|University of Iowa Libraries||Lichtenberger Engineering Library|
Laced Strut: A strut that has lacing of small bars running diagonally on the open face or faces.
Lacing: A system of bars not intersecting each other at the middle, used to connect two leaves of a strut in order to make them act as one member.
Lacing or Lattice Angle: An angle used in latticing.
Lacing Bar: Any bar used in a system of "Lacing."
Ladder Bracing: Bracing consisting of struts only.
Ladder Dredge: A dredge having buckets mounted on an endless, ladder-like chain.
Ladder-way: A space or opening for ascending or descending by a ladder.
Ladder Work: Work that is done from a ladder.
Ladle: A large vessel or pot for holding, transporting, and pouring molten metal.
Ladle-barrow: A special wheel-barrow for carrying a ladle of molten metal.
Lag: The amount of retardation of some movement, as the lag of the valve in a steam engine. To hang back. The outside covering of a steam boiler to prevent radiation. The vertical timbers nailed to a "Lag Pile." To fasten down with "Lag Screws."
Lag-bellied: Any construction having a slack, drooping belly.
Lag Bolt: Erroneously used for "Lag Screw."
Lag Screw: A large-sized wood screw with a square head larger than the shank for convenient turning with a wrench, and having a special thread to increase the holding power.
Lagged Pile: A pile having four or more long longitudinal timbers bolted to its sides for the purpose of increasing the area exposed to skin friction, and thereby obtaining an increased bearing capacity.
Lagging: Same as "Sheathing.(A covering or casing of planks. Used on caissons, cribs, and the like.)". Also planking or timbers fastened by lag screws.
Laid-up: A term used in riveting to denote that the dolly bar is tight against the head of the rivet preparatory to driving.
Laitance: Same as "Laitance of Cement."
Laitance of Cement: That portion of a hydraulic cement which escapes from concrete that is placed under water and which floats on the surface. It is injurious to concrete, and should be removed. Its formation in large quantities indicates a defect in the method of depositing the concrete.
Lamellar Structure: Composed of layers or lying in layers, usually applied to rock.
Laminar: Composed of thin plates or layers.
Laminated: Having plates or scales. Scaly.
Laminated Arch: A beam, having the form of an arch, constructed of several thicknesses of planking bent to shape and bolted together.
Lampblack: A fine, black pigment consisting of particles of nearly pure carbon, used for making paints, ink, etc.
Lance Wood: A light, yellow-colored wood used in surveying rods.
Lanch: Same as "Launch."
Land: The smooth uncut part of the faceplate of a slide-valve in a steam engine. To put on or to bring to shore.
Land Slide: Same as "Slide." -- A displacement of an unstable earth bank due to gravity and saturation.
Land Slip: Same as "Slip" (An earth slide.) or "Slide" (A displacement of an unstable earth bank due to gravity and saturation).
Land Tie: A tie-rod, used to secure a facing wall to the ground. Any anchorage to the ground. A surveying term used to denote the distance from any point to a nearby section corner.
Landing: Same as "Land." Also a resting place in a flight of stairs.
Lang-lay Rope: Wire rope in which the wires in a strand twist in the same direction as the strands are twisted.
Lantern Pinion: A small lantern wheel.
Lantern Wheel: A gear wheel composed of two parallel discs set some distance apart on an axle with round rods parallel to the axle, set at equal intervals around the periphery of the discs. These rods mesh with the teeth of another gear.
Lanyard: A cord or line used for convenience or safety in handling articles. A small rope attached to a bucket for taking materials out of a hole.
Lap: To place one piece upon another, so that its edge extends beyond that of the other.
Lap Joint: A joint in which the pieces extend over each other.
Lap Riveting: The making of a lap-joint by using rivets to fasten the overlapping ends of the plates.
Lap Seam: A seam in which the separate parts extend over each other. Seasoning: The process of becoming fit for use, as lumber becoming dry and hard through exposure.
Lap Splice: A splice made by placing one piece on top of another and fastening together with pins, nails, screws, bolts, rivets, or similar contrivances.
Lap Weld, or Scarf Weld: A weld in which the ends of the pieces are made to lap over each other and then joined by welding.
Large Knot: A sound knot in timber more than one and a half inches in diameter.
Larry: Same as "Lorry."
Lash: To secure by tying. To burst or break out.
