high water to that of ordinary spring tides, or 10-71 to 13:34 above ordnance datum, on which salt-water grass grows; 10 is alluvial matter chiefly derived from the erosion of clay banks brought up by the tides and deposited in Boston Dock, whence it was dredged, elevated from the barges, and discharged with a current of water on to low land, the sample being taken at the part furthest away from the place of deposit; 11 was taken from the "batches" on the banks of the river Parrett at about halftide level of spring tides, or 13.67 above ordnance datum, where the finest part of the alluvium in the river settles, and which is collected for making bath bricks; 12 was taken from Tilbury Dock basin on the Thames when the water was being stirred up by the eroding pumps; 13 is from clay used for brick-making30 per cent. of the particles of this material were from to 1006 inch in diameter, and the remainder smaller than this, the average size being Too of an inch. No. 14 was the alluvial matter contained in chalky boulder clay after the stones and sand had been screened out, the particles varying in size from 1000 to 2000 to the lineal inch.

TABLE SHOWING RATE OF SETTLEMENT OF SOLID MATTER IN FRESH AND

Direction of Travel. The direction of the littoral drift is governed by the direction of the flood tide and the shape of the

coast.

On a straight line of coast, the direction of the regular line of travel is in the same direction as the main set of the flood tide.

Where a coast-line is broken up by bays and indents, there is no continuous drift of beach material along the shore, each bay retaining its own characteristic shingle, which is prevented from leaving it when the headlands project out as far as low water and form natural groynes.

The South Coast between Start Point and Selsea Bill affords numerous examples of this. The cliffs consist of a series of rocks of varying geological character and degrees of hardness, the softer rocks having been wasted by the sea, leaving projecting headlands and indents of various shapes and depths.

Where a bay occurs with prominent headlands, the flood tide sets into it at the upper end at an oblique angle. The tide in

FIG. 6.-Plan showing Direction of Drift in a Bay.

the offing, moving faster than that in the shoal water of the bay, reaches the further headland before the bay tide, and, curling round, moves then in the opposite direction to that working round the shore of the indent. The drift of the shingle in the bay in this case is in opposite directions, and, according to the shape of the bay, either collects at the lower end or in the centre, as shown

by the small arrows in the illustration, the larger feathered arrows showing the set of the flood tide. Examples of this drift of the shingle in opposite directions are to be found in several of the bays on the Dorset coast, and on other coasts described in Chapter VII.

When there exists a sharp prominent projection from the coast-line, whether natural or artificial, the coast making an angle of 45 degrees or thereabouts with the projection, the flood tide, after passing the projection, strikes the shore beyond, as shown by the feathered arrows on the illustration, and, curling round, forms a counter tide running in the opposite direction to the main set in the offing, the beach material being drifted in the same direction. An example of this will be found in the description of the coast at Seaforth and Newhaven, Chapter VII.

In Start Bay there are several beaches on which the material varies from fine sand to shingle. At Slapton the shingle is different to that found on any other part of the coast; the majority of the pebbles are white in colour, and resemble peas in shape and size-three-fourths consist of quartz, and the remainder flints and stones derived from the metamorphic rocks which compose the cliffs. These pebbles do not travel beyond the eastern horn of the bay.

Between the headlands at the Dart, Berry Head, Hopes Nose, and Otterton Point are several indents, each having a beach, the pebbles of which are composed of shale, slate, hematite, greenstone, or limestone according to the character of the rocks which border them, while at Paignton and Goodrington the beach is entirely sand.

The boulders and shingle on the beach at Budleigh Salterton vary in size from stones weighing 10 or 12 lbs. to small pebbles, and consist to a great extent of pink quartzite, some of the stones having peculiar marks on them like blood-spots. These stones do not drift round the headland. The shingle on the beach east of Otterton Point and at Sidmouth consists of flints derived from inland gravels; while further east, at Seaton, the shingle is principally of chert and flint derived from the chalk cliffs at Beer Head.

