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Abacus
A mathematical instrument of simple but timeless form. The name, which has existed in English since at least the later 14th century, derives from the Ancient Greek word for 'disc' or 'table' (abakos). In the ancient world an abacus was a flat surface for reckoning accounts, not necessarily an object but sometimes just an area marked out in the sand and often with pebbles as tokens.

The oldest abacus yet discovered, on the Greek island of Salamis, dates from c.300 BC. Roman abaci took either the form of a wooden calculating board or a bead abacus with counters that moved along in slots. The latter form was convenient enough to hold in the hand. Bead-frame abaci developed in many countries including in the Far East where the beads adopted distinctive shapes. The beads can be slid along a frame of parallel rods or wires. The abacus is often seen as the symbol of the Victorian schoolroom, where despite its significance in the teaching of numeracy it may be dismissed as a 'toy' example. The Cranmer abacus is an adapted didactic tool for the visually impaired. More tongue-in-cheek, the abacus has sometimes be used as a symbol of the history of computing.

Also known as: counting frame

Pullan, J. M., 1968, The History of the Abacus, Books That Matter, London

Wikipedia: Abacus

Abney Level
A surveying instrument. A variant of the clinometer (q.v.) invented by William Abney of the School of Military Engineering, Chatham, Kent. It reads the angle through which a pivot has been turned.

Clinometers

Absorptiometer
A chemical instrument for measuring the solubility or concentration of absorbing constituents of gases or liquids. The first type grew out of the investigations into the solubility of liquid-forming gases by the Polish scientist Zygmunt Florenty Wróblewski (1845-1888) at the Jagiellonian University in Kraków in the late 1870s and early 1880s. Modern types operate by measuring the absorption of monochromatic radiation.

Absorptionmeter
A physical/chemical instrument utilising a photo-electric cell to measure the absorption of light by differing thicknesses of glass (or other transparent material, such as water). As well as their uses in research and development they are useful in engineering processes for purposes of quality control.

Also known as: A-meter

Accelerometer
A physical instrument for measuring the acceleration of a moving body. Accelerometers can also be used to analyse mechanical vibration and the effect of gravity. Modern accelerometers are useful in designing engines for the motor industry, the design of musical instruments and in protecting delicate electronic devices from impact damage.

A beginner's guide to accelerometers

Acetometer
Chemical instrument. A type of hydrometer (q.v.), originally a mid 19th century device to measure the amount of acetic acid in a liquid, especially vinegar.

Also known as: Acetimeter

Acidometer
Chemical instrument. A type of hydrometer (q.v.) or areometer (q.v.), originally designed in the 1830s, to measure the strength of an acid. Modern digital acidometers gauge the relative density of an acid solution although traditional instruments are still commonly encountered as accessories to wine making kits.

Also known as: Acidimeter

Acoumeter
Physical instrument. A precision device to determine hearing acuity or to measure small differences in sound perception.

Also known as: Acousimeter

See also: Audiometer

Actimeter
Physical instrument. A precision device used in various disciplines, particularly medicine and bio-engineeering to measure and record movements (locomotor activity), using (for example) mercury sensors or force plates scanned by infra-red technology.

Also known as: Actometer

Actinometer
Physical/chemical instrument. A device used to measure the intensity of radiant energy. The original actinometer was used by Sir John Herschel to measure the rays of the sun in 1825.

Also known as: Dosimeter

Acutometer
Optical instrument. A device used to measure the width of visual acuity by means of an ever expanding black line.

Adaptometer
Optical instrument. A device used to measure the time taken in retinal adaptation, first used by Willibald Nagel of Rostock in 1907. This instrument had an iris shutter in front of a plate of milk-glass, thus giving a stimulating surface of variable area and intensity. The change in area was also produced by changing the dis- tance of the observer from the instrument. Red filters or blue-green liquid could be interposed which transmitted only rays of the same colour. Various adaptometers and photometers have been devised since. The test is useful in determining night blindness, for instance amongst military and naval personnel.

Addition machine
A mathematical instrument for arithmetical calculation by means of a mechanical gearing arrangement. First invented by Wilhelm Schickhard in 1623 their development is associated particularly with Blaise Pascal in the 17th century. His addition machine of 1645 went into some form of pre-commercial production before 1652. In 1672 Gottfried Liebnitz introduced a variant that was capable of performing multiplication tasks.

Also known as: Pascalina, Pascaline, Arithmetique

Adjusting cone
Optical instrument. A device used to measure the distance between the axes of the eyes.

