Toricelli (1608-1647), who proved that air pressure is subject to variations, devised the first barometer in 1643. Goethe, the famous German playwright, later developed his own simple but effective barometer using the principles established by Toricelli. The Weather Ball, based on Goethe's design, is filled with colored, distilled water.
Once filled, the air inside the ball is no longer subject to variations in atmospheric pressure. The liquid in the indicator tube, however, remains open and is directly affected by atmospheric pressure. When atmospheric pressure rises, the liquid is pushed down in the tube, indicating clear weather. When the pressure lowers, the liquid rises, indicating bad weather. Includes complete instructions.