"I have a leech in a bottle that foretells all these prodigies and convulsions of nature. Not... by articulate utterances ... but by a variety of gesticulations, which here I have not room to give an account of. Suffice it to say, that no change of weather surprises him, and that, in point of the earliest and most accurate intelligence, he is worth all the barometers in the world"(letter to Lady Hesketh, 1789). Edward Jenner, to whom we owe the smallpox vaccine, was also an accomplished poet. In at least one (but not all) version of his Signs of Rain, the final lines read
"The leech, disturbed, is newly risen/Quite to the summit of his prison."Merryweather cited these lines as inspiration for his Tempest Prognosticator. The device required a leech in each of 12 jars. The glass was to be transparent so that the leeches could "see each other" and so agree amongst themselves as to their prognostication. If any leech climbed up and into the escape tube, its weight would dislodge a piece of whalebone, releasing a hammer that would ring the bell thus announcing the onset of inclement weather. The Great Exhibition's jury rendered no verdict on this, imaginative, device. Nor did the Admiralty or the Board of Trade show much interest in Merryweather's storm warning system. Who needs doppler radar anyway?