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THE COAST OF ENGLAND.
THE SOUTH COAST. Start Point to Portland Bill.—Between these two headlands, a distance of 48 miles, is Lyme Bay, the cliffs having been worn back in the centre 25 miles from the straight line.
This coast-line offers the most interesting study in littoral drift to be found anywhere round the shores of England. Its description has therefore been dealt with in some detail. While the softer rocks of which the cliffs are composed have been wasted by the action of the sea, the harder intrusive material has remained, forming projecting headlands between which the coast has been hollowed out during the lapse of ages into a great number of coves and small bays. Each of these bays has its own peculiar characteristic; and the beach its own distinctive shingle derived from the local cliffs, which is prevented from drifting westward into the next bay by the natural groyne formed by the western headland.
The general set of the flood tide is easterly, but its course is disturbed by the projection of these two headlands, the sea being agitated down to a depth of 29 fathoms off Start Point, and the surface water much broken. At Portland the tide runs with great violence, the velocity round the Bill reaching 7 knots at spring tides, causing great whirls and eddies.
The regular easterly set of the tidal flow along the bay is also disturbed by the numerous projections of the smaller indents, and counter currents are set up, the tide in some part of the bays swirling round the headlands and assuming a westerly set.
Although the general course of the drift of the beach material is also easterly, following the set of the flood tide, this course in some instances is reversed, and the shingle is drifted in two opposite directions in the same bay.
Off Start Point, at about a mile distant, there is a bank known
as “ The Skerries.” It is about half a mile wide, and extends in a north-easterly direction for about 37 miles. This bank consists of shells and fine gravel, its surface being from 1} to 4 fathoms below low water. A somewhat similar bank of shells, known as “ The Shambles,” exists off the other horn of the bay at Portland. This shoal has from 11 to 18 feet of water over it, and rises from a depth of 10 fathoms. Although the material of both these banks is in constant movement, and the sea breaks very heavily on them, their position has remained unaltered as long as any record exists.
Commencing at the westerly end, the headland at Start Point and the projection at Dartmouth, a distance of 10 miles, form an embayment 3 miles in depth. The flood tide, striking the projection at the northern end of the bay, sweeps round along the shore and sets southward for nine hours out of the twelve.
The coast of this embayment is cut up into several smaller bays divided by projecting points of hard rock. These bays are known respectively as Hall Sands, Bee Sands, Slapton Sands, and Blackpool Sands. The cliffs are composed principally of metamorphic rocks with bands of quartz, Start Point itself being chloritic slate, and that at Combe Point, near the mouth of the Dart, of diabase. The beach material diminishes in size from pebbles at Hall Sands to fine sand at Blackpool cove.
Slapton Sands.—The beach material in Slapton Bay is of a very peculiar character, the shingle with which it is covered resembling peas in shape, the average size being about one-eighth to a quarter of an inch in diameter. Amongst these are scattered a few flat pebbles varying from 2 to 6 inches in diameter, composed of slate or shale. Three-fourths of the shingle consists of quartz pebbles, the remainder being of the same material as the metamorphic cliffs, with a fair sprinkling of flints. There does not appear to be any local source from which these last have been derived. The beach is entirely covered with this shingle, which extends down to low water.
The shingle has been drifted across a deep indent in the middle of the bay, into which two small fresh-water streams discharge, and has accumulated into a bank enclosing this indent, and forming two fresh-water lakes about 2 miles in length and the sixth of a mile wide, known as Slapton Leys.
In south-easterly gales the shingle is torn down and the bank lowered by the action of the waves, but it returns again during calm weather or with off-shore winds.
In November, 1894, during a storm, the sea made a breach in this shingle-bank and let the salt water into the lakes and killed the fish. After the gale the shingle worked back and restored the gap.
In Blackpool Bay, the beach of which consists of fine sand, during storms the material is sometimes drifted from one end of the bay to the other, but after the gale the beach gradually resumes its normal condition. During a gale in 1881, the beach was denuded at the east end to a depth of 14 feet, and the sand piled up in a mound 16 feet high at the west end.
A large amount of shingle has been removed from the Hall Sands, and also dredged from the Skerries, for making concrete for the Government docks at Keyham and Plymouth.
Between the estuary of the Dart and Berry Head there are three indents with well-defined beaches known as Scabbacombe, Man Sand, and Mudstone Sand. On these there is no indication of the Start Bay shingle, the beaches being composed of the débris from the adjacent rocks, which consist of slate and other metamorphic rocks, hematite, and limestone. Some of the pebbles are round and others flat in shape.
Tor Bay.-Between the projection of Berry Head and Hopes Nose, a distance of 4 miles, is the deep indentation of Tor Bay, the coast-line being recessed 3 miles. In this bay are several minor indentations.
Under Berry Head is a small cove, the beach of which consists of nothing but wave-worn fragments of limestone thrown out from the quarry close by, and the same is the case with the strand from Berry Head to Brixham.
Beyond Brixham is Fishcombe Cove, which has two beaches, one exposed to the east, and the other to the north, and sheltered from other winds. The beach of the former consists of waveworn limestone pebbles from the adjacent quarry, and some large blocks of limestone are scattered about on the beach. The other beach is covered with small stones and sand.
From Fishcombe to Elbury there are several small coves cut out of the limestone, the beach consisting of pebbles above low water, with large stones below, changing to fine sand eastward. The drift of the stone here is westerly.
Beyond the headland at Elbury the character of the beach is changed, that at Broad Sands being composed of sand from the red sandstone cliffs, with a narrow ridge of rounded limestone pebbles. The beach at Goodrington and Paignton, in the centre of the bay, consists of sand with a few stones scattered about. The beach sand is derived from the sandstone cliffs which adjoin the coast here.
In the bight at Hollocombe, stones are more frequent, and are derived from the quarries at Rockend and Meadfoot, further to the east, the drift being in a westerly direction. At Livermead and Torre Abbey, the beaches, which consist of sand, have to some extent been affected by the sea-wall built for the protection of the road. Any drift that takes place is to the north and east.
The shore which bounds Tor Bay is being wasted by the sea in several places. The road running along the coast from Paignton to Torquay has had to be moved inland three times during the last hundred years. A sea-wall which was constructed for the protection of this road was demolished by the waves in 1859, during which storm the cliffs along this part of the coast were undermined at many points.
From this it will be seen that the shingle travels along the coast of the bay in two opposite directions, while in the centre, where there is little or no drift, the beach is sand. The drift thus follows the direction of the flood tide, which sets round the horn of the bay in a north-easterly direction on the south, and is deflected into the bay in a south-westerly direction on the north end by the projection of Hopes Nose, the movement being neutral in the centre.
Hopes Nose to Otterton Point. The bay lying between Hopes Nose and Otterton Point is about 14 miles in length, and has an embayment of about 3) miles.
Hopes Nose, the southern horn of the bay, is a limestone cliff, and is followed for about a third of a mile by greenstone and limestone cliffs, which stretch along the bay for about 2 miles to the New Red Sandstone, which forms the remainder of the cliffs to Otterton Point.
In the cove near Hopes Nose the beach is covered with rolled stones, with large blocks of stone lying at and below low-water mark.
The beach in Ilsham cove is covered with fragments of slate.
cription of the coaction of Waves out in January, 1893.cologist, 1861.
The description of the coast between Dartmouth and Torquay is principally taken from a paper on “ The Action of Waves on Sea Beaches,” read by Mr. A. H. Huut before the Torquay Natural History Society in January, 1893.
? Memoir by Mr. Pengelly on “ Waste of Devonshire Coast," Geologist, 1861.