HEATING AND VENTILATION. 692 HEATING AND VENTILATION. warmed air into the room. In cold climates fireplaces must be supplemented by more efl'ec- live means of heatintr. A STOVE is simply an inelosure of metal, brick, or earthenware, heated b}- burning a fire within it, and then giving out its heat to the air by contact, and to surrounding ob- jects by radiation. The simplest, and, so far as mere temperature is concerned, the most effective and economical of all warming arrangements is simply a hollow cjlinder or other form of iron standing on the floor, closed at top. and having bars near the bottom on which the fire rests. The door bv which the coals are put in being kept shut, the air for combustion enters below the grate, and a pii>e issuing from near the top carries the smoke into a flue in a wall. If this pipe is made long enough by giving it, if necessary, one or more bends, the heated gases from the fire may be made to give out nearly all their heat into the metal before they enter the wall ; and thus the whole heat of the comljustion remains in the room. The great objection to this form of stove is that the metal is apt to become overheated, which not onljr gives rise to accidents, but deprives the air of or increases its capacity for moisture, thus parching the skin and lungs, unless means be taken to supply the neces- sary moisture. An evaporating-pan or other con- trivance is an essential part of stoves and fur- naces. Improvements on this simple and rude form of stove aim at avoiding a high heat in the warming surface, b}' inclosing it in several cas- ings, so as to enlarge the heated surface. Furnaces. In ordinary hot-air furnaces the fire is burned in a small compartment within the inner case, and the air is warmed by cir- and the w-arm air is conveyed to the different parts of the building in pipes or flues, while frcsli air is drawn to the furnace through a fresh- air inlet and duct from outside the building to the openings in the outer casing of the furnace. The lieat-pipes are generally of tin, suspended Fig. ■. HOT-AIR SYSTEM. Fig. 1. FUUXACK. a, division-plate : b, smoke-pipe ; c, steel piate radiator; tf, body: e, lire-pot; f, water-pan; g, ash-pit; i. coid-air duct ; i, dust-fiue. culating between the inner and outer cases. When placed in the apartment or hall to be vanned, the outer casing has perforations about the top for the issue of the warm air. For heating churches and large buildings generally the furnace is placed in a separate room or cellar, from the ceiling of the cellar, or from the beams supporting the floor above, in their horizontal course, and carried upward in the partitions to the higher floors to be heated. The heat is admitted to the several rooms through registers. Each room to be heated should have a separate line of heat-pipes, pro- vided with a damper at the furnace. Each register should be supplied with a damper, so the heat may be regulated in the room. The several .small openings in the registers should have an aggregate area at least as great as the cross sectional area of the heat-pipe. The supply of fresh outdoor air to be heated and distributed should be ample, for otherwise air will be drawn in from the cellar or some room in the house. The fresh-air box should be as nearly air-tight as possible, and both it and the inlet should be Kept well a^■ay from any source of contamination. Economy and health alike demand that furnaces be large enough to serve their purpose without 1 eing forced, since forcing is wasteful of fuel and overheats the room air-supply. The latter is not only bad in itself, but increases the danger of contamination by the gases of combustion. Some means of mixing cold air with hot is de- sirable, in order to prevent the shutting off of the fresh-air supply when the room becomes too warm. STE.f AND Hot-Water Heating. Either steam or hot water is the most common medium for heating the better class of residences and large buildings and groups of buildings. Either may be conveyed long distances with ease, and both are practically unaffected by the direction or the strength of the wind, freedom from a. limitation which is one of the greatest drawbacks to the use of hot-air furnaces. Another ad- vantage of steam and hot water is that they may be produced in connection with a steam plant for power purposes, but this is of less account
