THOSE of our readers who have visited the watering-places and the Life-boat Stations of the NATIONAL LIFE-BOAT INSTITUTION on the south and south-east coasts of England cannot but have noticed with interest the vast quantity of shingle which fringes the whole line of coast in some parts; which, in the shape of bars at the entrances of harbours and in outlying banks, is a constant danger to shipping in stormy weather, and the accumulation of which on the shore is often an invaluable protection against encroachment by the sea. Hence we have thought that some information respecting it might be in- teresting to them.

Our shingle .beds and beaches have in fact always been objects of interest to men of science; to the geologist, the hydro- grapher, and the civil engineer; and to the commanders and pilots of ships they have been professionally so, whilst even to the casual observer they must often have occa- sioned wonder as to the origin and source of supply of the innumerable pebbles of which they are formed. The geologist, having traced the shingle to the cliffs of our coast, from which it has been ex- tracted by the action of the waves, aided often by water springs on the land, has in it an interesting field for thought and de- duction before him, as he endeavours to decipher its past history, picturing to himself the quiescent bed of the ancient sea, where the flints of our chalk downs were then living animals, and revolving in his mind the mighty changes in the earth's crust which converted those ancient seas to land and changed the ancient lands to seas. With interest he endeavours to ac- count for the vast deposits of gravel and of water-worn stones, commingled with clays and marls, that one of the latest great ocean disturbances deposited in the vast beds and mounds, whence a large proportion of our shingle deposits have sprung, and by which they are being constantly replenished.

To the hydrographer, how important and interesting is the study of the movements of the shingle and sand, which gradually change the soundings of channels, raise and extend shoals and banks, and form the bars which obstruct the entrances to our river ports? To our civil engineers, to whom we are chiefly indebted for the careful observa- tions they have made as to shingle move- ments, how necessary is it to be able to trace the laws by which they are regu- lated, so that in designing or improving an artificial harbour, or projecting a pier or breakwater, they may be able to calcu- late beforehand how it will be affected by the movements of adjacent shingle or sand, and may know how to prevent its accumulation in a bar or in shoals at or about the harbour's mouth ? 

So also the landed proprietor, by an acquaintance with these laws, may learn how to protect his land from abstraction by the sea, and even the casual observer may find pleasure, and add to his store of useful knowledge, by meditating on its character and history.

The subject may be conveniently ar- ranged under the following heads:— j 1. The origin and nature of the stones of ; which shingle is composed.

2. The sources from which they have been derived and transported.

3. The causes and manner of their transport.

4. The contrivances by which they may be wholly or partially arrested in their course, and caused to deposit and accumulate wherever required.

1. The origin and nature of the stones of which shingle is composed.

By shingle we especially refer to the extensive masses of loose stones, nearly all of which are flints from the chalk, or small, opaque, irregular-shaped stones of yellowish, brown, or drab colour, de- rived from the vast beds of gravel that form so large a portion of the alluvial deposits in the southern and south-eastern counties of England, as distinguished from the pebbled beaches, such, for instance, as those at Northam and Clovelly on the north coast of Devon, and at Wicklow on the east coast of Ireland, which are solely composed of broken pieces of rock, of various kinds, which have been worn into round, oval, or flat pebbles by constant friction against each other from the break- ing of the waves on the shore.

All such pieces of fractured rock, whether of limestone, sandstone, slate, granite, porphyry, jasper, serpentine, &c.

or even of quartz, have all their angles rapidly rubbed off and their general form rounded by attrition, whilst on the other hand the flints and gravel stones, from their greater hardness, nearly retain their original shapes, as evidenced by the cir- cumstance that the white or other opaque incrustation of the flints is rarely, if ever, found completely rubbed away.

