Face. The end wall at the inner or working extremity of any excavation in or into the mines. In bituminous mines the vertical plane of cleavage at right angles to the butt cleavage.
Fan. A machine used to force a ventilating current of air through a mine.
Fault. A displacement of strata in which the measures on one side of a fissure are pushed up above the corresponding measures on the other side.
Fire-board. A blackboard, fixed near the main entrance of a mine, on which the fire boss indicates each morning the amount and location of dangerous gases.
Fire boss. An official whose duty it is to examine the workings for accumulations of dangerous gases.
[Fire clay.] The geological formation which is usually found immediately underlying a coal bed.
Fire damp. Light carbureted hydrogen.
Fissure. A separation of rock or coal across the measures.
Floor. The upper surface of the stratum immediately underlying a coal seam.