Functionality of the storm glass
As far as we know, the storm glass exists since 1750 and was used on sailing boats as an early warning device for upcoming storms. The first actual record of the usage aboard a ship exists from 1831, when Charles Darwin sailed off to a circumnavigation of the globe. On December 27, 1831 Charles Darwin began his long journey with Captain Fitzroy (1805-1865) on the "HMS Beagle". Fitzroy used a storm glass during his entire career at sea and on land.
Fitzroy was admiral of the fleet and st the same time enthusiastic meteorologist who later on held the chair at the British Meoteorological Institue. He published the world famous "Weather Book" that made the possibilities of weather forecasting popular in public.
During the 18th century, Admiral Fitzroy's storm glass was used by sailors and navigators for weather forecasting. There is no doubt that this instrument actually works, but until today there is no full scientific explanation for how the storm glass exactly works.
As the glass tube is tighly shut, alterations in atmospheric pressure are certainly not a reason for the storm glass' accuracy.
Admiral Fitzroy was convinced that the functioning principle can be lead back to changes of static electricity fields surrounding the storm glass. A revolutionary thought, considering the time. Even if the exact functionality of the storm glass has never been defined, many people trust this interesting instrument and its accurate weather forecastings.
Storm glasses forecast weather. They consist of a glass tube that contains water and dissolved salt crystals. An alteration in weather causes the crystals to change, too. In other words, the better the weather, the clearer the liquid in the storm glass. Please find a detailed descriptions in the following:
1. Large fern-like crystals form - Cold and stormy weather is coming up
2. Fern-like crystals disappear - Temperature will rise
3. Crystals float downward - There will be frost
4. Crystals float everywhere in the liquid - Rain is to be expected
5. Clear liquid - Dry and sunny weather