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Glossary of Bridge Terminology



Pacific Type Locomotive: A locomotive having four pilot wheels, six driving wheels, and two trailers.

Pack: To arrange eye-bars on a truss pin. To insert some pliable or elastic material in a stuffing box around a moving rod so as to produce a water-tight, air-tight, or steam-tight connection.

Packing: The arrangement of the component parts of a member. The material used in packing a piston rod, etc. The arrangement of bars and other members on a pin.

Packing-block: A small member, generally of wood, used to retain the parts of a composite member in their proper relative positions.

Packing Bolt: A bolt which holds together the several parts of a composite member.

Packing Box: Same as "Stuffing Box." -- A device for securing a steam-tight, air-tight, or water-tight joint about a movable rod. It consists of two parts or glands held together by bolts and so arranged that packing of some kind can be inserted between the glands and compressed, by means of tightening the nuts on the bolts, against the movable rod.

Packing Diagram: A drawing showing the arrangement or packing of the parts of a composite member or the disposition of several members meeting at a panel point. Refers generally to arranging truss members on pins in pin-connected structures.

Packing-pieces: Short pieces, inserted between two others which are riveted or bolted together, to prevent their coming in contact with each other.

Packing Ring: An elastic metallic ring used for packing the piston of an engine.

Packing Spools: Same as "Separators." -- Small, cast-iron, wheel-like blocks, used to separate stringers in trestles, or the timbers that form the chord sections of a Howe truss bridge.

Packing Washer: A washer used between timbers to provide an open space between them when they are drawn together and bolted. The object in using them is to permit of a circulation of air between the sticks.

Pæne Hammer: Same as "Peen Hammer."

Paint: A mixture of pigment with a vehicle intended to be spread in thin coats on a surface for its protection, or its decoration, or both.

Paint-brush: Any brush used for applying paint.

Paint-skins: The residue in paint formed by the evaporation of the oil. Used for filling small voids in metalwork before applying the paint.

Painter's-torch: A torch burning gasoline or gas under pressure produced by forcing air into the reservoir. Used for burning off old paint.

Pale Brick: Under-burned brick and, therefore, lighter in color than the fully-burned brick.

Pall: A dog in a ratchet for preventing backward motion.

Pallet: A board on which green bricks are carried to the drying place. A cast-iron tool with chilled faces; used in forging. Also same as "Pall."

Palmer Truss: Same as "Burr Truss." -- A timber truss with counter-struts inserted throughout the entire length giving very great rigidity.

Pane Hammer: Same as "Peen Hammer."

Panel: That portion of a truss between adjacent panel-points lying in the same chord.

Panel Length: The distance between two adjacent panel points in the same chord of a truss.

Panel Load: Same as "Apex Load." -- The load at a panel point of a truss.

Panel-point: The point at which the axis of a principal web member intersects the axis of a chord of a truss.

Pannikins: Small pans or cups.

Pantograph: An instrument for the mechanical copying of engravings, diagrams, plans, etc., either to an enlarged or to a reduced scale. It consists essentially of four sticks pivoted so as to form a parallelogram with a fixed pivot at one end of the group, a tracing point at the other end, and a pencil at the intermediate apex.

Paper: A material composed of vegetable fibres made into thin sheets, used to write or draw on, etc.

Parabola: A plane curve such that the distance of every point in it from a fixed point, called the focus, is equal to the distance of the same point from a fixed straight line, called the directrix. Also the curve formed by the intersection of a secant plane with a cone when parallel to an element of the said cone. Also defined by the equation:


Parabolic Chord: A chord of a truss in which the panel points lie on the arc of a parabola.

Parabolic Curve: Same as a "Parabola."

Parabolic Formula: Any formula having the form of:

Parabolic Truss: A bow-string truss having the upper chord joints lying in a parabola. See Fig. 22s.

Fig. 22s

Paraffine: A whitish, waxy substance obtained by the dry distillation of wood, peat, bituminous coal, wax, crude petroleum, etc. A saturated hydrocarbon derived from methane.

Parallel: A condition of being everywhere equidistant, not intersecting. Applied to lines and planes.

Parallel-ruler: A draftsman's instrument for drawing parallel lines, consisting of two similar rulers connected by equal, parallel links pivoted at their ends, enabling the edges of the rulers to be spread apart a varying distance.

Parallelogram: A four-sided geometrical figure having the opposite sides parallel and equal.

Parallelogram of Forces: A name given to a method of determining the resultant of two forces, acting in the same plane, by constructing a parallelogram having sides equal and parallel respectively to the forces; whereupon, the diagonal of the parallelogram will represent in magnitude and direction their resultant.

Parallelopiped: A prism having parallelograms for bases.

Parapet or Parapet Wall: A low wall or barrier placed on top of an abutment to hold back the earth from encroaching on the end of the span.

Parapet Wall: Same as "Parapet."

Parcel: To wrap canvass or rags around a rope.

Parker Cement: Same as "Parker's Cement."

Parker Truss: A name sometimes used for the Pratt Truss when the upper chord is polygonal. See Fig. 22b.

Fig. 22b

Parker's Cement: A name used in England for natural, or Roman cement.

Partial Splice: A splice that is capable of developing only a part of the resistance of a member.

Parting Pulley: Same as a "Split Pulley." -- A pulley made of two parts, held together by bolts, and so arranged that it can be removed from its shaft without disturbing the latter.

Party of the First Part: A legal term for designating one of the parties executing a contract, usually the purchaser.