As above stated, the chalk flints were, at least for the most part, originally animals which existed on the bed of a former sea, into the substance of whose bodies, or into the empty spaces within their dead shells, or the sponges or corals which they inhabited, the silicious matter subse- quently infiltrated. Whether, however, that change took place whilst they were yet embedded in the ocean's floor, or by chemical action, possibly aided by sub- terranean heat, during the process of the induration of the chalk after* upheaval from the sea, may never, with certainty, be known, although in all probability the latter was the case. Of the origin of the stones of the red and yellow gravels, we have been able to find no reliable theory; but that they were deposited by the sea, above the chalks, is evidenced by the positions in which they are found.

From the geological question as to the origin of the stones composing our shingle beaches, we pass to that of our second head—the sources from which, in their present positions, they have been derived.

Whilst divided in opinion as to the ex- tent to which they have been transported by tidal currents in deep water, all the writers we have been able to consult agree that they have been almost wholly derived from the land on our own coasts, wrested from it by the sea, and transported by its action to varying distances from the spots where they had lain, through an unknown number of ages, imbedded in the rocks or alluvial deposits on the land.

We may revert to this division of our subject, but will now proceed to the third head—the causes and manner of their transport.

It might at first thought be expected that the debris of fallen cliffs, &c. would remain on the shore near the spot where it had been engulphed, unless at a few places where the tides were exceptionally strong close to the beach, and that it would merely be thrown up and again withdrawn, in endless succession, by the advancing and receding waves. Such would undoubtedly be the case if the waves of the sea always broke directly on the shore, that is to say, perpendicularly to it.

But a far more potent force than the tidal currents exists in the action of the waves when they are driven obliquely to the shore, when every advancing wave, as it breaks on a shingle beach, throws a greater or less number of its stones for- ward in the direction of its own progress, the receding water withdraws them sea- ward at right angles with the beach, only to be thrown forward again by the follow- ing wave. We have only then to imagine the countless myriads of stones which on a long line of beach are every moment thrown forward several feet by the cease- less breaking of the waves, and we shall readily conceive that many thousand tons will be transported by a single gale driving the waves with headlong violence obliquely on the shore.

If the direction of strong winds was equally proportioned in the course of a year, the shingle which was carried for- ward by some would be carried back in the reverse direction by others; but such is not the case, and hence, the prevalent or greatly preponderating winds on the • south coast of England being from the south-west, all shingle, as has been proved by repeated observations, travels on that coast from west to east, until its progress is stopped by either natural or artificial impediments.

Illustrative of the rapidity with which it is thus transported, it is stated by the distinguished meteorologist, ' the late Colonel REID, that in a single year pebbles from the Devonshire coast had been transported to the Chesil beach.

On being arrested in its progress, it accu- mulates, and in this manner the vast beds of shingle, such as those at Dungeness, Orfordness, Pevensey, Winchelsea, and the Chesil beach, have been formed.

As the same general principle applies to all shingle or pebble beaches, we will confine our remarks to those on the south coast of England, which will serve as examples of all others.

The first or westernmost system of shingle, if we may use the term, is that of West Bay between Start Point and the Bill of Portland, which latter promontory effec- tually arrests all further movement of the shingle to the eastward, beyond which another system of progressive shingle commences.

Accordingly, on the western side of Portland is found one of the largest masses of shingle in the kingdom, forming the celebrated Chesil beach, which, as being perhaps one of the most singular and imposing beaches in the world, we will select as an illustration of our subject.

All the stones of the Chesil beach have been traced to their sources in West 1 Bay. First come those from the red i sandstone cliffs between Torquay and Sidmouth; next, with the exception of a few jasper pebbles, traced to Aylesbere I Hill, and brought to the coast by the river Otter, are the flints from the chalk between Sidmouth and Lyme Regis, which form the greater portion of the shingle on the Chesil beach; and, lastly, those of the oolitic series of rocks between Lyme and Chesil.

