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SCALE 300
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See also:SCALE 300 . crooked for the purpose, causing them to revolve in a quadrant of a See also:cylinder under the See also:sill, known as the See also:drum; and they can be readily lowered by cutting off the flow from the upper See also:pool and putting the drum in communication with the See also:lower pool, which connexions can be adjusted by see-saw sluice-See also:gates, so as to put the upper paddles in any intermediate position between See also:vertical and See also:horizontal (fig. to). The merits of this See also:weir in being easily raised against a strong current and in allowing of the perfect regulation of the See also:discharge, are unfortunately, under See also:ordinary conditions, more than counterbalanced by the See also:necessity of carrying the drum and its See also:foundations to a greater See also:depth below the sill of the weir than the height of the weir above it. Accordingly, for several years its use was restricted to the See also:Marne; but in 1883–1886 drum weirs were 2 Proc. Inst. C.E., vol. exxix., p. 258 and See also:plate vi., fig. 2. Shutter weir. adopted for closing the See also:timber passes alongside the See also:needle weirs placed across the See also:Main, with a single upper See also:paddle 393 ft. See also:long and 5 ft. 7 in. high in each See also:case; and a still larger drum weir was erected about the same See also:time for closing the navigable pass of a weir across the See also:Spree at See also:Charlottenburg, with an upper paddle 324 ft. long and 9€ ft. high (fig. to). A See also:peculiar and cheaper See also:form of drum weir has been constructed across ten bays each 75 ft. wide on the Osage See also:river near its confluence with the See also:Missouri, where a hollow, wooden, cylindrical sector, stiffened inside by See also:iron framing and revolving on an See also:axis laid along the See also:crest of the solid See also:part of the weir, fits into a drum at the back lined with planking, having a See also:radius of 9 ft. The weir is raised by admitting See also:water from the upper pool into a See also:wedge-shaped space See also:left below the sector when it is lowered in the drum, which by its pressure lifts the sector out of the drum, forming a barrier, 7 ft. high, closing each See also:bay of the weir. See also:Provision has also been made for rendering the sector buoyant by forcing See also:air into it, so that it can be raised when the See also:head of water is insufficient to lift it by the pressure of the water from the upper pool. In spite of its high cost, the drum weir furnishes a valuable See also:hydraulic contrivance for situations where it is very important to be able to See also:close a weir of moderate height against a strong current and to regulate with ease and precision the discharge past a weir. (L. F. Additional information and CommentsThere are no comments yet for this article.
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