This mysterious weather predictor has been used since 1750. Admiral Fitzroy, the famous sailor and meteorologist, used the Stormglass aboard the HMS Beagle during his historic voyage with Darwin. After 250 years, how the Stormglass works is still a mystery, but it is believed that it has to do with the electromagnetic changes caused by weather and sun storms. The appearance of the crystals inside the glass indicates changes in the weather. The sealed glass chamber that holds the crystals is encapsulated in a beautifully crafted brass cylinder. It can be displayed freestanding or mounted to a boat bulkhead or wall using the wall mounting bracket. Polished brass.