A short description
of technical names or terms used in, or associated with, this website.
- Alchemy: Think of a bearded old man,
crouched in his medieval den and surrounded by his apparatus, trying yet again
to turn base metal into gold…without success. But many believed in the
art, from early times, including kings, princes and noblemen, up to the
late Renaissance. We have a good selection of early apparatus that can
make an authentic-looking set.
- Aneroid Barometer: A
smaller, more compact and easily portable version of the older Mercury Barometer,
“Aneroid” comes from the Greek, “without liquid.” It depends on a small
partially-evacuated and sealed capsule: the top moves in or out slightly
according to changes in the atmospheric pressure. Linkage transmits the
movement to turn a hand across a circular dial reading in inches or
centimetres (i.e. of mercury). Earlier versions often had an outer scale
that read in hundreds and thousands of feet, for mountaineers and
balloonists. First produced in France from 1865, they soon enabled
the Barograph to
- Astrology: A
false and inexact “science”, purporting to tell a person’s future by the
stars, but still believed in by many followers today. Do not confuse with Astronomy, next.
See also Zodiac.
- Astronomy: The
exact science of the study of the heavens – the stars, planets and
everything else out there. Until the invention of the telescope in 1608
all observations were by the naked eye. The first planet to be identified
by telescope was Uranus, in 1781.
- Armillary Sphere: A
spherical instrument composed of interlocking rings or circles, normally
brass but sometimes paste-board (as in 18th or early 19th
century French examples), representing the celestial sphere. They usually
have the Sun and (known) planets inside, and were often sold in pairs –
one Ptolemaic, or Earth centred, the other Copernican, or the correct
system, for comparison. Very decorative. See Globe Section, Items 74, 151, 300 and 379.
- Astrolabe: A
complicated flat circular brass instrument, invented by the early Persian
astronomers Before Christ, and introduced into Europe following the Moorish invasion
of Spain from AD700. An essential tool
of astronomers, Court astrologers and gentlemen scientists until the end
of the Renaissance, and a revered one to own. Among other things, they
could tell the time, provided you knew your latitude and could see the
stars, or, conversely, if you knew the time and could still see the stars,
you could work out your latitude. See Navigation Section, Items 80 and 81. See also Mariner’s Astrolabe.
- Barograph: A
barometer – but also produces a record of recent changes in the
atmospheric pressure as a trace round a drum of graph paper, marked in
days and hours. Thus, you can tell at a glance what the weather has been
doing, and might do in a few hours time. See Aneroid Barometer. Interesting-looking
things, in glass and polished wood cases, introduced in the late 19th
century. They are still produced today, to the same design. See the Weather
Section, Item No. 286.
- Backstaff: An
essential tool for mariners at sea, to measure the angle of the sun to the
horizon and thus calculate longitude: beautifully made, of rosewood with
boxwood scales. Used in the 17th and 18th centuries,
after the Cross-staff,
and until the introduction
of the Octant in
1748. See Navigation
- Bearing: A straight line between two
points on a map, chart or on land, given in degrees and minutes.
- Binnacle: The housing
for a Mariner’s compass, which, by means of two interlocking rings keeps
the instrument level and steady even during the most violent weather at
sea. See also Gimbals.
- Celestial Sphere (or Globe): A map of the heavens, as if seen with the observer standing in the
middle of it. Some have just the star positions and the outline of the
constellations indicated by a dotted line, but the more beautiful and
decorative ones have the constellations shown pictorially – animals, humans,
birds, fishes and objects. (First depicted by the engraver Albrecht Durer,
1471-1528.) See Globe Section, Items 62 and 69.
- Chronometer: A
highly accurate clock, used for determining Latitude, by mariners at sea or
explorers on land. First developed in the 18th century by John
Harrison and then refined by John Arnold and Thomas Earnshaw. Redundant
from 1972 with the introduction of SATNAV and now GPS.
- Co-ordinates: Two
values which fix your position: locally, on land, as compass bearings, or
both at sea or on land, (think explorers) as Latitude and Longitude.
- Cross-staff: An
instrument used for measuring the height (in degrees) of the sun or a star
above the horizon. An essential tool for mariners at sea for calculating
Latitude, used in the 16th and 17th centuries,
coming between the Mariners
Astrolabe and the Backstaff. See Navigation Section, item 218.
- Dead-reckoning: Navigation
by bearing and distance, without reference to the stars or the sun.
- Degree: The 360th part of a
circle, sub-divided into 60 Minutes.
- Electrostatic Generating Machines: Or,
spark machines, developed during the early investigations into the nature
of electricity. They produced a miniature bolt of lightning –
entertaining, but of no real practical application. Until recently many
school or college physics labs had a version called a Wimshurst Machine.
