| | | |

to the Firft Volume: 597

out being liable to ftick by fwelling. This is effected by the edges being made to flant or bevelinwards. The frame fhould likewife incline a little inward, but not fo muchas to retard the exit of the contained water. Where rivers or ftreams pafs through embanked grounds, the fides may frequently require to be raifed fuffici- ently to prevent their overflowing in times of floods. And where they are too low to be fully drained, it may be neceflary to form embanked channels or cuts for re- ceiving the water when thrown up by machinery.‘Thefe embanked channels may be converted to various ufes, fuchas irrigation,&c. in different cafes*,

Embankments have been divided into three different kinds, as thofe againft the fea, againft rivers, and againft lakes, each of which fhould be formed according to the refiftances required.‘The firft, however, in general require by far the ftrongeft and moft expenfive works+.

In embanking again{t the encroachments of the fea, it fhould firft.“ be confi- dered what is the greateft depth of water at the higheft fpring tides.. About two feet higher than that fhould be the fummit of the bank. Some have recommended only one foot higher, but it is beft to err on the fafe fide; for the confequences at- tending an overflow, after the whole is completed, may, in one tide, doa great deal more damage than all the expenfe of the additional foot in height. If the embankment be made at firft even three feet higher than the higheft rife of the tide, efpecially at thofe places expofed to the waves or fwell of the fea, it will be fo much the more fecure; for new works of this kind always fub- fide or fettle in fome degree after they are erected. It is a very neceflary precau- tion, particularly if the banks are large, to take the levels frequently for fome time after they are completed, left they fhould: fubfide too‘much, and thereby occafion a mifchief which it was imagined hadbeen fufficiently. guarded againft.- If the banks are but low, this precaution is not fo neceflary, for the fettling will always be more or lefs according to their height, and in low banks will be but very little. It. is hardly poflible to give one general rule refpecting the fize and dimenfions of fuch embankments. This muft be regulated according to circumftances and fituation, for which-a fkilful engineer will always make-the proper allowances. If the em- bankment to be made is to exclude the fea from a low marfhy piece of ground, over which it flows only at fpring-tides, the operation. is eafy, and may be effected atia fmall expenfe. If it is intended to reclaim a piece of land that is covered every tide, either in fome bay or creek, or onthe fides or windings of fome large river

* Marfhall on the Landed Property of England. + Beatfon in Communications to the Board of Agriculture, Vol, If.