RIVER. 



lo the channel prepared for it. And the Jlrength required, 

 depends upon the weight of water, the force of the current, 

 and the angle of deviation from the given direction of the 

 current immediately above. If the required direction of the 

 pier be nearly the fame as that of the current above it, it 

 has, it is contended, little more than the weight of water to 

 fuftain. Whereas a jutment run out, abruptly, into the 

 natural courfe of the current (as is commonly feen), has 

 not only the weight, but the force, of the water to with- 

 fland ; and requires threefold, or tenfold, the ftrength of 

 ftrufture that is necefl'ary in the other cafe. Another 

 circumftance to be particularly regarded in this fort of 

 bufinefs, is the height of the conductor. Where it is run 

 out from the bank into the channel of the river, in rather a 

 ftraight manner, and if it be not raifed high enough to pre- 

 vent the waters of floods from making their way over it, its 

 foundation may be endangered ; efpecially in a place where 

 the general fall of the river is confiderable. For an overfall 

 of water, unlefs it have a firm bafis to aft upon, naturally 

 fcoops out a pit at the foot of the fall ; and undermines the 

 precipice it tumbles over ; feldom failing to let down fuch 

 as are conftrufted by art. 



With refpeft to the means of obviating this effeft, they 

 are three, one of which is to raife the pier high enough to 

 prevent the overfall ; an expedient, however, which cannot 

 always be praftifed with propriety. Another is to form 

 the lower fide, or back part of the pier, with a (helving or 

 flatly inclining furface, to break or elude the fall. And the 

 other, to prepare a convex floor behind the pier, for the 

 waters to tall upon. This Iaft has been found fuccefsful in 

 the writer's own praftice. There is likewife another point 

 that demands particular care in the operator, which is that 

 of fecuring the point or outer end of the pier, not only at 

 the foundation, but in the fuperitrufture. For although the 

 main current cannot, if the pier is judicioufly placed, 

 exercife its ftrength upon this part ; yet, by reafon of the 

 weight of water there lofing its fupport, and part of it, 

 confequently, rufhing precipitately into the unguarded bay, 

 the lower end of the pier is peculiarly expofed to danger 

 in that way. It is fuppofed fcarcely neceflary to add, that 

 the upper end of the pier ought to be deeply inferted in the 

 firm bank of the river, to prevent the current from infinuat- 

 ing itfelf behind the facing, or that the face of the pier 

 fhould be carried up with a fufficient batter, to give it 

 tirmnefs ; or that the foundation ought to be fecurely laid, 

 and to be kept feduloufiy guarded in front, to prevent its 

 being undermined by the current. Rough ftones, thrown 

 down loofe, and with a flat (helving furface, againft the foot 

 of the pier, are, in mod cafes, the belt guard, let its 

 materials be of what fort they may. 



It is advifed, that the materials for this ufe (hould be 

 fuiiedto itsoccafion, where a choice is to be had. If a low 

 defence, only, is wanted, in a diftrift where large rough 

 ftones are plentiful, a long pile of loofe ftones, laid flatly 

 Hoping againft the bank of the river, or a flat ridge run out 

 from it, may form a cheap and durable barrier. For (hould 

 they be difturbed by an extraordinary flood, they may be 

 readily replaced when the water fubfides. Where a tall 

 pier is required to direft a large and rapid river, in a 

 place where ftones and ilrong cement may be procured 

 at a moderate expence, mafonry may be eligible. But 

 in expofed fituations, at lead, it ought to be guarded 

 with timber, efpecially at the top and the outer end 

 (as the piers of fea-ports, and the quays of navigable 

 rivers, are guarded), to defend thofe parts from injury 

 by ice, timber, or other large floating bodies, driven 



againft them in times of flood. And that where mafonry 

 cannot be ufed, but at a great expence, a ca'tjfoon, formed 

 with poits and planks of adequate dimenfions, and tilled 

 with pebbles, gravel, or other indiffoluble materials, to 

 give (lability to the fabric, may be found to laft as long 

 as its fervices may be wanted ; and, in fome cafes, may b<- 

 removed while its materials may yet be valuable. 



But this, though the prevalent method, is merely 

 palliative, and demands frequent repairs : it does not cure 

 the evil, or bring back the loft property to the owner who 

 has a right to it. Nor is it in fuch a cafe beneficial to a 

 ri?al owner, for the current, as has been (hewn, fweeping 

 circuitoufly along the banks of the bay, is thereby led to 

 direft its force againft the lands of the proprietor on this 

 fide, who cannot, under thefe circumftances, defend their 

 by the above means ; but who mult either fecure then; 

 by a lengthened land-guard, or leave them at the mercy of 

 a fweeping current. It is therefore concluded, that, in a 

 cafe of this kind, it is evidently the bell interelt of an oppolite 

 proprietor to fuffer his (and-bank, or gravel-bed, to be cut 

 through, in the manner fuggeited, and that he ought to 

 aflift in the operation ; as he will thereby not only get 

 rid of the circuitous current, but, by the aftion of the 

 floods, in the itraightened courfe, his bay will fcarcely 

 fail to be filled up with the fcattered materials that mav L-. 

 removed. 



There is another cafe in which this iort of pier or river- 

 guide may be made ufe of with luccefs ; which is that 

 where a ftream of the above defcription falls down a crooked 

 valley, and necci!arily takes, at certain pointc, a winding 

 courfe. 



In this cafe, where the quantity of water is confiderable, 

 its fall rapid, and efpecially where it is conducted to the 

 bend on the farther fide down a (traight, unobftrufted reach, 

 fcarcely any thing but natural rock can refill its force in 

 that part. In fuch fituations it is not unulual to fee earth- 

 banks fcooped out and undermined, until a perpendicular 

 cliff of twenty or thirty feet high be formed. But if a 

 pier be erefted at the upper part of the bend, with an eafy 

 curve from the natural courfe above, fo as to bend the 

 current without breaking it, and direft it into its natural 

 channel, in the valley below, it will have nothing to contend 

 with but the loofe gravel beds on the different fides, which, 

 if cut through, as in the former cafe, will prefently be torn 

 away, and a principal part of their materials be depofited in 

 the bays on each fide, but efpecially in the latter, or that on 

 this fide : fo that in this, as well as in that cafe, both fides of 

 the river may be benefited by the alteration which is thus 

 produced. It is however dated, that there are cafes in 

 which nothing but an immediate (heath, or land-guard ap- 

 plied to the injured part, can be properly ufed to prevent 

 further depredations. As, firft, where the river is confined 

 in the part where it is required to be bent, by rocks or 

 otherwile, to an unaltered channel ; as it frequently 

 is in fub-alpine fituations. And, fecondly, where a deep 

 pool occurs in that part at low water, fo as to render it dif- 

 ficult to get a proper foundation for a pier. It is obferved 

 that, in the former fituation, ftones are generally plentiful ; 

 and they require to be applied according to the circum- 

 ftances of the particular cafe. Where the foot of the in- 

 jured bank is covered with a pool at low water, it is advifed 

 to fhelve off the brink of the bank, and fhoot down loofe 

 ftones from the top of it ; fuffenng them to form their own 

 flope in the aftion of falling, and by the operation of fuc- 

 ceeding floods ; continuing to pour them down until the 

 bank be fecured, at lead from minor floods ; and then to 



flojc 



