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Engineer's and Mechanic's Encyclopedia

Piano Forte
Piano-forte. A Musical Instrument, Resembling The Harpsichord, (of Which It Is An Improvement,) In Which The Tone Is Produced By Hummers, Instead Of Quills, Upon The Strings. Of All The Keyed Instruments, As Observed In The Oxford Encyclopedia, The Piano-forte Seems To Merit The Preference, On Account Of The Superior ...

Pin
Pin. A Well-known Little Instrument, Chiefly Used To Adjust Or Fasten The Clothes Of Women And Children. Although Consisting Of Merely A Piece Of Wire, With A Head And A Point, Great Mechanical Ingenuity Has Been Exercised To Perfect Its Construction At A Cheap Rate; But Such Is The Extent ...

Pipes
Pipes, For The Conveyance Of Water And Other Liquids, Are Made Of Lead, Iron, Stone, Pottery, Wood, Indian-rubber, &c. Of Iron There Are Two Sorts,—wrought And Cast. Wrought-iron Pipes Are Made Out Of Plates Of The Required Thickness, Length, And Breadth ; So That When Coiled Into A Circular Form, ...

Piston
Piston. That Part In A Steam Engine On Which The Elastic Force Of The Steam Exerting Itself Puts It Into Motion ; And Which, Through The Medium Of The Piston Rod Connected Thereto, Actuates The Entire Machine. The Term Piston Is Likewise Sometimes Employed To Designate What Is More Generally ...

Pitch
Pitch. A Resinous Substance, Obtained By The Inspissation Of Tar. There Are Two Methods Of Obtaining It; One By Simply Boiling The' Tar In Large Iron Pots, Or By Setting It On Fire And Letting It Burn Until It Obtains Such A Consistence As, By Dipping A Stick In It, ...

Plane
Plane. An Instrument Employed For Shaving Wood And Other Substances To A True Plane Or Smooth Surface, Of Which There Are A Great Variety ; They Are Usually Divided Into Two Principal Kinds, Namely, Bench-planes And Moulding Planes ; Of The Former, The Principal Are The Long, Jack, Trying, And ...

Plane Table
Plane-table. An Instrument By Which The Draught Or Plan Of An Estate, &c. May Be Taken On The Spot, While The Survey Or Measuring Is Going On. It Consists Of A Perfectly Fiat Rectangular Board, Sufficiently Large For The Purpose, The Centre Of Which Moves Freely On A Ball And ...

Planetarium
Planetarium. An Astronomical Machine Of The Same Nature As The Orrery, Designed To Exhibit The Orbits, Motions, And Phenomena Of The Planets In The Solar System. In A Machine Of This Kind, Which Was Constructed By Huggens, And Is Presetved In The University Of Leyden, The Revolution Of The Primary ...

Platina
Platina. One Of The Metals, And The Heaviest Body Hitherto Discovered In Nature; Its Specific Gravity Being 21.54 When Pure. It Is Obtained From An Ore Or Metallic Sand Brought From South America, Which Contains, Besides Platina, Four New Metals, Namely, Palladium, Iridium, Osmium, And Rhodium ; Also Iron And ...

Plough
Plough. An Instrument Employed In Agriculture For Breaking And Turning Up The Soil In Furrows Expeditiously. The Invention Is Of Very Remote Antiquity. The Most Ancient Of Ploughs On Record Are Still Used In Their Simple Primitive Form In Many Parts Of The East Indies. In The Following Figures Are ...

Plum Bago
Plum Bago. Graphite, Or Black Lead, Is An Ore Obtained From The Mines Of Keswick And Borradaile, In Cumberland, From Ayr In Scotland And Other Places. It Occurs In Beds Of Various Thickness, And Constitutes An Important Article In Commerce. The Finer Kinds Are Boiled In Oil, And Afterwards Sawn ...

Pneumatics
Pneumatics Treat Of The Mechanical Properties Of Air, Gases, And Vapours. All Air, Gases, And Vapours Not In Contact With The Liquids From Which They Rise, Partake Of The Same General Properties; That Is, They All Possess Weight And Iner Tia, Impenetrability, Compressibility, And Elasticity. The Impenetrability Of Air May ...

Porcelain
Porcelain. A Fine Kind Of Semi-transearent Earthenware, In Imitation Of That Made In China, And Hence Called Chma-ware. The Combination Of Miles And Argil Is The Basis Of Porcelain ; And, With The Addition Of Various Pro Portions Of Other Earths, And Even Of Some Metallic Oxides, Forms The Different ...

Porosity
Porosity Is A Term In Physics, Opposed To Density, And Signifies The Rela Tive Proportion Of Matter And Space Included Within The Exterior Superficies Of A Body. The Volume Of A Body Is The Quantity Of Space Included Within Its External Surfaces. The 111885 Of A Body Is The Collection ...