Party of the Second Part: A legal term for designating one of the parties executing a contract, usually the seller.

Passenger Locomotive: A locomotive having large drivers used for hauling passenger cars.

Passometer: An instrument for registering the number of steps taken by a pedestrian. Called also a "Pedometer."

Paste Lime or Putty Lime: A thick mixture of lime and water.

Pat: A small, flat cake of cement mortar with the edges thinned out; used in cement testing to determine its soundness or freedom from cracking.

Patent Hammer: A stone-mason's hammer having knife-like ridges on its face, used for dressing stone.

Patent Hammered Dressing: A form of stone facing made with a patent hammer.

Patten: The base of a column or pillar. The sole for the foundation of a wall.

Pattern: A model made of wood to duplicate the desired object. It is used to form the cavity in a mould into which the molten metal is afterward poured.

Pattern Shop: A wood-working shop in which patterns are made.

Pavement: A surface covering for a roadway.

Paving: Regularly placed stone, brick, or wood blocks forming a floor.

Paving Brick: Any hard brick used in paving.

Pawl: A short bar pivoted at one end and engaging a toothed wheel at the other, thereby preventing a backward rotation. Also spelled "Pall."

Pawls of a Capstan: The stops on the bottom of a capstan to prevent backward motion.

Pay: To cover a surface with tar or pitch, etc.

Pay-out: To slacken or let out rope.

Peak: A projecting point; a cusp in a curve.

Pean Hammer Dressing: A form of stone facing made with a peen hammer.

Pean Hammer: Same as "Peen Hammer."

Peavey: A form of cant-hook with a spike in the end of the handle next to the hook; used by timber men.

Pecky Tie: A tie made from a cypress tree that is affected with a fungous disease, known locally as peck.

Pedestal: A footing for a tower post. A bridge shoe. See also "Shoe."

Pedestal Block: Same as "Base Casting" (A steel or iron casting upon which the bridge-shoe rests). Also a stone block to support a column.

Pedestal Cap: A block of stone or concrete placed on top of a footing to carry a loaded column.

Pedestal Pier: A combination of two pedestals on a common base, but having separate tops.

Pedestal Pile: A patented pile formed by driving a steel shell into the ground to the required depth, putting in small quantities of concrete, and hammering them down so as to force the concrete into the earth beyond the point of the shell; thus enlarging the end and greatly increasing the bearing area. The shell is afterward withdrawn gradually, as the hole that it made is filled with concrete. If the shell were left in, the method would be far more satisfactory; as the shaft of the pile is liable to be seriously imperfect. Sometimes dubbed a club-footed pile.

Pedestal Strut: A strut connecting and bracing two pedestals.

Pedestrian-way: That part of a bridge floor set aside for pedestrians. A footwalk.

Pediment: The triangular space in the face of a wall that is included between the two sloping sides of the roof and a line joining the eaves.

Pedometer: An instrument for numbering the paces of a person walking and thereby permitting an estimate to be made of the distance covered. Called also a " Passometer."

Peen: A form of hammer head or similar tool which terminates in some special shape, other than the ordinary flat face; such as an edge shape or rounded, or a coneshaped, hemispherical, or otherwise modified point. To treat by striking regularly all over with the peen of a hammer. Also spelled "Pane," "Pean," "Pæne," "Pein " and "Pene."

Peen Hammer: A hammer having a peen on one. or both faces.

Peg: A term sometimes used for a surveyor's stake. A small stick driven flush or nearly flush with the ground, to hold the rod upon when levelling. To fasten anything to the ground with pegs.

Pegram Truss: A form of truss having the panel points of the upper chord lying in the arc of a circle and inclined web members. See Fig. 22cc.

Fig. 22cc

Pein Hammer: Same as "Peen Hammer."

Pendulum: Anything that hangs down from a point of attachment and is free to swing.

Pendulum Pile Driver: A driver in which the leads are arranged to swing like a pendulum so that a pile can be driven at an inclination to the vertical.

Pene: Same as "Peen."

Pene Hammer: Same as "Peen Hammer."

Penetration: A term used in connection with piles to denote the depth to which a pile has been driven in the soil. Also used in connection with the testing of asphalts and asphaltic fluxes to determine viscosity. It is expressed in hundredths of a centimeter to which a standard needle penetrates the material.

Penetration of Pile: Same as "Penetration."

Pennsylvania Truss: A Petit truss with an inclined chord. See Figs. 22e and 22f.

Fig. 22eFig. 22f

Per Cent of Heart: The ratio of the area of heart wood to the entire area of the section of timber.

Percentage of Voids: The ratio of the unfilled space to the total space in an aggregate, expressed as a percentage.

Perch: A stone mason's unit of quantity varying in value from 16 1/2 cubic feet to 24 3/4 cubic feet, depending upon local usage. The use of this unit should be discouraged as far as possible, as its indefiniteness leads to uncertainty and confusion.

Percolation: The process of straining or filtering a substance. The passing of water or other fluid through the pores of a solid.

Percussion: The act of striking one body against another; the shock produced by collision.

Percussion Cap: A small copper cap, or cup, containing fulminating powder which explodes when struck a sharp blow.

Percussion Drill: A solid drill-rod having an action like that of a churn drill.

Percussion Fuse: A detonating fuse which is exploded by impact.

Perimeter: The outer boundary of a figure.

Period of Vibration: The time required for the vibrating particle to make one complete movement back and forth.

