Butterley Company correspondence file with the Derbyshire and Nottinghamshire Power Company on the supply of electric power to its collieries Including plan of proposed supply to Ollerton Colliery, 1942, accounts of power costs, 1942, and loose plan of overhead lines and underground cables connecting the Butterley Works, Colliery Offices at Ironville, Waingroves Brick Works, Waingroves Hall and the collieries of Hartshay, Britain, Ford's, Salterwood, Marehay, Denby Hall, Ripley, Western, Ormonde and New Langley Jun 1917-Jan 1944