"This book is a unique, concise resource for the history of the development of Line of Position navigation techniques from their invention in the 1840s to the end of the twentieth century. The point of crossing of two or three Lines of Position plotted on a chart quickly and accurately gives a fix of the navigator's position. We owe two nineteenth century navigators for the creation of the basic concepts of celestial navigation we still use today - Thomas H. Sumner, an American merchant captain, and Marcq Saint-Hilaire, capitaine de frâegates in the French navy. This book describes the new techniques they derived from their personal knowledge and experience."--Provided by the publisher.