Stormglass instruments have been used since the 1750s. Thought to have been invented for Italian sailors during a time when sailing vessels were heavily dependent on weather for timely arrivals to their destinations. The changing weather affects the solubility of the chemicals in the sealed glass tube, creating a series of crystal structures, informing owners of an impending weather disturbance. Enclosed in a beautifully crafted brass cylinder that screws to the marine lacquered solid wood plaque, it features a brass and black plate that displays history, and a key detailing the meaning of the crystal formations. Predictions are usually 24-48 hours in advance. The plaque can be displayed either freestanding or wall mounted. Mysterious, it requires no batteries or programming and it works indoors or out. Measures 10" x 8" x 4" and weighs 2 lbs 2 oz.