Lashing: A cord, rope, wire, or chain for binding or making fast one thing to another.
Latch: A device for catching or retaining something. A catch. To hold or retain in place with a latch.
Latch Bar: The sliding bar in the locking mechanism of a draw span. A bar used for latching.
Latch-catch: A catch which holds the latch in the locking mechanism of a draw-span.
Latent Heat: The amount of heat absorbed or liberated when a body undergoes a physical change, the temperature of the body remaining constant.
Lateral: At right angles to the line of motion; sideways. One of the pieces in a lateral system.
Lateral Bracing: A system of tension or compression members, or both, forming the web of a horizontal truss connecting the homologous chords of the opposite trusses of a span.
Lateral Clearance: Same as "Horizontal Clearance." -- The horizontal space allowed for the passage of any vehicle or craft through or near a construction.
Lateral Contraction: A lateral shrinking or shortening.
Lateral Diagonal: A diagonal member in a lateral system.
Lateral Rod: A tension diagonal of a lateral system.
Lateral Section: A section made by a secant plane parallel to the side of an object.
Lateral Strain: A deformation at right angles to the axis of the member.
Lateral Stress: A stress which acts at right angles to the axis of a member through which tension or compression is produced. Sometimes employed to mean the stress in a member of a lateral system.
Lateral Strut: A strut in the lateral system of a bridge.
Lateral System: A system of tension and compression members, forming the web of a horizontal truss, connecting the opposite chords of a span. Its purposes are to transmit wind pressure to the piers or abutments, to prevent undue vibration from passing trains or other loads, and to hold the chord members to place and line.
Lath: A thin, narrow strip of wood, used in buildings or for placing between rows of paving blocks in pavements on heavy grades so as to afford better foothold for horses.
Lathe: A machine tool for turning various materials, such as metal, wood, bone, etc.
Latitude: In surveying, one of the two coordinates of a point-usually referred to the east and west axis in a system of rectangular coordinates.
Lattice: Same as "Latticing."
Lattice Angle: Same as "Lacing Angle."
Lattice Bar: Any bar used in "Latticing."
Lattice Bridge: A bridge having riveted trusses with multiple intersection web systems.
Lattice Truss: A truss having several web systems. See Fig. 22t.
Latticed Girder: A riveted girder having the upper and lower flanges connected by latticing, or by diagonal bars or angles.
Latticing: A system of bars crossing each other at mid-length, used to connect the two leaves of a strut in order to make them act as one member. Generally the crossed bars are riveted together at their intersection.
Launch: To move heavy bodies by pushing. The sliding of an object, which will float, into the water. A small power boat.
Launching Ways: Same as "Ways." -- Supports or tracks set on a slope, down which a caisson slides at the time of launching. Used also for the apparatus by which cars are unloaded on a hill-side.
Launching Wedges: Wedges used in supporting a caisson on the launching ways.
Launhardt's Formula: A formula pertaining to the fatigue of metals.
|where||m = maximum stress|
|p1 = repetition limit when n = 0|
|n = minimum stress|
|f = ultimate static stress|
This formula does not properly apply to any part of bridge engineering.
Laws of the Lever: An early day expression used to denote the conditions of equilibrium of three forces in one plane. They are as follows: First, The three parallel forces applied to one body must balance each other and lie in the same plane. Second, The two extreme forces must act in the same direction. Third, The middle force must act in the opposite direction. Fourth, The magnitude of each force must be proportional to the distance between the other two.
Layer-out: The person in a bridge shop who lays out the steelwork with templates.
Layout: A plan or arrangement of the parts of a structure shown on a drawing.
Lazy Jack: A mechanism consisting of compound levers pivoted together.
Lazy Pinion: A pinion acting as an idle wheel.
Lead: One of the useful metals remarkable for its softness and durability, having a specific gravity of 11.3. To cover, fasten, smooth, or polish with lead.
Lead: The course of a running rope from end to end. In a steam engine, the arrangement of the valves. A passageway. The average distance required to be traveled to remove the earth of an excavation so as to form an embankment, or the average haul.
Lead Blocks: Blocks for guiding ropes or for holding them in a given position without impeding their motion. The blocks through which the lead lines run.
Lead Gray: Colored like lead.
Lead Joint: A joint in a pipe, filled with melted lead.