Aerial
A device for radiating and receiving radio waves.

Also known as: Antenna

Aerometer
Chemical instrument. A device used to measure the mass and specific gravity of gases. Essentially a late 18th century instrument, described by George Adams Jr in 1794, but the name was also used to mean a hydrometer (q.v.) in the ancient Hellenic world.

Aesthesiometer
An instrument used to measure the tactile sensitivity of parts of the human body. The simplest types are manual tools similar to a caliper. Sensory test devices to gauge the pain threshold of e.g. skin, were developed in the 20th century by Dr. Sidney Weinstein. The three-point Weinstein Aesthesiometer gives readings in millimetre gradients. A corneal aesthesiometer is used to test the sensitivity of the corneal nerve by using a controlled pulse of air. The device gives a reading in millibars. Thermal aesthesiometers are used to determine the sensitivity of thermal stimuli.

Also known as: Esthesiometer (US); Tactometer

Air pump
A pneumatic instrument used in physics demonstrations to create a vacuum within a container or space, or to condense air into a closed space. First invented by Otto von Guericke (1654)in the form of Magdeburg hemispheres, an improved single cylinder design was produced by Robert Hooke in Oxford in 1658 whilst he was assisting Robert Boyle's research into gases. On the European Continent the Van Musschenbroeks produced large-bore single cylinder models in the eighteenth century whereas in England the twin-barrel design as exemplified by the models of Francis Hauksbee attained popularity. An air pump is the subject of a famous painting by Joseph Wright of Derby: 'An Experiment on a Bird in the Air Pump' (1768) in which a cocaktoo within the flask is gradually deprived of oxygen before a mixed audience of adults and children.

Also known as: air compressor, vacuum chamber, vacuum pump

Hauksbee, F., 1709, Physico-Mechanical Experiments

Replica of Hooke's air pump

See also: Vacuum flask

Air Speed Indicator
Navigational instrument for measuring the velocity of an aircraft relative to the air through which it moves.

Alethiometer
(Fictional) Navigational instrument featured in the children's novel 'Northern Lights' by Philip Pullman, supposedly manufactured in the 16th century of a parallel world to ours, with four compass needles that can answer any question and seek out the Truth. Meaning has to be interpreted from combinations of readings taken from the 36 symbols on the decorative face of the instrument. The keeper of the instrument is a twelve-year old girl Lyra Belacqua, who was given it by the Master of Jordans College Oxford.

Also known as: The Golden Compass

Pullman, P., 1995, 'Northern Lights', Scholastic, London

Analytical machine
Mathematical instrument for performing calculations and, unlike the Difference Engine, capable of carrying out any mathematical operation. Charles Babbage designed his prototype in 1834 but he never started production as he still hadn't completed his Difference Engine and so no further funding could be obtained. If built, it would have been steeam powered and programmable using punched cards. A few working test models for specific components of the machine have survived including a portion of the 'mill' with printing mechanism to be found in the Science Museum, London.

Also known as: Analytical engine

Swade, D., 1991, Charles Babbage and his Calculating Engines, Science Museum, London

Component of the Analytical Engine

See also: Difference engine

Antigraph
Mathematical/Drawing instrument. An instrument for drawing parts of a figure the reverse hand to the original. It consists of a three-wheeled carriage, which is designed to run perfectly straight. It is centred on a line midway between the image to be copied and the location of the reverse image to be drawn. Two arms project forward of the carriage and are geared together such that the movement of one is mirrored by the other, One of these arms carries a tracing point and the other a pencil.

Stanley, W.F., 1900, 'Mathematical Drawing and Measuring Instruments', 7th edn, E & FN Spon.

Archimedean screw
A mechanical instrument often reproduced, since the 18th century, as a laboratory demonstration model in which a ball is made to rise up an inclined plane. The original device, to raise water for irrigation purposes, was traditionally ascribed to the invention of Archimedes circa 350 BC and consisted of a spiral helix or helices surrounding the inclined plane, sometimes within a tube and powered by a treadmill or waterwheel. Pescalators are a form of Archimedean screw designed to lift fish from a pond.

Also known as: Archimede's screw, Cochlea, Screwpump

Similar to: Caged screw, Pressurised screw

See also: Inclined plane

Architectural Proportional Rods
Mathematical instrument. Triangular brass rods, in sets of five, for calculating the elements of the five classical orders of architecture.

