RIVKIi 



Ill 



wrll a* those eooDccted with the materials to be used in the formation 



a purposes the improvement of small streams in thinly 

 nJLi^ nwmrtainou.rand woody districts, is slmost forcedly limitod 

 nriting them into floatable river* ; and this is often effected by 

 SwrtwaWt of dam* across the river*, so as to form as it were locks 

 water, in which the timber can be made into floats, and moved 

 t..,rd. the Juices formed in the dams, which are opened whenever 

 there is a sufficient accumulation of water to float the timber to 

 the next pond. The width of these Juices is usually mode about 20 

 fast, and the faU varies between 3 and 4 firt ; but as the Juice-gates 

 are opened suddenly and the waters escape as it were with n flash, it is 

 not desirable tn make the fall great. There are some very good works 

 "of thk lUstirlptinn on the Yonne, above Auxerre ; and the dimensions 

 of the one st Regilbert may perhaps be sdded, a* a model for our own 

 ~j^q.l engineers. The passage and Juice are formed by carrying out 

 wall* from both banks, in a species of funnel shape, with its wider 

 mouth towards the upstream, of 238 feet in width, and a length of 

 about 310 feet from its commencement to the passage, which is 20 

 feat in width and 33 feet in length to the sluice. Beyond the Juice 

 the wing wall* open out for a distance of 20 feet, and at the end to 

 the down stream they have an opening of 24 feet ; a floor, for the 

 purpose of obristing the inconvenience of the cataract produced by 

 the Bash of water, u continued beyond the wing walls ; tho water is 

 pondsd up to a height of 4 feet, and the Juice is opened, and in a fit 

 .tale to |M a raft, within about eight minutes. Occasionally it ,< 

 desirable to combine Juices of this description with locks, or, in fact, 

 to combine a navigable and a floatable system. In these cases tho lock 

 honld be placed in the still water, on the opposite side to the flashing 

 lain ; the Utter being itself near the bead of the lock chamber, and 

 the tail of the lock being placed at a sufficient distance from the end 

 . Jm to obviate any danger from the back-water, or cataract of 

 the Juice. 



Tho most generally successful mode of improving rivers of smnll and 

 irregular volume is, however, their conversion into still water, or canal 

 navigations, by the construction of locks, waste weirs, and moveable 

 A-nyj Th e position* which are the best fitted for the construction of 

 the lock* are upon the subsidiary channels formed by the islands in 

 the mid stream of the river ; and, unless some peculiar local circum- 

 stances should intervene, it is customary to form the dam and waste 

 weir near the head of the smaller branch, and to place the lock at the 

 lower end of the island ; so as, in fact, to convert the smaller branch 

 into the navigable channel, and to leave the wider branch as the storm 

 or waste water passage* or 9 oil > as it i* technically called. The prin- 

 ciples of construction of locks, Ac., arc of course the same in these cases 

 a* in canals [CANAL] ; and perhaps this portion of the subject may be 

 disuUMed, by saying that the only special works required for river 

 navigations are those by means of which sudden floods are allowed to 

 pass ; for TTfnHf 1 care must be taken to guard against the formation 

 of cataract* on the down Jde of the lock gates. The style of move- 

 able dam used upon the upper Seine appears to be one of the most 

 satisfactory of any yet tried, and it might advantageously be adopted 

 niy^jf our colonial torrential rivers. Their mode of construction 

 has been described in a special treatise, by their author, M. 1'oiree, 

 but a brief account of them will be found iu the ' Aidc-Mcmoirc ol 

 Military Sciences,' article, River Navigation. 



The position of the towing-path is, after all, one of the most important 

 part* of the operations connected with the improvement of the navigation 

 of an inland and non-tidal river ; and it may be stated that this path should 

 be placed, wherever it is possible so to do, by the Jde of the deepest 

 water, and immediately upon the banks of tho river. The theoretical 

 conditions required for such paths are, that they should be exposed to 

 a* few impediments to the passage of the tow-ropes as may be, and 

 that the direction of the haulage should not be too obUque. It is 

 desirable to keep the paths under the wind, in order to avoid the 

 action of the Utter upon the boats ; and when bridges are erected, to 

 carry the paths under the land arches, in order to avoid the necessity 

 for casting off the ropes. The width of the principal path should be 

 about 12 or 13 feet; and if, in consequence of the existence of any 

 rspid or current, it should be necessary to form a second path, so as 

 to allow another rope to be thrown out to keep the boat's head well in 

 the centre of the stream, the second path may be mode only 6 feet 

 fl inches wide. The height of the towing-paths should bo mode such as 

 to allow of their being overflowed directly the river rises to such a 

 height, during floods, a* to reader the navigation dangerous ; or per- 

 haps a safe general rule would be, to keep the top of the path only 

 3 feet above the ordinary winter flood line. Great attention ia required 

 in tho maintenance of the bank* and of the roadway of the towing- 

 path, especully if a rapid navigation be maintained ; the banks in this 

 case should be pitched, and the surface of the roadway macadamised. 

 Secondary streams or small affluents should be bridged over, so as 

 to avoid the necessity for casting off the tow-ropes on approaching 



RIVKK ENGBNEEBINO. 