Various types were popular throughout the 18th and 19th
centuries, (see Section of Physics Apparatus and Spark Machines, No’s 409, 410 and 411) - but
Michael Faraday showed that what was needed was Alternating Current, not
DC, which these items only produced. See also Van de Graaff Generator.
- Fusee: Part of an early clock or
watch, a brass cone cut with a spiral groove, with a chain wound round it
connected to the spring: it exerted a constant “pull” on the movement, no
matter whether the mainspring was fully wound or nearly unwound.
- Gimbals: Two inter-locking brass rings
that hold a compass level and steady at sea: the word comes from the old
Norman French, gemels = twins. See also Binnacle and Marine Barometer.
- Gnomon: The part of a sundial which
casts the sun’s shadow onto the hour-scale, and thus tells the time (only
when, of course, the sun is out). “I
am a sundial, and I make a botch/ Of what is done
far better by a watch”. (Hilaire Belloc.) Many early English Church towers often had, and still
have, a clock-face plus a vertical sundial on the South side: if the clock
stopped or went wrong, the locals always knew that the sundial would be
- Gregorian telescope: See Reflecting Telescope,
Navigation Section, Item 66
- Hydrometer: A small instrument for measuring the specific gravity
of alcohol. Initially used by the Excise Men in the 18th
century, to calculate the amount of duty to be paid on imported wines and
spirits, according to their strength, but now mostly used by home-brewers.
Do not confuse with -
- Hygrometer: A small instrument for showing the amount of
humidity, especially in a laboratory, but anywhere else, ie garden or greenhouse. First introduced in Switzerland from 1783, early scientists soon realised that
they needed it to replicate conditions in their own laboratory to verify
experiments performed elsewhere.
- Knot: A unit of ship’s speed, expressed as nautical miles per
hour. (One nautical mile = 1.15 normal mile)
- Latitude: The angular distance, in degrees and minutes, North
or South of the Equator. Normally used in conjunction with Longitude (next).
- Longitude: The distance, in degrees and minutes, East or
West of the Greenwich Meridian (or Zero) Line, which runs from Pole to
Pole. Always a problem for Mariners until the introduction of the accurate
Chronometer in the late 18th
- Log: Either a book, a daily record of ship-board
events, including changes in the weather or the ship’s position: or a
device for measuring the ship’s speed through the water.
ordinary slim mercury barometer but adapted for ship-board use by mounting
it in Gimbals,
on the end of a short arm, to counter the movement of the ship. The glass
tube had a narrow waist just above the cistern to prevent the mercury
bouncing up and down in rough weather. Early versions had mahogany cases,
later ones slim brass tubes. See also Mountain Barometer. Superseded by
the introduction of the smaller, less fragile Aneroid Barometer from the late19th
simplified version of the Astrolabe, used at sea between
the 14th and 16th centuries to determine the height
of the sun and so calculate Latitude. Superseded first by the Cross-staff, then the Backstaff, and then Octants and Sextants. See Navigation Section,
Items 80 and 81.
- Mercury Barometer: First produced by Evangelista Torricelli
(1608-1647), Galileo’s last assistant, he realised that the pressure of
the atmosphere would support a column of mercury: the top of the mercury,
inside a slim glass tube, would go up or down slightly according to
changes in the weather. Later, the French scientist Blaise
Pascal added a short scale at the top, divided into centimetres, with
additional comments: “Wind/Rain”, “Variable”, “Fair”, “Good Weather” etc.
See also Mountain
a version of the mercury type (previous), Alpine mountaineers had long
known that air pressure decreases with height. By the late 18th
century expeditions carried one to measure their ascent, or the heights of
peaks scaled. These instruments had a much thinner tube, with a narrow
“waist” just above the cistern, to prevent the mercury, during an awkward
climb, from slamming up to the top of the tube and bursting it. See also Marine Barometer.
telescope: See Reflecting telescope.
- Newton’s Cradle: Isaac Newton’s simple but elegant apparatus to
demonstrate kinetic energy, or work done by a moving body impacting on a
stationary one. (Think billiard balls.) We have a nice example in the Physics Section.
- Nocturnal: A small hand-held instrument, usually of boxwood but
sometimes brass, for telling the time at night by star positions. Mostly
used at sea, many mariners preferred to mark the passing of the night
hours by turning the half-hour glass, rather than fiddling with this more
complex instrument – that is, even if the stars were visible. 16th-18th
century. Redundant after the invention of the Chronometer.
