Navigation is the art of directing the course of a ship at sea and finding her position by observation of the heavenly bodies, the indications of the compass, calculation of distances traversed, and the use of charts. It is an art of great antiquity, but until the use of the compass became general it was necessarily pursued with difficulty and uncertainty. The Phoenicians were the most successful and venturous of early navigators, and there is good reason to believe that long before the Christian era they or their pupils visited not only Britain, but also the eastern and western coasts of Africa as far as points lying considerably to the southward of the equator. The subject is too extensive a one to be entered upon in detail here; but the inquirer may profitably refer for the history of the art to Locke's History of Navigation, and for information as to the practice of it to Norie's Epitome of Practical Navigation (1806), Raper's Practice of Navigation and Nautical Astronomy (1843), and the modern works, Harbord's Glossary of Navigation, Morris's Elementary Navigation, Lecky's Wrinkles in Navigation, Martin's Navigation and Nautical Astronomy, and Jeans's Nautical Astronomy and Naviyation. The works of Norie and Raper are standard ones, and new editions of them have often been published.