This book is a comprehensive guide to finding longitude and latitude using various methods, originally published in the mid-19th century. Andrew Mackay was a British astronomer and mathematician who applied his expertise to the practical problem of navigation. His book provides a fascinating glimpse into the science of navigation prior to the invention of modern GPS systems. 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.