Braithwaite Lead Smelt Mill This chimney, the short length of horizontal flue and some foundations, are all that remain of a small lead smelt mill. Locally mined lead ore was converted into metallic lead in a furnace called and ore hearth. Peat, dried wood and coal were the fuel for this smelting process. An air blast, to raise the temperature of the furnace, came from bellows powered by a large waterwheel. Poisonous fumes were taken away by the flue and chimney. A working shift of 12-15 hours produced about one ton of lead. The mill was last used in the 1870s.