John Harrison And The Longitude Prize

The Illustrated Longitude. By Dava Sobel and William J.H. Andrewes. (New York: Walker and Company, 1995. 216 pp. $ 28.00, ISBN 0-8027-7593-4.)

This book was created as a collaboration effort by the authors to help make a very dry subject into something more entertaining and enjoyable with the addition of many beautifully done drawings, paintings, and pictures. These pictures help bring the book to life, and because color was chosen over black and white it is a joy to read instead of the drudgery one would normally expect from a book of this type. Dava Sobel is a science writer for journals and publications, and William Andrewes the curator for scientific instruments at Harvard University. It is very telling that it took at least two years for Dava to find a place to publish the article once it was written, and only that seemed possible because the symposium the writer was supposed to report on was only a few days away! Publication editors just did not think that this subject matter was going to be anything that their readers would spend time with.

Longitude has been a huge issue for correctly navigating the oceans of the world since man starting expanding transportation and trading routes to other ports and countries. Sailors and captains knew about latitude, and how to sail from place to place depending on a variety of methods using ocean currents, star positions, and the angle of the sun. However, the main problem was not where a ship was located on a north to south trajectory, but where a ship was located east to west. This was much more difficult to figure out because of the shape of the earth and the lack of important astronomical knowledge about the heavens and how they move around in relation to the earth.

Captains had at best a rough estimation of the ships location on a map, where they were headed, and how long it would take to get there. They could be, and often were, off by thousands of miles if not many hundreds.

Even a degree or two of difference could mean ships crashing on the rocks or bottoming out in the shallows, often resulting in huge losses in life and cargo. Finally, with the emergence of strong national governments, awards and prizes were set up to encourage competition and to find a reliable method of handling the problems of longitude for the safety of ships and cargo. England was one country that had a very large award offered, 20,000 pounds, and soon there were all sorts of ideas being offered up as a possible solution. There were many ideas that would be laughed at today and had no scientific merit, but there were also some really interesting and sound ideas. Two main theories or ideas quickly came to the forefront, one by John Harrison of England and another promoted by Nevil Maskelyne, also of England. John Harrison was mainly concerned with creating a precision clock that the captain or navigator of the ship could set by the home port time before setting off, and then comparing that time to how far they sail east or west to calculate their longitudinal location. Nevil Maskelyne was an astronomer and was more concerned with precise observations of the heavens so that a navigator could determine his precise location at sea. Both were very solid ideas, and both were in the front running for the prize, and the authors show both sides of the competition with more of an emphasis on John Harrison and his clocks. Since this method ultimately won out over astronomical observations, the book seems to be a very matter of fact and non-biased historical reporting of a highly important race to help ships and their captains protect life, limb, and cargo in their duties at sea.

This book seems to be very well researched and an important piece of information for anyone seriously trying to understand longitude and how it affected shipping and trading throughout the centuries. It is easy to think that navigation was always a sure thing, and that there was never a problem with sailing from one place to the next, but the realities of it were much different. The ship and crew were totally dependent on the skill of the captain in order to make it safe and sound to their destination, and not smashed on rocks due to an error in navigation. The book should be required reading for any class dealing with the history and development of ships and their progress over the oceans.

John Harrison was a self educated man coming from a meager background, and rose through trial and error to become one of the most celebrated clockmakers in all England, if not the world! When the Longitude prize was announced in England, he was already a well established clockmaker in his home town. Harrison’s early clocks contained an “equation of time” table so that the user could rectify the true time (based on a sundial) with the mean time (based on a clock striking noon). Sun dials were still in wide use at that time, and the differences varied based on the seasons. Harrison worked out most of these equations himself with much study and observation, so he definitely was a brilliant man when it came to making very accurate clocks. Most clocks at that time lost about one minute per day, even the very best ones! Harrison and his brother worked on new ways and methods of building extremely precise and accurate clocks with pendulums and metallic strips that alternately expanded and contracted and counterbalanced each other to maintain very precise time. They also experimented with creating their clocks with wood, so that regular oiling would not be needed by the owner. Two inventions that they created, the gridiron and grasshopper, helped with the exact timekeeping. The two brothers became so successful at building these wooden clocks that they did not err more than a second in any month! That is quite extraordinary, and one of the reasons that Mr. Harrison soon became known as one of the best clockmakers in the country, if not THE best.

