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HMS Erebus, in company with HMS Terror, was lost on the ill-fated 1845 Franklin Expedition to the Arctic. They were previously in company on the successful Antarctic expedition of 1839–43 under Sir James Clark Ross and Francis Crozier.
For the 1845 expedition, each ship was equipped with an auxiliary engine driving a propeller. In each case the power was provided by a secondhand railway locomotive, installed transversely. The modification to the ships, and the changes made to equip them for the arduous service, are well-described in a 2011 Newcomen Society Paper. See also Peter Carney's blog 'Erebus & Terror Files' here for discussion on origin of engines.
The engines were presumably intended for manouvering and emergency use in the ice fields. The coal supply was limited to 12 tons, and the boilers were not suited to saline feed water.