Illustration: FIG. 1. (‡ SUCKING SYPHON.) Illustration: FIG. 2. (‡ GLASS BALL ON SUCKING TUBE.) Syphons are bent tubes for drawing off liquids from cisterns, butts, &c., where there is no tap, and where it would be inconvenient to make any second opening. Fig. 1 gives the outline of the most usual form of syphon; these are only used for liquids that may be drawn into the mouth without injury, such as spirits from casks. The mode of using the syphon is this--the bottom of the longest leg _a_ is stopped with the palm of the hand, the tap is then turned on and the mouth applied to the small tube _c_, the air is then drawn out by sucking; the liquid rises and fills both legs of the instrument, the tap is turned off, and the syphon is full. Now as the leg _a_ is longer than the leg _b_, the fluid in it weighs more than that in _b_, and sinking down draws the fluid in _b_ up, and so on till all is drawn from the cask. Syphons are generally made of copper, but gutta-percha would answer exceedingly well. Fig. 2 represents a contrivance for drawing off acids, &c., which would injure the mouth; the ball prevents the acid rising into it, as the mouth is removed directly it begins to fill, which as the instrument is of glass, can easily be seen. STOP-COCKS OR TAPS. Illustration: FIG. 1. (‡ OPEN TAP.) Illustration: FIG. 2. (‡ CLOSED PLUG.) Illustration: FIG. 3. (‡ OPEN PLUG.) Illustration: FIG. 4. (‡ CLOSED TAP.) Illustration: FIG. 5. (‡ SPOUTED TAP.) Taps are used for the purpose of letting off or stopping at pleasure the flow of liquids from vessels or through pipes. The forms of stop-cocks are very various, but the form shown at fig. 1 is by far the most general; it consists of a short curved tube, having an upright cylinder in the centre in which a plug with a handle turns; this plug is perforated in the direction of the length of the handle, so that when this is turned crosswise the communication is shut off (figs. 2, 3, and 4). The “nose” or end of the tap is sometimes prolonged into a spout, for filling bottles, &c., as in fig. 5. Illustration: FIG. 6. (‡ OPEN SAFETY TAP.) Illustration: FIG. 7. (‡ CLOSED SAFETY TAP.) Illustration: FIG. 8. (‡ AMERICAN WOODEN TAP.) Illustration: FIG. 9. (‡ SAFETY TAP KEY.) Illustration: FIG. 10. (‡ 4-WAY TAP (a-b, c-d).) Illustration: FIG. 11. (‡ 4-WAY TAP (a-c, b-d).)