Hambly, M., 1988, 'Drawing Instruments 1580-1980', Sothebys Publications

Areometer
A hydrostatic instrument to measure the specific gravity of liquids. The use of Nicolson's areometer (brass) was described by Frick in 'Physical Technics; Or, Practical Instructions for Making Experiments in Physics' (1862). In essence Nicholson's instrument drew upon the principles outlined by Boyle in 1675. Fahrenheit's areometer was made of glass so that it would not react with any of the liquids in which it was immersed.

Also known as: araeometer, hydrometer

Elements of Mechanics by W.G. Peck, 1859

See also: hydrometer

Arithmometer
A mathematical instrument produced in Paris in 1820, generally regarded as the first commercially successful calculating machine. The arithmometer of C.X. Thomas was a long wooden box with apertures through which to view the numbers. It owed much to the theory behind Leibniz's multiplying machine of the 1670s

Also known as: Thomas machine

A Brief History of Mechanical Calculators Part II

Armillary sphere
An astronomical instrument which has often been regarded by writers and artists as the very symbol of astronomy. The Ancient Greeks and Chinese both developed the instrument independently from the 3rd century BC and a similar form of device was developed by scholars in countries under Islamic rule from at least the 8th century AD. Large observational examples were erected in early observatories particularly before the advent of the telescope, but portable, often hand-held instruments survive from the 15th century onwards.These were usually demonstrational in function. Skeletal in appearance, the armillary sphere comprises numerous concentric rings that together indicate the heavens including the equatorial and celestial circles, the poles and tropics and against which the observer could plot the position of other celestial bodies. The design of armillaries changed as understanding of the solar system developed from a Ptolemaic arrangement with a ball to represent the earth at the centre, to a Copernican system centred around the sun. In the second half of the sixteenth century Tycho Brahe combined armillary spheres with astrolabes whilst Queen Elizabeth I of England had a pair of ear-rings in the shape of armillary spheres. Wooden and pasteboard examples were used for teaching but some very fine examples of precious metal and other materials were produced for aristocratic libraries where they often formed a set with one or more globes.

Also known as: celestial sphere, celestial globe, spherical astrolabe

The Armillary Sphere

See also: astrolabe

Artificial horizon
A Navigational instrument used on land, traditional forms of which consisted of a glazed wooden box containing a trough of liquid mercury. Modern examples employ a bubble level attached to a black glass plate supported by levelling screws. Attitude indicators are a form of artificial horizon used in aircraft to inform the pilot of his orientation relative to the earth.

John Charles Fremont - The Artificial Horizon

Astrolabe (mariner's)
Navigational instrument for plotting the altitude of the sun near the meridian. Thought to have been introduced around 1470 the oldest extant (dated) example is Portuguese, dates from 1550-1555 and resides in the McManus Museum, Dundee. Mariner's astrolabes are characterised by their heavy weight and and cut-away portions designed to lessen wind resistance.

See also: Astrolabe (planispheric) of which this instrument is a development

Also known as: Nautical astrolabe

Astrolabe (planispheric)
A mathematical instrument to facilitate angular measurement for purposes of surveying or astronomy. The name literally translates as 'star-taking'. Astrolabes are commonly of brass, circular in shape and outlined with a stereographic projection of the globe and the hemisphere of the heavens. The outer 'limb' comprises a 360 degree scale against which the rule (alidade) may be aligned to measure the altitude of a star by cross-reference to a revolving disc (rete). The instrument shows two distinct lines of development: Islamic and Western European. The Islamic type originated in Syria in the 9th century and penetrated to Spain via North Africa in the 10th century. They were still being manufactured in the 20th century due to their use as a calculating device for the times of Muslim prayers. Western astrolabes were produced around various centres including England, France, Germany and the Netherlands.

Chaucer, G., 1391 'The Treatise on the Astrolabe'

See also: Astrolabe (spherical)

Astrolabe (spherical)
A mathematical instrument to facilitate angular measurement for purposes of surveying or astronomy. Spherical astrolabes comprised a model of the globe and heavens. Only one complete example is known to exist.

Atwood Fall machine
A mechanical instrument. George A(t)twood's machine, described in 1784, was taller than a man and consisted of a complex pulley system atop a wooden column to demonstrate the acceleration and retardation of bodies according to Newtonian laws of motion. A simple Atwood machine can be rigged up with two masses (weights) suspended over a pulley and photogates or more traditional timing mechanism. The design of passenger lift machinery is dependent upon the same principles.

