and Shetland. Islands. I have been astonished, when walking along the edges of the great precipices of the island of Hoy, 1200 feet high, to find scores of flat pieces of sandstone strewn across the moor. These fragments had been torn from the face of the cliffs by a previous gale and swept upward and inland. Besides the impetus of the breakers, hurricanes of wind must have a considerable influence in the degradation of these sea-cliffs.

BROOKS AND RIVERS.

Instead of formally describing the geological work done by running water, let me in imagination transport the reader to the long bald scalp of one of the higher hills among the pastoral uplands of the south of Scotland, and ask him

But

The

to descend with me the course of a stream that we see furrowing the hillside below us. Striking across the bare moor we reach the spring or 'well-eye' whence the rivulet takes its rise-a patch of bright-green amid the brown heath, that may treacherously conceal a deep pool of water or a basin of liquid peat. Issuing from this source, the rivulet trickles at first along the heath and bent, but soon cuts through these into the black peaty layer below them, where it runs for a short distance as in a furrow or gutter. gaining volume and force as it works its way down the steeper slope, it digs its channel through the peat into the layer below, wherein the stones are bleached white by the solvent action of the organic acids in the peat. Every yard that we descend shows us more evidence of erosion. runnel has now cut deeply into the cover of rain-wash, drift or decomposed rock that lies on the more solid rock below. So great is the erosion, that the stream has excavated a deep narrow gully in this superficial layer of loose material, and the coherent stratum of peat projects in black cornices on either side. From time to time, these ledges break off, so that blocks of peat several yards in circumference lie in tumbled ruin at the bottom of the ravine, where they are eventually broken up and washed away down into the valley. The rapidity with which such a deep narrow trench may be formed on a steep hillside is sometimes strikingly exemplified by the fate of one of the sheep-drains cut on those uplands to carry away the surface-water. Sudden heavy rains, or what the shepherds call 'waterspouts,' occasionally discharge such a volume of water into one of these shallow trenches that it is quickly deepened and widened, and becomes for the time the channel of a swift torrent. When the drainage has once found its way into such a channel, it is apt to keep to it. Successive rains thus dig the gully

deeper and deeper, until in perhaps not more than six or eight years it forms a yawning chasm ten or fifteen feet deep (Fig. 5).

Following the track of the stream down the hill, we find that it eventually cuts into the solid underlying rock wherein it has gradually hollowed out a little gully, in the bottom of which it flows. At the foot of the steep hillside, it encounters a flat meadow, and there, its current being checked and its

carrying power being consequently lessened, it drops the burden of detritus which it has swept down in its bed. These materials are spread out in fan-shape on the plain, and in more mountainous districts form a striking part of the scenery of the valleys. Conspicuous examples may be seen, for instance, in the Pass of Drumouchter, through which the Highland Railway runs across the watershed of the country. There, on the flanks of the two mountains that face each

other across the glen, the Sow of Athol and the Boar of Badenoch

'Oft both slope and hill are torn,

Where wintry torrents down have borne,
And heaped upon the cumbered land

Its wreck of gravel, rocks, and sand.'

I will further suppose that after winding about in its flat valley, and being joined by similar rills from either side, our stream, growing in volume as it advances, at last enters a thick wood, from which issues the roar of a waterfall. Skirting the wood and rejoining the stream a little farther down, where the valley somewhat contracts, we find ourselves on the brink of a deep ravine, at the bottom of which the water dashes merrily onward between precipitous walls of ferntufted rock. The idea that naturally suggests itself in such a scene is to look upon this rent as due to some convulsion by which the solid earth has been broken open. But if that idea were true there ought to be some evidence of it in the dell itself. Yet were we to descend to the bottom and search for such evidence, we should almost certainly find the ledges of rock to be traceable unbroken across the bed of the brook. Had the ravine been a chasm produced by underground disturbance, not only would the rocks along its bottom have been fractured, but the gaping walls would have been separated, not by unbroken rock but by dislocated masses from either side. Nevertheless, to one who has never thought of the subject, nor given heed to the operations of running water across the surface of the land, the assertion that no earthquake or convulsion has had any share in the formation of such a ravine seems mere paradox, and he will incredulously ask whither he must turn to find another natural agency equally grand in its working and mighty in its results. Such a question reveals the true cause of the pre