Along the Dorsetshire coast there are accumulations of flint and chert shingle collected in mounds in the centre of the bays, while the beach at each end is either bare clay or covered with sand. There is no drift of shingle past the headlands at Golden

Cap or Thorncombe. The shingle on the beach on the west side of the pier at Bridport is of a different character to that on the east side, the latter consisting of small rounded pea-like brown pebbles, similar to that at Slapton, but of a different colour, and composed almost entirely of flint and chert. The same kind of shingle continues to Burton Bradstock. A little beyond this, at Abbotsbury, the Chesil Bank commences, the pebbles of which consist of flints of various colours, varying in size from to 4 inches at the western end; at the Chesil end the shingle consists to a large extent of the black chert from the beds in the Isle of Portland.

On the coast of Cornwall, in Mount's Bay, which lies between two headlands which project into 2 fathoms at low water, the beach is entirely covered with the débris of quartz rock, the shingle on the other side of the headland being of an entirely different character. In Padstow Bay, 90 per cent. of the sand consists of broken sea-shells.

In Barricane Bay, on the coast of Devon near Morte Point, the beach is also covered with sea-shells, being the only beach of this kind in Devonshire.

Where the coast-line is broken by estuaries or rivers, there is a continual struggle between the littoral drift and the inflowing and ebb water.

If the tidal currents are deep they have the mastery, and the drift is unable to cross them. In this case the drift sometimes turns round the coast-line and drifts up the shores of the estuary.

If the movement of the drift is stronger than the force of the current, the rivers become diverted from their course or blocked by a bar, or even become entirely closed; or the drift may be pushed out across the estuary in the form of a spur or promontory.

On the West Coast the shingle drifts up the estuary of the Wyre to Fleetwood.

On the north side of Harwich Harbour the shingle has been pushed out across the estuary till it has formed a triangular spit 11⁄2 miles long, and from 13 miles at the widest part to a tenth of a mile wide. There being deep water at the end of this spit, the shingle now works round it and travels up the shore of the estuary.

On the coast of Calvados the shingle drifts along the shores of the estuary of the Seine past Villerville.

At the mouth of the Humber the shingle drifting from the north, unable to cross the deep water of the channel, has worked out from the land and formed the spit 3 miles long and 500 feet wide, known as Spurn Point, round which the flood tide sets with considerable velocity.

Hurst shingle-bank extends out from the mainland across the entrance to the Solent for a distance of 4 miles, and is only prevented from joining the Isle of Wight by the deep narrow channel, about the third of a mile wide, through which the flood tides at springs flow into the Solent at a rate of 51⁄2 knots.

In some cases the drift has entirely diverted the mouth of the river or harbour; thus at Christchurch the sand, drifting along the coast from the west, has formed a spit across the bay, which separates and protects the harbour from the sea, leaving only a narrow entrance between the end of the spit and the land. This spit is still extending.

The Chesil Bank has entirely diverted the flow of the small streams which at one time entered Lyme Bay directly across the beach, but which now communicate with the Fleet, which runs at the back of the bank and communicates with Weymouth Bay.

The shingle-bank on the East Coast, which runs in a southerly direction from Aldborough, has diverted the rivers Alde and Ore for 9 miles out of their natural course, the bank which separates the channel of these rivers from the sea being in some parts only from 70 to 80 yards wide, the depth of the channel varying from 12 to 30 feet.

The river Yare, on which Yarmouth stands, has been diverted 3 miles southward from its original outfall by a narrow spit of sand and shingle.

The West Harbour at Rye, notwithstanding repeated efforts to keep it open, was entirely closed by the drift of the shingle along the coast, and the entrance to this port is now much further east than it was in the last century.

The Adur, on the Sussex coast, was forced by the drift of the shingle 4 miles eastward, the width of the shingle bank which intervenes between the channel of the river and the sea being a quarter of a mile wide. The present outfall and approach to the harbour of Shoreham, which is 1 miles eastward of the original position, was cut through the shingle-bank, and jetties had to be constructed to maintain it in position.

Along the Devonshire coast, at Seaton the river Axe, and at