ON EMBANKMENTS, PIERS, HARBOURS, &c. 375

SECTION XII.

On Embankments, Piers, Harbours, and gaining Land from the Sea.

IN various sections of the present chapter, and particularly that on Inundations, we have seen the dry land occasionally encroached upon to a very considerable extent by the natural action of different seas or rivers. In other instances, and particularly in the section of a preceding chapter, which treats of the formation of new islands, we have seen the dry land make similar encroachments upon the surrounding beds of water. "In this manner the boundaries of organized life are alternately extending and diminishing; in the former instance sometimes thrown up all of a sudden by the dread agency of volcanoes, and sometimes reared imperceptibly by the busy agency of corals and madrepores. Liverworts and mosses first cover the bare and rugged surface, when not a vegetable or any other kind is capable of subsisting there, they flourish, bear fruit, and decay; and the mould they produce forms an appropriate bed for the higher order of plant-seeds which are floating in the breeze or swimming on the deep. Birds next alight on the new. formed rock, and sow with interest the seeds of the berries, or the eggs of the worms and insects on which they had fed, and which pass through them without injury. Thus the vegetable mould becomes enriched with animal materials; and the whole surface is progressively covered with herbage, shaded by forest trees, and rendered a proper habitation for man and the domestic animals that attend upon him.

"The tide that makes a desolating inroad on one side of a coast throws up vast masses of sand on the opposite. The lygeum or sea-mat weed, that will grow on no other soil, thrives here and fixes it, and prevents it from being washed back or blown away. Thus fresh lands are formed, fresh banks upraised, and the boisterous sea repelled by its own agency, and there are a variety of other plants whose roots or ramifications have an equal tendency to fix the quicksand, and produce the same effect: such, especially, as the

elymus arenarius, arundo arenarius, triticum repens, and several spe cies of the willow *."

Mr. Anthony Tatlow, probably copying some previous experi ments of Sir Thomas Hyde Page, Bart. has ingeniously employed the common furze for the same purpose; and by forming it into an extensive hedge, has made the sea produce a valuable and regular embankment of its own sand. His account of this ingenious contrivance, as communicated to the Board of Agriculture, A.D. 1800, is as follows:

"The embankment against the sea, that I mentioned when last at the Museum, is upon the estate of the Earl of Ashburnham, at Pembrey, in the county of Carmarthen, whither his lordship sent me upon his coal and other business, and with directions to see if I could devise any method of preventing the sea from making further incroachment upon his property, which it had been doing for many years, and particularly in October 1795, had broke in and covered many hundred acres, damaged the houses, buildings, stack-yards, and gardens; and it was the general opinion, that a regular embank, ment must be formed, which would cost some thousand pounds, he having several miles of coast. The view that I first took was upon

a very windy day, and the shore an entire sand, which extended at low water many miles. In riding along, I perceived that any piece of wood, or accidental impediment to the course of the sand, raised a hill; it immediately occurred to me, that by making a hedge at the weak and low places, with wings to catch the sand as the wind blew it in different directions, I should obtain the desired effect. I therefore directed stakes nine feet long to be cut, and drove one foot and a half into the sand, at two feet and half distance from each other; betwixt which I had furze interwove, so as to form a regular furze hedge seven feet and a half high, Of this, since last June, I have done eleven hundred and thirty-seven yards; and in October last when I was there, a great deal of the hedge was covered, and since that time I am informed by letter, that a great deal more of it is so; and that the neighbouring inhabitants draw great comfort to themselves, from the security my furze embankment

* We are indebted for these remarks to the use of an unpublished Work of a literary friend, well known to the world, EDITOR,

gives them, as its present appearance plainly evinces, that at a trifling expense I can secure Lord Ashburnham's estate from being inundated; for, whenever the first hedge is not high enough to prevent the sea overflowing, another may be built upon the sand formed by that hedge, and so on in succession, till it is perfectly safe."

Similar meaus have not only been employed to prevent encroachments from the sea; but in various instances to gain land from it. It often happens, however, that the machinery must here be somewhat more complex, and intersected with drains and sluices. One of the simplest schemes of this kind which we have lately met with is the following by the Rev. Bate Dudley, which we shall copy in his own words, as communicated to the Society for the Encourage. ment of Arts, Manufactures and Commerce, and for which he received the gold medal,

"A tract of land, which I inclosed on the same line of coast within this parish about eleven years ago (for which I was then honoured with the Society's gold medal) being already under a profitable course of tillage, I was induced to undertake the present inclosure, as a lessee of the collegiate estate of St. Paul's. The front line of embankment against the sea is nearly one mile in length, and, with the returning banks on each wing to the old wall, forms an inclosure of contents, as expressed in the certificate already in your posses. sion. The whole of the embankment is composed of earth alone, borrowed from the irregular salting land in the front, called chatts, and taken at the limited distance of twelve feet from the base of the new work, to leave a sufficient foreland for its protection. I found, from experience, in my former embankment, that I had not given it a sufficient angular declension in front, for an easy ascent and descent of the waves. This error was therefore corrected in the last work. I began it on a base of thirty-two feet, and wrought it to the height of seven feet, leaving it a plane of five feet on the top, and making the land-side of the embankment, as nearly per pendicular as the security of the base would allow.

