The Fitzroy Stormglass was invented by Admiral Robert Fitzroy. The glass vessel contains a mixture of distilled water, ethanol, potassium nitrate, ammonium chloride, and camphor.

It is not explained how or why the stormglass actually works, as the physical changes cannot be explained from the conditions proceeding the weather event that is forecast. The basic explanation is that the pressure and temperature cause the liquid to change it's solubility, thus causing patterns of crystals to form within the tube.

I purchased my Stormglass from Weather in a Bottle many years ago, however is looks like the company closed in 2020 and therefore here is a link to their site that was archived by the Wayback machine from 2020. This is a real shame, as although there are a lot of far-eastern, Amazon purchasable StormGlass, they are not as accurate or nicely made as this one.

Images

The formation of these ferns should forecast windy conditions, in approx 2 days. This was quite accurate as we did experience windy conditions around 2 days later.