The Nautical Tendency Barometer Thermometer is a unique, high quality instrument by D&D of Belgium. The mercury free "eco celli" barometer is safe, similar to water barometers. The tendency barometer was patented on December 23, 1818 by Alexander Adie. It consists of two liquid filled tubes. One tube in a U-shaped which is open ended and filled with a red fluid; and one closed thermometer tube filled with a blue fluid, mounted parallel to each other. When the fluid levels are the same, the weather is changing. When the red fluid level is below the blue fluid level, the weather is fair. When the red fluid level is above the blue, stormy weather is predicted (low pressure allows the red fluid to move up the tube). The thermometer measures in both Celsius and Fahrenheit and the barometer measures in millibars/ hPa. The beautiful wood frame is made from European walnut with black trim and the unit has colorful nautical flags along the right side. The thermometer measures in Fahrenheit and Celsius. The tendency dial also measures air pressure in millibars. It measures 19 inches high by 7 inches wide and shipping weight is 3lbs. The unit comes fully assembled and includes a calibration kit to adjust the unit for altitudes above sea level. Normally ships in 1-3 business days. MSRP: $191.00.

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