Engraving depicting a fireman opening the door of the ventilating furnace at the bottom of a coal pit. This furnace would be connected to a shaft which acted as a chimney and the hot air from the fire escaped up the shaft; drawing air down either the main shaft or other special ventilation shafts by means of the draught it created. In this way the otherwise still air at the bottom of the mine was renewed and the danger of a build-up of fire-damp lessened. Dated 19th century 01/02/1877