Martins, D.R. and Providencia, J. da., 2000, 'The Poleni machines of the Universities of Padua and Coimbra and the instruments to study motion due to gravity', Bulletin of the Scientific Instrument Society 66, pp.23-25

Atwood's Machine

Atwood Fall machine

Audiometer
Physical instrument. A precision device to determine hearing acuity or to measure small differences in sound perception. The automatic type used as a diagnostic instrument in audiology, with oscillator, amplifier and attenuator, was introduced in 1946 by the Hungarian Georg von Bekesy (1899-1972) who had formerly worked on the development of telephone engineering.

Discoveries in Medicine: Audiometer

Bekesy and the Place Theory of Pitch Perception

See also: Acousimeter, Sonometer
Avometer

Avometer
Trade name. Electrical instrument. A particular multimeter made and trade-marked by the AVO company.

See also: Multimeter

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B

Back-staff
Navigational instrument for finding the meridian altitude of the sun. The most popular form was invented by John Davis circa 1594 and is illustrated in his book 'Seaman's Secrets'. The instrument was intended to replace the quadrant, mariner's astrolabe and cross-staff. It qualifies as a quadrant because it can measure 90 degree angles.

See also: quadrant, octant

Wikipedia: Backstaff

Seaman's Secrets (Transcription)

Also known as: backstaff, Davis quadrant, English quadrant, back-quadrant

Balance
Weighing instrument. The most basic form consists of two pans suspended from opposing ends of a beam. The beam attains a horizontal equilibrium at the point when the known fixed weights in one pan equal the weight of the items or goods to be measured. Jeweller's balances have a very thin beam and small pans and were mounted on a stand whereas apothecaries' balances, often with pans of glass were supported in the hand. Very precise chemical balances mounted on levelling screws were made by various important instrument makers in the 18th and 19th centuries but are quite rare.

See also: Scales

Barometer
Meteorological/philosophical instrument that measures the pressure or weight of air. Their invention is traditionally ascribed to Evangelista Torricelli in 1644. By the early eighteenth century makers such as John Patrick could be found specialising in barometers. A typical instrument has a glass tube with a vacuum at the sealed top and an open bottom end descending into a cistern of mercury. A variation, beloved of school physics experiments, consists of a bent or siphon tube. Eighteenth century barometers were mainly of the stick type, encased in mahogany or other ornamental woods and mounted on a wall or combined with thermomemters or clocks. Mountain barometers were used for measuring high altitudes from at least 1800. Some were used in conjunction with a thermometer and sent to altitude in a hot-air balloon. Barometers to measure the depths of mines employed a similar principle in the opposite context. The aneroid barometer (fluidless), which uses metal bellows, was invented by Lucien Vidie in 1845 and pocket versions were developed in the 1860s. Prominent barometer makers have included Daniel Quare, W & S Jones, Negretti & Zambra, W. F. Stanley.

Also known as: Weather glass

Barometer (Liegeois)
Meteorological/philosophical instrument for measuring air pressure. A particular type of barometer pioneered by the glass blowers of Liege in the early eighteenth century and thereafter common to the Netherlands. They are filled with water and pressure causes the water to rise up a spout, allowing the amateur prediction of storms.

Barometer (Marine)
Meteorological/philosophical instrument for measuring air pressure, in particular to predict storms, whilst compensating for the movement of a ship. The first successful model, with a constricted tube, was made by Edward Nairne and was taken on Captain Cook's second voyage to the Pacific in 1772. It seems these early marine barometers could swing freely while suspended within a four-legged frame. The partnership of Nairne & Blunt produced many from 1773. Later models did away with the stand and were instead weighted at the cistern or fixed to the bulkhead by a supporting arm. It has been suggested that Matthew Berge was the originator of the 'weighted chimney' form of barometer with a brass tube and lead collar. Gimbal arms were certainly in use by the early nineteenth century. Heavier brass-covered cistern barometers did away with the need for specific weighting by the 1820s.

McConnell, A., 2005, 'The Origins of the Marine Barometer', Annals of Science 62-1, pp.83-101

Marney, P. and McConnell, A., 2008, 'Weighted Marine Barometers', Bulletin of the Scientific Instrument Society 96, pp.10-13

Barometer (Wheel)
Meteorological/philosophical instrument for measuring air pressure. An early type of barometer devised in the 1660s working on the siphon tube principle but employing an addition weighted pully system to record the movement of the mercury against a circular dial, behind which the tube is concealed. It proved particularly popular in 19th century banjo-shape barometers, often made in Great Britain by workers of Italian origin, for example Negretti & Zambra.

Also known as: Banjo barometer

Binnacle
A navigational instrument comprising a weather-protective housing for a ship's compass, often of mahogany and brass with glass viewing ports and with spherical iron correctors to each side to counteract the magnetism on iron-hulled vessels.

