Priessnitz), of massage (Weir Mitchell), of climate (James Clarke), of diet (R.
- By the use of the complex variable and its conjugate functions, an attempt can be made to give a mathematical interpretation of problems such as the efflux of water in a jet or of smoke from a chimney, the discharge through a weir, the flow of water through the piers of a bridge, or past the side of a ship, the wind blowing on a sail or aeroplane, or against a wall, or impinging jets of gas or water; cases where a surface of discontinuity is observable, more or less distinct, which separates the running stream from the dead water or air.
A rapid in the Tagus, artificially converted into a weir, renders irrigation easy, and has thus created an oasis in the midst of the barren plateau of New Castile.
The Weir, the condensing water circulates upwards through the tubes; in others, e.g.
The weir across the Jumna was the first attempted in Upper India upon a foundation of fine sand; it is about 800 yds.
Assiut stands near the west bank of the Nile across which, just below the town, is a barrage, completed in 1902, consisting of an open weir, 2733 ft.
Banks thereupon retreated, and, high water in the river having come to an end, the fleet was in the gravest danger of being cut off, until Colonel Bailey suggested, and rapidly carried out, the construction of a dam and weir over which the ships ran down to the lower waters.
Weir, A Short History of the Hebrew Text (London, 1896); H B.
A weir is thrown across the Betwa about 15 m.
WEIR (from O.
The simplest form of weir is a solid, watertight dam of firm earthwork or rubble stone, faced with stone pitching, with cribs filled with rubble, with fascine mattresses weighted with stone, or with masonry, and protected from undermining by sheet piling or one or more rows of well foundations.
This serious defect of solid weirs, where the riparian lands are liable to be injured by inundations, can be slightly mitigated by keeping down the crest of the weir somewhat below the required level, and then raising the water-level at the low stage of the river by placing a row of planks along the top of the weir.
The discharge of a river at a weir can be regulated as required and considerably increased in flood-time by introducing a series of openings in the centre of a solid weir, with sluice-gates or panels which slide in grooves at the sides of upright frames or masonry piers erected at convenient intervals apart, FIG.
- Lifting-gate Weir and Foot-bridge at Richmond, Surrey.
By these arrangements the large draw-door weir across the Thames at Richmond, with three spans of 66 ft.
This weir retains the river above it at half-tide level, in order to cover the mud-banks which had been bared at low tide between Richmond and Teddington by the lowering of the low-water level, owing to the removal of various obstructions in the river below.
The weir is raised ¦ '.'
The ordinary form of frame weir consists of a series of iron frames placed across a river end on to the current, between 3 and 4 ft.
The barrier was originally formed of a number of long square wooden spars which could be readily handled by one man, being inclined slightly - from the vertical and placed close together for shutting the weir; but panels of wood or sheetiron closing the space between adjacent frames and sliding in grooves at the sides, and rolling-up curtains ?
The needle weir, so called from the long, slender spars being termed aiguilles in France, had the merit of simplicity in its earliest form; and by means of some ingenious contrivances, comprising a hook, winch, lever and rotating bar, for assisting the weir-keepers in placing and releasing the needles, the system has been applied successfully to the weirs of greater height required on the Meuse, the Main and the Moldau (fig.
The needle weir has, however, attained its greatest development in the United States across the Big Sandy river at Louisa, where, instead of needles 3 to 4 in.
The weir is opened by joining the needles of each bay by a chain passed through the eyes at the top and a line of wire through the central rings, so that when released at the top by the tilting of the escape bar by the derrick, they float down as a raft, and are caught by a man in a boat, or, when the cur rent is strong, they are 'mopes ?o drawn to the bank by a rope attached to them previously to their release.
The trestles of this weir are, as usual, hinged to the apron, so that in flood-time they can be completely lowered into a recess across the apron by means of chains actuated by a winch, leaving the channel perfectly open for the discharge of floods and for the passage of vessels when the lock is submerged.
Whereas, however, ordinary frames placed nearer together than their height overlap one another when lowered on to the apron, the trestles of the Louisa weir lie clear of each other quite flat on the apron.
