读Dava Sobel 的 “经度”（My book review on Longitude)

Book Review on "Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time " by Dava Sobel

Like many others, I took longitude for granted. It wasn’t until I came across the name of John Harrison during a visit to the Royal Observatory at Greenwich upon Thames in the summer of 2007 that I realized its true importance and challenges it posed in the 19^th century.



Originally, it was part of an insignificant plan for a London trip to a West End show and a boat tour along the Thames. Obviously, this tour doesn’t need the whole day. I decided to do some sightseeing in Greenwich as well as visit the Royal Observatory and the Cutty Sark. Afterwards, I would take the boat to complete the trip.

The Royal Observatory serves as the base for the Greenwich Mean Time (GMT) and is famous as the location of the Prime Meridian, which separates the Eastern Hemisphere from the Western Hemisphere. I have always wanted to stand across the Prime Meridian, one foot on the East and the other West, to stand upon both sides of the world.



The Cutty Sark is one of the most famous ships in the 19^th century. Many Chinese students, including myself, learn of her story from L.G. Alexander’s English textbook, New Concept English. It was a good opportunity for me to see the ship in person.

Upon arriving at Greenwich, I noticed that the Cutty Sark was not open to the public due to a fire. (http://en.wikipedia.org/wiki/Cutty_Sark) It was disappointing, but it gave me time to explore the Old Royal Naval College and the Greenwich Park. Afterwards, I went to the Royal Observatory at the top of the hill for the Prime Meridian. There, I noticed the National Maritime Museum. The centrepiece of the museum was John Harrison’s accurate marine chronometers, which were used to keep the GMT on ships.

A chronometer is a watch used by sailors to locate a ship in the ocean by finding the time difference between the local time and GMT. The time difference and the altitude determine the position of a ship in the ocean where no visible reference is available. I took a long thought but couldn’t figure out a better way to determine longitude than to use accurate chronometers.

It was a pleasant visit. I had a lovely chat with a museum keeper and he described to me in brief about John Harrison’s life, the making of accurate clocks, the scientific challenge to determine longitude, the 20,000 pound Parliament Prize, and John Harrison’s struggle with the those astronomers who supported to work out longitude by observing stars.

The short visit to the Royal Observatory aroused my interest in John Harrison and longitude. After my returning from London, I searched web and found the book Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time by Dava Sobel.

This book is well written and easy to read. Instead of focusing on technical details, it provides historical events on the horrors of getting lost in sea and John Harrison’s life. The longitude challenge had remained unsolved by many great minds, including Galileo and Newton. For a practical solution to the challenge, the Parliament set up a 20,000 pound prize, managed by the Board of Longitude.

Encouraged by the money, John Harrison, a Yorkshire clock maker, single-mindedly pursued a clock-based solution. He succeeded after overcoming many technical hurdles. However, the Board of Longitude, consisting mostly of astronomers, did not approve of John’s clock based solution. They paid him only 1,500 pounds as an expense claim, not as the Prize, as his method did not involve observing stars.

Angered and frustrated, Harrison clashed with the Board many times. Each time, the Board paid him a little more but added some extra demands. Eventually, Harrison’s son, William, turned to King George III for help. The King had an active interest in science, and was building a private observatory at Richmond himself, intervened. The Parliament compensated Harrison a lump-sum of 8,750 pounds to make up for the Prize and for his unfair treatment by the Board. Under the presure, the Board was forced to accept Harrison’s method.

In a later chapter of the book, the board commissioned Larcum Kendall, a watchmaker, to build a chronometer called K-1, an exact copy of Harrison’s H-4. This clock aided Captain James Cook on his triumphant second voyage around the world. It wasn’t long before chronometers were mass produced, and it was common for ships to carry multiple sets of such instruments. A famous example, The Beagle, which carried the young Charles Darwin, had twenty-two chronometers.

It is an interesting read. In addition to clockmakers, the book has many other topics on sailing and astronomy. I also learned that sauerkraut, and later lemon and lime, was first used to subsidy sailors’ vitamin C to beat scurvy. In short, clockmakers and lemon suckers changed the British Navy forever!

It’s a very good book. I highly recommend it.