« Within, on the land-side, is cut a ditch, twelve feet wide, five feet deep, and four feet at bottom; the earth from which was thrown into the mound. My former sea-embankment, in Bradwell parish, had nearly given way to the great inundating tide of February 1792, from this erection of new earth being made on the surface. To guard against similar danger in the present work, a

spit deep trench, six feet wide, was previously cut along the centre of the whole line, on which the mound was to rest; this, by admitting the new earth into an incorporate adhesion with the base soil, renders a future separation almost impossible. Before this, the main rills had been filled and rammed, to give these parts equal solidity with the rest.

"The whole operation was performed by a gang of twelve seawallers, with barrows and planks only, at one pound ten shillings the marsh-rod, of twenty feet, and perfectly inclosed in seven months: but, it must be observed, that the soil, composed of rich vegetable matter, is without one particle of stone or gravel, and cuts with an iron edged scoop-tool, so as to load the barrows with great facility. At each end of the front line is laid an out-fall gutter, or sluice, through the whole embankment, five feet in width, by three deep deep, clear in the run; and another of smaller dimensions in the centre, for discharging the land waters freely to sea. The construction of these aqueducts is too well known to require farther description here: probably, however, the little addition given to those erected on this occasion may be found of some use. Observing it often happen, that, either from accident or design, the outward lid of the sea-sluices remained open, and admitted the tide to the great injury of the fresh waters within the marshes, I introduced here a light fly-lid within the centre of each sluice, which is out of reach, and yields to the slightest pressure of the water going out; but shuts closely against that of the tide, when it passes inwardly the external flap. These sluices are laid upon as solid a foundation as can artificially be made on such soils, to prevent the crabs, and other sea-fish, from undermining them, which must otherwise be the case. The frame and flooring are of fir, which lies under water as durable as oak.

"The land thus inclosed is partitioned into four nearly equal parts, by new out-ditches, twelve feet wide, five deep, and four at the bottom, which, with small intersecting rills, from various parts, give the whole a good drainage of its salts, on the fall of heavy rains and, by a course recently made from a distant brook, each division of this land is now amply supplied with fresh water. Not less than eight hundred South-Down sheep, and from sixty to eighty horses, are almost constantly grazed, and even winter thereon remarkably well. The established opinion of the best farmers of

the country was, that land, thus taken from the sea, would not grow corn under thirty years at least after their inclosure. But as no experiment had been made, by which this fact could be clearly ascertained, as soon as I had shut out the sea from a part of it, about six yards square were immediately dug, and sown with horsebeans and oats, which, though the summer proved very dry, and consequently unfavourable, produced of each a fair return of sound good corn; and the last harvest the same spot being sown with wheat, yielded an excellent crop. The next spring I mean to try it with barley and turnips. My first inclosed lands in this parish have produced two succeeding crops of fine oats, and are now growing a very promising breadth of rape for seed.

It may here be remarked, that the lower oozy parts of the new inclosure, on which no vegetable ever grew before, begin to be coated with various grasses; and as the saline parts die away in other spots, for want of their natural moisture, fresh grasses replace them, so that the whole is now nearly covered with grazing plants of good quality, amongst which appear the different clovers, trefoil, and rye-grass, &c. Hence I conclude, but contrary to the general opinion, that though all these grew artificially from seed sown, it does not follow of necessity that they cannot be produced without. I think that the natural operation of the suu and air, upon certain soils will alone effect it; and my experience in lands taken from the sea confirms very strongly this opinion."

The construction of canals, reservoirs, locks, piers and quays, are dependent upon the same principles, extended to a more scientific survey. In this view the art of embankment, observes Dr. Young, is a branch of architecture entirely dependent on hydrostatical and hydraulic principles. In Holland, and in some parts of Germany, this art is indispensable to the existence of large tracts of country; and even in this island, it has been of extensive utility, in gaining and securing ground on the sea coast. The construction of canals, and the management of rivers and harbours, are also dependent on the same principles; and these important subjects have been discussed by various writers, in many copious treatises, expressly devoted to hydraulic architecture.

When a bank or dike is to be constructed, it must be composed of materials capable of resisting, by their weight, the effort of the fluid to overturn them; by their lateral adhesion, the force tending