Periodic Curve: A curve which represents a repeating, or periodic function.

Periodic Deposit: A payment made at regular intervals to a sinking fund.

Periphery: The boundary line of a closed figure, same as "Perimeter."

Periphery Lines: Lines forming the periphery of an object or figure.

Permanent Load: Same as "Dead Load." -- The weight of all the parts of a bridge itself and anything that may remain upon it for any length of time, such as tracks, water mains, telephone and telegraph lines, snow, dirt, moisture, etc.

Permanent Set: Same as "Final Set" in cement. Also the residual deformation in a member when the load is removed.

Permeability: The quality or condition of being permeable, or capable of being traversed by liquids or gases.

Perspective: The art of representing solid objects on a flat surface so that, when they are viewed, the eye is affected in the same manner as it would be by viewing the objects themselves from a given point.

Perspective Drawing: A drawing showing in perspective any structure. See also "Perspective."

Pestle: A rounded, pear-shaped tool with a handle, used for the grinding and pulverizing of materials in a mortar.

Pet Cock: A small cock used for draining pipes, etc.

Petit Truss: A modified form of the Pratt truss having subdiagonals. See Figs. 22c, 22d, 22e, and 22f.

Fig. 22cFig. 22d
Fig. 22eFig. 22f

Philadelphia Rod: A level rod having two sliding parts and a movable target. The graduations are painted on as well as the numbers; and the rod can, therefore, be read at considerable distances without setting the target. Where great precision is not required, this rod is well adapted for rapid work.

Phoenix Column: A fabricated column made up of rolled steel segments riveted together forming a circular section with either four or six exterior projections through which the rivets pass.

Phosphor-bronze: An alloy of copper and tin containing from one-half to one per cent of phosphorus. It makes hard castings and has an ultimate tensile strength varying from 50,000 to 100,000 pounds per square inch.

Phosphorus: A chemical element having a strong affinity for oxygen, encountered as an impurity in iron ores. Its presence causes cold shortness in steel.

Pick: A hand-tool for excavating hard soils, consisting of a heavy curved bar, having one end pointed and the other wedge-shaped, and having a hole in the enlarged central portion for the insertion of a handle.

Pick Axe: A hand tool similar to a pick, but having broader blades set at right angles to each other.

Pick-pole: A small pike pole without the hook.

Pick-up Bar: A hand bar with two prongs riveted on one end; used, after the concrete is poured, for picking up and shaking the reinforcing steel lying on the bottom of the form.

Picked Dressing: A facing of stonework made by a mason's pick in reducing the surface to an approximate plane.

[Picket man]: As used in Waddell's "De Pontibus" in connection with triangulation, appears to be equivalent to the surveying term "chainman or chain man", the person laying out the surveying chain under direction of the surveyor.

Pickling: The treatment of iron or steel with dilute acids for the purpose of obtaining a clean surface by removing the scale (oxide).

Picture Drawing: A general drawing attempting to show as a picture the actual way the structure would look.

Pier: A structure, usually composed of masonry, which is used to transmit the loads from a bridge superstructure to the foundation.

Pier Footing: A footing under a pier.

Piercing: Producing a hole in a body by forcing a pointed instrument through it, the displaced material being forced into the body. Distinct from punching.

Pierre-perdue: Lost stone. Rough stones thrown into the water and left to find their own slope. Used for pier and wharf protection.

Pig: The name given to cast iron which is drawn direct from the blast furnace and run, for convenience of later handling and transporting, into shapes known as pigs.

Pig Iron: A term applied to cast iron when first run from the blast furnace into moulds, giving small-size bars convenient for handling.

Pig-washing: A process of refining or removing much of the phosphorus and silicon, in which the molten pig iron is treated with fused oxides of iron (and in some cases is mixed with oxides of manganese) in a reverberatory furnace.

Pigment: The fine, solid particles used in the preparation of paint, and substantially insoluble in the vehicle.

Pike-pole: A long, slender hand-pole with a steel point and hook at one end, used for handling timber.

Pilaster: A thin, flat projection from the face of a wall made to resemble a column, for ornamental purposes.

Pile: A long, heavy post or pole of timber, concrete, or steel driven into the ground to compact the soil, to shut out water, to carry a vertical load, or to resist a horizontal force.

Pile Band: An iron band put around the head of a pile to keep it from splitting and brooming during driving.

Pile Bent: A bent having piles for supporting posts.

Pile Bridge: A bridge consisting of pile bents and timber caps, stringers and bracing.

Pile Cap: An iron casting shaped to fit over the head of a pile, and having a conical recess on top to carry a tough wooden block which receives the blows of the hammer. Jaws are provided on the sides of the cap to engage the leads. The function of the cap is to distribute the blow of the hammer and to prevent the brooming of the pile head. Also a timber cap across a row of piles.

Pile-cluster: Several piles driven close together forming a group or cluster.

Pile Disk: The large, flat, circular casting which forms the footing of a disk pile.

Pile Driver: A machine for sinking or driving piles.

Pile-Driver Hammer, or Pile Hammer: A drop hammer or a steam hammer used in driving piles.

Pile Ferrule: Same as "Pile Band."

Pile Follower: Same as "Follower." -- A temporary piece of pile or timber set above a pile that is to be driven below the leads of the pile-driver.

Pile Foundation: A foundation formed in soft soil by driving a group of piles to a depth which will give them the requisite bearing capacity to carry the load.

Pile Hammer: Same as "Pile-Driver Hammer."

