. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Sloffin, % , DETERMINATION OF LOST HEAD. The exact amount of ftf (fig. 1) must be determined. Where a water column is used, say at gauge No. 2, the elevation JE^ is the gauge reading added to the elevation of the gauge zero above an assumed datum, with proper corrections (see p. 5). Where a mercury manometer of the U-tube pattern is used, the reasoning is as follows: It is desired to know the elevation Ex (fig. 1) for a water column which is the equivalent of a mercury column in a U-tube placed as for
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. Sloffin, % , DETERMINATION OF LOST HEAD. The exact amount of ftf (fig. 1) must be determined. Where a water column is used, say at gauge No. 2, the elevation JE^ is the gauge reading added to the elevation of the gauge zero above an assumed datum, with proper corrections (see p. 5). Where a mercury manometer of the U-tube pattern is used, the reasoning is as follows: It is desired to know the elevation Ex (fig. 1) for a water column which is the equivalent of a mercury column in a U-tube placed as for gauge No. 1. Referring to figure 2, the mercury in the two legs of the U-tube below Q will beseen to balance. There- fore the pressure of the water at Q is just balanced by the-column of mercury *QT. But the pressure at c equals that at d. If the mercury X were replaced with water it would reach an elevation sR above Q, where s is the specific gravity of the particular mercury in the gauge, compared with the par- ticular water in the pipe. But the elevation to which this water column would reach is the desired eleva- tion, Ex. As applied to these experiments, refer- ring to figures 1 and 2, the difference in elevation be- tween the readings of the low gauge and the high gauge multiplied by the specific gravity of the mercury and added to the elevation of the low-gauge readings gave the elevation of the equivalent water column when the proper corrections had been applied. MEASUREMENT OF MEAN VELOCITY. As a rule, each pipe tested presented its own problem as to the method to be adopted to determine the mean velocity of the water, and in case this method digressed from one of the following standard methods it is described. 164725°â20âBull. 852 2 r? stop cock. 3/i' â ^'*-- %^ Pipe, lO"long, -â ; threaded. J Set flush with ;\~Cap, tvith /£."' diam. i ho/g in centra, t^rouf: â. Please note that these images are extracted fr
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