4029. Embankments for firing drifting-sands, shells, or mud. In several tracts of coast, the sea at ordinary tides barely covers a surface of sand; and these sands in dry weather, during high winds, are drifted and blown about in all directions. Great part of the north shores of the Solway Frith, of Lancaster Bay, and of the coast of Norfolk, is of this description. Young, in his Farmer's Letters, informs us, that a considerable part of the county of Norfolk was drift sand, even as far inland as Brandon in Suffolk, before the introduction of the turnip culture; and Harte (Essay I.) states that some of what is now the richest land in Holland, was, about the middle of the sixteenth century, of this description. The suggestion of any mode, therefore, by which, at a moderate expense, such tracts could be fixed, and covered with vegetation, must be deemed worthy of notice. The mode which nature herself employs is as follows: After the tides and wind have raised a marginal steep of land as high as high water-mark, it becomes by degrees covered with vegetation, and chiefly by the elymus arenarius, triticum junceum, various species of juncus, and sometimes by the gallium verum. With the exception of the first of these plants (the leaves and stalks of which are manufactured into mats and ropes in Anglesea, and the grain of which is sometimes ground and used as meal in Ireland), they are of no other use than fixing the sands, which, being composed in great part of the debris of shells, expand as they decay, and contribute to raising the surface still higher, when the fibrous roots of good grasses soon destroy the others. 4030. To assist nature in fixing drift-sands, it is only necessary to transplant the elymus, which is to be had in abundance in almost every sandy coast in Britain; and as it would be liable to be blown away with the sands, if merely inserted in the common way, it seems advisable to tie the plants to the upper ends of willow or elder rods, of two or three feet in length, and to insert these in the sand, by which means there is the double chance of the grass growing, and the truncheon taking root. The elder will grow exposed to the sea breeze, and no plant throws out so many and such vigorous roots in proportion to its shoots. 4031. The mode by which such sands were fixed in Holland was by the formation of wickerwork embankments, and by sticking in the sands branches of trees, bushes, furze, &c, in all directions. These obstructed the motion of the sands, and collected masses of sand, shells or mud, and sea-weeds around them, which were immediately planted with some description of creeping grass; or, what was more frequent, covered with a thin coating of clay, or alluvial earth, and sown with clover. Though the most certain and least expensive mode of gaining such lands be undoubtedly that of seconding the efforts of nature, by inserting bushes, and planting the elymus in this way; yet it may sometimes be desirable to make a grand effort to protect an extensive surface, by forming a bank of branches, which might, in a single or several tides, be filled with sand and shells. It is evident, that such a bank might be constructed in various ways; but that which would be most certain of remaining firm, and effecting the purpose, would be one regularly constructed of framed timber, the section of which would resemble a trussed roof; each truss being joined in the direction of the bank by rafters, and the whole inside and surface stuck full of branches. To retain it firm, piles would require to be driven into the sand, to the upper parts of which would be attached the trusses. The height of such a barrier would require to be several feet above that of the highest spring-tides; and the more its width at base exceeded the proportion of that of an equilateral triangle the better. 4032. A mode suited to a less extensive scale of operation, is to intersect a sandy shore in all directions, with common dead, or wicker-work hedges, formed by first driving a row of stakes six or eight feet into the ground, leaving their tops three or four feet above it, and then weaving among these stakes, branches of trees, or the tops of hedges. The Dutch are said to weave straw ropes in this way, and thereby to collect mud in the manner of warping. This mode being little expensive seems to deserve a trial in favorable situations; and, in so doing, it must not be forgotten, that much depends on the immediate management of the surface, after it is in some degree fixed. In an extensive trial of this sort at present in progress on the west coast of Scotland, under an English gentleman, seeds and roots are baked in a mixture of loam and dung in the gravel, and then formed into masses, and scattered over a sandy surface. These, from their weight, will not, it is thought, be moved by the water or the wind; but becoming more or less covered with sand, the mass will be kept moist, and the seeds and roots will grow, and, fixing themselves in the soil, will in time cover the surface with verdure. The experiment is ingenious, and we hope will be crowned with success. SECT. II. Of guarding the Banks, and otherwise improving the Course of Rivers and Streams. 4033. The subject of guarding the banks of rivers, is of considerable interest to the proprietors of lands situated in hilly districts, where, in the valleys and on the hill sides, the streams often produce ravages on the banks, and sometimes change their courses. 