Pile Head: The top of the pile as driven. Also applied to the short pieces sawn off the tops of piles to bring them to a uniform elevation; sometimes called cut off ends.

Pile Line: The rope or cable used to pick up a pile and land it in place between the leads of a pile driver.

Pile Pier: A pier formed by driving a cluster of piles and capping them with heavy timbers in the form of a grillage to carry the shoes of the span.

Pile Planks: Planks driven like piles.

Pile Ring: Same as "Pile Band."

Pile Ring Puller: A device for pulling a pile ring from the head of a pile after it has been driven. Usually a cant hook is employed for this purpose.

Pile Shoe: A conical iron point with projecting prongs, by means of which it is fastened to the end of the pile before driving.

Pile Splice: The joining of two piles, end on end, by means of wooden scabs or iron plates bolted to them or by means of a cylindrical steel shell slipped over and bolted to the ends.

Pile Trestle: A trestle having pile bents for supporting the deck.

Pile Work: A general term covering pile construction.

Piling: A general term for a number of piles taken together.

Pillar: A post or column.

Pillaring: The act of supplying with pillars. A system of pillars.

Pillow: Same as "Pillow Block."

Pillow Block: A type of journal bearing having a removable cap. Also called a plummer block.

Pillow Joint: Same as "Ball and Socket Joint."

Pilot Nut: A round nut, having one end tapering, which is screwed on a pin in order that it may be pushed through the eyes of the several eye-bars and other members meeting at a panel point. After the pin is in place, the pilot nut is removed, and a Lomas nut is screwed on in its place.

Pilot Punch: A machine punch in which the cutting tool is provided with a small central plug which fits into a hole in the material and acts as a guide for punching the larger hole.

Pin: A round bar of steel used for connecting members of a truss. Also any round bar which fills a hole. A pivot.

Pin Bearing: A type of end support for a girder or a truss in which a pin is used to transfer the load to the shoe.

Pin-bolt: A bridge pin having a head and a nut.

Pin-connected: A term applied to the method of joining the members of a truss by pins instead of using riveted connections.

Pin-connected Truss: Any truss having its main members joined by pins.

Pin Drill: A drill for boring pin holes in truss members.

Pin-end or Pin-ended: The condition of having a pin connection at the end of a member.

Pin-end Column: A column that is free to turn at either end about a pin.

Pin Filler: A ring placed on a pin between connecting members to keep them in position.

Pin Joint: Any joint in which the parts are held together by a pin.

Pin Knot: A sound knot in timber not over one-half inch in diameter.

Pin Maul: A bridge erector's maul, having one end pointed with a long taper for entering rivet holes and the other end flat for hammering.

Pin Metal: The metal called for in the specifications, from which pins may be made.

Pin Nut: A special flat nut used on truss pins.

Pin Pilot: Same as "Pilot Nut."

Pin Plate: A plate riveted to the outside of the end of a member to give additional strength and greater bearing on the pin.

Pinch Bar: A form of crowbar with a short projection like a heel, or fulcrum, at the end; used to pry forward heavy objects.

Pine: A species of the conifers, or evergreen trees.

Pinhole: A hole in a member through which the pin passes and connects with other members.

Pinhole Cutter: An apparatus for cutting pinholes in the chords or web members of a truss.

Pinion: Any toothed gear of small size as compared with the gear which it engages.

Pinion Shaft: A shaft carrying a pinion for transmitting motion.

Pinner: In masonry construction, a small stone used to prop up a larger stone. The process involved (a most objectionable one) is termed "Pinning-up" or "Underpinning." It causes the pressure on the block to be thrown on a few points instead of being equally distributed over it, and exposes the stone to cracking.

Pinny: An English term for a metal which contains enclosed particles of metal harder than the rest.

Pipe: A tube, a conduit, a hollow metallic cylinder.

Pipe Clamp: A vise for holding pipes.

Pipe Coupling: A threaded sleeve into which are screwed the ends of the two pieces of pipe to be coupled.

Pipe Cutter: A plumber's tool consisting of two beveled edged steel cutting wheels mounted in an adjustable jaw that partly encircles the pipe. A rotation of the tool by a suitable handle and the closing up of the jaws severs the pipe.

Pipe Die: A tool for cutting threads on a pipe.

Pipe (in metal): A defect in an ingot due to the metal cooling from the outside inward, and the resulting contraction leaving a cavity near the center at the top.

Pipe in Steel: A defect in the top of an ingot due to the shrinking of metal while cooling, thus leaving a cavity.

Pipe Joint: The joint between two pieces of pipe.

Pipe Line: A series of pipes connected up to form one system.

Pipe Rail: A handrail, used on bridges, composed of wrought-iron pipe and fittings.

Pipe Tongs: A hand tool for grasping and turning pipes, consisting of two specially bent bars forming a jaw near one end, where it works on a pivot, and having the other end fashioned into handles.

Pipe Union: A form of pipe connection, employed for making a closure in a system of pipes. Its essential features are two end pieces which screw on the pipe ends and fit into each other, also an outer ring or sleeve having an inner shoulder at one side, which bears against one of the end pieces as the ring is turned and screwed on the other end piece, thus pulling the two ends together.

Pipe Vise: A vise with jaws notched to receive a pipe.

Pipe Wrench: A wrench having its jaws shaped and adapted for holding a pipe.

Piping: A general term used to denote a group or system of pipes taken collectively. A defect in rolled steel due to cavities that were formed as the ingot cooled. See "Pipe."

