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Posts Tagged ‘leeches

“It was impossible to tame, like leeches”*…

A replica of the Tempest Prognosticator in the Whitby Museum. (Badobadop/Wikimedia Commons)

Or maybe just not worth it…

If you’re like me, one of the few remaining artifacts of the pre-Internet age that you’re able to regularly revel in is the mail order catalog. I particularly love the desk toys highlighted they show off—often, some of the most luxurious are vintage weather prediction devices. Today’s tedium is about the Victorian “Tempest Prognosticator,” a vintage weather forecast device you’re not likely to see as a desk toy any time soon—because maintaining one also means taking care of a dozen leeches…

George Merryweather, a member of Whitby, North Yorkshire’s then-thriving intellectual scene, masterminded the “Tempest Prognosticator” as a years-long hobby that culminated in its public display in 1851.

As a physician, Merryweather would already have been quite familiar with leeches, but in his essays, Merryweather said he was inspired by a poem, which spoke of how the common “medicinal leech” tends to move up in a jar of rainwater as a storm nears, then settle to the bottom in clear conditions…

To harness this instinct, Merryweather placed 12 leeches in their own jars of rainwater, arranged in a circle to keep each other company. Atop each jar, he rigged a piece of whale bone to a chain that, when yanked, would hit a bell he had placed in the center. As leeches rose to the top of their jars in advance of a storm, they would come into contact with the bone and sound the bell. The more bells that sounded, the more likely there was to be a storm, and the more intense it was likely to be…

At the time, consensus among the leech-invested appears to have emerged that these behaviors were due to the creatures’ innate ability to sense electromagnetic energy gathering in advance of a storm. Merryweather himself was a major proponent of this belief, dedicating a significant portion of his essays to reiterating Michael Faraday’s contemporary work on electromagnetism.

Unfortunately for him, we now know this acknowledgement was likely both unnecessary and uncalled-for. Leeches’ faculties for weather prediction turn out to actually be pretty patchy, and their “instincts” for this are far simpler than it seemed to him at the time. Leeches “breathe” through their body walls by absorbing the dissolved oxygen in the water they inhabit. When atmospheric pressure drops, a fractional amount less oxygen remains dissolved, and they move toward the surface, where the water is more oxygen-rich.

In effect, the “Tempest Prognosticator” was one of the world’s most elaborate barometers…

More of the remarkable story– and what it can teach us– at “The Leech Machine,” from Nathan Lawrence (@NathanBLawrence) in @ShortFormErnie‘s wonderful @readtedium.

* Daniel Handler (Lemony Snicket), Who Could That Be at This Hour?

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As we consult the Almanac, we might recall that on this date in 1949, after two days in which a few flakes fell, Los Angeles “enjoyed” a real snow fall.

Snow at Jet Propulsion Laboratory, La Cañada Flintridge, January 1949. Photo courtesy of NASA/JPL Archive.
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