4034. The natural licence of rivers, Marshal observes, is not only destructive of landed property, frequently of lands of the first quality; but is often the cause of disputes, and not unfrequently of legal contentions, between neighboring proprietors. A river is the most unfortunate boundary line of an estate. Even as a fence, unless where the water is unfordable, a river, or rapid brook, which is liable to high floods, is the most tormenting and inefficient. Proprietors have therefore a double interest in accommodating each other, as circumstances may require, with the lands of river banks, so as to be able to fix permanent boundary lines between their properties. When the owners of estates cannot, by reason of entails or settlements, or will not for less cogent reasons accommodate each other, they have a line to tread which they cannot deviate from with prudence, much less with rectitude; namely, that of cautiously guarding their own lands, without injuring those of their neighbors; for a lawsuit may cost ten times the value of the sand banks, and islets of gravel, to be gained by dexterity of management. 4035. The operations for improving rivers have for their object that of preventing them from injuring their banks, accelerating their motion, and lessening the space of ground which they occupy, or altering their site. These purposes are effected by piers or guerdes for altering the direction of the current; works for protecting the banks; and by changing or deepening the river's course. 4036. The principles on which these operations are founded are chiefly two; first, that water like every other body when it impinges on any surface, is reflected from it at a similar angle to that at which it approached it; and, secondly, that the current of water, other circumstances alike, is as the slope of the surface on which it runs. On the first of these principles is founded the application of piers for reflecting currents; and on the second, that of straightening rivers, by which more slope is obtained in a given length of stream, and of course greater rapidity of motion obtained. SUBSECT. 1. On guarding River Banks. 4037. A common cause of injury to the banks of rivers is produced during floods. A tree or branch carried down by a stream, and deposited, or accidentally fixed or retained in its banks, will repel that part of the stream which strikes against it, and the impulse (contracted more or less by the general current) will direct a substream against the opposite bank. The effect of this continual action against one point of the opposite bank is, to wear out a hole or breach; and immediately above this breach it is customary to place a protecting pier to receive the impulse of the substream, and reverberate it to the middle of the general stream. But if this pier is not placed very obliquely to the substream, as well as to the general stream, it will prove injurious to the opposite bank, by directing a subcurrent there as great as the first; and, indeed, it is next to impossible to avoid this; so much so, that Smeaton, in almost every instance in which he was consulted in cases of this sort, recommended removing the obstacle where that could be done, and then throwing loose stones into the breach. 4038. Injuries by floods, according to Marshal, are to be remedied in two ways; the one is to sheath the injured banks of the bays (fig. 519 a, b, c), with such materials 1 The as will resist the circuitous current; and let the river remain in its crooked state. rent, and directed it into its wonted channel. And in almost any case, by judiciously placing, in a similar manner, a pier or other obstruction proportioned to the magnitude of the power to be counteracted, the like effect may be produced. 4039. In the use of piers great caution is requisite, for a very little reflection will show, that they are more likely to increase than to remedy the evil they are intended to cure. We have seen the injurious effects of such piers on the Tay and the Dee; and on a part of the Jed near Crailing they are so numerous, that the stream is, to use a familiar phrase, banded about like a foot-ball, from one shore to the other; behind every pier an eddy is formed, and if the stream does not strike the pier exactly, a breach in the bank takes place. Many of these piers have, in consequence, been taken down. The use of such piers can only be justified where the obstruction, from ill-neighborhood or some such cause, cannot be removed from the opposite bank; or where, as is sometimes the case, it arises from an island of sand or gravel thrown out by the river near its middle, and which, however absurd it may appear, the interested parties cannot agree as to who may remove it. The case of buildings also being in danger, may justify such a pier for immediate protection; but if such breaches are taken in time, a few loads of loose stones dropped in the breach, as recommended by Smeaton, will effect a remedy without the risk of incurring or occasioning a greater evil. 4040. In the construction of piers, attention is required to secure the foundation, either by first throwing in a quantity of loose stones, which the water will in a great measure dispose of so as to form a flat surface; or by the use of piles either under, or in single or double rows around those parts of its base in contact with the river. (fig. 520 a.) The elevation (b), where it is not