718 PRACTICE OF AGRICULTURE. Part III. 



4352. The sea ivall (Jig. 670. ) is an embankment formed to protect abrupt and earthy 

 shores or banks of rivers, and consists of a wall, vary- 

 ing in thickness, and in the inclination of its surface, 

 according to the required height, and other circum- 

 stances. Belidor, in his Traite de Hydrmdique, has given 

 the exact curve which the section of such a wall ought 

 to have (, b), in order to resist loose earth, and which 

 is somewhat greater than where the earth behind the 

 wall is supposed to be chiefly firm. Some fine exam- 

 ples of such walls, for other purposes, occur in the 



Caledonian Canal ; and perhaps the finest in the world are the granite walls which 

 embank the Neva at Petersburgh, the construction of which may serve as an example of a 

 river cased with stone on a foundation of soft bog earth. 



4353. Embankments for fixing 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 Sohvay Frith, of Lancaster Bay, and of the coast of Norfolk, is 

 of this description. Young, in his Tarmers Letters, informs us, that a considerable 

 part of the county of Norfolk was drift sand, and 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 'lymus arenarius, Triticumjunceum, 

 various species of Juncus, and sometimes by the Galium 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 for 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 soot^ destroy the others. The ^rundo 

 arenaria is planted in Holland for the purpose of binding sands, and was extensively 

 introduced into the Highlands of Scotland for the same purpose, by Macleod of Harris, 

 in 1819. (Trans. Highl. Soc vol. vi. p. 265.) 



4354. To assist nature infixing drift-sands, it is only necessary to transplant the lymus, which is to be 

 had in abundance on 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 v.'ill grow ex- 

 posed to the sea breeze, and no plant throws out so many and such vigorous roots in proportion to its shoots. 



4355. The mode by which such sands were fixed in Holland was by the formation of wicker-work embank- 

 ments, 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 is undoubtedly that of seconding the efforts of nature, by inserting 

 bushes and planting the ^'lymus 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 regu- 

 larly 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 j and the more its width at base exceeded the proportion of that of an equilateral 

 triangle the better. 



4356. 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 oi warping. This mode, being little expensive, seems to deserve a 

 trial in favourable 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, dung, and 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 in- 

 genious, and we hope will be crowned with success. 



4357. Embankments of cast iron have been proposed to be constructed by Deeble, a 

 civil engineer of London. He proposes to combine a series of caissons, made of cast 

 iron, in ranges, agreeable to the required form of the intended embankment. The 

 caissons are to be fastened together by dovetails, and, being hollow, are, when fixed in 

 their intended situations, to be filled with stones and other materials, making them up 

 solid. (Neivton's Journal^ vol. ii. p. 202.) 



