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HMS Discovery was a Royal Navy ship launched in 1789 and best known as the lead ship in George Vancouver's exploration of the west coast of North America in his famous 1791-1795 expedition. She was converted to a bomb vessel in 1798 and participated in the Battle of Copenhagen. Thereafter she served as a hospital ship and later as a prison hulk until 1831. She was broken up in 1834.
During the 18th and 19th centuries, a sloop-of-war was a warship of the Royal Navy with a single gun deck that carried up to 18 guns. The rating system of the Royal Navy covered all vessels with 20 or more guns; thus, the term encompassed all unrated warships, including gun-brigs and cutters. In technical terms, even the more specialised bomb vessels and fire ships were classed by the Royal Navy as sloops-of-war, and in practice these were employed in the role of a sloop-of-war when not carrying out their specialised functions.
In World War I and World War II, the Royal Navy reused the term "sloop" for specialised convoy-defence vessels, including the Flower class of the First World War and the highly successful Black Swan class of the Second World War, with anti-aircraft and anti-submarine capabilities. They performed similar duties to the destroyer escorts of the United States Navy, and also performed similar duties to the smaller corvettes of the Royal Navy.