Lead Line: The line attached to the sounding lead for measuring the depths of water, marked in either fathoms or feet. See also "Leading Line."
Lead Pipe: Pipe made by squeezing lead through a die.
Lead Slag Concrete: A concrete made with lead slag in place of the usual broken stone.
Leading Beam: A beam placed as a guide for other beams.
Leading Line, or Lead Line: A line attached to the hammer in a pile driver. The line or cable which runs from the load to be lifted to the first sheave or block in a hoisting tackle.
Leading Pile: A pile at the head of a row of piles.
Leading Wheels: The wheels in a locomotive placed in front of the drivers.
Leads: The two upright timber or steel guides on a pile-driver in which the hammer moves.
Leaf (of a member): One of the vertical component parts of a built-up member; consisting generally of one or more web plates with top and bottom angles, or one rolled channel. Usually two in number and sometimes three.
Leaf Bridge: A form of draw bridge in which the rising leaf, or leaves, swing vertically on hinges.
Leaf Valve: Same as "Clack Valve." -- A valve hinged at one end so as to permit the flow of the liquid in one direction only.
Leaf Work: The ornamental work done on cast-iron which is sometimes used on portal bracing in bridges for appearance only; also scroll work on cast-iron columns and lamp posts.
Leak: The escape of gas, air, water, or steam through an opening. A gutter is often termed a leak. To drip or ooze out of an aperture of any sort.
Least-work: A method of determining stresses in the members of a redundant system.
Leaves: The cogs of pinions. The portions of a moving bridge which actually revolve. The two or more main components of a built member of a truss or trestle.
Ledge: A part projecting over like a shelf. A narrow strip of board nailed across other boards to hold them together.
Ledger: A bar, beam, or stone that lies flat, or horizontal. A piece of timber used in forming a scaffold. A book for keeping accounts. Leeward: The side opposite to that from which the wind comes.
Left-handed Nut: A nut having a left hand thread.
Left-handed Screw: A screw having a left-handed thread.
Left-handed Thread: A spiraling in such a direction that a counter-clockwise rotation of the bolt or screw produces a forward motion of the bolt.
Leg: Anything that resembles the limb of an animal or serves a similar purpose, as in supporting a load; e.g., the inclined legs in an A frame, or the two portions of an angle-iron separated by the bend.
Leg Bridge: A bridge resting on legs, formed by a downward extension of the end posts, instead of masonry abutments.
Lemniscate: A curve resembling a figure eight. More precisely defined as the locus of the point at which the tangent to the equilateral hyperbola meets the perpendicular let fall upon it from the center.
Lemniscatic Curve: Same as "Lemniscate."
Length: Extension from end to end. Distance measured along a line.
Lens: A piece of transparent substance, usually glass, bounded by two curved surfaces having the power of refracting light.
Lenticular Arch: An arch which has a rib composed of two lens-shaped trusses.
Lenticular Truss: Same as "Double Bowstring Truss" (A truss in which the joints of each chord lie in curves concave to each other.) See Fig. 22r.
Letting: The awarding of a contract to a bidder.
Level: To make horizontal, or to bring into a plane parallel to the horizon. To bring to a common level. To work with a leveling instrument. An instrument for securing a horizontal line of sight.
Level Book: A field book in which to record level notes.
Level-man: The man in a survey party who operates the level.
Level-notes: Records of back-sights, heights of instrument, foresights, and elevations as written by the observer in the level book.
Leveler: One who does leveling work. A small stone used illegitimately in masonry to adjust the elevation of a large, cut stone.
Leveling Instrument: A surveyor's or engineer's level.
Leveling Pole: Same as "Leveling Rod."
Leveling Rod: A surveyor's graduated rod. See "Rod."
Leveling Staff: Same as "Leveling Rod."
Lever: A mechanical element, or simple machine, consisting of a bar or rigid piece of any shape which is acted upon by two forces severally tending to rotate it about a fixed axis. Any rod or bar used for prying.
Lever-arm: The perpendicular distance from the centre of moments to the line of action of a force; or in the case of a couple, the distance between the lines of action of the two equal and parallel forces.
Lever Draw Bridge: A draw bridge operated by means of a lever.
Lever Hoist: A form of lifting jack employing a lever.
Lever Jack: A jack worked by a lever.
Lever Valve: A valve having a lever and weight attached to keep it closed until the pressure on its disk exceeds a predetermined amount, at which time it opens and permits some of the fluid to escape. An old form of safety valve, used on steam boilers.