112 



In riven with light and easily moved beds, and which arc subject to 

 violent flood*, the navigable channel will be found to run between 

 numerous islands, and occasionally to shift from one to the other bank 

 of the strsam. In such cases it frequently become* necessary to 

 rectify the bed by forming a now channel, or to fix the current in it 



original direction by works which should confine it in one of its 

 irevioiis channels. This class of operations is one which requires eon- 

 luuiinato skill, for the nature of the foundations is such as to render it 

 more than usually difficult to contend with the undermining action of 

 he stream itself, and any injudicious diversion of the current will in 

 all probability endanger the banks of the river for a great distance. 

 The most simple rules of a general nature hitherto applied in settling 

 ,ho dimensions and directions of new channels may be stat 

 bllows : it being always observed that local circumstances may modify 

 heir application in a very serious manner. Firstly, with regard to 

 he conditions of flow in the channels, it is known that the velocities 

 ary in the inverse ratio of the cube roots of the widths ; and secondly, 

 hat the cubes of the depths are in the inverse ratio of the widths ; iu 

 >ractice the capacity of the new channel should be made equal to tli .1 

 )f tho ancient one, but the capacity in question should be obtained, 

 vhorever it is possible, by increasing the depth at the cxpcn-r of the 

 width. All obstacles to the navigation, in the shape of trees, rocks, 

 shallows, &c., should be removed ; and the new channel should be con- 

 nected with the old one by curves of considerable radius. The 

 of the now channel on the side opposite to the towing-path should bo 

 made in such a manner as to allow the water to flow into tin 

 wash as soon as the floods bring down an abnormal quantity of water ; 

 and it is very seldom, in ordinary river-barge navigations, that tho 

 crowns of the dams forming the bye-washes are raised more than two 

 Eeet above the full summer level of the stream. Excellent example* 

 of the mode of constructing these lateral banks are to be found iu 

 Smeaton's works on the Carron, Tclford's on the Weaver, and 

 D. Stevenson's on the Kibble, though in some of these cases the tidal 

 action intervened ; perhaps the best treatises to be consulted on this 

 subject are, however, a ' Memoirs on the Rectification of the Bed of the 

 Midouze,' in the ' Annales des Fonts et Chausse'es,' 1831 ; a ' M<5moiro 

 on the Defence and Improvement of the Navigable Channel of the 

 Rhine,' by M. Defoutaine, in the same publication for 1833 ; in 

 Sganzin's ' Cours de Construction ; ' and in Brook's, Calver's and 

 D. Stevenson's treatises on River and Canal Engineering. 



The treatises last mentioned are, it is to be observed, more particu- 

 larly composed with reference to the engineering works required for 

 the improvement of the tidal or of the salt-water portions of rivers ; 

 but it may be added that, in all cases, the results of experience show 

 that the most certain mode of regularising and deepening the bed of a 

 river is by the establishment of continuous longitudinal embankments. 

 With respect to the tidal or marine parts of the streams, the only 

 remarks to be made in addition to those previously applied in the 

 course of this notice are, that so long as the rivers discharge into seas 

 wherein the tidal action takes place without interference, the navi- 

 gation may be improved, and the depth of the channel maintained in 

 an efficient state simply by the construction of lateral embankments, 

 diminishing gradually iu width according to the quantity of water 

 flowing inland. Any sudden widening or contraction of the channel is 

 injurious ; but nature will eventually remedy the former disadvantage, 

 for alluvial matters will be thrown down in the species of bay thus 

 formed, and aU that will then be required will be to keep the main 

 channel open, in the precise direction required, by works of compara- 

 tively easy execution. In rivers like the Thames and Medway, the 

 Seine, Rhine, &c., whore the flood tide is enabled, by the peculiar laws 

 of the deep sea currents, to carry in more alluvial matters than the ebb 

 can remove (and in discussing this question of the movement of 

 alluvions in rivers, the difference in the specific gravities of salt and of 

 fresh water must not be lost sight of), in such rivers there must always 

 be a danger of the channels becoming gradually silted up. The proper 

 course to be adopted in such cases is to combine an efficient system of 

 dredging with a regularisation of the upper portions of the channel, so 

 as to develope and to concentrate the scouring action of the tide and 

 of the current to the utmost extent ; but it must always be understood 

 that rivers placed under the action of this peculiar set of laws can only 

 be kept open by the exertion of great skill, energy, and enterprise. It 

 is true that hitherto little inconvenience has been felt in the Thames ; 

 in the Medway, however, a gradual shoaling up of. the tidal portion of 

 the river has been observed ; the mouths of the Rhine are successively 

 being .choked ; the mouth of the Scheldt is becoming less and less 

 adapted for large vessels; and the Seine has been shown to present, 

 this peculiar characteristic, namely, that even at Rouen the alluvial 

 mud consists rather of materials brought in by the flood tides from 

 the sea, than of materials brought down from the interior by the fresh 

 water. It may also be added, that, as the height and volume of water 

 in a tidal river depend far more on the quantity of the tidal stream 

 than upon any supply from the interior, it is comparatively easy to 

 calculate the height to which the water may under any circumstances 

 rise ; and, when this has been ascertained, the banks on either side 

 should be carried above the highest water-line ; where towing-paths 

 are used in rivers of this description, they should, if possible, be formed 

 on both sides. A tidal current of about two to three miles per hour is 

 usually considered to be advantageous for the trafe of a river ; and it 

 is to the extraordinary facilities offered by the tides of the Thames 

 that we may attribute the singular form of bar^e used upon it. These 

 barges are in fact little better than logs which float on the top of the 

 | tide, and they contrast strangely with the barges used on the Seine, 

 Rhine, RhOuo, &c., which are built in such a way as to offer the least 



