Fig. 8 is the =bell=-trap, so called from its shape. Much used for the drains of paved areas, yards, and cellars; liable to retain dirt, and needs frequent cleaning; not a good trap. Fig. 9 is a =running=-trap, used in house-drains and other pipes that are nearly horizontal. Fig. 10 represents a =mason’s= trap. Is built of brick or stone and cement. Used in brick-drains and sewers, in receiving-basins at street corners, etc. Requires frequent cleaning, and should never be used inside a building. Fig. 11 represents the method of trapping a cesspool. The same plan is also used for =grease=-traps, the outlet-pipe dipping below the surface of the contents so that it is never obstructed by the grease, which floats on top. [Illustration: Fig. 11.—Trapped cesspool.] A few patent traps are shown as samples: [Illustration: Fig. 12.—Adee trap.] [Illustration: Fig. 13.—Bower trap.] Fig. 12 is the Adee trap, a modification of the D-trap. Fig. 13 is the Bower trap, claimed to be secured against siphonage or back pressure by a rubber ball which floats up against the entering-pipe. Modification of the bottle-trap. Fig. 14 is Bedell’s trap, with a metallic flap or valve, and an opening on the sewer side of the valve, to relieve pressure. Fig. 15 is Stewart’s trap, intelligible from the diagram. Traps are also made of iron or glass, with a mercury seal, which, it is claimed, are proof against siphoning, pressure, or evaporation. [Illustration: Fig. 14.—Bedell’s trap.] [Illustration: Fig. 15.—Stewart’s trap.] 4. A =louvered sky-light= is one with slats at the sides inclining outward, so that air can escape but rain can not enter. 6. =Calked with lead.= (See 26.) 7. =Tempered-up cement.= Cement which has been used once, and has been broken up and ground, for using a second time. 9. =House-drain=, of iron. (See “Bad Odors, 2, _a_.”) 10. =Water-closets.= Four principal classes, with innumerable varieties, mostly patented. 1. The =pan-closet= (Fig. 16). Its chief advantage is its cheapness and the ease with which it can be repaired. Its disadvantage is the odor that usually attends its use. When the handle (_a_) is raised, the contents of the pan (_b_) are thrown against the side of the iron container (_c_), and some filth adheres there and decomposes, filling the container with a noisome stench, which escapes into the room every time the closet is used. An abundant flush, an enameled container, and proper ventilation of the container, reduce this nuisance materially. Generally condemned by sanitarians. [Illustration: Fig. 16.—Pan-closet.] [Illustration: Fig. 17.—Hopper-closet.] 2. =Hopper-closets= (Fig. 17). Rather unsightly, because the water and floating matter in the trap are visible, and matters often cling to the sides, but, with an abundant flush suddenly discharged, are very inoffensive.