Leverage: Lever power, or the arrangement by which lever power is gained.
Lewis: A device composed of two or three pieces of metal, let into a wedge-shaped hole in a block of stone, and having a ring or loop at their upper end for attaching the hook of a hoisting apparatus.
Lewis Bolt: A wedge-shaped-ended bolt inserted like the shank of a lewis in a hole drilled in a stone and fastened therein by pouring melted lead into the unoccupied part of the hole. An eye bolt similarly inserted and used like a lewis for lifting heaving stones.
Lewis-hole: The hole drilled in a block of stone for the reception of a lewis.
Liatier Cement: Same as "Slag Cement" or "Puzzolan Cement" (A variant of Pozzuolana Cement which is a true natural cement made from volcanic ash and slaked lime.) In this country blast-furnace slag is substituted for the volcanic ash and the product is called "Puzzolan Cement."
Lift: To move or heave upward. The apparatus used in lifting. An elevator, a hoist.
Lift Bridge: A type of movable bridge which travels in a vertical plane, sometimes called a hoist bridge.
Lift Hammer: A drop-hammer of a pile driver.
Lift Pump: A pump having a cylinder with a suction valve at its lower end which is connected by a suction pipe to the water supply. The movable piston has an upward opening valve so that the water may pass through it on the downward stroke and lift by it when closed on the upper stroke.
Lift Span: A span of a bridge that is raised for the passage of vessels.
Lifting Bridge: Same as "Lift Bridge."
Lifting Deck: A deck without trusses which raises or lowers vertically.
Lifting Jack: A screw jack worked by a worm wheel to which a handle is attached.
Lighter: A scow, barge, raft, or other small vessel for unloading ships at a distance from the shore.
Lime: A product made by heating limestone, marble, or shells to a high temperature in kilns. As it comes from the kilns in a pure state, it is (CaO) calcium oxide.
Lime Cement Mortar: A mortar in which lime and cement are used together. Not a proper mixture for bridge construction, the only reason for its use being to reduce first cost, which it invariably does at the expense of the effectiveness of the construction.
Lime Kiln: A furnace in which limestone is calcinated.
Lime Mortar: A mortar made from lime. Should never be used in bridgework.
Lime-wash: Same as "White Wash" or "White Lime." To white-wash.
Limestone: A rock of sedimentary origin consisting largely of calcium carbonate (CaC03).
Limit Load: The greatest load which a structure is permitted to carry as set forth in the specifications. A safety load.
Limit of Elasticity: Same as "Elastic Limit." -- The unit stress at which the deformation begins to increase in a faster ratio than the applied loads.
Limits: The precise boundaries between two contiguous regions of magnitude or quantity.
Limnoria: A small crustacean about the size of a grain of rice requiring both air and water for its existence. It works on the surface of wood with its claws or mandibles taking off at one time a layer about one-half inch thick. It is usually most active in brackish waters at low water level.
Linch Pin: A pin, near the end of an axle, used to hold on a wheel.
Line: A unit of length, as one tenth or one twelfth of an inch. A row of anything. A limit, division, or boundary. A length without breadth, or the trace of a moving point. A string, cord, or slender rope. A mark drawn by a pen or pencil. To cover or fill the inside of anything. To keep things in line. A railway.
Line of Gravity: The line along which the centre of gravity would move, if the body were free to fall.
Line of Resistance: Same as "Axis of Resistance." -- A line connecting the centres of resistance of successive sections of a member.
Lineal: Relating to length only. Often written "Linear."
Lineal-foot: A running foot.
Lineal Velocity: The rate of lineal motion.
Linear Arch: A linear arch is the equilibrium polygon for the system of loads applied to the physical arch. In an actual arch the resistance line is the linear arch for the actual loading.
Linear: Same as "Lineal."
Lining: The covering of the inner surface of anything.
Link: A ring or element of a chain, a loop. Anything serving to connect one thing to another. To unite or connect. A crook or winding in a river.
Link Belting: A belt for the transmission of power, composed of a series of detachable links.
Link Block: A block in a steam engine attached to a valve stem.
Link Chain: A chain made of links.
Link Lever: A controlling lever for moving the link of a valve gear in a steam engine.
