This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1793 edition. Excerpt: ... error in the altitude of an object near the meridian may produce a considerable error in the apparent time; and because the altitude of a star cannot always be so accurately observed as is necessary for establishing the apparent time; nor can the time, inferred from the Moon's altitude, be depended on, unless its declination and right ascension are reduced to the time of observation, by applying the equation of second difference--it therefore seems most eligible to use the Sun for this purpose. Hence, if this object is too near the meridian at the time of observation of the distance, it becomes necessary to observe its altitude, when in a more proper situation, either previous, or subsequent thereto. Hence the error of the watch will be known, which being applied to the time of observation of the distance, will give the apparent time of observation, agreeable to the meridian for which this error was determined. Or, if the change of longitude in time, between the meridians of the places where the observations were made for ascertaining the time and longitude, be applied to the above found apparent time, by addition or subtraction, according as the ship's course made good has been in the eastern or western quarter, the apparent time will hence be known, for the meridian of the place where the observations were made for determining the longitude. If the watch gains or loses considerably, allowance must be made for its rate in the above interval. October 17, 1786, in latitude 360 12' S. and longitude, by account, 480 15'W. the following observations were taken in order to determine the error of the watch, the height of the eye being 17 feet. Time Towards noon, the following observations were made, the height of the eye being 16 feet....

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.

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 was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work. 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.As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. 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.