some old people then alive, it had formed one continuous tract of firm ground. Nay, it appears that during the ten years previous to 1816, the channel had been worn down at least two feet.

Probably no part of the British coast-line affords such striking evidence of the violence of the waves as may be seen along the margin of the Shetlands. These islands are exposed to the unbroken fury at once of the North Sea and of the Atlantic, the tides and currents of both seas running round them with great rapidity. Hence their seaboard wears in many places an aspect of utter havoc and ruin. Against their eastern side, the North Sea expends its full violence, tearing up the rocks from the craggy headlands, and rolling onwards far up into the most sheltered fjords. On some of the projecting headlands the breakers, during easterly gales, burst with incredible violence and bury the cliffs in yeasty water and foam. Where the structure of the rocks favours the progress of demolition, narrow gullies or 'voes' are cut out of the cliffs, at the end of which there is often a cave or tunnel, with an opening at the farther end of its roof, whence the spray is ejected over the land. The flagstone cliffs repeat the mural scenery of the Orkney and Caithness coasts (Fig. 14).

A little farther north the crystalline schists of the main island are prolonged eastwards in a group of islets and skerries that project into the North Sea. Among these outlying islands, Whalsey, lying about the middle of the Shetland group, is completely sheltered from the gales of the Atlantic. Yet in the Bound Skerry of Whalsey, the breakers have torn up masses of rock sometimes 8 tons in weight, and have heaped them together at a height of no less than 62 feet above high-water mark. Other blocks, ranging in bulk from 6 to 13 tons, have been actually quar

ried out of their place in situ at levels of from 70 to 74 feet above the sea. One block of 70 tons, lying 20 feet above the water, has been lifted from its bed and borne to a distance of 73 feet from S.S.E. to N.N.W. over abrupt opposing faces of rock as much as 7 feet in height.1 On the west side of the Shetland Islands the fury of the Atlantic has produced scenes of devastation which it is hardly possible adequately to describe. In stormy winters, huge blocks of

FIG. 14.-Noss Head, Shetland. A cliff of flagstone which overhangs, owing to the inward dip of its leading joints.

stone are overturned or are removed from their native beds to a distance almost incredible.

Dr. Hibbert found that in

1 See an interesting paper by Mr. T. Stevenson. Proc. Roy. Soc. Edin. iv. 200; also his work On the Design and Construction of Harbours (1864), pp. 30-38. Mr. Peach, in his paper on the traces of Glacial Drift in the Shetland Islands (British Association Report, 1864), noticed further proof of the power of the breakers among these islands. On the top of the cliffs of the island of Honsay, about 100 feet high, the waves break in stormy weather, tearing up the rock and piling its huge fragments into a semicircular wall a considerable way back from the edge of the cliff. 'Between this wall and the cliff a deep river-like gully is scooped out, down which the water rushes again to the sea, a great distance from the spot whence it was thrown up.'

the winter of 1802 a tabular mass, 8 feet 2 inches in length by 7 ft. in breadth and 5 ft. 1 in. in thickness, was dislodged from its bed and removed to a distance of from 80 to 90 feet. In 1820, he found that the bed from which a block had been carried the preceding winter, measured 17 ft. by 7 ft. and 2 ft. 8 in. in depth. The removed mass had been borne a distance of 30 feet, when it was shivered into thirteen or more fragments, some of which were carried still farther, from 30 to 120 feet. A block 9 ft. 2 in. by 6 ft. and 4 ft. thick, was hurled up the acclivity to a distance of 150 feet. 'Such,' he adds, 'is the devastation that has taken place amidst this wreck of nature. Close to the Isle of Stenness is the Skerry of Eshaness, formidably rising from the sea, and showing on its westerly side a steep precipice, against which all the force of the Atlantic seems to have been expended: it affords refuge for myriads of kittiwakes, whose shrill cries, mingling with the dashing of the waters, wildly accord with the terrific scene that is presented on every side.'1

The result of this constant lashing of the surge has been to scarp the coasts of the Shetlands into the most rugged and fantastic cliffs, and to pierce them with long twilight caves. Dr. Hibbert describes 'a large cavernous aperture, 90 feet wide, which shows the commencement of two contiguous immense perforations, named the Holes of Scranda, where, in one of them that runs 250 feet into the land, the sea flows to the utmost extremity. Each has an opening at a distance from the ocean, by which the light of the sun is partially admitted. Farther north other ravages of the ocean are displayed. But the most sublime scene is where a mural pile of porphyry, escaping the process of disintegration that is devastating the coast, appears to have been left

1 Hibbert's Shetland Islands, p. 527.

as a sort of rampart against the inroads of the ocean. The Atlantic, when provoked by wintry gales, batters against it with all the force of real artillery-the waves having, in their repeated assaults, forced for themselves an entrance. This breach, named the Grind of the Navir, is widened every winter by the overwhelming surge, that, finding a passage through it, separates large stones from its side, and forces them to a distance of 180 feet. In two or three spots the fragments which have been detached are brought together in immense heaps, that appear as an accumulation of cubical masses, the product of some quarry.' In other places, the progress of the ocean has left lonely stacks, or groups of columnar masses at a distance from the cliffs. Such are the rocks to the south of Hillswick Ness, and the strange tower-like pinnacles in the same neighbourhood called the Drenge, or Drongs, which, when seen from a distance, look like a small fleet of vessels with spread sails. Many 'blowholes' have likewise been drilled in the roofs of sea-worn caves, and from these during storms sheets of foam and spray are shot high into the air.

The most stupendous sea-cliff in Shetland towers some 1300 feet above the Atlantic on the west side of the island of Foula. It consists of Old Red Sandstone, and bears impressive testimony to the variety and dignity of the rock-scenery which is characteristic of that formation in Scotland.

The Hebrides, not less than the Shetlands, illustrate the power of the ocean in working the degradation of the land. The most careful observations of the force of the breakers in this part of the British seas are those made during the progress of the erection of the lighthouse on Skerryvore—a rock lying to the south-west of the island of Tiree, and exposed to the full fury of the Atlantic, there being no land

between this point and the shores of America. The average results of these experiments for five of the summer months during the years 1843 and 1844, give to the breakers a force of 611 lbs. per square foot; and for six of the winter months of the same years 2086 lbs. per square foot, or thrice as great as in the summer months. The greatest result obtained was during the heavy westerly gale of 29th March 1845, when a pressure of 6083 lbs. per square foot was registered. This was a force of little short of three tons on every square foot of surface. The next in magnitude was a

force of 5323 lbs.1

North-west of Skerryvore lies the island of Barra Head, the last of the long chain of the broken and deeply embayed Hebrides. It is recorded that on this island, during a storm in January 1836, a mass of gneiss containing 504 cubic feet, and estimated to be about 42 tons in weight, was gradually moved five feet from the place where it lay, having been rocked to and fro by the waves, until a piece broke off, which, jamming itself between the block and the rock below, prevented any further movement.2

Fortunately the rock which has had to withstand this tremendous battery, is a tough gnarled gneiss. But where the coast is low, and more especially where the hard gneiss passes under a covering of blown sand, the Atlantic breakers have made sad inroads even within the last few generations. 'The most destructive process of nature,' says the author of the description of the Isle of Harris in the old Statistical Account of Scotland is the continual wasting of the land on the western shore by the perpetual drifting of the sand, and the gradual encroachment of the sea. This is evinced by the clearest testimonies. Lands which were ploughed within

1 T. Stevenson, Trans. Roy. Soc. Edin. xvi. p. 25.

2 Ibid. p. 28.