Sometimes there is an obvious answer to a complex problem, but there is a missing piece that confounds even the greatest minds and resists the efforts of large-scale government programs to develop a solution. Such was the case of a reliable and accurate method for calculating longitude in the first centuries of European naval mastery and the associated rise of colonialism and global trade. The inability of sea captains to tell precisely how far east or west they were resulted in more than just lost time and inconvenience, it was positively deadly. In 1707, some two thousand British sailors lost their lives when their ships ran aground of the southeastern English coast because of a failure to determine longitude. The disaster prompted Parliament to offer a substantial reward for anyone able to solve the longitude problem.
The obvious answer to the problem was to keep a clock onboard the ship set to the precise time in the homeport. If the homeport time was known, with great accuracy, the captain could rather quickly determine local time and then mathematically determine how far he was from a set location, thus providing his longitude (latitude is relatively easy to determine and had been known for centuries). But there was a rub with this simple solution – 17th century clocks were notoriously unreliable, especially at sea, where the rolling of the deck wreaked havoc on the pendulum system of time keeping and severe fluctuations in temperature and humidity caused sensitive metal to expand or contract and oil to thicken or loosen. The end result was a clock that could lose minutes a day. Over the course of a six-week voyage, the clock would be so far off that determining longitude from its readings would be useless.
The weight of distinguished international scientific opinion held that a shipboard clock would never work. The solution, they believed, could only be found in the celestial clock of the heavens above that had long guided sailors through their voyages. One method, proposed by Galileo, was to monitor the revolutions of the moon of Jupiter, which occurred at regular intervals and could actually work – provided a sea captain had clear skies and could observe the distant bodies while standing on the deck of ship tossing about the ocean.
But there was a self-educated clockmaker from England named John Harrison who believed that he could build a clock rugged enough to survive the hostile environment of an 18th century sailing vessel, while remaining accurate enough to keep homeport time to allow the calculation of longitude to within half a degree. Dava Sobel has written Harrison’s story in a way that is satisfying to read, informative, and, in the end, uplifting.
Sobel sees Harrison’s experience as a classic tale of a lone, self-effacing genius battling the maddening inefficiencies of government bureaucracy and the malign influence of elite opinion hostile to (and quite possibly envious of) his remarkable success. It just so happened that at the time Harrison released his revolutionary timepieces, advances had also been made with a celestial-based method for determining longitude called the lunar distance model, and one of the main proponents of the method was the “Astronomer Royal” of England, Reverend Maskelyne. Sobel describes Maskelyne as an almost literary anti-hero, intent on sabotaging the clock trials of the Harrison clock and adding new and unreasonable terms to be met before agreeing to pay Harrison his justly deserved prize. At one point all of Harrison’s clocks were seized by Maskelyne and poorly kept under lock-and-key.
Harrison’s story as told by Sobel is inspiring. Her prose is clear and her explanations of the competing methods and ideas are entertaining and easy to grasp. Overall, this is a real gem more than worthy of its many accolades and commercial success.
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