As the subtitle suggests, this is the story of the man, John Harrison, who came up with a workable method for finding longitude while at sea. He did this by means of a clock, while many other people favoured an astronomical solution, and there's some interesting description of the conflict between the two groups, which was probably increased by the fact that there was a huge monetary prize associated with finding a solution. I enjoyed reading about the eighteenth-century scientific community.

I would have enjoyed reading a bit more about the actual science, too. This is a pretty light and quick read--actually a bit too light for my liking. Sobel mentions various improvements that increased the accuracy of clocks, but I felt like most of the descriptions of the inner workings of clocks were a bit too vague to really give me an understanding of what goes on in there. For example, we learn that "the grasshopper escapement--the part that counted the heartbeats of the clock's pacemaker--took its name from the motion of its crisscrossed components. These kicked like the hind legs of a leaping insect, quietly and without the friction that had bedeviled existing escapement designs." This is all that's said about it, so it wasn't at all clear to me how exactly an escapement worked, and I would have liked to know.

Still, this was a fairly informative book, and probably worth reading, even if it's not anything outstanding. A lot of people will probably be grateful for the fact that Sobel doesn't go into more scientific detail. ( )

I won't claim to be able to explain or review this book. I think I understood about 1/2 of it, but it was short, and well written. It's the story of the development of the chronometer and the discovery and standardization of measuring longitude for sailors at sea. There is political intrigue, some history, and lots of technical science. If you're a sailor, and do any celestial navigation, you'll probably love it.

I wish there had been a few diagrams, and illustrations....I think it would have helped a lot. ( )

A history of the solution to finding the longitude of ships at sea (and also cartographers on land) to a degree of accuracy. Explains how easy it was for sailors to figure out their latitude but how poor their methods for calculating longitude were and what the costs were in terms of ships, treasure, and men lost. An interesting book that is a very quick read. ( )

I enjoyed this book. If you are into history, then the history of marine chronography is for you. Dava Sobel gives us a good look and the physical, and, probably more difficult issue, the political problems encountered in finding a timepiece that would fix the longitude for sea captains.

A good read. Recommended. ( )

Sailors have been able to calculate latitude almost since men first set out onto the ocean. Calculating longitude, on the other hand, is a technology that has only been perfected in the relatively recent past. Many of the famous explorers whose names students now commit to memory set out with no reliable method of telling how far east or west they were, resulting in many deaths and extensive hardships for the crews involved.

Dava Sobel's book details the story of the Longitude Prize enacted by the British Parliament, the bizarre and impractical solutions offered to win the prize, and the lifelong efforts of John Harrison, a man who finally fulfilled the conditions necessary to win the Longitude prize, but due to the prejudices and conflicts of interest of the commissioners charged with awarding the prize, was never actually awarded the bounty, despite having the backing of King George himself.

The method for determining longitude is fairly straightforward. One must calculate the local time where one is, and compare it to the time at some known position, which is now always assumed to be Greenwich in the United Kingdom. The difference in the local time and the Greenwich time can be expressed in hours, minutes, and second, and then plotted on a globe, showing the longitude of the ship in question. The prime difficulty facing the aspirants for the Longitude Prize was how to determine Greenwich time when one was presumably hundreds or thousands of miles away.

Astronomers, who favored methods using stellar and lunar observations, eventually settled upon a method that involved tracking the path of the moon across the sky, comparing its location to the locations of designated guide stars, and measuring the distance between the Earth and the moon. This method was complicated and difficult, and required massive numbers of celestial observations to be made before the required charts could be made to begin with. This method was also somewhat unreliable - on a cloudy night, one could not locate the stars needed, many days out of the month the moon is not visible (as it is located on the opposite side of the Earth), and so on.

John Harrison, on the other hand, sought to build a very accurate clock. Once such a clock was set to, for example, London time, one could simply refer to the clock at noon local time, and determine by seeing how far away from noon the clock was how many minutes and seconds of arc one was from London. However, the clock would have to remain accurate over long periods of time, in humid conditions, and across a wide span of temperatures. When the Longitude Act was passed, clocks were not even accurate to within several minutes per day, and even an error of a couple seconds per day would cause the navigator to miscalculate a ships position by dozens or even hundreds of miles.

The book describes Harrison's attempts to build such a clock, eventually settling upon an oversized watch. The book also describes the hostility many of the astronomers on the longitude board evaluating his submission had towards him. While Harrison was a tradesman, and a self-educated mechanic to boot (earning the derision of many of the highly educated aristocratic astronomers on the board), he was their competitor for the extremely lucrative board. Under the guidance of successive Royal Astronomers, the board imposed more and more difficult obstacles to Harrison's watch, until in frustration he appealed directly to King George. Eventually, with the King's assistance, Harrison was awarded a prize by a special act of parliament. The obstinate longitude board never awarded the full Longitude Prize to anyone.

Sobel has created a compelling story out of what could have been a rather boring event in history. In a roundabout way, Harrison's story explains to a certain extent why pirates and privateers were common before the 1800s, and vanished almost completely thereafter. One thing made clear (to me at least) is that many writers of historical fiction, or even fantasy, make sea travel in the pre-Longitude era too reliable, and too easy. It is probably the measure of the success of a technological advance that it becomes so prevalent and accepted that the difficulties faced in the days before are forgotten by the general public. On that score, Harrison's watch is one of the most significant technological developments in history.

One nitpick I have is with the subtitle of the book. It seems to me that the longitude problem was not a scientific problem, but rather an engineering one. That failing aside, this is an excellent book. ( )