STEAM HE A TING. 737 
ciency of heating disappears ; and since the usual practice is to trust for ventila- 
tion to the accidental influx of air through crevices in the window and door 
casings, the use of stoves is quite sure to lead to a vitiated atmosphere. Owing 
to the fact that the heating appliances of both the open fire and the stove are 
confined almost entirely to the room or apartment in which the fuel is burned, 
the heating of a building comprising many apartments, by these methods, can 
only be accomplished by increasing the number of fires or stoves. The economy 
which might be practicable for a single room then disappears to a great extent, 
owing to the increased cost of attendance, as well as waste. 
Two modes of heating are in vogue by which the demands of economy and 
comfort are then met, viz.: the hot-air furnace and the steam-heating apparatus. 
The hot-air furnace is simply an encased stove outside of, and away from, the 
apartments to be heated, generally in the cellar or basement of a building. The 
casing or chamber within which the stove is placed is put in communication 
with the external air by an inlet conduit, which serves the double purpose of 
furnishing air for combustion and for supplying a number of rooms with heated 
air. To effect this two-fold purpose, there is a chimney direct from the stove 
for the removal of the gases of combustion, and one or more flues leading from 
the air-chamber around the stove, with branches for the different apartments, 
for that portion of the air which comes in contact with the heated surfaces of 
the stove and casing, and which then passes to the rooms. The air is usually 
heated to a temperature of 250° to 400°, and by mixture with cold air may be 
brought down to 150° to 200°, at which temperature it will enter the rooms. 
Air at these high temperatures must be further reduced in temperature and 
mingled with cold air in the rooms to be warmed, and for effecting this object 
reliance is generally placed on the accidental leakage at doors and windows. 
The expulsion of the heated air is accomplished by a spontaneous draft through 
flues from the heated apartments to the roof, or into halls and thence to upper 
stories. 
A single furnace may thus heat very economically an ordinary dwelling; 
but the disadvantages and defects of the system are numerous. Beyond a cer- 
tain limited distance from the furnace the difficulty of conveying heated currents 
in this manner increases very rapidly ; and where there are branch ducts leading 
to many rooms, one branch may overpower another, causing excessive heat in 
one room and a deficiency in another. The proper ventilation of apartments is 
difficult, and the highly heated currents, having an increased capacity for mois- 
ture, are apt to convert the rooms to be heated into drying chambers, to an 
extent that is neither agreeable nor healthful. A few open fires, arranged to 
produce proper ventilation, mitigate very much some of these evils. For large 
buildings several hot-air furnaces must be provided, and the economy is propor- 
tionally diminished. 
All of the above described methods have been supplanted to some extent, 
in this country at least, by steam-heating apparatus, or its practical equivalent 
in limited circuits, the hot-water apparatus. Even for ordinary dwellings, this 