required to act with great violence on the opposite shore, ought to be bevelled back on all sides exposed to the water, towards the middle of the structure (c). In the most important cases stones are the only fit materials, and these should be regularly jointed and laid in cement according to the best practice of masonry. But, in general, a case of wicker work, of the proper shape, may be filled in with loose stones, some earth, together with the roots of such plants as tussilago petasites, elymus arenarius, gallium, &c. These will form a barrier of considerable durability for some years, and probably till the evil is so far subdued that, when the wicker case decays, its contents will have sufficiently consolidated to effect the object without further care. If not, the wicker case may be renewed. In ordinary cases, a mere wicker hedge projecting into the water will effect the object without further trouble. 4041. The sheath, or land-guard of loose stones, which Marshal recommends, and which, in effect, is the mode already mentioned (4037.) as preferred by Smeaton, is applicable to the following cases: First, where the river is confined in the part where it is required to be bent, by rocks or otherwise, to an unaltered channel; as it frequently is, in subalpine situations; and, secondly, where a deep pool occurs, in that part, in low water, so as to render it difficult to get a proper foundation for a pier. Where the foot of the injured bank is covered with a pool at low water, shelve off the brink of the bank, and shoot down loose stones from the top of it; suffering them to form their own slope, in the action of falling, and by the operation of succeedin floods continuing to pour them down, until the bank be secured, at least from minor floods, and then slope back the upper part, to give freedom to floods of higher magnitude. 4042. When the channel of a rapid river is narrow and the banks undermined and washed away by the torrents, what Marshal terms the land-guard is to be used. 4043. In forming a land-guard for this purpose, he says, the foundation should be laid pretty deep, to guard against any accidental scoopings from the floods. The wall ought to be carried up dry, or without mortar, the stones being laid with their ends outward, their inner ends pointing to the same centre, like those of an arch, and to be backed with gravel, or earth, rammed in firmly behind, as the facing is carried up. The coping or uppermost course of the stones is to be securely bound, with thick tough sods (8 or 10 inches deep), whose surfaces, when beaten down, ought to lie even with that of the stonework; and similar sods require to be laid, with a gently rising slope, until they unite smoothly with the natural turf of the land to be defended; so that the waters of floods, when they rise above the stonework, may have no abruptness to lay hold of, but may pass away smoothly over the surface of the land, as they commonly do over smooth greensward, without injury. Finally, the stones are to be beaten forcibly into the bank, with a ram mer, a mallet, or a small battering-ram, adapted to the purpose; thus rendering the whole compact and firm, to resist the current. Where vacancies or fissures still appear, long splinters of stone are to be driven in, as wedges, to increase the firmness, and prevent the current from tearing out an unguarded stone. It follows, in course, that the largest and longest of the stones ought to be used where the greatest resistance is known to be required. 4044. The repairs of a bulwark of this sort, like every other species of river fence, require to be attended to from time to time, especially after great floods. If the foundation be laid bare, it requires to be re-covered with rough gravel, or with stones thrown loosely against it. If any of the facing stones be displaced or loosened, they are to be replaced with others, or to be wedged in afresh. Or, if the turf which binds them at the top be disturbed, the torn part should be cut out square, and be firmly and completely filled up with fresh turves. SUBSECT. 2. Of Changing the Course of Rivers. 4045. A river whose course is in a straight line, or nearly so, hardly ever makes any encroachment on its banks, unless perhaps in very large rivers, when they rise above their usual level, either by an increase in their own waters, or their flow being in some degree interrupted by the tides. Hence, whenever a river is narrow in its channel, and winds considerably, any mischief it commonly occasions may be prevented by deepening and straightening the course of the stream. (Code of Agr. p. 319.) 4046. The alteration of the course of a river or brook is attended with difficulty and expense, according to the particular circumstances belonging to it. In a simple case, in which one straight cut only is required, the principal difficulty, and that which requires the best skill of the artist, lies in directing the current of the first flood, out of the old into the new channel. But if a bend of the old channel can be made use of, this difficulty may be said to vanish. The mouth of the new cut receives the current with a straight course; consequently, if it be made of sufficient capacity, the river, in a flood, can have no propensity left towards its old channel: and the loose materials which rise in forming the mouth of the new cut, will generally be sufficient to turn the stream at low water into it. But if a suitable bend cannot be approached by the new cut, a directing pier will be required to bend the flood current, and give it a straightforward course into the new channel: a watertight dam being formed between the point of the pier and the firm bank of the new channel to prevent the water from regaining its wonted course.. 