The frame weir closed by sliding panels or rolling-up curtains (fig.
- Needle Weir, River Moldau.
- Spar Weir, Louisa, Big Sandy River, U.S.A.
The frames hang vertically from the bottom of the overhead bridge, and rest against a sill at the bottom when the weir is in operation, the openings between the frames being closed below the water-level by rolling-up curtains or sliding panels, which are lowered or raised by a travelling winch carried by a small foot-bridge formed by hinged brackets at the p ack of the frames, and situated a little above the highest floodlevel.
The weir is opened by removing the sliding panels or rolling Scale 'kW.
- Frame Weir with Rolling-up Curtain, Port Villez, Lower Seine.
This system, which has been employed for the lowest weir on the Moldau, and for a weir at the upper end of the Danube canal near Vienna to shut out floods and floating ice, as well as on the Seine, possesses the merits of raising all the movable parts of the weir out of water in flood-time, and rendering the working of the weir very safe and easy.
- Suspended Frame Weir, Poses, River Seine.
The earliest form of shutter weir, known as a bear-trap, introduced in the United States in 1818, and subsequently erected across the Marne in France, consists of two wooden gates, each turning on a horizontal axis laid across the apron, inclined towards one another and abutting together at an angle in the centre when the weir is closed; the up-stream one serves as the weir, and the down-stream one forms its support, and both fall flat upon the apron for opening the weir.'
By means of chains worked by a winch .2 The shutter weir, introduced on the upper Seine about the middle of the 19th century and subsequently adopted for weirs across several rivers in France, Belgium and the United States, consists of a row of wooden or iron shutters turning on a horizontal axis a little above their centre of pressure, borne by an iron trestle at the back of each shutter, which is hinged to the apron of the weir, and supported when raised by an iron prop resting against an iron shoe fastened on the apron (fig.
The weir is opened by releasing the iron props from their shoes, either by a sideways pull of a tripping bar with projecting teeth laid on the apron and worked from the bank, \\\\\\\\\\\\\ [[Scale Zoo.
- Bear-trap Weir, U.S.A.
The weir is raised again by pulling up the shutters to a horizontal position by their bottom chains from a special boat, or from a foot-bridge on movable frames, together with their trestles and the props which are replaced in their shoes.
The discharge at the weir whilst it is raised is effected either by partially tipping some of the shutters by chains from a foot-bridge, or by opening butterfly valves resembling small shutters in the upper panels of the shutters.
The addition of a foot-bridge greatly facilitates the raising and lowering of these shutter weirs, and also aids the regulation of the discharge; but it renders this form of weir much more costly than the ordinary frame weir, and where large quantities of drift come down with sudden floods, the frames of the bridge are liable to be carried away, and therefore boats must be relied on for working the weir.
The straight, upper paddles form the weir, and can be raised against the stream by making the water from the upper pool press upon the upper faces of the slightly larger lower paddles, .
- Shutter Weir with Foot-bridge, Port a l'Anglais, Upper Seine.
The merits of this weir in being easily raised against a strong current and in allowing of the perfect regulation of the discharge, are unfortunately, under ordinary conditions, more than counterbalanced by the necessity of carrying the drum and its foundations to a greater depth below the sill of the weir than the height of the weir above it.
High in each case; and a still larger drum weir was erected about the same time for closing the navigable pass of a weir across the Spree at Charlottenburg, with an upper paddle 324 ft.
A peculiar and cheaper form of drum weir has been constructed across ten bays each 75 ft.
- Drum Weir, Charlottenburg, River Spree.
In spite of its high cost, the drum weir furnishes a valuable hydraulic contrivance for situations where it is very important to be able to close a weir of moderate height against a strong current and to regulate with ease and precision the discharge past a weir.
Which should flow over a waste weir initially r in.
In neither case is there a waste-weir, the surplus water being allowed to pour over the crest of the dam.
For this system two syphons will be required near the head, regulating bridges under all the embankments, and an escape weir back into the river.
This has now been rectified, in the same way as in Lower Egypt, by the construction of a weir across the Nile, intended to Assiut give complete control over the river and to raise the Weir water-surface 8.2 ft.