RIVER. 



like that juft noticed in the above cafe, can be made ufe of, 

 this difficulty may be faid to vanifh. The mouth of the 

 new cut receives the current with a llraight courfe ; confe- 

 quently, if it be made of fufficient capacity, the river in a 

 flood can have no propenfity left towards its old channel ; 

 and the loofe materials which rife in forming the mouth 

 of the new cut will generally be fufficient to turn the 

 ftream at low water into it. But if a fuitable bend 

 cannot be approached by the new cut, a directing pier, 

 like that in the above cafe, will be required to bend the 

 flood-current, and give it a llraight-forward courfe into the 

 new channel ; a water-tight dam being formed between the 

 point of the pier and the firm bank of the new channel, to 

 prevent the water from regaining its former courfe or di- 

 rection. 



But in regard to the cutting of the new channel, it is 

 merely a work of manual labour ; being attended with no 

 other difficulty than what may arife from the expence ; which 

 will depend on the fize of the river, the nature of the ground 

 to be cut through, and the value of labour in the given 

 diftrict. It is moflly to be afcertained with fufficient accu- 

 racy, by previous calculations. And it is added that the 

 required Jive of the new cut is fmall compared with that of 

 the old channel. For the currents of floods, by carrying 

 off the earthy particles with which they come in contact, 

 will foon enlarge it. It is neverthelefs right to give ample 

 room in the new channel, left the firft flood fhould prove 

 high, and, by burlting its bounds, force its way back to its 

 former courfe. Therefore, in order to give the required 

 capacity to the new channel, and to allow for its widening, 

 the materials which arife in making it ought to be formed into 

 regular embankments on cither iide of it, and at fufficient 

 diitances from its brink, to obtain the above purpoles ; and, 

 moreover, to protect the adjacent lands from the injurious 

 effects of unreitrained floods. And it is further fuggeited, 

 that a new river courfe requires to be carefully attended to, 

 during a few years after it is opened, to fee that its channel 

 preferves its itraightnefs, and that no breaches are made or 

 threatened in its banks. And that, confidering the uncer- 

 tainty of extraordinary floods, it cannot be laid to be out of 

 danger in lefs than three years. Of courfe, in contracts for 

 thefe works, in thefe cafes they fhould be upheld lor that 

 time, and then delivered up in the Hate fixed upon in the 

 agreement. 



There are Hill other cafes of rivers in lowland iituations, 

 where the currents of them are generally fluggifh, and their 

 beds deep funk and narrow, with few fhoals or firm bafes 

 on which to found piers or bulwarks, and few ftones with 

 which to raife them ; and even if erected, the fluggiflinefs 

 of the current may render them ineffective. In thefe cates 

 the banks are fteep, and often of the tendered earths, liable 

 to the fiighteit attacks of agitated water, efpecially near 

 their feet, where they are naked of vegetable covering. 

 Hence, it is from the frettings of the minor floods, or the 

 waves of the dead water which occupies the channel of a 

 river of this description, that its banks are worn away ; 

 efpeciallv at a bend which faces a length of reach, in which 

 the waves have room to rife. Thefe fretting again ft the 

 foot of the bank undermine it. The face of the bank, in 

 confequence, fhoots down ; and the proltrated foil is du- 

 perfed by the next flood. Il is confequently obferved, that 

 the moft efTential work, in a cafe of this kind, is to guard 

 the foot of the bank up to the level, and fomewhat above 

 the level of low water. And, this done, to Hope back, 

 fmoothly, the upper part of the bank, to enable it the bet- 

 ter to fupport a vegetable covering, and withftand the at- 

 tacks of higher floods, as well as to render it lefs dangerous 



to pafluring nock, and enlarge their field of pailurage. 

 And that when, with the increafe of capacity, the channel 

 is flill unable to contain the waters of great floods, lines of 

 embankment may be raifed on either fide of it, witli the foil 

 removed in forming the Hopes ; and thus rellrain them within 

 due bounds. Likewife in particular parts, as at fharp 

 bends, when ordinary fward, or paft 'arable turf, is not able 

 to prevent the current, in this trying lituation, from breaking 

 up the foil, it fhould be bound more fecurely together by 

 ftronger rooted plants; of which the ofier is laid to be pro- 

 fitable to be planted upon the top of a rich river-bank ; but 

 it is altogether unfit to occupy its face for the purpofe here 

 required, though commonly ufed ; as it tends to counteract 

 one of the intentions propofed in Hoping back the face ot 

 the bank ; by Idling up the fpace thereby prepared for the 

 waters of high floods to ipread in ; and thus increales the 

 current at the foot of the bank. A much more eligible and 

 effectual guard prefents itfelf, Mr. Marfhall fays, in the 

 furze, whofe roots not only form a mat of llrong fibres in 

 the foil, but bind it down to the fubflratum in a fingular 

 manner. Yet even the furze, if fuffered to run up to its 

 greatelt height, may frultrate the intention of propagating 

 it. It ougkt, therefore, to be cut down from time to time 

 as fuel ; or to be kept dole mown, fo as to form an invul- 

 nerable fiiield to the face of the Hope. But it is oblerved 

 that if we examine into nature's practice in guarding the 

 foil of river-banks, we fhall find it carried on with the bell 

 effect by tl-.e butter bur [tujjtlago pttafites) . 



But in thefe cafes of fecuring the banks of rivers, Dr. 

 Anderfon has long fince given more full and ample direc- 

 tions. He remarks, that when a river runs in a bed of rich 

 vegetable mould, the leaft accident that may chance to di- 

 rect the Hream towards any particular part of the bank, 

 caufes it to fweep away large tracts of fine ground, to the 

 very great detriment of the proprietor, as well as the public ; 

 as this fine mould is ufually carried to the fea, and the ma- 

 terials that the water leaves, to occupy the new bed that it 

 thus forms for itfelf, is generally of a much worfe quality, 

 confiding chiefly of Hones, land, and gravel. And that 

 where the whole force of the current is quite clofe to the 

 bank, and the materials neceffary for fencing it are not 

 to be there found, it'may perhaps be impofiible, or very dif- 

 ficult, totally to prevent this evil : but, for the moil part, 

 it admits of a cure, that can be obtained at a pretty mo- 

 derate exper.ee. For if you carefully obferve the banks ol 

 rivers, you will readily remark that thefe ravages are always 

 molt confiderable at thofe places where the banks rife per- 

 pendicularly to a pretty confiderable height above the or- 

 dinary furface of the water, and never at thofe places where 

 the banks flielve down gradually towards the water's edge : 

 for when the river is fwe'led to a great height by rains, and 

 runs with a greater force and rapidity than ufual, it (Irikes 

 violently again It thefe perpendicular banks that directly op» 

 pofe its courfe ; and as they are compofed of earth, quite 

 bare and uncovered, they are eafily foftened by the water, 

 and quickly waffied away ; fo that the upper part of the 

 bank, being thus undermined, falls by its own weight into 

 the river, and is carried off in prodigious quantities. But 

 when the river rifes to any confiderable height, it generally 

 glides along the furface of thofe parts of the bank which 

 (halve gradually downwards to the water's edge, which 

 being defended by the matted roots of the grafs, with which 

 it is covered, fcarcely fuitains any damage at all, and is 

 nearly the fame after the water has retired within its banks, 

 as before the inundation took place. He thinks that thefe 

 are facts, which no one, who has bellowed the leaft atten- 

 tion to this fubject, can fail to have obferved ; and that they 



I - clearly 