A certain portion of the stones west of Lyme are detained by the projecting pier j of that harbour, the remainder being I washed over it or carried round it, con- tinuing their course until distributed on the Chesil beach.

j This extraordinary accumulation is no less than lOf miles in length, and has two striking peculiarities, the most striking being the distribution of its pebbles in regular gradation as regards size, ranging from very coarse sand at its western I extremity to stones of several pounds' weight at Portland. This gradation is so regular that the native boatmen can tell, in the darkest night, on what part of the beach they are by the size of the stones; a knowledge which, it is said, the smug- glers in the good old times of high duties turned to account, knowing which direc- tion to take, with their kegs of spirits, when " making a run," as it was termed, by ascertaining the size of the stones at the first landing on the beach.

The second speciality is that the beach deepens from its western to its eastern end, at which latter it is so steep that there is 50 feet depth of water at 250 yards from the shore line at high water of spring tides, causing the sea, which in a south- west gale breaks at right angles to that end of the beach, -to fall over in such enormous breakers as are said not to be equalled in size in any other part of the United Kingdom.

Here, then, we see that by a great natural barrier running out to seaward the onward movement of shingle is effec- tually stopped, and a vast accumulation of it is deposited, from which, and similar natural impediments, a practical lesson is learned by the civil engineer, which brings us to the consideration of our fourth head, viz. the contrivances by which shingle may be wholly or partially arrested in its course, and caused to deposit and accu- mulate wherever required.

The means adopted for this purpose are the erection of wooden barriers or groins, formed of rows of stout piles driven deeply into the beach, and the spaces between, from pile to pile, filled in with planking, the structure being further laterally supported by strong wooden shores. These groins are mostly placed at right angles with the beach line, and are carried sufficiently to seaward to pre- vent the shingle passing round their outer ends on the receding of the tide, and made high enough to prevent the sea from carrying it over them. They are made highest at their inner ends, where the shingle is thrown up to its highest level at high water, and taper gradually to the level of the beach at their outer ends.

They are familiar objects to all visitors to the watering-places on our south and east coasts.

If at any place it is desired to accumu- late shingle, lines of groins are run out at sufficient intervals, the one farthest to leeward, i.e. farthest from the direction whence the shingle travels, being planked high enough and carried far enough to seaward to prevent any shingle passing it; the others are then only partially planked up, so as to retain a portion only of the shingle, the rest passing over their upper planks. When a sufficient quantity has accumulated between the leeward-most groin and the next one to it, the latter is also planked fully up to the tops of the piles, and so on in succession until the whole area over which the accumulation was desired is covered, after which all superfluous shingle would pass over the groins successively, and follow the same course as before.

An instance of the importance of pre- serving shingle as a barrier to sea en- croachment, and a protection to low-lying lands, has recently occurred at East- bourne, and which, in fact, originated these remarks on the subject.

Those of our readers who have visited that modern and pleasant watering-place will remember that at the eastern ex- tremity of the sea-wall fronting the esplanade an extensive area of shingle deposit exists, which affords a convenient beach for launching and hauling up the fishing and pleasure boats of the place, and forms the only barrier to prevent the sea, at high tides, from inundating the adjacent country and low-lying districts' of the town.

On the top of this bank of shingle the NATIONAL LIFE BOAT INSTITUTION, in 1867, erected a new Boat-house for its Life-boat there, at which time the shingle extended to quite 30 yards immediately in its front. In consequence, however, of a mistaken view as to the effect of the groins that had hitherto arrested the east- ward progress of the shingle, the upper planks of the groins were removed, as a consequence of which the shingle has been gradually swept away to the east and added to the great shingle bed called the Pevensey Levels, and in the autumn of 1877, the sea having encroached quite to the doors of the Boat-house, the NATIONAL LIFE-BOAT INSTITUTION had to erect a solid barrier of piles and planking, backed by lime concrete, to prevent the under- mining and destruction of the building at the ensuing spring tides, which would undoubtedly have occurred, had not that precaution been taken, whilst at the pre- sent moment, unless sufficient preventive measures are speedily taken, there is every probability of the remnant of the shingle bank being swept away, and an incalculable amount of valuable property destroyed by inundation of the sea.

The inhabitants of the town and the landowners of the district having, how- ever, become seriously alarmed, and alive to the necessity of prompt remedial measures being taken, it is to be hoped such a disaster may be prevented.

