High Quality Content by WIKIPEDIA articles! HMS Niger was a 8-gun (later 14-gun) screw sloop launched on 18 November 1846 from Woolwich Dockyard. She had been intended as a sailing sloop but her design was lengthened to fit a steam engine, and she was fitted with screw propulsion at Deptford Dockyard in 1847-48 prior to completion. She was reclassified as a corvette in 1852.