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"Enormous care has been devoted to the illustrations and captions. Readers will finish this book considerably more educated about geography and navigation."— USA Today
"This new illustrated edition of Sobel's 1995 study of Harrison's remarkable instrument strikingly illuminates this largely unknown but crucial discovery."— Dallas Morning News
Posted November 1, 2009
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Christopher Columbus's most vital skill as a navigator was his ability to read tides, currents and winds. In his day sailors had tools to tell them how far north or south they were (latitude). What they could only approximate was how far east or west they were (longitude). If they knew the latitude of Havana, for example, they would sail south from Lisbon as fast as they could, find that parallel of latitude and head due west. They would also make use of towed "logs" to estimate their speed. Sailing masters were also alert to major currents such as the Gulf Stream. But they could and did make catastrophic errors. *** This blindness in calculating east-west location at sea, out of sight of land, and how it was finally overcome by the late 18th Century is the central topic of THE ILLUSTRATED LONGITUDE, co-authored by science writer Dava Sobel and historian William J. H. Andrewes. The two authors document and evaluate the works of dozens of renowned mathematicians and astronomers over the two preceding centuries. Those highly educated men created and used maps of stars and the solar system fleshed out by elaborate numerical tables to help seaman know where they were. Before the 1760s astronomers had created a reasonably accurate method that, when the weather was clear, permitted a trained observer to calculate his longitude in only four hours. This was reduced to 30 minutes by the book's "villain," Reverend Nevil Maskelyne. A great astronomer in his own right, Maskelyne was the last great champion of the astronomical school of longitude solvers. He was "villainous" only to his chief rivals: a father and son team creating timepieces as the decisive instruments for calculation of whereabouts at sea. *** Father was John Harrison. His son was William. In 1737 John Harrison displayed the world's first practical marine timekeeper. By 1815 there were 5,000 of them in use on the world's oceans. (p. 193). Both methods, star charts, etc. and timekeepers, remained in use. But chronometers were the clear winner, although astronomical observations and charts were still needed from time to time at sea to assure that the timepieces were staying accurate through storms and cannonades. Hundreds of astronomers had lost to one man, John Harrison, ably assisted over the decades by his son William. Astronomer Nevil Maskelyne stood on the shoulders of giants like Sir Isaac Newton. John Harrison was a carpenter who read Newton and taught himself to be a clockmaker. The heavenly school of learned, university-educated longitude solvers could easily understand each others' equations and physics. By contrast, John Harrison wrote possibly the most undecipherable English ever published. He was, moreover, secretive and reluctant to explain himself to potential rivals unless paid to do so. Yet the little man won! *** Even if you do not read a word of this book's narrative, sidebars, and chapter headings quoting Robert Burns and Lord Byron, you will nonetheless be drawn to its colorful portraits of principals, including amateur astronomer King George III, to its maps, photographs and drawings of clocks and other sea instruments and to its diagrams of inner workings of sea chronometers. *** The pace quickens throughout the 18th century. Names fly at you of astronomers and watchmakers. It would be easy to lose track of Maskelyne, Arnold, Earnshaw, Mudge and company unaided by their portraits from life. A grand book! -OOO-Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.