The external stonework was replaced between 1850 and 1870 in a restoration by J. S. Crowther, who also replaced the internal stonework of the nave walls and arcades with exact reproductions of the originals. The west tower was heightened in 1868 by J.P. Holden, who also replaced its external stonework. Basil Champneys added the vestry, canons' library and western porches in 1898; while Percy Worthington provided further accommodation to the South-east, originally as a choir school, but subsequently converted to offices. Consequently, the cathedral gives the impression of being a 19th-century structure. To accommodate upgrading work on the cathedral's heating system, in 2013 a temporary wooden cathedral was built on Victoria Street to allow worship to take place. Furniture Angel minstrels The nave roof brackets are supported by fourteen angel sculptures, each playing a different late medieval instrument, believed to be the gift of James Stanley II. South side (from the east): Portative organ, harp, psaltery (plucked), dulcimer (played with hammers), lute, fithele, hurdy-gurdy North side (from the east): clavicymbal, trumpet, shawm, Scots pipes (mouth-blown), Irish pipes (bellows-blown), recorder, tabor It is supposed that, in the 19th century restoration of the nave, the clavicymbal and organ were inadvertently transposed; as otherwise the south side has stringed instruments, and the north side mostly wind instruments. Only the organ presents an instrument that would commonly have been heard in church in the early 16th century; the other instruments would have been more typically used to accompany secular songs and dances. All these instruments, however, might well have been heard accompanying mystery play performances in the street, and in popular religious processions. Misericords The cathedral has thirty 16th-century misericords, considered to be among the finest in Europe. They are similar in style to those at Ripon Cathedral and Beverley Minster. Although Manchester's are of a later date, they were probably carved by the same school at Ripon. One of the most notable is N-08, the earliest known depiction of backgammon in the UK. Stained glass All the Victorian stained glass was destroyed during the Manchester Blitz in 1940. Until the late 1960s, only two windows had been replaced, notably the Fire Window by Margaret Traherne (1966). The dean and chapter commissioned Tony Hollaway to prepare a scheme for reglazing the cathedral, with priority to the five western windows: St George (1973), St Denys (1976), St Mary (1980), The Creation (1991) and The Apocalypse