One thing the book does do is to wait until much later on in the reading to bring forth John Harrison and his part in the whole Longitude prize award. The book really goes into lots of detail about how the prize came to be and the early participants and theories. The astronomers studied and observed Jupiter’s moons to find out exact details about the position and time that they should be passing over Jupiter. The only way to actually see the moons at that time was to wait until they passed in front of Jupiter and then they could decipher the position in relation to location on earth, which would help with the understanding of longitude. The trouble with this method, are the incredible amounts of observations required in many different places in order to compile an in depth set of tables that the mariners could use when out to sea. It was also a very time consuming method of figuring longitude, and could take upwards of four hours per reading. Still, it was a favorite among many different people, and was a strong contender for the ultimate prize.

In the end, it was John Harrison who won out with his precision time keepers. The story behind that is extraordinary, because of the delays and foot dragging by the official committee members in charge of the competition and its results. There were many in the committee that favored one side (Harrison) or the other (Jupiter’s moons), and much bickering and delay tactics were put forth so their side could ultimately win the prize. In reality, Harrison did not have nearly as many supporters as the other side, and he was quite frequently required to pass tests that were over and above the stated ones in the contract. Harrison spent many long years perfecting his precision clocks, from H1 to H4, and they all performed almost perfectly with small exceptions here and there. Sobel and Andrewes spent much time on how Harrison was abused by the system and how long it actually took for him to finish his clocks and compete for the prize. They hint that if Harrison had not been such a perfectionist, he may have received the 20,000 pound prize with his H1 effort, which more than met the requirements of the contest. However, he stated that he still had some tinkering to do, and spent another two years working out some kinks that he saw. During that time, he lost some supporters on the longitude committee, and that made it much more difficult to win the competition outright with regard to the Jupiter’s moons effort.

With eventual test voyages to Jamaica, Harrison’s clocks proved up to the task even if he still had a tough time collecting the full amount of the award. The committee gave him half the award, 10,000 pounds, after some further testing, but would not give him the rest because they felt that Harrison’s timepieces did not fit all the requirements of the testing. Harrison did receive just about all the total prize money later, when the King of England interceded for him. The King was a big science enthusiast, and he followed the results with great interest. Thus, toward the end of his life, Harrison received all the respect and praise due to him, and especially since others trying to duplicate a person’s work is always the highest praise! There were many others trying to help mass produce the fine precision clocks that Harrison had made, because the only way that his invention could help a great deal of mariners is to make it affordable enough and available enough for every sea captain to have one. There were many who tried, and actually improved on Harrison’s designs in order to bring the price down dramatically. Today, all mariners have quartz crystal time pieces, or actually to be more precise ships depend on satellite navigation to know exactly where they are at all times when at sea, and it seems superfluous what all the commotion was about at that time. But Harrison and his magnificent clocks really made a difference in the lives and safety of sailors and their ships, and he was much appreciated.

The authors did a fine job in explaining in detail the history and progression of the race for the prize, and once they brought out Mr. Harrison and helped to define him to the reader it really made the situation much clearer to all. For someone who has never really heard of the vast problems associated with longitude and trying to affix a ships position mainly through the use of latitude, it comes as a great story full of heartfelt adventure and a dash of mystery! Placing one in that day and age, and time and place, it is easy to wonder what it was like to have such limited knowledge of the earth and universe as known today. This is definitely a recommended book for all those who have ever pondered the ocean and man’s relationship to it.

Jeffrey Ferris I’ve been self-employed with internet marketing for several years now, and also into jet skiing, boating, travel, and adventure sports. To learn more about internet marketing please visit or for more great info about boating, catamarans, travel, and other topics visit

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