Storm forecasting machine using live leeches

Some animals have the ability to instinctively predict changes in the weather. For example, when a thunderstorm is approaching, frogs croak, birds return to their nests, and cows, sheep, and ants become restless.

George Merryweather, a 19th-century English physician and inventor, noticed his medicinal leeches behaved strangely when the weather worsened. Placed in small glass jars filled with water, leeches will relax at the bottom when the weather is good, but a few hours before the sky turns overcast and the wind begins to blow, the leeches show signs of restlessness. If it’s going to rain, it will move out of the water, and if a storm is coming, the leech will curl up into a ball and stay that way throughout the storm. When the weather stabilizes, the leeches will return to the bottom of the jar.

Merryweather decided to exploit this ability of leeches by creating a storm forecasting device described as an “Atmospheric electromagnetic telegraph, controlled by animal instincts”, briefly called “Forecasting Machine”. storm”.

The storm forecaster consists of 12 glass bottles, each containing a live leech in about 3.8 cm of water. The top of the glass bottle has a piece of whale bone placed at the neck of the bottle, connected to a small hammer used to knock on a large metal bell. 12 bottles arranged in a circle around a metal bell.

When a storm is coming, the change in atmospheric pressure causes leeches to crawl out of the water, reach the neck of the bottle, push the whale bone out of place and ring the bell. Multiple bells ringing in a row means the machine predicts a storm is coming.

In a description of the device, Merryweather said, leeches were placed in glass bottles in a circle to prevent them from feeling distressed when kept alone. Around 1850, he spent more than a year testing the device and sent letters to the presidents of the Philosophical Society and the Whitby Institute every time the “leech advisory board” predicted thunderstorms. Merryweather then lobbied the government to use his design around the British coast, but they decided to use Robert FitzRoy’s storm forecasting glass tube.

Merryweather’s storm forecaster was not as popular as he expected. Even the original device displayed at the Great Exhibition in 1851 was lost. A replica of this weather forecaster is currently on display at the Whitby Museum, England.