Centuries ago, mariners, explorers and others relied on stormglasses to predict the weather. Crystals form in a liquid that is sealed within a glass cylinder; with a little practice, you can read changes in the crystals to predict a range of weather up to 48 hours in advance. For example, clear liquid in the glass indicates sunny conditions ahead, while the appearance of fern-like crystals means a storm is on the way.
This one is made by Weems & Plath®, manufacturer of nautical instruments since 1928. The liquid is based on a formula developed by Admiral FitzRoy, commander of the HMS Beagle on Darwin’s 1831 voyage to the Galapagos Islands. The supplied instructions are drawn from FitzRoy’s observations, linking certain crystal formations and various weather types. The glass chamber is held within a turned brass housing with a durable lacquer coating. About 6-1/2" tall, it comes with a freestanding base as well as fittings for wall-mounting, and is supplied in a form-fitting black leatherette gift box.
Although you can use this device to impress friends with your uncanny ability to predict the weather without consulting the Internet, keep in mind that its 17th-century technology is no match for modern-day meteorological instruments. Provides a unique glimpse into history.