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GEORGE MERRYWEATHER was a dab hand with a leech. He was a doctor, tending to the needs of the people of Whitby on the North Yorkshire coast, where he applied the worms as often as a modern GP might prescribe antibiotics. Merryweather was also an observant and educated man. He had read a poem by the acclaimed physician and inventor of the smallpox vaccine, Edward Jenner, in which he described how as rain approached, “The leech, disturbed, is newly risen; Quite to the summit of his prison”.

Intrigued, Merryweather observed how the leeches in his own surgery became excited shortly before thunderstorms hit Whitby. “The ordinary medicinal leech is peculiarly sensitive to atmospheric conditions before the occurrence of electrical storms,” he wrote in his journal.

Being a practical man, he decided to turn this observation to advantage. He built “an atmospheric electromagnetic telegraph conducted by animal instinct”, better known as the Tempest Prognosticator, which he unveiled in February 1851 before the Whitby Philosophical Society.

Looking rather like a miniature Indian temple, the Prognosticator was “adapted for any drawing room”. It was about a metre high and incorporated 12 pint-size glass bottles, each of which contained a leech and some rainwater. The bottles were arranged in a circle so the leeches “might see one another, and not endure the affliction of solitary confinement”.

But however preoccupied the leeches were by their social lives, whenever the air became electrically charged they unfailingly attempted to climb up the jar and into a narrow brass tube at the top. As each leech did this, it dislodged a whalebone hammer that was attached by a chain to a central bell. The more leeches that rang the bell, the more likely a storm was brewing.

For the whole of 1850, whenever the bells rang, Merryweather fired off a note to the President of the Philosophical Society predicting a storm, apparently with success. Only then did he go public, entering the Prognosticator for display at the Great Exhibition in London.

The Weekly Dispatch reported: “The inventor states the apparatus will communicate at all times the processes that are taking place at the higher regions of the atmosphere, and for hundreds of miles in extent will foretell, with unerring certainty, any storm that is about to take place.” Lloyds of London conducted experiments on the Prognosticator, which was, according to the Dispatch, “found to be perfectly accurate”.

There were sceptics. Merryweather’s invention formed part of a mid-19th-century craze for bizarre instruments incorporating living things. The most celebrated, a hoax, was known as the “snail telegraph”, in which pairs of snails were reared together so that they developed a “telepathic link”. A pair was allocated to each letter of the alphabet, and then the individuals were separated. When one was given an electric shock in say, Paris, its partner in New York would become agitated. In this way, it was claimed, a message could be telegraphed.

At least Merryweather’s machine worked. Indeed, some said the idea was old hat. In 1851, Chambers’ Journal noted sniffily: “That leeches are sensitive to thunderstorms is well known. Cowper the poet gives an account of a leech which he kept as a barometer, in a letter to Lady Hesketh in 1787.”

But Merryweather was confident. He told the philosophical society of his hopes that “our Whitby pigmy temples will be distributed all over the world”. And he went on a national lecture tour to persuade the British government to install stripped-down versions at ports all round the coast.

The time seemed right. Tempest forecasting was all the rage after a storm had wrecked a naval expedition at Balaclava in the Black Sea in 1854. But Merryweather met his match in Robert Fitzroy, former sea captain and governor of New Zealand, who was installed after Balaclava as the first Meteorological Officer to the Board of Trade.

Fitzroy pioneered instant weather charts using the new telegraph system, and persuaded The Times to publish them. He was an enthusiastic supporter of mercury barometers, as well as storm glasses. These cocktails of camphor, ammonia, alcohol, potassium nitrate and water reacted to pressure changes and electrical charge in the air, with small crystals forming in the cloudy liquid whenever storms threatened.

There is no known record of Fitzroy and Merryweather ever meeting. But certainly Fitzroy rejected Merryweather’s repeated overtures to install bottled leeches around the nation’s shores. Instead, he persuaded the Board of Trade to adopt a system of barometers and storm glasses at ports and coastal villages.

Gradually Merryweather’s speaking engagements dried up. The original “pigmy temple” disappeared, but a replica was built a century later for the Festival of Britain in 1951. It survives today in Whitby Museum, but has never been primed with leeches. Now, another 50 years on, meteorological historian Philip Collins of the Barometer Museum in Okehampton has built a working model—complete with leeches.

It works, Collins insists. And it has explained one oddity about the original—why each leech had its own bottle. “We noticed during our research that leeches seem to have a pecking order,” says Collins. “When they were in a tank only one of them was allowed to the top. I think that is why Merryweather put them in separate bottles, so they had their own domain.”

So what happened to our two Victorian meteorological innovators? Fitzroy is now hailed as the father of modern meteorology. But in his day, he was roundly criticised in Parliament and the press for his failed forecasts. So much so that one spring morning in 1865 he cut his throat and died.

But Merryweather, whose other exploits in the backwaters of innovation included a lamp that could burn continuously for a fortnight on a mixture of whisky and pure alcohol, fared better. He died in his bed at the age of 77, apparently content with his contribution to world affairs.