THE FARMER'S MAGAZINE. 



407 



nicety. The surface is covered with qrassy turf, jointcil, 

 fitted, and beaten together, so that no opening or inequality 

 present an obstacle or opposition to the waters, where to 

 make a breach aud a beginning of destruction. The 

 safety of the bank and the whole success of the under- 

 taldng depend on a level and unbroken surface being 

 formed, on which the water rolls without a ripple, and finds 

 no obstacle of contention. In low countries and on level 

 grounds where embankments are required to confine the 

 overflowings of the rivers, the flow of water is sluggish 

 and lazy in the movements, so that no great difficulty is 

 presented in constructing a barrier against its force. The 

 pressui'e being lateral, aud not in a forward direction, the 

 level slope prevents the extension of the water, supports 

 the downward pressure, and permits the water to roll along 

 as if running on the base of the embankment. The turf 

 must be very gi-assy and matted, of vivacious herbage, 

 and of good soil. Hooked pegs of timber are driven into 

 the mound in several cases, in order to hold the turf in the 

 required position. This use understands a degree of rapidity 

 in the water over the fence. The growth of grassy surface 

 presents the best of all materials on which waters roll with- 

 oat inflicting damage, and it is fed by the alternate benefits 

 of being dry and having a watery covering. The entire 

 construction must be duly attended and repaired, will soon 

 become a bamer of great strength, and will bear an intru- 

 sion much beyond its appearance. The outward point of 

 the slope dips underneath the turf of the level ground 

 which is raised to receive the outermost apex of declina- 

 tion, fonning a raised continuation of grassy turf that 

 allows the rolling of the water, and merely prevents its 

 spreading over a greater extent of surface. The course 

 of the water is only changed to a slope from a level 

 course. 



A trough is the natural channel of a river ; and the devia- 

 tions from this form are occasioned by steep banks, a 

 barrier of rocks, or greater or less resistance of the surface 

 strata, when the stream of water is diverted into pools, 

 shallows, and eddies, and excavation of the banks. The 

 solidity and permanence of the bank depend in part on the 

 inclination of the surface, the hardness, tenacity, and 

 smoothness of the materials, and on the degree of parallel- 

 ism that is preserved between the course of the bank and 

 the impinging current. Tortuous courses of bodies of 

 water present an angle of resistance to the moving fluid, 

 which, being enlarged in volume, acts with violence against 

 an earthy deposit, tears the mass, and carries away the dis- 

 solved materials. The peat soils of alluvial formation are 

 gradually wasted and reduced in the superficial area by the 

 invasion of watery bodies ; and the protection of the culti- 

 vated lands becomes a business of constant attention. In 

 these flat countries the rivers move slowly, and generally 

 stand deeply, making a pressure on the banks at the bend 

 or turn ; in other places, a current is produced in rather 

 higher situations, which runs from one pool to another ; 

 aud the force being directed against the bank, a demolition 

 takes place of the earthy stratum , at all times of the river 

 being swola by rains and thaws. A straight course not 

 being possible, by reason of natural obstacles, it becomes 

 necessary to turn the stream of water into as many straight 

 runnings as can be got from one place to another, by means 

 of fences to turn the course at the bendings of the channel. 

 The rolling volume of water sometimes rushes against the 

 opposing bank at a right angle, but most frequently at an 

 angle of divergence, or strikes the bank laterally, when the 

 destruction is much greater than when the stream rolls 

 directly against the bank. Impinging bodies ai'e reflected 



from obstacles at an angle equal to their incidence ; and 

 the smaller that angle, the less force is exerted against the 

 body that is presented to oppose their progress. Accord- 

 ingly, in raising fences to protect earthy banks, by tm-ning 

 from them the force of water that rolls against the deposit, 

 it is required that the position of the fence is directed 

 aslant the current of water, so as to receive the impression 

 at an acute angle, throw it off in the same divergence, and 

 direct the stream into a mid-channel. For this purpose, the 

 fence must cut a direct current of water at less than an 

 angle of 45 deg., receive the impression at the most acute 

 angle possible, turn the volume of water from rushing 

 against the bank, and direct the course into a mid-channel. 

 In alluvial countries, the substratum is generally deep in 

 earthy deposits, aud allows the driving of piles shod with 

 iron into the bed of the river, in two or more rows, and 

 placed in the slanting direction that has been determined. 

 The distance from the bank will depend on circumstances, 

 according as the water rolls against the bank in a direct or 

 slanting course. The space between the bank and the piles 

 is filled with large stones, that are rolled promiscuously into 

 the vacant extent, aud settle into position by their own 

 weight. The force of the water is broken by tho piles and 

 stones; and though it flows among the stones, no injury is 

 done to the bank that is behind, and the water finds a slow 

 escape along with the main current. In the absence of 

 large stones, baskets made of strong osiers are filled with 

 small stones, and sunk in the bed of the vacant space behind 

 the driven piles ; and in other cases, bundles of brushwood 

 are placed behind the piles, and held in position by liga- 

 ments of some kind being fastened around the stakes ; in 

 this position the sediment lodges among the twigs, and con- 

 solidates into an earthy bank. The large piles of timber by 

 which the whole provision is sustained must be used in 

 quantities as they appear to be necessary. from the materials 

 that can be obtained. The weight of large stones quickly 

 finds a bed of repose; it onlyjemaius to have piles fronting 

 the river, to prevent the stones rolling into the deep trough 

 of the channel. Small stones will require the front piles to 

 be thickly planted, and also cross rows at no great distance, 

 extending to the bank. The placing of the piles must be 

 thicker for brushwood, the bundles of which are pressed 

 and held down by planks that are joined to the driven piles, 

 A very efi'ectual defence is erected by forming a slope bank 

 of stones and planks, extending from the top of the bank of 

 the river forwards to the bottom of the water, of which the 

 surface is lozenged with cross and longitudinal plank of timber, 

 The water rolls up this sloping surface as upon the grassy 

 banks that have been described, and though it is costly, it 

 forms the most complete barrier that can be furnished. But 

 in most cases the rows of piles, with some hai'd or conso- 

 lidating materials placed behind, will be adopted. A slant- 

 ing fence of the description now given, will be required at 

 ever bend of the riyer, and all places where the current 

 tears the bank, and always placed to throw the cun-ent into 

 a mid-channel, The stream must not be directed against 

 the opposite bank, to produce the evil that is sought to be 

 avoided ; the fence must form a line with the cun-ent of 

 the stream. 



When waters run in a straight course, little or no damage 

 is done to the banks wliich confine the current ; but when 

 the bed is narrow, and the line crooked, the water is broken, 

 and is placed in the particles, and the agitation that is pro- 

 duced carries forward violence and destruction to all op- 

 posing obstacles. The course of rivers must be straight, or a3 

 nearly so as possible, and all attempts to alter or improve 

 the line of currents must approach to that design. All 



