A true sea shanty: the story behind the Longitude prize
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Version 0 of 1. Jonathan Betts, senior curator of horology at the Royal Observatory, Greenwich, and I met in a workshop tucked away behind an impressive display of ships' chronometers and a very strange brass contraption with two swinging, double-ended pendulums manacled by springs. This machine was the first of John Harrison's clocks, known as H1, predating all those other chronometers, and representing his first attempt to make a timekeeper that would remain accurate on board ship. Harrison made this clock in an effort to provide a reliable means of measuring longitude (the east-west position). An inability to calculate longitude had been the cause of many disasters at sea, prompting the British government to launch the Longitude prize in 1714. There would be a reward of £20,000 – several million in today's money – for the person who solved the problem. While some attempted astronomical solutions, Harrison, a clockmaker by trade, was sure that an accurate timekeeper was the key to the problem. At sea, you could tell the time by looking at the position of the sun. If you then knew the time in a distant place with known longitude – in London, for instance – you could use the difference in time to calculate your own longitude. Each four minutes of difference translated into one degree difference in longitude. The problem was that the most faithful timekeepers of the age were pendulum clocks and you can imagine what would happen to one of those if you took it out with you on the high seas. Waves aren't at all conducive to the regular swinging of a pendulum. Any hope of accurate timekeeping would be dashed on the rocks, just as you were now likely to be, with an inability to pinpoint your position correctly. In the design of his H1, Harrison opted for two double-ended pendulums, or balances, but the odd-looking machine was still disturbed at sea and not accurate enough to win the reward. Nevertheless, the members of the Board of Longitude, led by the astronomer royal, saw some promise in the inventions of the Yorkshire clockmaker. They funded his continued work on the longitude problem. Harrison made two more clocks, attempting to improve on the design of H1. It looked as though he was heading in the right direction, but then, in 1755, he suddenly changed tack. It must have seemed that he'd lost his mind. While pendulum clocks were known for their accuracy on dry land, pocket watches were notoriously bad timekeepers. And his new instrument looked for all the world like an oversize pocket watch. It was ludicrous to imagine that this watch would be the answer to the longitude problem. Despite sceptics and detractors, Harrison's H4 would prove itself on not one, but two long voyages to the Caribbean. Inside that perhaps unassuming exterior, Harrison had packed innovative components that would make H4 the most reliable timekeeper at sea the world had yet seen. It would make sure that sailors would be safe – or at least, the chronometers that followed in its wake would allow them to avoid the dangers that they'd faced when ignorant of their precise position on the globe. Betts had invited me into the workshop to show me H4. I waited with bated breath as he opened a safe and with gloved hands removed the watch and placed it on the table in front of us. It was a beautiful thing, in a polished case, like a perfect silver pebble. It had an ornate face, painted in thin black lines on white enamel, and delicate hands. I gazed at it with a mixture of awe and astonishment – it was actually quite unprepossessing. I could see why it would have caused raised eyebrows among the Board of Longitude. "Would you like to see inside it?" Betts asked, like a curator with a key to the tomb of a pharaoh. Of course I would! He opened the case and took the instrument out. It was even more ornate inside. An incredibly beautiful and intricate brass machine lay under that white face. And the upper, visible surfaces of the brass components were engraved with extravagant, baroque tendrils and curls. The guts of this instrument were designed to be admired. "Would you like me to start it?" he asked, with the knowing air of someone who had just delivered a gobsmacking suggestion. I was suitably gobsmacked. He took a tiny handle, fitted into a hole and gave it a quarter-turn. Nothing happened. But this was one of the reasons that Harrison was thought so eccentric when he produced H4 – because, going against everything that every good watchmaker learned, H4 would not self-start. All pocket watches self-started! That was the thing about pocket watches – you wound them up and they sprang into action immediately. All they needed was that slight kick when you took the key out… and they'd be off. Not Harrison's H4. He'd designed a watch that needed more of a boot up the backside to get it going. Betts knew this – but I gasped as he gave the unique, the priceless, the surely delicate H4 a short, very sharp twist… and it whirred into action. The ticking was incredibly fast: five ticks per second. This was the real breakthrough, the real secret of H4, that would make it imperturbable at sea. It beat so fast, and the balance wheel rotated so far, with such high energy, that it could not be pushed off-balance, even by a raging sea. The watch that was so hard to start was also hard to stop, hard to perturb. Harrison had solved the problem with what seemed like a crazy idea. He was a maverick and a genius (and eventually he even managed to extract most of the £20,000 reward out of the Board of Longitude). He had made it his life's work to create this accurate timekeeper: it had taken decades to achieve it, but he realised his ambition. This week, exactly 300 years since its namesake, the new Longitude prize will be launched; £10m for the solution to one of the greatest challenges facing us right now, a problem that the public will vote to decide. Somewhere out there is a 21st-century Harrison or even a whole of team of them. Alice recommends Rebekah Higgitt's blog on longitude and horology |