MANUAL OF NAVIGATION. BY ROBERT ASSHETON NAPIER, LIEUT. R.N.R., MEMBER OF THE INSTITUTION OF NAVAL ARCHITECTS. SECOND EDITION. GLASGOW: JAMES MACLEHOSE, ST. VINCENT STREET, Publisher to the University. 1880. All rights reserved. 184. h PREFACE. THE Author has been induced to publish this Manual owing to the inconvenience he has at different times experienced from the want of a book containing all the rules and examples required for daily use at sea. The principal object kept in view has, therefore, been to furnish a compact book of reference for all calculations necessary for the efficient discharge of navigating duties, and while there is nothing included in its pages but what will be of use to the careful seaman, it is hoped that nothing has been omitted which might advantageously have been inserted. The conclusions to be derived from a careful study of the ever-varying signs of the weather have been placed before the reader as clearly and consecutively as possible. Considerable care has been taken to produce in a concise form rules for finding and applying the Deviation of the compass. Attention is also directed to the practice of reducing the soundings found by the lead in thick weather, at night, or at any time when standing into shoal water, to the mean height of low water at ordinary spring tides, for exact comparison with the depths marked on the chart. Ignorance or neglect of this simple correction too frequently causes a disastrous termination to a hitherto successful voyage. All that has been undertaken in connection with observations of celestial objects are a few detailed calculations under various conditions, for purposes of easy reference. Obsolete and approximate methods, which tend to retard rather than advance the science of navigation, have been avoided as far as possible. The Lunar problem for ascertaining Greenwich time, and hence the longitude, is beyond the scope of this manual, and Sumner's method of equal altitudes, used in conjunction with |