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DISCHARGE FROM ORIFICES]
55
HYDRAULICS


owners below the reservoirs a right to a regulated supply throughout the year. This compensation water requires to be measured in such a way that the mill owners and others interested in the matter can assure themselves that they are receiving a proper quantity, and they are generally allowed a certain amount of control as to the

FIG. 72. g, ,', ,, Fig. 74 shows an arrangement designed for the Manchester water works. The water enters from the reservoir a chamber A, the object of which is to still the irregular motion of the water. The admission is regulated by sluices at b, b, b. The water is discharged by orifices or notches at a, a, over which a tolerably constant head is maintained by adjusting the sluices at b, b, b. At any time the mill owners can see whether the discharge is given and whether the proper head is maintained over the orifices. To test at any time the discharge of the orifices, a gauging basin B is provided. The water ordinarily flows over this, without entering it, on a floor of cast-iron plates. If the discharge is to be tested, the water is turned for a definite time into the gauging basin, by suddenly opening and closing a sluice at c. The volume of How can be ascertained from the depth in the gauging chamber. A mechanical arrangement (Hg. 73) was designed for securing an absolutely constant head over the orifices at a, a. The orifices were formed in a cast-iron plate capable of sliding up and sg ' l;;»;s

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fd, , z%QiQ%{5%», %//£61/3% if//?//='//?2/245 éff 2/CQ///fr FIG. 73.-Scale Th. down, without sensible leakage, on the face of the wall of the chamber. The orifice plate was attached by a link to a lever, one end of which -rested on the wall and the other on floats f in the chamber A. The floats rose and fell with the changes of level in the chamber, and raised and lowered the orifice plate at the same time. This 1/ TZ Ji 2 Z Z/ ) f/ t 12/ f ¥ '§

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g//4/f;¢;/ff/%»;;4w 7 //Z, “&'q}'#f', .6f 5;;, %//, //, ,, /., /Zz-f im im mf 411.:MZ 1 fl f/21/2 m. A /4, /az/», rx/ /////ffm* av//:ffm/%z%¢ Fig. 74.-Scale 555. mechanical arrangement was not finally adopted, careful watching of the sluices at b, b, b, being sufficient to secure a regular discharge. The arrangement is then equivalent to an Italian module, but on a lar e scale. 60. Professor Fleeming ]enkin's Constant Flow Valve.-In the modules thus far described constant discharge is obtained by varying the area of the orifice through which the water Hows. Professor F. Ienkin has contrived a valve in which a constant pressure head

is obtained, so that the orifice need not be varied (Roy. Scot. Society