Sir Howard Douglas (1776–1861) fought in the Napoleonic wars in Spain, taught at the Royal Military College, served as lieutenant-governor of New Brunswick, lord high commissioner of the Ionian Islands, and as a Conservative MP for Liverpool. A military scholar, fellow of the Royal Geographical Society and Royal Society and associate of the Institution of Naval Architects, he wrote widely on bridges, systems of defence and attack, and on Britain's North American provinces. Written in retirement, when Douglas became an unofficial advisor to a succession of prime ministers, this work addresses the use of steam to propel ships, with detailed analysis of design, steering, propeller and paddle engineering and considerations of speed and manoeuvrability. The book goes on to examine tactics, including breaking the line, fuel economy and fleet arrangement. Built upon by others, this important work, first published in 1858, remains of interest to military historians.