The story of the sextant: Since 1759, the indispensable navigational tool guided two centuries worth of sailors. David Barrie tells of its invention, the mariners who used it to fare the open seas, and of the explorers who braved dangerous voyages to map the world. The sextant is a familiar symbol of the maritime world, but to most people - including many of those who enjoy sailing -- the purpose of this beautiful instrument remains mysterious. So crucial are they to navigation that, even with the sophisticated GPS systems of today, no ship would dare leave port without one. In the long distant past, sailors began to use the height of the Pole Star above the northern horizon to measure roughly how far they had travelled in a north-south direction (a change of latitude). To fix their exact position, however, they needed also to be able to measure displacement in an east-west direction (a change of longitude), and this proved to be a much, much tougher challenge. Solving the "longitude problem" became an urgent priority when European vessels began to make frequent transoceanic voyages, starting in the fifteenth century. Finding a way of measuring time accurately at sea was crucial, and the invention of the sextant in 1759 enabled solutions.

With the sextant, the ancient, complex art of celestial navigation had come of age at last. In Sextant , author and sailing expert David Barrie tells the enthralling story of how this crucial tool came into being, how it saved the lives of many navigators in wild and dangerous seas, and of its underappreciated role in mapping the world. Among the protagonists in this story are James Cook, Matthew Flinders, Robert Fitz-Roy, Frank Worsley of the Endurance, and Joshua Slocum, the redoubtable old "lunarian" and first single-handed round-the-world yachtsman. Their stories are interwoven with the Barrie's account of his own maiden voyage, and of his years as a practiced seaman and navigator. Infused with his sense of wonder and dramatic discovery, Sextant is a beautiful, eloquent elegy to one of the most important and unsung instruments in history.