The hot-air furnace costs least to install. (We leave stoves out of consideration.) It is also supposed to be easiest to manage. That, in a sense, is true. A good furnace will act pretty well even under indifferent direction; a bad one cannot be made much worse by the greatest of stupidity.

However, the average person can run the average furnace with a fair degree of satisfaction to the household, if not to himself. For a house of six to eight rooms the furnace may be considered an efficient means of heating. It requires more fuel than some other apparatus, but there are compensations.

Since ventilation and heating are inevitably associated, the argument that the furnace provides for ventilation is a strong one. If the air is taken from outdoors, passed over the radiating surface into the rooms, and then sent on its way, something like perfect ventilation is assured. If the air is simply taken from the basement - a poor place to go for air - heated, passed through the rooms, returned, and heated over again, we may well pray to be delivered from such "ventilation." The success of the furnace depends not upon ability to keep up a rousing fire but upon a proper regulation of air currents. Many a first-class furnace, properly installed, fails to work satisfactorily because the principle of heating is not understood. Even with the best of knowledge, the air is hard to regulate, and the very principle that gives the furnace its standing as a ventilator must prevent it from being a perfect heater.

Unless some artificial moisture is provided, not only will the air be too dry for comfort and health, but an excessive degree of heat must be attained in order to warm the rooms, thus increasing the consumption of coal. A water pan is usually provided in the furnace, but too often it is neglected.