The teardrop-shaped measuring instrument with long spout that was filled with water was once a farmer’s best, if not indispensable, friend. The weatherglass showed the farmer whether it was going to be wet or sunny and if the sun was going to shine, the harvest could begin.
Not surprisingly then, the instrument was called a farmer’s barometer, or a water barometer because the water level inside recorded the air pressure. But it’s more widely known as a „Goethe Barometer“ – a label that’s based on a mistake.
When the poet, Johann Wolfgang von Goethe died in Weimar in 1832 a water-filled receptacle was discovered on his bedroom wall and nobody really knew what it was for. As Goethe’s interest in the natural sciences was well known it soon became clear that it was in fact some sort of weatherglass. Barometers were in use at the time, but appear to have been less widespread in Germany. Thus, for a long time, Goethe was thought to have invented the weatherglass.
When the sun shines the water level in the spout sinks because the higher pressure of the surrounding air pushes the water into the glass flask. If it rains, the external air pressure reduces and the water rises in the spout, but should the water drip out of the spout – a storm is approaching!