Butterley Company correspondence file on the sinking of Kirkby Colliery to lower seams Including on tenders, with details of sinking gear for Ormonde Colliery, plan of proposed arrangement of doors for deepening shaft at Kirkby Colliery, Sep 1911, specification for sinking a shaft from the Top Hard and Blackshale or Silkstone Seams at Kirkby Colliery, section of strata sunk through the Top Hard and Silkstone Seams at Bentinck Colliery, and schedule of wages to be paid to contractor's men when employed by the Butterley Company May 1911-Jun 1913