Longitude by Dava Sobel
- 180 pages (5 pages of Acknowledgments, etc.)
- Consider this quick read the next time you fly east or west from your hometown
Latitude and longitude, the lines on a Mercator projection map, have differing histories. On the globe, latitude makes rings that get progressively smaller from the equator as one moves north or south. One notices differences in latitude by the hours of daylight experienced in a given season. Ptolemy wrapped his head around the question of latitude about 19 centuries ago. Meanwhile, longitude, the measure of east and west, was much, much trickier. As recently as 1714, England’s Queen Anne was persuaded to pass the Longitude Act, establishing enormous cash prizes for methods of determining longitude to within one degree or less. And that’s when things started to get ugly among the powdered wig-types.
First of all, why did Queen Anne, her navy and her merchants care so much about that kind of accuracy? One degree of longitude equals sixty nautical miles (sixty-eight geographical miles), not an insignificant span when one needs to be sure which little island is visible through the spyglass, to avoid grounding on shoals, etc. Ships were often lost at sea in large part because the captains had acted on poor or incomplete navigational information. One would expect Queen Anne’s loyal subjects to agree, generally, that losing ships was bad for warfare or business, so where was the conflict?
The Longitude Act established a board including prominent figures in trade, the military, the government and scientists. These august individuals determined to whom these substantial awards—the top prize equivalent to millions of modern dollars—should go. The Royal Astronomer was necessarily a member, and he held a great deal of sway. The stars, after all, had been used as a navigational tool for centuries. Astronomers and other scientists in England were, as a rule, of at least a moderately noble pedigree and in need of something to do with their educations.
In the meantime, word of the cash prizes caused a stir among the general population. Sobel describes some of the many suggestions submitted to the board in pursuit of the prizes—many of them make for entertaining reading. Among the more serious contenders were the clockmakers. Clocks actually can give an indication of longitude: to calculate it, one needs to know the time at the home port and the time at one’s present location. The difference allows the calculation of longitude (assuming a known value for the home port). The difficulty: the pendulum clocks of the day didn’t withstand the roll and pitch of the waves, and clockwork lubricants didn’t function as well at high humidity. Technology hadn’t caught up with an otherwise sound principle. Plus, clockmakers were considered to be middle- or working-class by the nobility. They learned their craft through apprenticeship, not universities, and the astronomers looked down on them.
Enter the Harrisons, especially John Harrison. John Harrison worked independently as a clockmaker, fashioning his clocks entirely out of wood with exquisite precision. His detailed knowledge and specific uses of particular kinds of wood for particular parts of a clock allowed him to avoid the need for lubricants. His machines also got around problem of expansion and contraction of metal pendulums at differing temperatures. Exceptionally accurate with these innovations, here finally were the clocks that might prove useful in determining longitude.
Harrison had difficulty being taken seriously by the board, but Edmund Halley became curious about his work and championed him enough to get the board’s attention. After Halley’s death, though, it was more rough going for Harrison, and eventually, his son. Astronomers other than Halley were less intrigued, and their influence with the board and its purse strings remained substantial.
To some degree, the astronomy camp was stalling for time. Where the clockmakers had started with a reasonable principle for determining longitude and needed to bring their technology up to speed, the astronomers had the opposite problem: astronomers had to constantly adjust their ideas about how to determine longitude using the heavens because the telescopes kept getting better.
This author definitely has heroes and villains in the telling of this curious story, something I normally don’t respond to well. However, Sobel’s easy writing style made for a book I could read even when tired from a full day—refreshing after Morris’ conceptually dense The Tycoons. I’ll admit to skimming some of the more detailed astronomy bits (just not my bag), but don’t skip them even if science isn’t your comfort zone. This particular and largely ignored historical topic is a fun story in its own right and an example of the human influence on the pace of science and technology.