Water-power; an outline of the development and application of the energy of flowing water . d the like, is generally foundmissing after any considerable rise of water, and never survivesthe running of ice. Permanent arrangements for observingthe height of water in such situations arc shown at Figs. 238and 239. The first assumes a rock formation. Commencingat the stream, a little below low-water level, cut a channel inthe rock back to yi, where a vertical face of 5 feet or more can GA UGES. 547 be obtained. Cut such a face and bolt on the gauge. Fromthe level of the top of A cut back to B, and
Water-power; an outline of the development and application of the energy of flowing water . d the like, is generally foundmissing after any considerable rise of water, and never survivesthe running of ice. Permanent arrangements for observingthe height of water in such situations arc shown at Figs. 238and 239. The first assumes a rock formation. Commencingat the stream, a little below low-water level, cut a channel inthe rock back to yi, where a vertical face of 5 feet or more can GA UGES. 547 be obtained. Cut such a face and bolt on the gauge. Fromthe level of the top of A cut back to B, and bolt on B go to C, thence to D, etc., till the highest possibleflood is covered. The graduation of B commences where Aterminates, C where B terminates, etc. Fig. 239 assumes agravel formation. Here we do not use a connected scale ofheights. We drive down the iron rods A, B, C, etc., each 12or 15 feet long. The first is driven to a depth sufficient toinsure that it will never be above water, and the tops of theothers successively about 5 feet higher. The levels are carefullv. W Fig. 239. taken and recorded. The heights are taken by means of aportable graduated rod placed on the head of the iron rod. Adiscarded level-rod answers very well for this purpose. Inhigh water a skiff is used to observe the heights. To meet thepossibility of the malicious driving of the rods, the levels shouldbe repeated at intervals. On great rivers, such as the Mississippi, ^Missouri, and Ohio,floods of 40, 50, and 60 feet often occur. Excepting the con-paratively rare case of a bridge, there are no vertical structuresto which a gauge can be attached, and the situation is usuallythat of Fig. 239, which may be taken to represent the slope of a 548 DATUM PLANE. natural bank or a levee, the latter being 2 or 3 base to i perpen-dicular. In this case the bank is dressed to a uniform slope,sometimes paved, and the gauge-plank, some 9 inches wide and 2or 3 inches thick, laid thereon, the face com
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Keywords: ., bookcentury1900, bookdecade1910, booksubjecthydraulicengineering
