A device that can be alternately expanded and contracted, first drawing in air through a valve, then forcibly expelling it out an exit tube. For giving furnaces a forced draft, the bellows are more efficient than mere fanning, or the antiquated lung-powered hollow reeds and blowtubes also used for this purpose. The construction of bellows was simple: A bag mounted on a frame or base was attached to a tube leading to the furnace, which tube may have been of iron, or reed tipped with fire-resistant clay. Hand-operated bellows were useful for small forges; but for large high-temperature furnaces, dual foot-powered bellows were employed, one under each foot of the operator, who pumped down alternately, first one foot and then the other, each time pulling a cord to refill the compressed one. To give these big furnaces a constant draft, two men worked two pairs of bellows. The Hebrew word for bellows is map·puʹach, which comes from the root na·phachʹ, meaning “blow.” (Ge 2:7) This instrument is specifically mentioned only once in the Scriptures (Jer 6:29), though perhaps alluded to at Isaiah 54:16 and Ezekiel 22:20, 21. In these texts the references are figurative, and the illustrations are drawn from the methods used for refining metals.​—See REFINE, REFINER.