Tempest Prognosticator: look out, leeches!

by Jo Brodie, Queen Mary University of London

raindrops on a window
Image by Kranich17 from Pixabay

When we leave our homes we might check a weather app to give us predictions from number-crunching computers, to see if we’ll need an umbrella, but in the mid-1800s the appropriately named George Merryweather thought he’d make use of the alleged weather predicting properties of leeches to create a ‘leech barometer’ to measure the weather. His notion relied on the belief that leeches, kept inside small glass bottles, would try and escape when a storm was due (because they might be more sensitive to subtle changes in electrical conditions in the air that we humans would miss). The escaping leeches would trigger a small hammer placed above the bottles which would strike a bell and alert everyone in earshot that a storm might be imminent and also that your living room was about to be overrun with leeches. Not surprisingly it wasn’t very popular, though Merryweather claimed to have great success with it.

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This article was funded by UKRI, through Professor Ursula Martin’s grant EP/K040251/2 and grant EP/W033615/1.