A glossary of mining and metallurgical terms

A GLOSSARY OF MINING AND METALLURGICAL TERMS. 67
Poll-pick. A pk-l: with a head for breakin*^ away hard partinys
in coal-seams or knocking down rock already seamed by blading.
Polroz (pronounced Polrose), CoRN. The pit underneath a water-
wheel.
Ponsard furnace. A furnace in which the escaping combustion-
gases, passing through tubular flues, heat the incoming air continu-
ously through the flue-walls.
Poppet-heach', Corn. A timber frame over a shaft to carry the
hoisting pulley.
Post. 1. A pillar of coal or ore. 2. An upright timber.
Post furnace. See Pernot furnace.
Post-and-stall. A mode of working coal, in which so much is
left as pillar and so much is taken away, forming rooms and thir-
lings. The method is called also bord-and-pillar, pillar-and-breast,
etc.
Potstone. Compact steatite.
Potter's clay and Pipe-clay. Pure plastic clay, free from iron, and
consequently white after burning.
Poicer-drill. See Rock-drill.
Precious metals. See Noble metals. .
Precipitation process. The treatment of lead ores by direct fusion
with metallic iron or slags or ores rich in iron; performed generally
in a shaftfurnace, rarely in a reverberatory. Often combined with
the roasting and reduction process.
Prian, Corn. Soft white clay.
Pricker. See Needle.
Prill, Corn. 1. The best ore after cobbing. 2. See Button.
Pringap. The distance between two mining possessions in Der-
byshire.
Produce. 1. The marketable ores or minerals produced by min-
ing and dressing. 2. Corn. The amount of fine copper in one hun-
dred parts of ore.
Producer. See Gas-producer.
Prop. A timber set to carry a roof or other weight acting by
compression in the direction of the axis.
Prop-crib timbering. Shaft-timbering with cribs kept at the
proper distance apart by meajis of props.
Prospecting. Searching for new deposits; also, preliminary ex-
plorations to test the value of lodes or placers. The prospect is good
or bad.