Admiral Fitzroy’s Storm Glass

“Don’t knock the weather. If it didn’t change once in a while, nine out of ten people couldn’t start a conversation.” ~ Kim Hubbard

I am told that I am a difficult person to buy a gift for.  Come Christmas, I’m the one my family hope they don’t pick in the Kringle.   So a few months ago, when it was my birthday, I was so annoyingly vague about what I wanted that my sister ended up giving me some cash.

But it wasn’t long in my purse before I discovered the perfect gift for me.

While wandering around in yet another garden centre, I found something wonderful that appealed to all my geeky, gadgety, historical, weathery obsessions.

An Admiral Fitzroy Storm Glass.

My Admiral Fitzroy storm glass, freshly calibrated and clear.
My Admiral Fitzroy storm glass, freshly calibrated and clear.

I had never seen or heard of one before, but I was immediately intrigued.  A quick wiki-check filled me in.

Admiral Robert Fitzroy was Captain of the HMS Beagle, the very same ship that ferried Charles Darwin around the Galapagos in the 1830’s.  While Darwin contemplated the origin of the species, Admiral Fitzroy was testing an hypothesis of his own.  He was road (sea?) testing a new weather predicting instrument.

In a sealed glass, he mixed  potassium nitrate, ammonium chloride, ethanol, camphor and water.  Admiral Fitzroy observed his new-fangled, technologically advanced device and recorded his examinations thus,

  • 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.*

Fresh from it’s box, the glass was clouded with fine crystals (predicting snow?) and the instructions precisely detailed how to set it up in its new home.   To calibrate my storm glass, I had to dissolve the existing crystals back into the solution until the fluid was clear.  This required some rather careful, but vigorous shaking with the combined application of heat from my hairdryer.  One wonders how Admiral Fitzroy accomplished the same feat (probably close to an open fire, risking a scorched eyebrow or two) but given my general clumsiness, I was rather chuffed that my combined shake-and-heat performance didn’t result in a smashed storm glass and tears of remorse.

Once every crystal was dissolved, I placed it proud atop my seed bank drawers away from curious little grabby hands.  For accuracy’s sake, it apparently cannot be moved or disturbed.  I have since wondered how Admiral Fitzroy kept his storm glass perfectly still as he sloshed about the high seas?

Thanks to our weather here, it seems for at least six months of the year, I will be admiring a glass tube of clear water.  And for a few weeks, nothing happened.

The storm glass crystals have all settled to the bottom of the glass, forming a beautiful feathered effect...
The storm glass crystals have all settled to the bottom of the glass, forming a beautiful feathered effect…

Today it looks like this…

Frankly, when it rained last week, it looked like that.

When it was frosty this morning, it looked like that.

During our recent, unseasonably sunny weather, it looked like that.

When gale force winds swept our neighbour’s trampoline onto our roof, it looked like that.


It appears my doubt regarding the storm glass’s accuracy were shared by others who have had the inclination to do the appropriate scientific tests.  The results concluded that the Admiral Fitzroy Storm Glass can predict the weather half of the time.

So yes, half the time it is completely wrong.

Flipping a coin will produce the same weather-predicting result.  Other research has determined that it is ambient temperature, (perhaps not quantum tunnelling) responsible for the beautiful crystals forming.  It seems no one really knows for sure.

On the down side, I have a pretty, but otherwise useless crystal making tube.  But, I’ll keep my eye on it and hope it’s debated quantum mechanics kick in and it starts to reliably work.  In this actual universe.

In the meantime, when I want to know if it is going to rain, I’ll checkout my weather app.  One wonders what Admiral Fitzroy would have made of an iPhone?

I would love to hear from you if you have discovered a sure-fire way of predicting the weather, please leave a comment below…

* You can read more about Admiral Fitzroy’s Storm Glass experiments here.



  1. says

    Oh, that seemed like such a great idea at the start of your post! At least it has a really interesting story attached to it, even if somewhat lacking in accuracy… I wonder if it would react differently if it was kept outside?

    • says

      Oh lord, the thought of calibrating it again to move it outside is enough incentive to keep it where it is! Haha! I am fond of it, in it’s time it was a cutting-edge scientific device, the best they had….. so a good reminder of how far we have come…

      • says

        I try to have, buy, rent or… at least one weather instrument of all kinds that somewhere in history people used them to predict the weather.

        We still have thousands killed each year from weather. Weather we see coming days ahead.

        I love all these type weather instruments. They fascinate me. Work or don’t work. Who cares. People died believing in these instruments.

        Just like today…some things do not change, but we argue that they do change, knowing better.

        Melissa, you go girl.


  2. says

    I received one of these as a Christmas gift. I likewise placed it in an area where it would not be disturbed after first dissolving the crystals. My glass quickly took on the same appearance as described above and stayed that way. Repeated recalibrations always gave the same result. I’m waiting for warmer spring weather when the house temperature varies less and slower crystal growth can start. Perhaps I’ll then start to see different crystal patterns develop. It may not predict the weather (at least mine doesn’t) but it is an interesting conversation piece.

  3. abi says

    I bought a second hand storm glass today. Could you give me instructions on how to calibrate it? I dont want to break it! Thank in advance x

    • says

      Hi Abi,

      I followed the instructions that came with my storm glass, dissolving the crystals using a bit of heat and agitation to calibrate it back to “base”. I did it using a hairdryer, it took forever and I almost dropped it a few times.

      BUT, since writing this, a few people have mentioned that all you really need do is set it down the place you intend to keep it and don’t disturb it. It should react to your weather conditions straight away.

      Frankly, I’m not going to calibrate mine again if I move it.

      Hope this helps!

  4. Stephanie says

    I got one for myself awhile back. It works the exact same as yours. Once in awhile I find a crystal floating on the top, but that is about it. It is cold, rainy and overcast today but it looks the same as a few days ago when the sun was out bright and everyone was running around in short sleeves.

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