This Tendency Barometer is mounted on a sandblasted solid glass frame. The crisp modern look is accented by the colorful measuring tubes.
The Tendency Barometer was patented on December 23, 1818, by Alexander Adie. It consists of two liquid-filled, mercury-free tubes. One tube in a U-shape is open-ended and filled with a red fluid; and one closed thermometer tube is filled with a blue fluid. These two tubes are mounted parallel to each other so they're both easy to read.
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 (high pressure pushes the red fluid down in the tube).
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 inches and millibars/hPa. The overall instrument measures 18 inches tall by 4.7 inches wide and weighs two pounds.