Piston: A movable disk-like piece fitted to fill the cross-section of a pipe or cylinder and capable of a backward and forward motion.

Piston-head: Same as "Piston."

Piston Rod: A steel rod connecting the piston with the cross-head of an engine.

Piston Valve: A reciprocating valve, having the form of a piston working in a tubular passage, which opens and closes successively the ports of a cylinder of a steam engine.

Pit: The effect of steam, water, or gas on metal causing small holes to appear on the surface. A hole in the ground.

Pit Planer: A type of planer located in a pit so that large work may be placed thereon.

Pit Saw: A large hand saw worked vertically by two men, one of whom (the pitman) stands in a pit.

Pitch: The distance measured along the pitch line from center to center of teeth on a cogwheel. The slope of a roof. The distance from center to center of rivets. The distance between the adjacent threads of a screw. The degree of descent of a declivity. A thick, tenacious, black or dark-brown substance obtained by boiling down tar. The resinous sap that exudes from pines. Bitumen or asphaltum, especially when unrefined. To smear, cover, or treat with pitch.

Pitch Circle: That circle of a gear, passing through the teeth, having a diameter measures the velocity ratio of the gear in respect to another which engages it.

Pitch Line: Same as "Pitch Circle."

Pitch of Rivets: The distance between the centres of adjacent rivets in the same line.

Pitch of Thread: The distance between adjacent threads of a screw.

Pitch Streak: A well-defined accumulation of pitch at one point in a piece of timber.

Pitch Wheel: One of a pair of toothed wheels working together.

Pitched Dressing or Pitched Faced Dressing: In stonework, a finish dressed to neat lines or edges with a pitching chisel.

Pitching Chisel: A stone mason's chisel for making a well-defined edge to the face of a stone block.

Pitching Tool: A hand tool used by masons for cutting the arris on a stone.

Pith Knot: A sound knot in timber with a pith hole not more than one-quarter inch in diameter.

Pitman: A rod which connects a rotating with a reciprocating part in an engine or other machine.; also one of two operators of a "Pit Saw."

Pivot: A pin or shaft on which any object turns.

Pivot Gearing: A system of gearing so divided as to admit of shifting the axis of the drive so that the machine can be set in any direction with relation to the power.

Pivot Pier: The pier supporting a swing span and upon which it turns.

Pivot Span: A span in a bridge that revolves; called also "draw-span" and "swing-span."

Pivoted: Arranged to work on a pivot.

Plain Dressing: In stonework, a facing rubbed smooth to remove tool marks.

Plain Hammer: Same as an "Engineer's Hammer." -- Usually a two faced cylindrical hand hammer, though some times having a cylindrical poll and a triangular peen.

Plain Rod: A level rod made of one piece of wood with figures on one side and graduated in feet and decimal parts thereof.

Plan: The general layout of a structure; the horizontal projection of an object or structure.

Plane: A surface generated by a straight line moving parallel to its original position.

Plane Curve: A curve lying in one plane.

Plane of Gravity: Any vertical plane passing through the centre of gravity of a body.

Plane of Rupture: The plane along which failure occurs.

Plane of Symmetry: A plane about which the parts of a figure or a body are symmetrically disposed.

Plane Table: A surveyor's instrument consisting of a drawing board mounted on a tripod, and having on its upper surface a movable straight, edge arranged with sight vanes or a telescope.

Planed Finish: A finish produced by planing.

Planed Joint: A joint in which the contact surfaces have been planed or the exterior surfaces finished in a machine.

Planer: A machine tool for planing metal.

Planimeter: An instrument for measuring a plane area by carrying a tracer around its periphery and noting the change of reading on the index of the rolling wheel.

Planish: To polish metals by rubbing with a hard, smooth tool.

Plank: A piece of lumber thicker than a board; usually measures from two to four inches in thickness and from six inches upward in width.

Plank Pile: A pile built of planks.

Plant: The fixtures, machinery, tools, apparatus, etc. used to carry on any manufacturing or erecting business.

Plate: A flat piece of metal or wood.

Plate Gauge: An instrument for measuring the thickness of metal plates.

Plate Girder: A girder built of structural plates and angles.

Plate Washer: Any plate used as a washer.

Play: A looseness in a joint or in parts of a machine or structure permitting some freedom of motion.

Plenum Process: The pneumatic process for sinking piers. See "Pneumatic Process."

Pliability: The capacity of a body to change its form, temporarily, under different stresses.

Pliers: A hand tool for manipulating and cutting wires.

Plinth: The square block at the base of a column or pedestal.

Plow Hammer: Same as "Plain Hammer."

Plug: A small block of any material used to stop a hole. Also a wedge-shaped piece of steel used to drive between the feathers in the "Plug and Feather" method of splitting or quarrying stone.

Plug-and-feather Method: A method of breaking a stone slab by drilling holes, a few inches apart, to a convenient depth less than the thickness of the stone; then inserting steel feathers in each hole and driving a long slim wedge, or plug, between them. This causes an expansion and a cracking along the line of holes.

Plug and Feathers: A combination of two feathers and a tapering plug inserted in a hole in a rock, the plug being driven with a hammer so that great lateral pressure is produced and the rock broken.

Plug Cock: A cock or a faucet which has a tapered plug, with a transverse hole, fitting into a prepared seat in a pipe.

Plugged: Stopped up with a plug.

