[1682]. Oscillating valve.
[1683]. Gas purifier centre valve, for four purifiers; to work one purifier off and three on, or all four on at once. It is similar in plan to [No. 1684], but has an additional top valve which allows the gas to pass into the fourth purifier; the top valve has an independent sleeve and lever motion.
[1684]. Gas purifier centre valve, employed to deliver and discharge gas into and out of any one, two, or three out of four purifiers. The motion of the gas is shown by the arrows.
[1685]. Conical grating valve with radial slots, opened or closed by revolving motion.
Section 90.—WATER WHEELS AND TURBINES.
[1686]. Simple undershot wheel.
[1687]. Breast wheel.
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