Some of the most striking instances occur along the south coast of Devon and the coast of Dorset between Sidmouth and Lyme Regis. At Dowlands the Chalk and Greensand stretch over the denuded edges of the Lower Lias, Rhætic beds, and Red Marl, all of which are of a clayey nature. The Cretaceous beds dip slightly towards the sea, and numerous springs are given out at the junction of the Greensand with the lower Secondary strata. Portions of the lower sandy beds of the Greensand moreover would be actually removed by springs. Therefore we have every condition favourable to the production of landslips, and they have FIG. 23.-Diagram-section of Landslip near Lyme Regis.

occurred in great magnitude along the coast at different periods. The great landslip of Bindon took place at Christmas 1839. (See fig. 23.)

The length of the great chasm caused by this subsidence was 1,000 yards, the breadth 300 yards, and the depth varied from 130 feet to 210 feet. Twenty-two acres were sunk in the chasm.1

Landslips have occurred along the coast between Flam

1 A model of this landslip by Mr. W. Dawson may be seen at the Museum in Jermyn Street, London. Fig. 23 is partly taken from a drawing by Mr. Dawson.

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borough Head and Filey Point, where the Chalk and Speeton Clay are exposed.

They are not unfrequent in the London Clay cliffs of Sheppey.

In the Isle of Wight the beautiful scenery of the Undercliff has been produced by the Upper Cretaceous strata, Chalk and Greensand, foundering over the Gault Clay, which for this reason has been called 'the blue slipper.' There is an Undercliff also at Folkestone.

Large landslips occur in the Woolhope district, where the Upper Ludlow rocks, owing to their jointed nature and steepness of dip, have tumbled into the valleys.

In the neighbourhood of Bath vast masses of the Great Oolite are frequently spread over the slope of the Fuller's Earth, and the Inferior Oolite is similarly tumbled in places over the Lias.

Eolian or Blown Sands.

On coasts where a great quantity of sand is formed, and which is exposed to the winds at low tide, hillocks or dunes' of sand are raised along the shore, and the ground for some distance inland is coated with a sandy soil. Sometimes the beds of Blown Sand contain marine as well as common land shells, as on the hill above Sennen Cove, overlooking Whitesand Bay (Land's End), and on the Warren at the mouth of the river Ex. Wind ripple marks' are sometimes met with.

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Blown Sand occurs at Phillack, Upton, and Gwythian Towans, near Phillack and Lelant, at Perran, and Constantine

1 It is necessary to be particular in discriminating between such deposits and Raised Beaches. See Pengelly on Raised Beaches, Trans. Devon Assoc. 1866.

Bay, in Cornwall; also at Braunton Burrows, Burnham, and Woodspring, near Candleston Castle (South Wales), Barmouth, &c.

In the district between Liverpool and Southport, and in that of Wirral, are certain sand dunes, the base of which Mr. De Rance found to consist of a bed of sandy silt, the result of wind blowing sand into pools in which peat was forming. It contains Bithynia tentaculata, and he has named it the Bithynia Sand.

Much Blown Sand also occurs at Lowestoft, and along the Norfolk coast, also at Romney, and at Poole in Dorsetshire. The formation of sandstone generally is instructively illustrated by recently-consolidated sand at Newquay in Cornwall, and many similar examples exist around our western coasts, where hills of Blown Sand prevail. The water percolating through the upper layers dissolves the carbonate of lime, or of iron, and sometimes silica, which are re-deposited as cementing materials, on the evaporation of the water as it filters through the lower strata of the porous sand.2

Submarine Forests.

While the Raised Beaches indicate an upward movement in the land, there are many traces of old land surfaces along our coasts, submerged or partly so, which contain fragments and stumps of trees, sometimes erect and with their roots embedded in the old soil on which they grew. They occur in estuaries or near the mouths of rivers.

1 Towan (towyn) means Downs; Les Landes, or 'barren heaths,' is a sandy district on the south-west coast of France, hence Lelant. (Edmonds.)

2 Hunt and Rudler, Descriptive Guide to the Museum of Practical Geology.

Such Submarine or Submerged Forests may be of very different dates, according to the organic remains they may contain. For instance, the Cromer Forest Bed (see p. 291) is of Pre-Glacial age.

Submerged forests occur at Poole Harbour, off Bournemouth, Southsea Castle, Pagham, Bracklesham, and Portsmouth.'

At Portsmouth it is considered that the washing out of an overlying sandy stratum may have produced inundation and the appearance of submergence: a cause which it is considered may have influenced the production of other socalled Submerged Forests.

A Submerged Forest occurs at Porlock Bay, and another at Swansea Bay. That at Stolford and Bridgewater Bay seems to be connected with the peat-beds of the Somersetshire Levels. (See p. 330.) A similar Submerged Forest has been noticed at Sharpness, Gloucestershire.

Numerous Submerged Forests have been noticed on the coasts of Devon and Cornwall.

In South Devon they occur in Torbay, at Blackpool, at North and South Sands in the Salcombe estuary, and in Bigbury Bay, &c.

Mr. Pengelly has stated that we may not unreasonably believe that, if attention were given to the subject, they might be detected beneath the extensive sands which occupy other parts of the coast line. During stormy seasons, these sands are liable to sudden and great displacements. Were opportunities of this kind carefully watched, we should probably find that, with the exception of its rock-bound portions,

1 From Lewes Levels to Chichester Harbour, and on to Hurst Castle, the coast exhibits signs of undergoing elevation at the present day. The coast of the Isle of Wight, opposite, seems, on the contrary, to be suffering depression; whilst the back of the island exhibits some curious signs of local oscillation. (Godwin-Austen.)

the entire coast of South Devon is engirt with Submerged Forests.

Peat.

Peat is an accumulation of vegetable matter varying in composition, but often formed to a large extent of the Bogmoss (Sphagnum palustre).

The whole of this matter is in some stage of decomposition. Near the surface the substance is light coloured and spongy, and the vegetable remains are but little altered; deeper down it is brown, dense, and decomposed; at the bottom it is black, and the peat becomes earthy in its texture.

The Bog-moss continues growing upwards from the points of the shoots, while decay is advancing in a similar manner from their lower extremities, thus forming a thick close mass of vegetable matter, which rots below as it increases in height.

When peat accumulates on a clayey surface abounding in springs, the water sometimes oozes out beneath the peat, and between it and the natural soil in such quantities as to raise up the layer of peat so that it floats.'

Peat beds vary in thickness from a few feet to 20 or 30 feet. The peat is largely dug for fuel, being cut in the summer season and stacked. It holds a large amount of water, but the slowness with which it parts with it is a great hindrance to its being largely worked.

Peat is sometimes divided into Hill-peat, Bog-peat, &c., according to the situation in which it is found, and the conditions under which it has been formed, whether on mountain sides, in marshes, forests, lakes, or near the sea.

Peat-bogs are not uncommon on our bills, in North

1 See article on Peat in Ure's Dictionary. Peat is well known to store up water on mountains.