This intriguing and useful guide offers readers a detailed look at the methods used by mariners and navigators in the early 19th century to measure longitude and determine their location on the open sea. Drawing on his extensive experience as a ship's captain and navigator, author David Thomson provides detailed tables and instructions for using the movements of the moon and stars to make precise calculations of longitude. With clear, concise language and insightful analysis, this book is an indispensable resource for anyone interested in the history of navigation and the use of celestial bodies for time-keeping and orientation. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.