4047. An entirely new bed or channel, however, is much to be preferred where it can be obtained; for in an altered course, when the stream passes alternately through new soil and through a part of its old bed, its action on surfaces which are so different in regard to induration ends, if great care is not taken, in holes and gulleys in the new bank, which require to be constantly filled up with loose stones thrown in, and left to be fixed by the pressure and, motion of the water. In the case of a river passing near a house (fig. 521.) this is sometimes of considerable importance. 521 4048. Cutting the new channel is merely a work of manual labor; being attended with no other difficulty than what may arise from the expense, which will depend on the size of the river, the nature of the ground to be cut through, and the value of labor in the given district. It is mostly to be ascertained with sufficient accuracy by previous calculations. (See 3082.) 4049. The size of the new cut may be small, compared with that of the old channel. For the current of floods, by carrying off the earthy particles with which they come in contact, will soon enlarge it. It is nevertheless right to give ample room in the new channel, lest the first flood should prove high, and, by bursting its bounds, force its way back to its former course. 4050. A new river course requires to be carefully attended to, during a few years after it is opened, to see that its channel preserves its straightness, and that no breaches are made or threatened in its banks. Considering the uncertainty of extraordinary floods, it cannot be said to be out of danger in less than three years; hence it becomes prudent, when a work of this nature is contracted for, or undertaken to be done by measurement at an estimated price or prices, previously agreed upon (as it generally ought), that the undertaker should agree to preserve the straightness of the channel, and uphold its banks, during that or some other time fixed upon; and to deliver them up at the end of the term, in the state and condition specified in the contract. 4051. A case of straightening the course of a river is given in The Code of Agriculture." The waters, which in their crooked course were formerly almost stagnated, now run at the ordinary rate of the declivity given them. They never overflow their banks. Cattle can now pasture upon those grounds in which they would formerly have been swamped. The surface of the water being now in general four, and sometimes six feet, below that of the adjacent fields, this cut serves as a general drain to the whole valley; so that three hundred acres of meadow may be converted into arable land; sixty acres of moss may be improved into meadow; and five hundred acres of arable land are rendered of double their former value. (p. 319.) CHAP. III. Of Irrigation or the Improvement of Culturable Lands and Farmeries, by the Means of Water. 4052. The improvement of lands by water is of three kinds : -irrigation, or the application of water to the surface of the soil, and especially of grass lands, as a species of culture; warping, or the covering the soil with water to receive a deposition of earthy matter; and the procuring or preserving of water by wells, reservoirs, and other means, for the use of farmeries, live stock in the fields, or the domestic purposes of the farmer or cottager. SECT. I. Of Irrigation or the Preparation of the Surface of Lands for the profitable Application of Water. 4053. Irrigation in its different forms may be considered an operation of culture as well as of permanent improvement. It is accordingly in many cases effected by tenants, but always, as in the case of improving wastes, in consequence of extraordinary encouragement from the landlord, by long leases, money advanced, or other advantages. 4054. The application of water to the surface of lands for the purpose of promoting vegetation has been practised, as we have seen (180.), from the earliest ages in warm countries. It is an essential article for the culture both of the cereal and pasture grasses, and indeed of most herbaceous crops in all the tropical climates, and even in a great degree in the south of Europe. In the greater part of Italy and Spain, few crops are raised without being irrigated; and even in the south of France, potatoes, maize, madder, and sometimes vines, and orange trees, as at Hieres,) have water applied to their roots, by furrows and other gutters and trenches formed on the surface. The system of watering grass lands was revived in Italy in the ninth century, and seems to have been practised in a few places in Britain from the time of the Romans; there being meadows near Salisbury which have been irrigated from time immemorial. In 1610, the public attention was called to it by Rowland Vaughan, in a work entitled, "Most improved and long experienced Water Works; containing the manner of summer and winter drowning of meadow and pasture, by the advantage of the least river, brook, fount, or water mill adjacent; thereby to make those grounds (especially if they be dry) more fertile ten for one." |