_Basket._ The outer casing or netting of a foot valve which forms a strainer on a pump suction pipe. _Bends._ In pipe, the turns in lines of pipe may be angle bends (called “elbows“) or offset bends. _Bibb-cock._ This is a plug cock having an elbow or curved outlet directing the outflow downward. [Illustration: BIBB-COCK.] [Illustration: BIBB COMPRESSION.] _Bibb Compression._ A bibb-cock having in place of the plug a stem with thread and handle to open by unscrewing; the valve contains fibrous packing and is made tight by compression. _Bonnets._ These are covers for the opening into valve chambers of pumps. _Boss._ Any round protuberance on a casting to support a stud or to strengthen a steam chest cover, etc. _Bushing._ A nut used in pipe fitting, threaded inside and outside to accommodate two sizes of pipe. [Illustration: BUSHING.] _Check Valve._ A valve through which fluid can pass only in one direction; used between pump and reservoir or boiler. See swing-check. _Check-Nut._ A second nut screwed against the first to hold it firmly in place; also called a lock-nut. _Circulating Pump._ A pump arranged to force water through the tubes of a surface condenser. Frequently a _centrifugal pump_ is used as a circulating pump. _Clack Valve._ This takes its name from the noise it makes in seating; it is made of leather with a metal weight on top, the leather forming a hinge on one side. In the cut the lifted valve is the “clack.” [Illustration: CLACK VALVE.] _Clearance._ The space or distance by which one piece clears another. The space between piston and cylinder head. _Cock._ A faucet or device for opening or closing a passage. The illustration shows a straight-way cock. [Illustration: PLAIN COCK.] _Column Pipe._ A column may be considered as a beam set on end and a column pipe may, similarly, be defined as a pipe set on end. The pipes leading from a water column to boiler. _Compression Gauge Cock._ A device having a threaded steam spindle and made tight by compression. The figure exhibits an outside view of a locomotive compression gauge cock. [Illustration: COMPRESSION GAUGE COCK.] _Corrosion._ Rusting or wasting away of the surfaces of metals. _Crow._ A claw with a screw attached to support and feed a drill brace for drilling holes in pipes. _Cup Leather Packing._ The leather packing used around the ram of a press. In section it resembles a cup—hence the name. [Illustration: CUP LEATHER PACKING.] _Cushioning._ This term applied to the operation of pumps, etc., is the imprisoning of steam, water or air between the piston and cylinder head to prevent the piston from impact with the head. _Cylinder Head or Cylinder Cover._ A plate which encloses or covers the end of a cylinder. _Dead end of a pipe._ The closed end of a pipe or system of pipes.