Storm Glass? What was Lovecraft Talking About?

Caveat: Do NOT try to make this at home.
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In HPL's 1907 summary of Providence weather, he mentions he has access to a storm glass? What?

Read this query to an antique site: "I have seen a device called a storm glass which consists of a glass tube filled with a liquid containing crystals. The shape of the crystals is supposed to change according to the pressure. How does this device work? Apparently, Darwin used one on board the Beagle."

Here is an answer from some sites, and some history: The storm-glass, sometimes known as the chemical barometer or camphor glass, is an ancient weather forcaster. It consists of a sealed glass bottle containing a mixture of chemicals that undergo interesting and unusual crystal growth in response to changing weather conditions. It has been around since around 1750 but was not in common use until the 19th century.

Robert Fitzroy described the storm-glass in The Weather Book published in 1863. In this book he offers some interesting thoughts on the operation of the storm-glass suggesting atmospheric pressure, temperature, electrical disturbances and even the direction of the wind being the cause of the changes in crystal formation.

The storm glass may have been invented by an alchemist for Italian sailors. One can make a storm glass by mixing 10 grams of camphor, 40 cubic centimetres of ethanol, 2·5 grams of potassium nitrate, 2·5 grams of ammonium chloride and 33 cubic centimetres of distilled water, then placing the mixture in a corked test tube.

Changes in the liquid are supposed to show how the weather will change. Clear liquid means bright weather; dim liquid means rain. If it is dim with small stars, expect thunderstorms. Large flakes mean it will be overcast or, in winter, snowy. Crystals at the bottom mean frost and threads in the upper part mean it will be windy. If the liquid contains small dots, expect humid or foggy conditions, and if it contains small stars on sunny winter days, expect snow in a few days.

Was it useful? Read this letter:

About forty years ago I found a recipe for the liquid in a storm glass. I prepared a sample, sealed it in a glass tube and left it on the roof of a factory in south London for six months. I examined the tube every day and tried to correlate atmospheric conditions with changes in the crystals in the tube. I could find no correlation, but as the tube was sealed, its contents could only react to temperature changes and not pressure. - From South Africa.

A warning from a writer in London: There is the possibility that somebody may be seriously hurt trying to make this device without having first thought about what they are going to do. Camphor is a pungent organic chemical, which is combustible. It has a history of use as a plasticiser in explosives and is readily oxidisable; ammonium chloride decomposes when heated, releasing toxic fumes and potassium nitrate is an oxidising agent. Mixing these three chemicals together in a dry state could very probably result in the potassium nitrate oxidising the camphor, causing it to combust and the ammonium chloride to decompose. The consequences may be fatal. If this device really must be made, probably the safest way to do this is to dissolve the potassium nitrate and ammonium chloride in the water, then add the ethanol and finally the camphor.

Luckily Lovecraft did not try to make this!

... a description of a practical storm-glass taken from the book Pharmaceutical Formulas by Peter MacEwan, published in 1908. The article includes notes to assist in the reading of the instrument.

Camphor - half ounce
Ammonium chloride - half ounce
Potassium nitrate - half ounce
Rectified spirit - one ounce
Distilled water - two ounces

Weigh the spirit into the bottle and dissolve the camphor, then add the salts and the water (warm). Shake, and when dissolved filter.
Long narrow tubes of glass are filled with this solution and hermetically sealed or corked. The tubes are then affixed to boards by means of wires in the same way as barometers are fixed. The changes of the solution signify the following:
Clear liquid : Bright weather.
Crystals at bottom : Thick air, frost in winter.
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.

And here is another from a pharmacopedia:

Nearly fill a glass tube 10 in. long and ¾ in. diameter with the following liquid, then hermetically seal:-

Camphor - 2 drachm
Potassium nitrate - ½ drachm
Ammonium chloride - ½ drachm
Absolute alcohol - 2 ounces
Water - 2 ounces

Disolve.

Temperature is the main factor in changing the appearance of the solution. The indications are as follows:-

(a) During cold weather beautiful fernlike or feathery crystallisation is developed at the top, and sometimes throughout the liquid. The crystallisation increases with cold, and if the structure grows downwards the cold will continue.
(b) During warm and serene weather the crystals dissolve, the upper and greater part of the liquid, becoming perfectly clear. The greater the proportion of clear liquid, the greater the probability of fine dry weather.
(c) When the upper portion is clear and the flakes of crystals rise to the top and aggregate, it is a sign of increasing wind and stormy weather.
(d) In cold weather if the top of the liquid becomes thick and cloudy, it denotes approaching rain.
(e) In warm weather if small crystals rise in the liquid, which still maintains its clearness, rain may be expected.
(f) Sharpness in the points and features of the fern-like structure of the crystals is a sign of fine weather ; but when they begin to break up and are badly defined, unsettled weather may be expected.

Note: 1 drachm = 3.89 grams.

And finally, a caveat by a "storm-glass" maker in Australia: ... it soon became apparent that they were all designed for use in regions with a colder climate than the mild winters of Perth, Western Australia. Consequently, the quantities of the ingredients were altered to give good results for warmer climes. The end result is a storm-glass that gives results very similar to those described in the old texts. Another problem relates to the comfort of the modern home. As the storm-glass is an instrument that reacts to environmental temperature changes, it works best in a draughty, un-insulated and unheated home.

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So we see that Lovecraft's love of chemistry merged with meteorology and so he must have loved watching the changing shape of the crystals and charting the results.

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I was unable to locate the "Large Company" on Da Google for obvious reasons. The words are so common that the search was overwhelmed by modern news blurbs about large companies. The items presented should suffice for illustrative purposes, however.