On leeches and storms

For centuries, storms were one of the greatest nightmares for seafarers, leading to the invention of all kinds of devices and methods capable of predicting their appearance. But those methods were little less than mere superstitions, nothing practical, so a risky British doctor decided once and for all to create a “Tempest Prognosticator”.

The invention of George Merryweather, known as “Atmospheric Electromagnetic Telegraph, conducted by animal instinct”, was something like a barometer that, in order to offer its reading of the coming atmospheric weather, was based on nothing less than the “instinct” of leeches.

Good old George worked in North Yorkshire, near the coast, which led him to take a keen interest in the serious issue of storms, especially when many of his patients were seafarers. And what instruments did he use in his therapies? The usual in the mid-nineteenth century, namely, a whole arsenal of metal utensils and some very willful helpers, hungry, slippery and, for many, repulsive. They were leeches, very useful to “purify” the blood, thanks to their great sucking capacity. Although they have long since ceased to be used, the leeches have now become seen as an interesting source of chemicals for pharmacy applications.

In those days, no one was surprised to see doctors use leeches and other natural remedies. Merryweather was a very observant person, not only using leeches, but interested in her behavior. As time went by, after writing down impressions about his investigations with those little parasites, he thought he detected a pattern of curious behavior. It turned out that whenever a thunderstorm approached, the leeches were restless.

But this nineteenth-century doctor also liked machines. So, on second thought, he decided that such curious behavior could be exploited for practical purposes. In this way, he built his invention capable, in his words, of predicting storms, presenting it in 1851 to the Philosophical Society of Whitby.

The apparatus was rather strange. Basically it consisted of a set of bottles containing leeches and rainwater. When a storm approached, and according to the doctor’s affirmations, leeches felt the air charged with electricity and were shaken, climbing up the walls of the bottles to their mouths, capped by a metal mechanism that, when pressed by the leeches, transmitted the movement through a cord to a bell, thus warning of the arrival of a tempest.

During her experiments, Merryweather scored all the hits. Apparently, it didn’t seem to be working so badly, as he obtained official funding to improve the invention and managed to exhibit such a curious device at the Great Exhibition in London, at the legendary Crystal Palace, back in 1851. Regrettably for that restless inventor, the exhibition already featured more sophisticated and precise machines, the mercury barometers, with which he could not compete. However, his machine surprised by the strangeness of his conception.

More information: Dr. George Merryweather’s 1851 Tempest Prognosticator.