Description of a Sounding Board in Attercliffe Church, invented by the Rev. John Blackburn, Minister of Attercliffe cum Darnall, Sheffield Read June 5 1828 [Phil Trans 1828 p 361] The church at Attercliffe had long been remarkable for the difficulty and indistinctness with which a voice from the pulpit was heard. These defects have been completely remedied by the erection of a concave sounding board, having the form resulting from half a revolution of one branch of a parabola on