Admiral Fitzroy Storm Glass Barometer came into general use during the 1700s and was in widespread use for nearly 250 years. Sailors attached this instrument to the mast of their ship and by interpretation of the constantly changing crystal formations, relied upon it to forecast good weather and bad. Admiral Robert Fitzroy, Captain of the HMS Beagle and later, Governor of New Zealand, sailed around the world with Charles Darwin and conducted a detailed study of the instrument. He refined the formula and published observational guidelines which are also included with each storm glass.
If there are large flakes throughout the liquid, it will be overcast in temperate seasons or snowy in the winter.
If there are threads near the top, it will be warming or windy.
If the liquid contains small stars on sunny winter days, then snow is coming.
If there are crystals at the bottom, this indicates frost.
A cloudy glass with small stars indicates thunderstorms. If the liquid in the glass is clear, the weather will be bright and clear.