Leech lore for `Tempest Prognosticator'

Should you ever have occasion to visit the museum in the town of Whitby, Yorkshire, you will see there a strange contraption …

Should you ever have occasion to visit the museum in the town of Whitby, Yorkshire, you will see there a strange contraption like a model merry-go-round that is alleged to be a predictor of bad weather.

It was designed in the 1840s by the appropriately named Dr George Merriweather, a Yorkshire medical man who was strongly attracted to pseudo-scientific gadgets.

The good doctor's apparatus was based on the activities of the medicinal leech, whose behaviour he had studied very closely. Leeches housed in water, it seems, relax at the bottom of their bottle in fine calm weather, but half a day or so before a change they move steadily upwards towards the surface.

If rain is at hand they move out of the water altogether, and if a storm is imminent, a clever leech will curl himself into a ball, and remain thus for its duration. Once the weather settles down, the leech drifts slowly down again to the bottom of his bottle, ready to leap into action again at the slightest hint of change.

Merriweather's strange device to harness these meteorological inclinations comprised a central stand that was surmounted by a bell with 12 hammers. Twelve pint bottles, half filled with water, were arranged around the base, and each one was fitted with a trap-door that was in turn connected by a chain to its respective bell.

A leech was placed in each bottle, and when it detected a coming storm its gymnastics near the trap-door should result in a ringing of the bell. With 12 leeches independently on the quivive in such a way, the device was obviously foolproof.

The proud inventor first demonstrated his "Tempest Prognosticator", as he liked to call it, to the members of the Whitby Literary and Philosophical Society in 1850, giving discourse which "occupied nearly three hours".

The following year the Great Exhibition of 1851, epitomising the new self-confident, almost arrogant, optimism of Victorian Britain, was housed in the magnificent Crystal Palace in Hyde Park. The giant hall of glass covered 19 acres of industrial and cultural displays, and its stated aim, with understandable hyperbole, was to "seize the living scroll of human progress, inscribed with every successive conquest of man's intellect".

Needless to say, it was decided that Dr Merriweather's Tempest Prognosticator merited a space.

Later Dr Merriweather mounted a campaign to have a network of "leech-warning stations" established around the English coast. The government of the day, perhaps wisely, failed to act on the suggestion, but the good doctor's brain-child can still be seen today in Whitby Town Museum.