There is on the market a dosing apparatus which does not involve a siphon, and which is shown in Fig. 18. This is made by the Ansonia Manufacturing Company, 30 Church Street, New York City, and its operation may be described as follows: It consists of two floats connected by means of a chain which passes over a wheel supported in the upper part of the chamber. As the water in the chamber rises, the left-hand float shown in the drawing rises and the right-hand float falls, thereby communicating a rotary motion to the wheel. A projection on this wheel at a certain point when the left-hand valve has reached the desired height communicates with an inside portion of the wheel, to which a chain connected with the valve is attached. Thus the valve is opened at the right height, and remains open until the water has fallen to the bottom of the chamber. Then the left-hand float falls, and the apparatus is ready to repeat the operation. This apparatus, for a small installation, will probably cost, set up in place, about $15. [Illustration: FIG. 17.—Flap Valve with Loose-link Hinges.] Fig. 19 shows the simplest form of siphon arranged to discharge water from a tank. It will be noticed that it consists of an inverted bent pipe, one leg being longer than the other, and extending into a pool of water formed in the end of the discharge pipe. When the water level in the tank reaches the bent portion of the siphon pipe, the water begins to flow out, and will continue to flow until air is drawn in at the lower end of the short leg. This stops the flow and the tank begins to fill again. Fig. 20 shows another method of working the siphon and insuring its rapid initial action. This is known as the Van Vranken flush tank, and the feature of this arrangement is the movable bucket, which in one position seals the lower end of the longer leg. Then, however, the siphon begins to act, and the bucket, which is hung on trunnions, is disturbed and its contained water is dumped out. This allows the escape of the water in the longer leg and insures a vigorous starting up of the siphon into action. [Illustration: FIG. 18.—Intermittent Dosing Apparatus made by Ansonia M’f’g Co.] A more simple type, however, is the inverted siphon arrangement, developed perhaps most completely by the Pacific Flush Tank Company under the Miller patents. Fig. 21 shows their ordinary design, the upper part of the siphon being replaced by a bell and the discharge starting when the level of the water in the long leg of the siphon has been depressed sufficiently to reach the curved part of the pipe. The principle on which this siphon works is as follows: [Illustration: FIG. 19.—Simplest form of Automatic Siphon.]