Plugged Rivet: Same as "Calked Rivet." -- A rivet which has not been properly driven so as to fit tightly in the hole, but to which a seeming tightness has been given by turning the edge of the head under with a cold cut or similar tool.

Plumb: Vertical.

Plumb-bob: A conical piece of metal attached at its large end to a cord. Used to place an object in a vertical position or directly over some desired point.

Plumb Line: A vertical line. A tool consisting of a weight suspended by a cord, used for plumbing members of a structure, or for setting a surveying instrument over a point.

Plumb Pile: A pile driven vertically, usually one of the inside piles of a bent.

Plumb Post: A vertical post, usually applied to timber construction.

Plumbago: Same as "Graphite."

Plummer Block: Same as "Pillow Block."

Plummet: A ball of metal attached to the end of a line used in sounding the depth of water.

Plunger: The piston in a pump.

Ply: A term used to designate the number of layers in a fabric, as a three-ply hose or a four-ply belt.

Pneumatic: Pertaining to air, processes using air, or machines worked by compressed air.

Pneumatic Caisson: A bottomless box or caisson, surmounted by a crib or shaft, into which air is pumped so as to drive out the water and thus permit workmen to enter for the purpose of excavating the bottom and sinking the mass to the required depth.

Pneumatic Car: A car running on rails and driven by compressed air motors.

Pneumatic-clippers: Shears or clippers operated by compressed air.

Pneumatic Cutter: A cutter operated by compressed air.

Pneumatic-cylinder: The cylinder of a pier sunk by the pneumatic process. The cylinder in an air-compressor in which the air is compressed.

Pneumatic Drill: Any drill operated by air.

Pneumatic Elevator: A hoisting apparatus operated by compressed air.

Pneumatic Excavator: An excavator operated by compressed air.

Pneumatic Hammer: A hammer operated by compressed air.

Pneumatic Hoist: Same as "Air Hoist." -- A hoisting device, usually consisting of a cylinder, piston, and piston-rod, operated by compressed air.

Pneumatic Pier: A pier sunk by the pneumatic process.

Pneumatic Pile: A small diameter steel cylinder sunk by the pneumatic process.

Pneumatic Process: The process of sinking caissons by pumping air into the working chamber, in order to exclude the water, and thereby affording a dry space in which excavation may be carried on.

Pneumatic Riveter: Same as "Air Riveter." -- A riveting machine which is operated by compressed air.

Pneumatic Riveting Gun: A rivet hammer operated by compressed air.

Pocket: A recess. A hole in rolled metal, as a cinder pocket.

Poetsch Freezing Process: A method of freezing quicksand, soft mud, or silt by driving tubes down into it and circulating a freezing mixture through them until the surrounding material is converted into a frozen mass like a wall. Excavation can then be carried on inside of the wall.

Poetsch-Sooysmith Process: Same as the "Poetsch Freezing Process. This term is used to denote the American right, held by Mr. Charles Sooysmith, to use the process.

Point (stone dressing): A short steel bar with one tapering end sharpened to a point, used by masons for dressing stone.

Point of Curve: On railroad work, the point at which a tangent ends and a curve begins, called P.C.

Point of Gear Tooth: The outer end of a tooth on a gear wheel.

Point of Intersection: The point where two tangents cross. Used in railroad work and called P.I.

Point of Tangent: In railroad work, the point where a curve ends and a tangent commences, called P.T.

Point Switch: Same as "Split Switch." -- A switch having a point on one rail which fits closely against the other rail, thus giving a continuous track effect.

Pointed Dressing: A form of stone facing made by chipping off projections with a mason's point or similar tool.

Poisson's Ratio: The ratio of the lateral deformation to the longitudinal deformation under longitudinal external forces.

Polar: Relating to a pole or axis.

Polar Axis: An axis at right angles to the plane of rotation.

Polar Coordinates: A system of coordinates in which the position of any point is defined by an angle and a distance from a fixed line and point.

Polar Distance: Same as "Pole Distance."

Polar-equation: An equation connecting polar coordinates.

Polar Moment of Inertia: The moment of inertia about an axis perpendicular to the plane of rotation or to the plane of the area considered.

Polar Planimeter: A planimeter having a hinged arm, one end of which is pivoted while the other end carries the tracing point.

Pole: Any long, round, slender piece of wood. Either of the extremities of the axis of a sphere. A point about which an object rotates. A point from which lines radiate.

Pole-distance: The perpendicular distance, in a force diagram, from the pole to the load line.

Pole-plate: A longitudinal timber resting on the ends of tie-beams of roofs; used for supporting the feet of the common or jack rafters.

Pole Tie: A tie made from a tree of such size that not more than one tie can be made from a section-hewed or sawed on two parallel faces.

Poling: The stirring of molten metal, either in a furnace or in a ladle, with a pole of green wood; the heat distilling off the volatile products which stir up the metal and, together with the charcoal formed, help to reduce any oxides present. Also propelling a barge or vessel by long poles.

Polished Dressing: A finish in stonework made by rubbing a tooled surface down to a reflecting surface.

Poll Axe: An ax with a rounding blade on one side and a blunt head or pole on the other. It is the most common form of axe.

Polygon: An enclosed figure having many sides and angles.

Polygonal Top Chord: A top chord composed of panel length segments which form a polygon.

Pontoon: A boat or light float. A metal cylinder closed at both ends for floating. A floating bridge.

Pontoon Bridge: A platform or roadway supported on pontoons or barges. A floating bridge.

Pony Truss: A low truss without any overhead bracing.

