(1 lb.)
. The contained liquid—a mixture of distilled water, potassium nitrate, ammonium chloride, ethanol, 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; a clear glass predicts calm weather. Although how it functions remains a mystery, the ability of the storm glass to predict atmospheric change is well documented. HMS BEAGLE Storm Glass Used to predict weather since 1750, this mysterious forecasting instrument was employed by soon-to-be Admiral FitzRoy of the HMS BEAGLE, when he and passenger Charles Darwin, voyaged to the Galapagos Islands in 1831.