The Mariner?s Stormglass displays Victorian technology in a contemporary housing. The premise is that changing weather affects the solubility of the mixture of chemicals in the sealed glass tube. Thought to have been invented by an alchemist for Italian sailors, stormglass instruments have been in use since the 1750s. Admiral Fitzroy, the famous sailor and meteorologist, mounted an instrument similar to the Mariner?s stormglass on the mast of HMS Beagle as a storm warning instrument during his historic voyage with Darwin in the 1830s. Some believe that the changes in crystal structures have to do with the electromagnetic changes caused by weather and sun storms. Finish Brass Size 4-5/16" x 1-7/8"