Porosity: The condition of perviousness.

Port: The narrow slot in the ends of a cylinder for the passage of steam. In a vessel, the left-hand side looking forward -- termed also "larboard." A harbor or shelter for vessels.

Portal: The space between the batter braces at one end of a bridge. Sometimes the term is applied to the portal bracing.

Portal Bracing: The combination of struts and ties in the plane of the end posts at a portal which helps to transfer the wind pressure from the upper lateral system to the pier or abutment.

Portal Rod: A tension member in the portal bracing of a truss. This is an antiquated type of construction.

Portal Strut: A strut in the portal bracing of a bridge.

Portland Cement: A cement obtained by finely pulverizing clinkers produced by burning to semi-fusion an intimate artificial mixture of finely ground calcareous and argillaceous materials, this mixture consisting approximately of three parts of lime carbonate to one part of silica, alumina, and iron oxide.

Portland Cement Concrete: Concrete in which Portland cement is used with water as the cementing material.

Portland Cement Grout: Grout in which Portland cement is used.

Positive Moment: A moment acting in the opposite direction to a negative moment, or acting clockwise.

Positive Print: A blue line print on white background made by a direct process without a negative.

Positive Reaction: A reaction caused by and opposed to a direct load.

Positive Rotation: Rotation in the same direction as that of the hands of a clock.

Positive Shear: A relative term usually applied to a shear producing an upward motion.

Post: A vertical, or nearly vertical, compression member.

Post Extension: Same as "Jaw Plate." -- The unsupported portion of the end of a compression member remaining after the outstanding legs of flange angles have been cut away, and its pin plates, which extend below the transverse diaphragm to allow the packing of other members on the same pin.

Post-hole Auger: A large size hand tool for boring holes in earth.

Post-Oak: A variety of white oak.

Post Reamer: Same as "Post hole Auger."

Post Truss: See Fig. 22q.

Fig. 22q

Pot Metal: A poor grade of cast iron.

Potential Energy: Energy that is due to position.

Pounce: Powdered talc or chalk used for rubbing on tracing cloth to remove the slightly greasy surface so that the ink will adhere better.

Pound-foot: A unit of moment, equal to that produced by a force of one pound acting with a lever arm of one foot.

Powder: Same as "Gun Powder." An explosive used for blasting. Any very finely pulverized substance. To reduce to powder. To pulverize. To sprinkle with powder.

Power: The rate of doing work. Often loosely used for force, strength, or resistance.

Power Capstan: A capstan in which cog-wheels are used to multiply the force and reduce the speed.

Power Hammer: A hammer used for forging work.

Power House: The building containing the machines and equipment used in generating power.

Pozzuolana Cement: A true natural cement made from volcanic ash and slaked lime. The name is derived from Pozzuoli, Italy, where it was first made in large quantities. In this country blast-furnace slag is substituted for the volcanic ash and the product is called "Puzzolan Cement."

Prairie Type Locomotive: A locomotive having two pilot, six driving, and two trailer wheels.

Pratt Truss: A type of truss having parallel chords and an arrangement of web members of tension diagonals and compression verticals. See Fig. 22a.

Fig. 22a

Pre-cast Pile or Pre-moulded Pile: See "Precast or Premoulded Pile."

Precast Pile or Premoulded Pile: A form of concrete pile made in a mould and allowed to harden or season before being driven.

Precipitation: A general term for the several kinds of moisture from the atmosphere deposited on the earth's surface, such as dew, mist, rain, frost, snow, sleet, hail, etc. The process by which a substance in solution, after another substance has been added, reacts upon the latter, forming a new insoluble compound called precipitate.

Precise Level: A modification of the Y level with improvements and additions permitting of more accurate work.

Premoulded Pile: Same as "Precast Pile."

Present Worth: The present worth of a sum of money due a number of years hence is that principal which at compound interest will produce the desired amount at the end of the given time. The present worth of a sinking fund is equal to the present worth of the amount of the fund, and is the sum of the present worths of the deposits.

Press: A machine for exerting pressure upon an object.

Pressed Brick: A brick moulded from dry or semi-dry clay and pressed in a machine until it is very hard and smooth.

Pressed Thread: A thread made by pressing instead of cutting.

Pressure: The effect of pressing; the result of thrust.

Pressure Gauge: A gauge which indicates the pressure of a fluid.

Prick Punch: A hand tool for marking metal. A centre punch.

Pricker: A needle point mounted in a handle, used by draughtsmen to transfer the position of a point on one plan to another by superposing one on the other and pricking through.

Primary Member: Same as "Main Member." -- A principal part of a truss or floor system [but] generally restricted to trusses.

Primary Stress: Same as "Direct Stress." -- A stress resulting from a direct application of the load.

Primary Truss: A main truss which supports smaller trusses.

Prime: To pour water down a pump in order to start the suction.

Primer: The first coat of paint on a structure; an exploder for blasting powder.

Priming Coat: The first coat of paint on a structure. Sometimes called "Primer."

Principal: A sum of money upon which interest is paid or computed.

Principal Stresses: Conjugate stresses that are at right angles to each other.

Principle of Least-work: The stresses in the members of a redundant system have such values that the internal energy of all the stresses is a minimum.

Print: An impression; a copy.

Printing Frame: A frame with a padded cloth back and a glass front, used in the process of making blue prints.

Printing Machine: An apparatus for making blue-prints by either natural or artificial light.

Prismoid: A solid having two parallel plane bases with sides generated by straight lines.