Potassium
Potassium. A Metallic Substance, The Base Of Potash: It Was Discovered By Sir H. Davy, In 1807. It Was Prepared By Causing Hydrate Of Potash, Slightly Moistened For The Purpose Of Increasing Its Conducting Power, To Com Municate With The Opposite Poles Of A Galvanic Battery Of 200 Double Plates ...

Pottery
Pottery. The Art Of Making Vessels From Earth. In The Earliest Ages Upon Record Pottery Was Manufactured. The Chief Establishments In England Are In Staffordshire. In A District Called The Potteries, At Worcester, Derby, Coal-port, And Liverpool The Potteries In Staffordshire Employ Many Thousands Of Persons, And The Value Of ...

Press
Press. A Machine For The Compression Of Any Article. Or Substances, By The Application Of Screws, Levers, Wedges, &c. In A Convenient Manner. As The Combinations Of The Mechanical Powers Are Almost Illimitable, It Follows That There May Be Presses Made Of An Almost Infinite Variety Of Forma ; But ...

Pressure Gauge
Gauge, Pressure. An Instrument To Determine The Pressure Exerted In Hydrostatic Or Pneumatic Machines, As The Hydrostatic Press, Air Pump, And Steam Engine. When The Pressure Exerted Is Less Than The Pressure Of The Atmosphere, As In The Condenser Of A Steam Engine, The Gauge Is Usually Termed A Barometer, ...

Prevention Fires
Fires, Prevention Or. Among The Various Modes Which Have From Time To Time Been Proposed For This Purpose, The Most Useful And Important Are Those Relating To The Manner In Which Buildings Are Constructed. The General Prin Ciples To Be Attended To Are Simple And Briefly Stated, Viz. The Use ...

Printing
Printing. The Art Of Taking Copies By Impression Of Type, Engraved Plates And Blocks, Or Of Any Design Or Work Whatever, In Black-ink Or Pigments Of Various Colours; But The Word Printing, Standing Alone, 'without Any Distinctive Addition, Is Usually Understood To Imply Typography, Or Printing From Type, Usually Called ...

Projectiles
Projectiles. The Laws Of Projectiles, Or Bodies Projected By Any Impul Sive Force Into The Atmosphere, Are Identical With Those By Which The Motions Of Bodies Falling Perpendicularly In Free Space Are Governed; So That When Their Relation Is Utiderstood, A Knowledge Of The One Necessarily Leads To An Acquaint ...

Protractor
Protractor. An Instrument Used For Protracting, Or Laying Down On Per The Angles Of Any Figure. The Protector Is Commonly A Small Semicircle Of Brass, Nicely Divided It Into 180 Degrees; The Ends Of The Arch Are Connected By A Straight Rule, The Outside Edge Of Which Is The Diameter ...

Pumps
Pumps. Machines For Raising Water And Other Fluids; Usually Consisting Of' A Tube Or Tubes, In Which Valves And Pistons, Or Buckets, Are Made To Operate, To Pro Duce The Effect. Engines Differently Constructed, And Particularly Those Upon A Larger Scale Than Ordinary Pumps, Are Generally Termed Hydraulic Machine., Which ...

Pyrometer
Pyrometer. A Machine Contrived To Measure The Expansion Of Metals, And Other Bodies, Occasioned By Heat. Muschenbroeck Was The Original Inven Tor Of The Pyrometer; The Nature And Construction Of His Instrument May Be Understood From The Following Account.—if' We Suppose A Small Bar Of Metal, Twelve Or Fifteen Inches ...

Pyrotechny
Pyrotechny Is, Properly Speaking, The Science Which Teaches The Management And Application Of Fire In Various Operations; But In A More Limited Sense, And As It Is More Commonly Used, It Refers Chiefly To The Composition, Structure, And Use Of Artificial Fireworks. The Ingredients Are, 1. Saltpetre, Purified For The ...

Quarry
Quarry. A Cavity Or Opening Made By Miners In Rocky Ground, From Which Are Procured Marble, Freestone, Slate, Limestone, Or Other Materials ; One Of Which, In The Island Of Jersey, Is Represented In The Subjoined Cut ; From Whence Is Obtained Large Quantities Of Stone For The London Pavements. ...

Raft
Raft. A Float Formed Of An Assemblage Of Pieces Of Timber Fastened Together, For The Convenience Of Transporting Them Without Dispersion ; Or For Sustaining Goods In Transport; And Sometimes For The Saving Of The Lives Of Persons Shipwrecked. A Few Years Ago, Mr. Harrington Took Out A Patent For ...

Railway Or
Railway Or Railroad, And Tramroad ; Are Narrow Tracks Of Rails, Or Plates Of Iron, Wood, Or Other Tenacious Material, Made With Very Smooth Or Level Surfaces, And Laid Down With Great Solidity And Truth, To The Required Planes ; So That The Wheels Of Carriages May Meet With The ...