Tempest Prognosticator

Dr George Merryweather was a Whitby GP, Curator of Whitby Museum between 1840 and 1861, and inventor. In 1850 he invented the ‘Atmospheric Electromagnetic Telegraph conducted by Animal Instinct’ or Tempest Prognosticator. The Tempest Prognosticator consisted of 12 pint glass bottles, each containing a live leech, set around a circular stand under a bell which was surrounded with 12 hammers. Each hammer was attached by wire to a piece of whalebone set loosely in the neck of one of the bottles. The whole apparatus was designed in the form of an Indian temple (with the odd Egyptian feature thrown in!) in honour of the supposed origin of the design of the Crystal Palace, since the Prognosticator was to be demonstrated at the Great Exhibition of 1851.

Changes in atmospheric pressure before a storm would drive the leeches to the neck of the bottle where they dislodged the pieces of whalebone and rang the bell at the top of the device. When several bells rang in succession a storm was ‘prognosticated’. Merryweather had tested his machine for over a year in 1850, posting a letter to Henry Belcher, President of the Whitby Literary and Philosophical Society as soon as each storm was predicted. Multiple postal deliveries every day ensured that the letter would be postmarked (date and time) before the storm developed, thus proving the prediction true.

Bottle with leech

Six different versions of the Prognosticator were designed to suit differing pockets, and Merryweather anticipated they would be widely used on ships and around the world. However, the device failed to catch on, and even the original from the Great Exhibition was lost. In 1951 a copy was made for the Festival of Britain and given to Whitby Museum. Unfortunately the bell was made from cardboard, so this is not a working model, a genuine working model was produced at the Barometer World at Merton (near Okehampton), Devon where it resided until the closure of the museum due to the retirement of its founder. The working model now resides at the National Meteorological Library and Archive in Exeter where it is on display in the Library.

Close-up of bell