air furnace (arfernas)

1. A reverberatory furnace (which see, under furnace ).-2. An air-heating furnace for warming apartments. Air is led into a space formed between an outer casing and the sides of a fire-pot and combustion-chamber, and, after becoming heated by contact with the walls of the latter, flows to the apartments which are to be warmed. See air - stove, furnace, and heater. air-gage (argāj), n. An instrument for indicating the pre ure of air or gases. It consists of a gla tube of uniform caliber, closed at the top and having its lower end dipped into a cup of mercury on the surface of which the air or gas pre es, thus forcing mercury into the tube, and compre ing the air within it to an amount directly proportioned to the pre ure. This pre ure can be read from a scale attached to the tube, the zero of the scale being usually placed at the upper surface of the mercurial column when the instrument is exposed to the ordinary atmospheric pre ure. Also called air-manometer.