Engine House, Part of Killifreth Mine, at SW 737442 SW

The engine house, part of Killifreth Mine, is a mid to late 19th-century ruin featuring an attached chimney. It is constructed from killas rubble with granite quoins, jambstones, and bonding stones, along with brick arches. The round rubble chimney has a brick upper stage on the south side. The building has a gable end to the west and a rectangular, single-cell plan with the round chimney attached to the west of the south wall. It originally stood three storeys tall but is now floorless. The east side has a bob wall, and all openings feature round arches, including holes for second-floor beams that were originally cantilevered over the shaft. The walling remains intact, although the roof and the framed, weatherboarded upper part of the bob wall are missing. The chimney is topped with a corbelled brick collar and cornice. The engine house is part of the development scheme of Killifreth Mine and Great Wheal Busy, which began sinking shafts to greater depths in 1865.