Link-motion: In steam engines, a system of gearing for controlling the valves, regulating the position of the cut-off, and starting or reversing the engine.
Lintel: A horizontal beam across an opening in a wall. Same as "Breast
Linville Truss: Same as "Whipple Truss." -- A double intersection Pratt truss.
Lip Washer: A washer having a lip or projection that can be bent over after the nut is screwed on, thereby preventing the nut from working loose.
Liquidate: To pay off a debt.
Liquidated Damages: Damages determined, as to amount, either by agreement or by a judgment.
Live Load: A moving load on a structure.
Live Load Stress: Any stress caused by the application of a moving load.
Load: The weight carried by a beam, girder, truss, span, or structure of any sort, or any part of such structure, including its own weight.
Load Diagram: A diagram showing the amounts and arrangement of loads on a structure. The diagram taken off an engine by an indicator.
Load Line: A rope or cable which carries the load. In graphic statics, the line of a force polygon on which the loads are laid off.
Loading: A system of loads on a structure. The act of placing loads on vehicles.
Loblolly Pine: A variety, of pine tree of large size. It has a wider ringed, coarser, lighter, and softer wood with a larger area of sap wood than the long-leaf yellow pine. Its needle-like leaf is of short length.
Lock: To close and fasten in. Any form of a brake or drag for wheels which prevents their turning. A barrier to confine water in a stream. A portion of the air shaft to a caisson shut off by two doors and used by the workmen for entering or leaving the caisson.
Lock Bar: Sheet piling which is locked together, and which can be pulled after being used for forms.
Lock Joint: A joint made by the locking together of two halves of a concrete pipe around a pile by inserting wooden keys, soaked with hot tar, in the scarf joints.
Lock Nut: A nut having some special provision to prevent turning.
Lock-nut Washer: A ring-shaped washer cut on one side and having the ends sprung laterally. Used for preventing a nut from turning.
Lock Pit: A pit in which the locking machinery is installed.
Lock Sleeve: A sleeve connecting two parts of shafting and arranged to lock with one of them by means of a shifting motion.
Lock Tender: The man who operates the air-lock in pneumatic sinking of bridge piers.
Locke Level: A type of hand-level consisting of a small tube with a spirit bubble mounted on the upper side and a refracting prism or a reflector to show the bubble in the field of vision.
Locking Gear: A mechanism which locks a movable span when closed.
Locomotive: A steam engine which travels on wheels turned by its own power, or an engine designed and adapted to travel on a railroad. A railroad engine.
Locomotive Balance: A spring used in place of a weight to control the safety valve of a locomotive. Locomotive Boiler: See "Boiler."
Locomotive Boiler: A form of steam boiler in which the fire-box is connected by a number of flues with the smoke box under the chimney.
Locomotive Car: A locomotive and railroad carriage combined in one.
Locomotive Crane: A locomotive, or steam engine on wheels, with a crane attached. Used in yard work.
Locomotive Diagram: A diagram showing the wheel loads and spacings in a locomotive.
Locomotive Driver: One of the large driving wheels of a locomotive. Also the man who operates or drives a locomotive.
Locomotive Excess-load: An early method for computing stresses in a span by the use of a uniform carload with one or more engine excesses. No longer employed in American bridge designing.
Locomotive-pilot: The truck and its wheels set in front of the drivers of a locomotive.
Locomotive Pump: The feed pump which supplies water to a locomotive boiler.
Locus: In mathematics, a curve considered as generated by a moving point, or a surface considered as generated by a moving line; the partly indeterminate position of a point subject to an equation or to two equations in analytic geometry; a curve considered as generated by its moving tangent or by a moving curve of which it is the envelope; any system of points, lines, or planes defined by general conditions, and, in general, partly indeterminate.
Log: An abbreviation for "Logarithm." A bulky piece or stick of timber.
Logarithm: The exponent of the power to which a fixed number, called the base, must be raised in order to produce a given number.
Logarithmic Curve: A curve in which the ordinate are logarithms of the corresponding abscissas.
Logarithmic Spiral Curve: A spiral curve in which the radius vector varies as the logarithm of the angles.
Logarithmic Table: A table which gives the logarithms of consecutive numbers and of trigonometric functions of angles.
Lomas Nut: A nut having a recess on the bottom which permits it to be screwed down on the pin until the edges of the nut bear on the eye-bars packed on the said pin.
Long Column: A column which will fail by buckling.
Long-leaf Yellow Pine: A variety of pine tree of large size, having a hard, dense, strong wood and a needle leaf of great length.
Long Pinion: A pinion having long teeth such that the gear meshing with it can move latterly without becoming disengaged.
Long Ton: A unit of weight equal to 2,240 pounds, generally employed for coal and steel rails. It is the English ton.
Longitude: Same as "Departure." -- A term used in surveying to denote the perpendicular distance from one of two assumed rectangular coordinates-often from the one running north and south.
Longitudinal Axis: An axis in the longitudinal direction of the figure or body considered, and generally passing through the centre of gravity or the centre of figure.
Longitudinal Bracing: Bracing extending lengthwise of the structure, or parallel to its centre line.
Longitudinal Component: A component in a direction parallel to the plane of the trusses.
Longitudinal Girder: The main girder in a structure running parallel to the centre line thereof.
Longitudinal Section: A section made by the secant plane passing parallel to the long axis of the member.
Longitudinal Shear: A shear parallel to the longitudinal axis of a member.
Longitudinal Stress: Stress parallel to the axis of a member.
Longitudinal Thrust: A thrust along the longitudinal axis of a member. Thrust Angle: See "Angle."
Loop: A folding or doubling of a string, cord, or chain. The bend in a river. To fasten or secure with loops. A knot or burr, often of large size, on trees. A slotted bar or ring at each side of any piece of machinery, designed to control the movement of another part. An elongated eye in a small eye-bar.
Loop Eye: An eye on the end of a rod or square bar elongated in the form of a loop.
Loose Joints: A joint in which the parts are loosely held together.
Loose Knot: A knot in timber, not firmly held in place by growth or position.
Loose Pulley: A pulley which turns loosely on its shaft.
Loricated Pipe: A pipe, having an inside coating of bitumen, used as a conduit for electric wires.
Lorry: An English term for a tramway wagon, i.e., a long wagon having a very low platform and four small wheels used for carrying freight. At the present time it is used to denote a motor truck and also a hand car. In the United States, a drop-bottomed car running on a track, such as that around a blast furnace. Also spelled "Larry."
Lorry Rail: Same as "Lorry Track.
Lorry Track: A track on which a lorry runs, usually a narrow-gauge track found around blast furnaces and coal tipplers.
Low Bridge: A bridge over navigable water so low that some vessels cannot go beneath it without an opening passage being provided in the structure.
Low Steel: A soft steel containing a small amount of carbon-less than one-fourth of one per cent.
Low Water: The condition of a stream when discharging a small amount of water.
Low-water-mark: A mark left by any low water.
Lower Chord: Same as "Bottom Chord." -- The lower member of a truss, usually resisting tension.
Lower Deck: The bottom deck of a span.
Lower Falsework: The falsework built below the level of the bottom chords.
Lower Lateral Bracing: Same as "Bottom Lateral Bracing." -- Lateral bracing in the plane of the bottom chords of a truss.
Lower Laterals: Same as "Bottom Laterals." -- Laterals in the plane of the bottom chords.
Lubricant: Any material used on rubbing surfaces to reduce the friction and thereby also the resistance to motion.
Lubricate: To reduce the friction of two surfaces that are in contact by the interposition of oil or other material so as to lessen the friction between them when one moves on the other.
Lubrication: The act of lubricating; the state of being lubricated.
Luff: To bring a vessel into the wind. To swing the boom of a derrick.
Luff Tackle: The tackle used to hold the boom of a derrick from swinging sideways.
Lug: Any kind of a projection for carrying or supporting something.
Lug Angle: Same as "Clip Angle." -- A short attaching angle that takes a portion of the stress of any main member
Lug Bolt: A round bolt to which is welded a flat iron bar.
Lug Hook: Same as "Lug Bolt."
Lumber: Timber that has been sawed or split for use.
Lumber Kiln: An enclosed chamber artificially warmed, in which sawn lumber is placed to be heated so as to free it from moisture and prevent warping.
Lump-sum: An adjective applied to the method of paying for different kinds of work, all lumped together as one unit. A single payment.
Luster: A term used in describing the character of the reflections obtained from the fractured surfaces of minerals and from the broken ends of metal test-pieces.
Lute: A mixture of fire-clay, used to seal cracks when heat is applied.