A tendency barometer allows you to make your own accurate weather forecast by observing the changes in the atmospheric pressure.
A tendency barometer displays the changes in air pressure allowing for an accurate weather forecast to be made. The Tendency Barometer was patented on December 23, 1818 by Alexander Adie, a Scottish optician. Ross used it on his expeditions. The tendency barometer consists of two liquid filled tubes. Barometers tube in a U-shape, which is open-ended and filled with a red fuid, and also a closed thermometer tube filled with a blue fluid, mounted parallel to each other.
You can forecast the weather from across the room simply by watching the fluid levels. 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 below the blue, stormy weather is predicted (low pressure allows the red fluid to move up in the tube). The thermometer measures in both Celsius and Fahrenheit and the barometer in millibars/hPa. weeks for delivery. Wall mountable or free standing. Made in Belqium.