barometer /bərom″ətər/ [Gk, baros + metron, measure] , an instrument for measuring atmospheric pressure, commonly consisting of a slender tube filled with mercury, sealed at one end, and inverted into a reservoir of mercury. At sea level the normal height of mercury in the tube is 760 mm. At higher elevations the mercury column height (barometric pressure) is less. Fluctuations in barometric pressure may precede major changes in weather. −barometric, adj.