Having selected the above instance of the serious evils which may result' from neglect of effectual measures to preserve an accumulation of shingle, where required i to prevent encroachment by the sea, we I will, in contrast, select another where ! incalculable advantages have arisen from suitable measures being taken to preserve it. We allude to Brighton, where there formerly existed a complete town, with fortifications, the site of which is now beneath the waves.

By the construction of the sea-wall which now skirts its magnificent esplanade, the further encroachment of the sea was effectually prevented, and by a "well- designed system of groins" so large an accumulation of shingle has been secured that the esplanade wall is now effectually protected by it from even the juncture of the highest spring tides with a southerly If the labour and expense of these measures had been grudged and withheld, who can tell whether this queen of Eng- lish watering-places, this London on the sea coast, as it has been termed, would ever have arisen above the level of an obscure and neglected sea-coast town ? There is, however, yet another effect of shingle movement which we have as yet only referred to, viz. the formation of bars across the entrances of ports. We have already stated that the pier of Lyme harbour does not prevent the passage of the stones round it on their way to join their congeners on the Chesil beach.

When, however, two parallel piers of equal length are run out to form an entrance to a harbour, the shingle is carried round the first one, and being interupted in its onward course by the ebb tide running out between the two piers and the flood tide setting in, the combined forces cause an accumulation of it off the entrance, called a bar, which is often a serious obstruction by preventing all vessels of more than a certain draught of water from entering the port, and limiting the time of entry and exit to near high water in the case of all vessels larger than boats.

To remedy this evil, it has been ad- vocated by Smeaton and other eminent engineers that the pier next to the direction of the prevailing winds and advancing shingle should be carried obliquely beyond the further one, so as to overlap it and conduct the shingle past the entrance and deposit it on the farther shore.

The probable correctness of their views would seem to be indicated by the natural disposal of shingle when interrupted in its onward march by an interposing river or harbour's mouth, unprotected by piers or other artificial works. The shingle on the windward side, which would accumu- late on being arrested by any solid barrier, such as a groin or pier, gradually en- croaches on the entrance, and drives it further to leeward, its accumulation thus forming a spit or peninsula on the wind- ward side, which will be continually elongated, and the entrance carried farther and farther from its original position, until averted by either natural or artificial counter obstruction.

Illustrative of this principle may be quoted Shoreham harbour, on the coast of Sussex, where the shingle westward of the harbour's original entrance had gradually shifted jt from west to east about 3 miles, when a new entrance was artificially made; likewise Aid borough, on the Suffolk coast, where the shingle movement is from N.E.

to S.W., and where the present entrance to the harbour is several miles farther to leeward, i.e. to the S.W., than it no doubt originally was.

The space at our disposal has neces- sarily required onr curtailing our remarks, or we might relate many interesting details of other systems of shingle, but the description of the Chesil beach, taken chiefly from an admirable descrip- tion and explanation of it by Sir JOHN COODE, read to the Institution of Civil Engineers, in the year 1853, will serve to illustrate the principle on which all others have been formed, viz. the disintegration of the matter of the cliffs and land bound- ing the coast, and the gradual movement of the stones contained in it in the direc- tion of the predominant winds, chiefly caused by the oblique action of the waves, until arrested in its course by a natural or artificial projecting barrier of sufficient extent, beyond which another system again commences wherever the sea encroaches on the land, and the latter contains the material of which shingle is composed.

As this article is intended to interest the general reader only, and does not pretend to be a scientific treatise, we have not quoted step by step the several authorities whose writings we have con- sulted, but may briefly state that it coin- cides with the opinions and observations of Colonel REID, of the Royal Engineers, Sir JOHN COODE, C.E., Mr. H. E. PALMER, C.E., Mr. DE LA BECHE, Mr. RIDDER, C.E., Admiral FITZROY, Professor AIRY, Mr. W.

B. PRICHARD, C.E., Mr. J. B. REDMAN, C.E., and others who have written or spoken on the subject.