In the dwelling-house, chap, ii., part ii., Fig. 7, a cast-iron pipe is made in sections, which are to be united, and the whole fastened at top and bottom in the centre of the warm-air flue by ears extending to the bricks, and fastened when the flue is in process of building. Projecting openings to receive the pipes of the furnace, the laundry stove, and two stoves in each story, should be provided in this cast-iron pipe, which must be closed when not in use. A large opening is to be made into the warm-air flue, and through this the kitchen stove-pipe is to pass, and be joined to the cast-iron chimney-pipe. Thus the smoke of the kitchen stove will warm the iron chimney-pipe, and this will warm the air of the flue, causing a current upward, and this current will draw the heat and smells of cooking out of the kitchen into the opening of the warm-air flue. Every room surrounding the chimney has an opening at the top and bottom into the warm-air flue for ventilation, as also have the bath-room and water-closets. The pure air for rooms on the ground-floor is to be introduced by a wooden conductor one foot square, running under the floor from the front door to the stove-room, with cross branches to the two large rooms. The pure air passes through this, protected outside by wire netting, and delivered inside through registers in each room, as indicated in Fig. 7. In case open Franklin stoves are used in the large rooms, the pure air from the conductor should enter behind them, and thus be partially warmed. The vitiated air is carried off at the bottom of the room through the open stoves, and also at the top by a register opening into a conductor to the exhausting warm-air shaft, which, it will be remembered, is the square chimney, containing the iron pipe which receives the kitchen stove-pipe. The stove-room receives pure air from the conductor, and sends off impure air and the smells of cooking by a register opening directly into the exhausting shaft; while its hot air and smoke, passing through the iron pipe, heat the air of the shaft, and produce the exhausting current. The large chambers on the second floor (Fig. 18) have pure air conducted from the stove-room through registers that can be closed if the heat or smells of cooking are unpleasant. The air in the stove-room will always be moist from the water of the stove boiler. The small chambers have pure air admitted from windows sunk at top half an inch; and the warm, vitiated air is conducted by a register in the ceiling which opens into a conductor to the exhausting warm-air shaft at the centre of the house, as shown in Fig. 23.