The H.M.S. Beagle Stormglass.

Used to predict weather since 1750, this mysterious device was employed by Admiral FitzRoy, captain of the H.M.S. Beagle, when he and his lieutenant, Charles Darwin, voyaged to the Galapagos Islands in 1831. Although how it functions remains a mystery, the ability of the stormglass to predict atmospheric change is well documented. One theory states that the stormglass responds to electromagnetic fluctuations caused by weather and solar storms. The contained liquid--a mixture of distilled water, potassium nitrate, ammonium chloride, alcohol, and camphor--appears cloudy when precipitation is approaching; when crystals are visible in the liquid, humid or foggy weather can be expected; a cloudy glass with small stars indicates thunderstorms. The hermetically sealed glass chamber is housed in a handcrafted brass cylinder. Includes brass hook for wall mounting and a chart to interpret stormglass readings. 5 3/4" H x 1 2/3" Diam. (15 3/4 oz.)