Finding a Ship's Position at Sea

Many navigators wanted easier, more accurate methods of determining their position at sea. One of the most important developments in the second half of the nineteenth century was Capt. Thomas H. Sumner's contribution in his book, A New and Accurate Method of Finding a Ship's Position at Sea by Projection on Mercator's Chart. Discovered in 1837, and first published in 1843, by the time of this 1851 Third edition it had become the standard method.