List of Physical Visualizations
and Related Artifacts

1850 – Merryweather's Leech Barometer


In 1850, British doctor and inventor George Merryweather built a barometer that uses live medicinal leeches to predict storms:

The twelve leeches are kept in small bottles inside the device; when they become agitated by an approaching storm they attempt to climb out of the bottles and trigger a small hammer which strikes a bell. The likelihood of a storm is indicated by the number of times the bell is struck.

The device, which Merryweather called the "tempest prognosticator", was shown at the 1851 Great Exhibition in London. Merryweather tried to convince the British government to make use of his design, but "it was thought to be impractical, since the leeches needed to be fed once a month and have their water changed every five days". The efficacy of the device is yet unproven.

The original device was lost, but several replicas were made. The images above show a replica from 1951 currently exhibited at the Whitby museum.


  1. Wikipedia - Tempest prognosticator.
  2. Natasha Frost (2017) The Rise and Fall of the Leeches Who Could Predict the Weather.
  3. Left image: The Guardian; middle image:; right image: Wikipedia.

Added by: Pierre Dragicevic, sent by: Aurélien Tabard. Category: Measuring instrument  Tags: leeches, sonification, weather