Prismoidal Formula: A formula for finding the exact volume of a prismoid.

LetA1 = area of one base
A2 = area of other base
M = area of middle section parallel to bases
l = distance between bases
V = volume

Prison Dressing: A type of stone dressing in which the surface is wrought into holes.

Profile: The outline of a vertical section through a country or line of work, showing actual or projected elevations and hollows, generally with the vertical scale much greater than the horizontal.

Profile Book: A surveyor's note book. A case in which a continuous strip of profile paper is carried.

Profile Paper: A standard, double-ruled paper in which the scale in one direction is a multiple, usually five, of the scale in the other.

Progression: A series of numbers bearing a definite sequential relation to each other.

Projection: The act, or its result, of constructing rays or lines through every point of a figure, according to some system or law, and extending or projecting them to some plane upon which the figure or object is to be represented.

Prony Friction Brake: A brake used for measuring the effective power developed by an engine or turbine.

Proof Load: The greatest load that can be applied to a member without producing permanent distortion.

Proof Strength: The greatest resistance that a body can offer to an external force without the stress exceeding the elastic limit of the material.

Prop: A temporary support or extraneous brace.

Pry: A lever. To raise with a lever.

Puddle: To compact, and work into place, as to puddle concrete. To convert cast iron into wrought iron by melting and stirring in a reverberatory furnace. A mixture of sticky clay moistened with water, used to stop leaks in cofferdams, etc. To place such a mixture.

Puddle Ball: A lump of red-hot, plastic iron taken from the puddling furnace for hammering or rolling.

Puddle Bar: Same as "Muck Bar." -- The bar made by the first rolling of the bloom (A "Bloom" being a roughly prepared mass of iron or steel nearly square in section and comparatively short in proportion to its thickness).

Puddle Cinder: Cinder removed from the molten metal after the process of oxidizing the impurities has been completed.

Puddle Dyke: A dyke with a puddle wall running longitudinally through it.

Puddle Rolls: A machine having heavy, grooved rollers, between which lumps of plastic iron, taken direct from the puddling furnace and hammered into rough bars, are first rolled.

Puddle Steel: A steel made by the puddling process in a reverberatory furnace in which the carbon is reduced at a low temperature to one-half of one per cent. This process is seldom used nowadays.

Puddle-train: A set of rolls for rolling puddle balls into muck bar.

Puddle Wall: A wall of plastic clay tamped in between two rows of sheet piling to prevent seepage of water.

Puddler: A workman who is employed in the process of converting pig iron into wrought iron. The attendant at a puddling furnace.

Puddler's Candle: One of the jets of flame which spring from molten iron while the carbon is being removed in a puddling furnace.

Puddling: The act of making a puddle. See "Puddle."

Puddling Furnace: A reverberatory furnace in which cast iron is converted into wrought iron.

Pug-mill: A machine for grinding and tempering clay.

Pull-back Draw Bridge: A movable span which retreats longitudinally to allow the passage of vessels.

Pulley: A wheel over which a belt, chain, or rope passes; used to transmit motion or to deflect such belt, chain, or rope from one course to another. The face may be flat, crowned, conical, or grooved. Also applied to a combination of sheaves, or grooved pulleys, and the shell or framework containing them. Also called "Pulley Block." See "Block."

Pulley Block: A movable block or frame supporting and partially enclosing one or more grooved pulleys or sheaves.

Pulley-check: An automatic device to prevent the rope from running backward through the pulley block.

Pulley Clip: A clip attached to a pulley to prevent the wire rope (passing over it) from slipping.

Pulley Clutch: An automatic device in the form of a grappling tongs for fastening a hoisting pulley to a beam.

Pulley Sheave: Same as "Sheave." -- A wheel with a grooved face for carrying a rope or cable.

Pulsometer, or Pulsometer Pump: A pump in which the condensation of steam in a chamber causes a partial vacuum therein, inducing the water to rise so as to be expelled therefrom by an incoming fresh supply of steam.

Pulsometer Pump: Same as "Pulsometer."

Pulverize: To reduce to a powder.

Pump: A machine for moving liquids or gases by setting up a flow of same.

Pump Jet: Same as "Jet Pump." -- Any pump in which the fluid is impelled through the discharge pipe by the action of a jet of the same or another fluid.

Punch: A machine for forcing or shearing holes in metal. To make a hole with a punch.

Punching Machine: Same as "Punch."

Punish: To subject material to very severe or abusive treatment.

Purchase: A firm or advantageous hold used in prying a heavy object with a crowbar. A pivot, a fulcrum.

Purchase Block: A double-strapped pulley block having two grooves in the shell.

Pure: Unadulterated.

Pure Stress: A term used for cases where only one kind of stress exists.

Purlin: A piece of timber laid horizontally upon the principal rafters of a roof to support the common rafters on which the covering is laid.

Push: To strike or force with a thrusting motion.

Pusher: A sub-foreman, in charge of one gang, who sees that the men do the work assigned to them as rapidly as possible.

Put-log: A horizontal piece supporting the floor of a scaffold, one end being inserted in a hole left in the masonry for that purpose.

Putty: A paste composed of soft carbonate of lime and linseed oil, used by glaziers for holding window-glass in a sash.

Putty Joint: A pipe joint made tight with putty.

Putty Lime: Same as "Paste Lime."

Puzzolan Cement: A variant of "Pozzuolana Cement" in which blast furnace slag is substituted for volcanic ash.