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ADMIRAL FITZROY STORMGLASS

This device has been in existence for more than two hundred years, but the name of the inventor is unknown. Some attribute the honour to an Italian sailor, whilst others say it was discovered by alchemists who were constantly experimenting with substances, composing the solution with which it is made. According to Admiral Fitzroy, who described them in his Weather Book in 1863, without much enthusiasm, they were introduced around 1750 and were on sale at the shop ‘Under the Goat and Compasses’ on Old London Bridge.

The storm-glass is simply a glass bottle, about 6 inches long and hermetically sealed, containing crystals of potassium nitrate and ammonium chloride in an alcohol solution of camphor, with some distilled water. It was claimed to be helpful in prognosticating changes in the weather, particularly high winds, storms or tempests. In fine weather the crystals are said to settle at the bottom of the tube, while in stormy weather they are said to rise, making the solution turbid; this is why the glass is usually marked with the words ‘Fair’ near the bottom of the glass, ‘Change’ at the centre and ‘Rain’ near the top of the glass.

There are certainly changes in the appearance of the solution from time to time, but they are more likely to be from variations of light and heat. These changes certainly take place when there is no change in the barometer reading and Fitzroy was of the opinion that they were dependant on the wind direction, but not its force, and the electrical tension in the atmosphere. In his Weather Book he wrote…

"Since 1825 we have generally had some of these glasses, as curiosities rather than otherwise, for nothing certain could be made of their variations until lately, when it was fairly demonstrated 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, preferably, in the 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 ).

As the atmospheric current veers toward, comes from or is only approaching from the polar direction, this chemical mixture – if closely, even microscopically watched – is found to grow like fir, yew, fern leaves or hoar-frost – or like crystalization."

As the wind, or great body of air, tends more from the opposite quarter, the lines or spikes – all regular, hard or crisp features – gradually diminish till they vanish.
Before, and in a continued southerly wind, the mixture sinks slowly downward in the vial till it becomes shapeless, like melting white sugar.

A confused appearance of the mixture, with flaky spots, or stars, in motion, and les clearness of the liquid, indicates south-easterly wind, probably strong to gale.
Repeated trials with a delicate galvanometer applied to measure electric tension in the air, have proved these facts, which are now found useful for aiding, with barometer and thermometer, in forecasting weather.

The glass should be wiped clean now and then and once or twice a year the mixture should be disturbed by inverting and gently shaking the glass vial.
The storm-glass is really an irregular form of thermometric barometer.

It must be balanced as to the solubility of the camphor and salts and there are several formulas.

CLEAR LIQUID – BRIGHT WEATHER
CRYSTALS AT BOTTOM – THICK AIR, FROST IN WINTER
DIM LIQUID – RAIN
DIM LIQUID WITH SMALL STARS – THUNDERSTORMS
LARGE FLAKES – HEAVY AIR, OVERCAST SKY, SNOW IN WINTER
THREADS IN UPPER PORTION OF LIQUID – WINDY WEATHER
SMALL DOTS – DAMP WEATHER, FOG.
RISING FLAKES WHICH REMAIN HIGH – WIND IN THE UPPER AIR REGIONS
SMALL STARS – IN WINTER ON BRIGHT, SUNNY DAYS, SNOW IN ONE OR TWO DAYS
THE HIGHER THE CRYSTALS RISE IN THE GLASS TUBE IN WINTER, THE COLDER IT WILL BE.
ALL THE FOREGOING IS EMPIRICAL !

Bairnsdale Clocks
704 Princes Highway, Bairnsdale, Victoria, Australia 3875
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