science

Storm glass

Storm glass is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Storm glass rather than just read about it. In short: The storm glass or chemical weather glass was an instrument claimed to help predict weather. It consists of a special liquid placed inside a sealed transparent glass.

Key takeaways

Storm glass belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Storm glass to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Storm glass from memory before moving on to harder problems.

Reference excerpt

The storm glass or chemical weather glass was an instrument claimed to help predict weather. It consists of a special liquid placed inside a sealed transparent glass. The state of crystallization within the liquid was believed to be related to the weather. The inventor is unknown but the device became popular in the 1860s after being promoted by Royal Navy Admiral Robert FitzRoy who claimed that "if fixed, undisturbed, in free air, not exposed to radiation, fire, or sun, but in the ordinary light of a well-ventilated room or outer air, the chemical mixture in a so-called storm-glass varies in character with the direction of the wind, not its force, specially (though it may so vary in appearance only) from another cause, electrical tension". The composition of the liquid in a storm glass varies but usually contains "camphor, nitrate of potassium and sal-ammoniac, dissolved by alcohol, with water and some air." These devices are now known to have little value in weather prediction but continue to be a curiosity.

Description

The liquid within the glass is a mixture of several ingredients, most commonly distilled water, ethanol, potassium nitrate, ammonium chloride, and camphor. This specific mixture was promoted by Admiral Robert FitzRoy although similar devices existed even two decades earlier with variants in Italy, France and Germany. FitzRoy carefully documented his claims on how the storm glass would predict the weather:

If the liquid in the glass is clear, the weather will be bright and clear. If the liquid is cloudy, the weather will be cloudy as well, perhaps with precipitation. If there are small dots in the liquid, humid or foggy weather can be expected. A cloudy glass with small stars indicates thunderstorms. If the liquid contains small stars on sunny winter days, then snow is coming. If there are large flakes throughout the liquid, it will be overcast in temperate seasons or snowy in the winter. If there are crystals at the bottom, this indicates frost. If there are threads near the top, it will be windy. A version of the device was available in the 18th century in France but the inventor is unknown. In 1859, violent storms struck the British Isles. In response, the British Crown distributed storm glasses, then known as "FitzRoy's storm barometers", to many small fishing communities around the British Isles for consultation by ships in port before setting sail.

Accuracy In 1863, Charles Tomlinson published an analysis in The Philosophical Magazine concluding that, while attractive, "I think it may fairly be concluded from these experiments and observations that the storm-glass acts as a crude kind of thermoscope, inferior, for most of the purposes of observation, to the thermometer." In 2008 an article in the Journal of Crystal Growth similarly concluded that temperature change is the sole cause of crystal growth in storm glasses.

See also Tempest Prognosticator – an alternative to the storm glass that the British government investigated

References

External links

Admiral FitzRoy's remarks on barometers and thermometers The appearance of crystals in storm glass, when weather changes (video)

Illustrations

Worked examples

Example 1 — a first encounter with Storm glass

Start with the simplest possible case. Write down what Storm glass claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Storm glass before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Storm glass ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Storm glass

In research: Storm glass appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Storm glass in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Storm glass is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glass applications, Meteorological instrumentation and equipment, so understanding it makes those chapters shorter.
In everyday life: Look for Storm glass outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Storm glass in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Storm glass means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Storm glass out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Storm glass in simple terms?

The storm glass or chemical weather glass was an instrument claimed to help predict weather. It consists of a special liquid placed inside a sealed transparent glass.

Why does Storm glass matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Storm glass?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Storm glass.