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375

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pa tt jf e operation of the tides would break the superficial'''•th ^ le s 'de next the sea, unless prevented by coating its °me durable substance, such as paving stones, bricks,

o r

oth,

fia T S ' m '' ar materials.

I kijj nas °f various kinds, between this and the first naturalftatj 0 ’ 111 a y be invented, differing only in the degree of incli-iti yhich they have towards the sea ; that which slopesOver 6 . o^est degree, as Figure 1, having the surface coveredas sand or gravel; and that which has the least slope,

8, may be covered with pavement; the different5 qu a p e< ^ ate slopes being protected by materials which havebetween the two, such as coarse gravel, chalk-stones,Hol{ atl< ^ sand. The embankment, shown in Figure 9, isBattle ^ instructed of a sandy loam deposited upon a soil of theW. ^ality ; but as it would not, for some time after beingis„„ .’besu

of ^ eu upright in the middle, from the clayey substratumThis • 80 '• underneath, as is shown at x x, in the section.Jjj 13 c alled Puddling.

Oftib ® ase s where the shores are of a very sandy nature.VSh may be made wholly of a sort of wicker-work,f 6 i"htg lree ° r ^° Ur r ° WS Da ^ nar are T)Ut ^ own ' different

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•0. These substances, by detaining the mud and’ as the tide passes through them, or during high floods

t UlS O Oaw4< AmKAVkbmnvil 1 Annn a n 4* l~t rk + a n All fA m +li/

sufficiently impervious to water, a column of clay

or four rows of paling are put down, of differentorei'Vnd the vacant spaces between them well filled, by\ n ,/ urze > brush-wood, or even straw, as represented at

«t r ,

o Vft '® s a sort of embankment, such as that shown in theia 6 v,f e P resen tation. It should afterwards be covered withP ant , which i

is capable of binding and giving it solidity,the elymus arenarius. An embankment, so con-Sl ill i ’ Would continue, during extraordinary tides, to retainr 5i8 6( j S®r quantities of the sandy materials, until, ultimatelyubove the range of the highest floods, a safe bankBy banks formed in this way, large quan-

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? o uid r

'dies -a® formed.

hi

ft a „ anf l might be gained in a very few years, in differentId a j. the rivers Severn, Humber, Frith, &e.

'^els Cases °f embankment, however they may be formed,Se 5 0r atl( l sluices of a proper kind, with valves towards the%‘^ers, must be occasionally placed, according to cir-'' f itlii ri , Ces > so as t° permit the water that may be collectedPass away, and that of the sea or rivers, to flow11 different intentions in the view of improving the

■I'h

utility °f Projecting points is very considerable, inr 3 and ® ases > on the sea-coasts and rivers, in defending the°t tli e , ln lets of the former, as well as guarding the banks?Ppoai at _ter, by diverting their streams or currents to the^c 0ftle 8l des. Hence arises the formation of piers, which^ the V|®hiy beneficial in defending embankments, as wellJjJSeSj ^ 0l 'ders of rivers and brooks. In the first of thesei 3 atn ^ tna y generally be constituted and coated over withsL^ec sort of material as that of which the embankment® 0 a>e s e< * > while, in the latter, they should be formed ofa to ^ 1 °f stony matter, being constructed in such a waya te Pr Clease m every direction as they advance outwards,8 r S, ho^ ente< ^ ’ n Figure 11. In each of these cases, theyA Ure d v, eVer ’ capable of being constituted of brush-wood,j "4 it f me ans of stakes, often with more perfect success.•h?'® 1 of ( * Uentl y happens, that a simple rude wicker-work

Suffl not more than three or four yards in length, may be. ctent for the purpose. Embankments formed off ° v e fi less constructed in the manner represented at theF e > are a pt to cause eddies below them ; while those

^ i, °f brush-wood cannot have this effect.

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■ U .-- CilMJIUl nave imj cucw

io ^ ec 'din Vl0US> '"hat considerable attention must be requireda ^ le most proper situations for constructing this• ‘ejection in, and the distances to which they should

extend into the rivers ; as a too extended projection may behighly dangerous to the opposite bank, and of course doharm, instead of being beneficial; while not carrying themout sufficiently far may prevent the effect which is wanted.In cases where piers are to be formed of stone, as in riverswhere the bottoms are of a rocky nature, the plan representedat Figure 11, is a good one, as it will scarcely cause anyeddy, and be nearly similar to that of the wicker-work, in theeffect which it produces. Different works of these severalkinds have been constructed in the northern parts of theisland with much success.

Proper Materials for Embankments. —It will be obvious,that different sorts of materials may be made use of indifferent situations and kinds of works of this nature, withmore advantage than others, both in so far as duration andexpense are concerned.

Those steep upright embankments, which are constructedwith the view of protecting bold shores, or coasts, and thebanks of particular rivers, may probably be best formed ofgood brick, rubble, or ashlar work, in the manner of a wall,as seen at Figure 6, in the Plate, the materials being laid inthe strongest mortar that can be made. But where this is notthe case, they may be built in the common way, and pointedwith puzzolana earth, or what is termed the Roman cement,prepared by Messrs. Parker and Co., London . Concrete hasbeen used most successfully and extensively for the purposeof embankments, as we have shown under that article.

The different kinds of sloped embankments may be formedeither with”common earthy materials, clay, mud, or a mixtureof these several different substances ; and any other matterswhich are capable of uniting into a solid, firm, compact mass,may be had recourse to for the same purpose. Where thesides next the sea or other waters form angles of from 20to 30, or even 35 degrees with their bases, they may becoated with sand, the shells from the sea, or coarse gravelfrom the borders of the shores. And stones, broken downto uniform sizes of a few pounds in weight, may be employedin a similar manner. Where none of these substances canbe procured in sutficient abundance, a method practised inHolland, of covering them with such perishable materialsas mats, reeds, straw, bark, and others of the same nature,may be had recourse to ; but these are obviously disadvan-tageous, as requiring very frequent renewal. They mightlikewise be protected by a low fence of brushwood, fixed inan erect manner all along at the bottom of the bank, of anequal height, as tending to break off the violence of thewaves. Another method might also be employed, which isthat of covering the whole front of the bank with brushwood,either made into bundles, or in the manner of wicker-work,or fixed down in a neat manner by means of long poles andstrong hooked stakes. And farther, they may be laid in theform of a causeway, with stones in moss, or covered withwicker-work applied upon the mossy material when spreadout over the bank. Many other modes also may be adoptedunder particular circumstances.

In all cases where the sides and slopes towards the seaconstitute angles of from 35 to 45 degrees with their bases,as in Figure 8, recourse may be had to stones of the flag kind,as coverings, which should be jointed with cement mortarsformed in some of the ways we have mentioned above. Andwhere these sorts of stones cannot be provided, if clay canbe found, proper kinds of bricks may be made, and used inthe same way as the stones. Where the slopes or inclinedplanes are from 40 to 45 degrees, it is freqnently more cheapand economical to have them covered with stones of aboutsix or eight pounds in weight, applied to the thickness of afoot and a half, or nearly two feet; or these may be used on