Weather Notebook
Bryan Yeaton

Storm Glass
Fri May 07, 2004

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The HMS Beagle became famous through its naturalist Charles Darwin. But equally important was her captain: Robert Fitzroy, father of the British Meteorological Service. Hi, I'm Bryan Yeaton for The Weather Notebook.

Among Fitzroy's studies was the application of the various storm glasses in widespread use during the 1800s to weather forecasting. The first storm glasses likely appeared around 1750, but their first documented shipboard use dates to the Beagle's famed 1831-36 circumnavigation.

Storm glasses are hermetically sealed glass tubes containing a supersaturated mixture of chemicals. The premise of the storm glass is that changing weather affects the solubility of the mixture. Under changing conditions, users believed, the chemicals produced crystals in strange, fascinating shapes, or alternately, existing crystals could melt back into solution. The functioning of the storm glass is, however, not fully understood even today, and they are now more a curiosity than a practical instrument.

Fitzroy found one specific mixture, containing camphor, ammonia, alcohol, potassium nitrate, and water, most suitable for weather forecasting. In his 1863 Weather Book, Fitzroy described the various crystal shapes and patterns that would develop within the storm glass according to different wind directions and weather conditions.

Clear liquid meant bright weather; dim liquid, rain. Large flakes meant overcast or, in winter, snowy skies. As its name implies, many believed the instrument was especially sensitive to the coming of stormy weather. Thus, if small stars are seen in dim liquid, expect thunderstorms.

In 1859, violent gales struck the British Isles, causing many marine casualties. Hoping to prevent further catastrophes, the Crown distributed storm glasses, then known as Fitzroy's storm barometers, to the many small fishing communities around the British Isles.

Thanks to our contributing writer, meteorologist Keith Heidorn. The Weather Notebook is generously supported by the National Science Foundation and Subaru: Driven By What's Inside. We are a program of the Mount Washington Observatory, online at

Today's Links

Fitzroy\'s Storm Glass

Admiral Fitzroy\'s Remarks

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