=Sinks= are not uncommonly the source of offensive smells, when made of wood or stone. A hard glazed sink should be provided; as this is non-porous and can be kept clean. The sink should be placed against an external wall, so that the waste pipe can be carried through the wall to a gully-trap outside the house. Formerly the sink-pipe was joined below directly into the drain, the only obstacle to the entry of sewer or drain gases into the kitchen being a bell-trap at the sink. This is quite insufficient for the purpose. The waste-pipe from the sink should have a syphon trap under it, with an inspection opening at its lowest point (Fig. 19), and should discharge in the open air over a gully-trap (Fig. 20), as in the case of rain-water and bath-waste pipes. It is usually stated that the waste-pipes from sinks, etc., should discharge at least 18 inches distant from the grating of the gully. This is too far, because some of the foul water may become dried up in the channel, and its solid particles be blown about. They may be allowed to discharge directly over the grating of the gully (Fig. 20) or even into the side of the gully below the grating, but above and on the house side of the water-seal shown at B. Fig. 20. The gully-trap is connected with the socket of the first drain-pipe, and the junction is made water-tight by means of a cement joint. On this account, and because it gives a better water-seal than the bell-trap or D trap, the gully-trap should be always used. The best form of gully-trap, the P trap, is shown in Fig. 20 B. This is better than the S trap (Fig 19), which involves a bend in the drain at its junction with the trap. =Water-closets= require to be skilfully constructed and well-situated, if they are not to become a serious nuisance. In building a house, the _position_ of the closet should be carefully considered. In all cases it should be in an out-standing part of the house, against an external wall, and separated from other parts of the house by a passage, preferably a passage which is cross-ventilated. Instead of this, one commonly finds it in any convenient recess, abutting on a bedroom, or where it cannot be properly ventilated. Usually the closet is placed at the back of the house; and as the main-sewer is generally situated in the front street, it follows that the drain must in terrace houses pass under the house. Hence the importance of having it completely water-tight. Water-closets in bathrooms are very inadvisable. The _ventilation_ of the closet should be good—if possible, by two opposite windows; and where practicable a cross-ventilated lobby should intervene between the closet and the rest of the house. This is now always provided in hospitals.