Plate from 18th century encyclopedia showing an illustration of different types of chemical laboratory aparatus. The illustration shows various furnace types, bellows, reverboratory and assay device. A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing.