A Glossary of Possibly Unfamiliar Terms

ACCURACY: The closeness of a measurement, or of an action, to a desired result. Hitting a bull’s-eye displays accuracy.

ARMILLARY SPHERE: An elaborate framework of intersecting brass rings created to represent the various astronomical and other features—the ecliptic, say, or the lunar orbit or the tropics—around planet Earth.

ASTIGMATISM: Distortion in vision, or in the function of a camera or telescope, caused by refractive irregularities in the shape of a lens.

ASTRARIUM: A mechanical device, with similarities to both a planetarium and an astronomical clock, which can predict celestial events and planetary passages across the sky.

ASTROLABE: A graduated metal disc with rotating parts used to calculate astronomical events.

AVOGADRO NUMBER: The number of particles—atoms, photons, molecules—contained in the amount of a substance given by the SI unit of one mole. The number is expressed as 6.0221415 × 10²³.

BIMETALLIC STRIP: Given that different metals behave differently at different temperatures, joining small pieces of two such metals together will allow the resulting strip to bend as the temperature changes—a phenomenon used to trip switches in, say, a thermostat.

BLOCK (MARITIME): A pulley or system of pulleys mounted inside a case and used to hoist the rigging of a sailing ship, and to raise great weights.

BRAZING: A means of employing heat to join metal to metal, the result less permanent than welding, more so than soldering.

BREVET D’INVENTION: A French patent.

BRITISH STANDARD WHITWORTH: A set of standards for the making of screws and screw threads.

CALIPER: The jaws of a measuring instrument, one fixed and the other either pivoted or sliding, used to determine the outer dimensions of an object.

CARBINE: A gun, slightly shorter and lighter than a musket, and generally carried by mounted cavalry.

CARBON FIBER: A phenomenally strong and light form of carbon first made in the 1960s and enjoying all kinds of uses in mechanical construction.

CHAMFER: To smooth away a sharp edge or corner.

COMA (IN TELESCOPES): A result of spherical aberration in a lens, when objects are surrounded with blur.

COMPLINE: The final religious service of a monastic day, and by extension, the evening hour when it is held.

DIFFRACTION GRATING: A plate ruled with very fine parallel and equidistant lines which produces a vivid spectrum when light is passed through them.

DIVIDING ENGINE: A device, usually a large wheel advanced by a worm gear, used to incise graduations onto a measuring instrument.

DOWEL: A rod, or peg, usually smooth, often made of wood, used as a fastener.

EDM: Electrical discharge machining, in which high-intensity sparks are used to create shapes in metal workpieces—often used to drill tiny holes in inconveniently shaped items.

ETHER: An invisible substance formerly believed to fill all space and which permits the carriage of radiation of all kinds.

FAB: A fabrication plant for the bulk manufacture of electronic components.

FLINTLOCK: The device that more or less reliably produces, by striking a metal piece against a flint, the spark that will ignite the powder in a gun.

FOUCAULT’S PENDULUM: Named for the nineteenth-century French physicist who discovered the phenomenon: a very long and slow-moving pendulum which will keep oscillating in one direction while the Earth can be shown—by means of a dial under the bob—to be rotating beneath it.

FRIZZLE: The metal part of a flintlock (q.v.) that, when struck against the flint, produces a spark.

GLIDE PATH: The most prudent line of descent for an aircraft about to make a landing.

GO AND NO-GO GAUGE: An inspection tool, with two tolerance options—one a part (a rod, or a screw) into which the piece to be inspected will fit, and the other that will not fit, and from which one can then determine the dimensional correctness of the piece.

GOVERNOR: A mechanical device attached to an engine which can regulate and limit the engine’s speed.

GRAPHENE: A form of carbon, produced in barely-visible sheets one molecule thick, artificially created in 2004 and now widely studied because of its formidable strength and lightness.

HA-HA: An artificial ditch created, often in large estates, as a near-invisible boundary around fields, meadows, and gardens.

INTERCHANGEABLE PARTS: A basis for modern manufacturing whereby all the component parts are made to be identical one with the other, so they will always fit when assembled. The concept, first developed in eighteenth-century France, dominated the American manufacturing industry of the nineteenth century.

INTERFEROMETER: A highly accurate optically based measuring device which splits a beam of light in two and recombines it such that differences in length along the paths followed by the beams cause the light waves to interfere and produce colored patterns from which differences in length can be deduced.

JIG: A guide, or support, often made by hand, and which helps position a tool or drill so that an operation can be repeated many times.

LATHE: A turning machine, its origin of great antiquity, in which the piece to be turned—usually wood or ivory or metal—is firmly held in a horizontal position and rotated while tools are brought to bear upon it.

LIGNUM VITAE: Usually refers to the wood of a West Indian tree, known for its exceptional hardness and self-lubricating properties. It was long used to make gearwheels and other mechanical parts. It will sink in water.

LIGO: The Laser Interferometer Gravitational-Wave Observatory, though usually referring to the two American-based observatories in Louisiana and Washington, can extend to a worldwide network of devices recording and measuring the passage of gravitational waves through the fabric of space-time.

MACHINE TOOL: A usually nonportable tool used for drilling or milling or shaping metal; often said to be a machine that makes machines.

MAGNETO: A small device that, employing magnets and coils of conducting wire, will produce a spark when turned mechanically.

MATINS: The first of the daily religious rituals of a monastic day, of which compline (q.v.) is the last.

MICROMETER: A measuring device, often based on a finely made screw and a graduated means of turning it to advance and retard its parts, employed for the highly precise determination of dimensions.

MRI: Magnetic Resonance Imaging—a means of examining the invisible internals of items—usually human parts and organs, though the technique can be applied to non-living entities—with the combined use of powerful magnetic fields and high-frequency radio waves.

ORRERY: A usually clockwork mechanism which simulates, for entertainment or study, the motion of the celestial bodies around the sun or Earth.

PANTOGRAPH: A mechanism composed of jointed metal parallelograms which permits the exact copying of plans, diagrams or solid objects, since tracing the outline by one end of the device produces exactly similar movement of pens or cutting implements at the other.

PERMIAN: A 50-million-year-long geological period, beginning about 290 million years ago, and following the Carboniferous era. Often large thickness of sandstone or salts were laid down to form the capstone to oil and gas deposits from earlier times.

PHOTOLITHOGRAPHY: A form of printing in which a photographic image is transferred to a printing surface; today used in the manufacture of semiconductors.

PLANCK CONSTANT: Named for Max Planck, the German physicist, it relates the energy of a quantum of electromagnetic radiation to its frequency. It is usually represented by the symbol h.

PLASMA: A gas, usually formed at very high temperature, characterized by the presence of free electrons and positive ions.

PRECISION: Though often synonymous with accuracy and exactness, it is taken by engineers to mean the degree of refinement in a specification, the greater the number of zeroes after the decimal point suggesting the greater the precision of a measurement.

QUANTUM MECHANICS: The branch of physics concerned with the interaction and duality of atomic and subatomic particles and phenomena.

RATE (OF WARSHIPS): The classification of warships, in days of sail, according (by and large) to the number of guns: a first-rate ship would carry 100 cannon, a second rate 80, and so on.

REMONTOIR: The part of a clock that, by a system of weights and springs, keeps a constant power supply to the balance.

RUNAWAY: If an engine governor fails it is probable that the engine will run away, unchecked—which can be exceptionally dangerous.

SANSCULOTTE: So named—“without trousers”—because of their usual shabbiness, the term refers to the revolutionary poor in France who did much of the dirty work during the “Terror.”

SEMICONDUCTOR: A material—silicon, germanium—that has conductivity which can be altered. It forms the basis of almost all transistors in small electronics.

SEXTANT, OCTANT: A mariner’s hand-held instrument useful for employing the stars and planets for navigation. GPS has almost entirely supplanted the use of the sextant and its kin, the octant, though navigators still have to know how to use them.

SI: Only Burma, Liberia, and the United States have declined to sign up for the International System of Units, signified by the initials SI.

SILICON: One of the most common molecular constituents of the rocks that make up this planet, and a component now at the heart of most computer chips.

SLIDE REST: That part of a lathe which holds the various tools that can be brought to bear on a workpiece.

SLIDE RULE: Until recently all engineers carried a top-pocket slide rule, a portable calculating device of great speed and limited accuracy, which employed sliding rules marked with logarithmic scales, and the movement of which could give instant answers to arithmetical questions.

SPRINGS (BOATMANSHIP): The ropes which are used to secure a vessel to the dockside were called springs; the order to ease springs meant to loosen the ropes in preparation for sailing.

SPUD (OIL INDUSTRY): To begin the drilling of an oil well the bit is bounced up and down against the surface until a foot-deep hole has been created, after which drilling proper can begin.

TALLEYRAND: An eighteenth-century French diplomat and bishop—and prince—whose cunning, craftiness, and hauteur became a byword.

TAPPET: A small piece within a machine that rises and falls on contact with a camshaft, and can in doing so impart motion to a larger piece, such as a valve.

TEST MASS: The name given to the cylinder of fused silica mounted, along with a complex set of compensatory weights and springs, at the end of each chamber of the LIGO observatories.

TETSUBIN: A Japanese cast-iron kettle, with lid and handle, usually heated over a charcoal fire for making tea.

TOISE: Until it was phased out in the early nineteenth century, the toise was a measure of length in France, equivalent to about 1.9 meters. It was divided into 6 pieds.

TOLERANCE: The permissible variation in size from a specified standard allowed for a machined part. High precision demands high tolerances.

TRACEABILITY: The term refers to a chain by which any measurement may be traced back to a standard—so that, for example, the second on a wristwatch may be connected to and ultimately measured against the signal of constant time put out by an atomic clock.

TREMBLER COIL: An early spark generator used in the ignition systems of cars, such as the Model T Ford.

VANADIUM: The addition of this heavy silvery-gray element to steel greatly increases its hardness, and so forms the additive basis for many sophisticated alloys.

VERNIER: The sixteenth-century French mathematician who first created the scale that bears his name, and which allows for the measurement of fractions of the graduations on the main scale, against which a vernier scale is designed to slide.

VESPERS: Sunset prayers in a monastery, coming close to the end of the liturgical day.

WABI-SABI: The polar opposite of perfection; the aesthetic represented by this currently much-favored term denotes the appreciation of impermanence, roughness, and the quiet liking for craft.