Binoculars (Galilean)
Optical instrument. 'Binoculars' can comprise any device designed for use with both eyes, i.e. which can be described as having binocular use. There are two main types of binoculars, Galilean and Prismatic (q.v.). Galilean binoculars use the so-called Galilean system of lenses (a convex objective lens and a concave eyepiece) in each tube. Binoculars of this sort were first made as early as 1608, but became common in the nineteenth century, in particular as opera glasses (q.v.). They have limited application due to their restricted field of view and relatively low magnification.

Watson, F., 1995, Binoculars, Opera Glasses and Field Glasses, Shire Publications, Princes Risborough

Wikipedia: Binoculars

See also: Binoculars (Prismatic), Opera Glasses

Binoculars (Prismatic)
Optical instrument. 'Binoculars' can comprise any device designed for use with both eyes, i.e. which can be described as having binocular use. There are two main types of binoculars, Galilean (q.v.) and Prismatic. The latter type of binoculars use a more complex combination of the Keplerian lens system (with convex objective and eyepiece lenses) and prisms. This gives a higher magnifying power and a greater field of view than Galilean binoculars. A prismatic optical system of this sort was first patented by a former Italian artillery officer and military surveyor, Ignazio Porro, in 1854, but his ideas were only fully taken up at the end of the nineteenth century when German firms like Zeiss overcame the difficulties of producing good prisms relatively cheaply. Following their introduction, prismatic binoculars rapidly replaced both Galilean binoculars and hand-held telescopes for many functions.

Watson, F., 1995, Binoculars, Opera Glasses and Field Glasses, Shire Publications, Princes Risborough

Wikipedia: Binoculars

See also: Binoculars (Prismatic), Opera Glasses

Bismar
Weighing instrument. A form of balance (q.v.) with arms of unequal length. The counterpoise weight is fixed at one end and the fulcrum can be moved until the axis of the beam reaches equilibrium at which point the position of the fuclrum is read off a scale. Bismars were particularly popular in Northern Europe and the Baltic in the 18th and 19th centuries.

Burning Glass

Spargo, P.E., 1984, 'Burning Glasses', Bulletin of the Scientific Instrument Society 4, pp.7-8 [N.B. Errata concerning figure captions corrected in Issue 5 p.23]

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Cross-staff
Mathematical/navigational instrument used to measure the angular distance between different bodies. The instrument was first described in Europe in the fourteenth century by Levi Ben Gerson. Slightly different versions were then developed for use in astronomy, surveying and, by the sixteenth century, navigation. Usually made of wood, the navigational version consisted of a staff and up to four vanes that could move along the staff’s length. To use the cross-staff, the observer rested one end on the bone just below their eye and moved one of the vanes until its lower edge was in line with one of the bodies and its top edge with the other. They then read off the angle on the corresponding scale on the main staff. At sea, the cross-staff was used to determine latitude by measuring the maximum height of the sun or the pole star above the horizon.

Also known as: Jacob's staff

Morzer-Bruyns, W.F.J., 2009, Sextants at Greenwich, OUP/National Maritime Museum, Oxford and Greenwich

Morzer-Bruyns, W.F.J., 1994, The Cross-Staff, Zutphen

Wikipedia: Cross-staff

Curves (Flexible)
A drawing instrument. A thin, flexible band of steel or celluloid which could be formed to the shape of the desired curve and drawn around. Mr J W Brooks invented four different types. A more recent form of flexible curve consisted of lead core, sheathed in plastic.

Curves (French)
A drawing instrument. Drawing templates with curves of varying radius and irregular shape made in many patterns. Originally made of thin wood, they were also made from vulcanite, celluloid and plastics.

Also known as: irregular curves.

Curves (Railway)
A drawing instrument. Drawing templates of constant radius sold in sets of from 25 to 100 and typically varying in radius from 1.5 to 30, 120 or 240 inches depending on the size of set. Similar were Railway Degree Curves, sold in sets of 40, with tangents from 30 minutes to 11 degrees to a scale of 1 inch to 100 feet. Typically made of mahogany, varnished card or celluloid.

Curves (Ship)
Drawing instrument. Drawing templates of varying radius and irregular shape intended for use by naval architects. The Admiralty Pattern consisted of 40 different curves and sets of nine, fifteen or forty were sold. Kemp’s Pattern consisted of five heart-shaped curves. Sets of Yacht Curves were also made, broadly similar to Admiralty Pattern Ship’s Curves.

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