- Octant: A navigation instrument, introduced from the
1750’s and the fore-runner of the Sextant. See also Quadrant. All were used for
measuring the angle at sea from the horizon to the sun, and thus to
See Navigation Section, Item 77.
- Orrery: An intriguing mechanical device showing the (known)
planets as they revolve outwards from the Sun. First made in the UK for the Earl of Cork and Orrery (hence the name) by John Rowley in
1712, later and cheaper versions were produced until the end of the 19th
century. By mid-Victorian times, many gentlemen amateur-astronomers or
scientists had one in their study. They are all highly decorative. (Think
of Joseph Wright of Derby’s wonderful painting “A Philosopher Giving a
Lecture on the Orrery”.) See
Globe Section, Item 72.
- Pantograph: An instrument used by architects (including naval
architects) to reproduce plans or drawings to a larger or smaller scale.
When opened out for use it looks like a large inverted W.
- Pedometer: An instrument the size of a pocket watch, worn by a
walker, to record his paces, and thus a distance covered. 18th/19th
century. A version in 18th century Germany was made to be worn by a horse.
- Plane Table: Not an ordinary piece of furniture, but a small
table with a folding tripod base, taken out by surveyors: on a map pinned
to it they would record the angles measured by the Theodolite. 18th/19th
century. Early versions had a compass that slotted underneath, and a
folding boxwood ruler, divided into 360 degrees, that fitted round the
- Quadrant: Normally associated with the Octant and the Sextant, for observations at sea,
but much larger versions were made for astronomers, mounted on a wall or a
tall stand. (See the mural quadrant at the Old Royal Observatory, Greenwich.) Early versions were small, usually boxwood,
sometimes brass, with engraved lines and punch-stamped numbers and
letters. See Navigation Section, Items 371 and 372.
- Reflecting Telescope: These use a system of two polished metal
mirrors, an ingenious invention by James Gregory in Scotland 1664, hence the name Gregorian. He never made one, but his plans were seen
by Isaac Newton, who did, four years later, and then modified it: hence
the other name, Newtonian. (NB:
In this case, “Gregorian” has nothing to do with plain-song: that was
Saint Gregory of Tours, in the 6th century AD.) See
Navigation Section, Item 66.
- Refracting Telescope: The more usual type, with glass lenses arranged
along a sliding tube.
Small and portable, in the olden days they were often called a
“spy-glass”, a “ship’s captain’s long-glass”, or a “bring ‘em near”.
- Sextant: The 19th century development of the Octant, by now brass, with a
silver scale. See Navigation Section.
- Stadia Rod: Used in land survey, a telescopic pole, marked with
graduations, held upright by the Surveyor’s assistant some way from the Theodolite, which focussed on it.
known as Gunter’s chain, after its inventor Prof Edmund Gunter (1581-1626)
of Gresham College. Used as measurement, and as the name implies, a chain 66 feet long made up of 100
links, which formed the base-line for the start of a survey. Mid 17th
to early 20th centuries. Ten square Chains became one acre, an
area up to then generally accepted as the amount of land that a man with a team of two horses could
plough in one working day. Superseded from 1908 by the more
familiar circular steel tape-measure. A Chain is still, traditionally, the
length of a cricket pitch, 22 yards.
as the name implies, a globe of the Earth. On a
film set, the known geography of the time must conform to the period of
the film – you cannot have a late 19th century globe in a film
about Queen Elizabeth 1st and the Spanish Armada in 1588. See
Globe Section, Items 385 and 424.
- Theodolite: Mounted on a tripod, a complicated and
beautifully-made instrument used for land survey, it measures angles in
both the horizontal and vertical planes. The earliest versions used in England followed the Dissolution of the Monasteries
under Henry VIII in 1534, when the (considerable) Church lands were seized
and divided up between the King and his Court favourites.
- Traverse Board: A handy but simple wooden device, kept by the
Watch on a ship, and then handed over to the incoming Watch. It provided a
temporary record of course and wind direction. Introduced during the Renaissance, they were
still being used by mariners in the late 19th century. By then
they had a brass face. See Navigation Section, Item 65.
- Van de Graaff Generator: The ultimate in Electrostatic Generating Machines, capable
of producing a massive spark of millions of volts. Invented by Dr Robert
J. Van de Graaff at the Massachusetts Institute of Technology in 1926
(yes, as late as that) it was not used for serious scientific research until
1932. It soon became a favourite prop in early Frankenstein-type films.
See Physics Apparatus and Spark machines, No.150. A now largely-forgotten rock
band in the 1970’s adopted the name.
- Waywiser: (Sometimes called a Hodometer.) A device for measuring
distance, along a road or round the boundary of an estate, consisting of
an iron-rimmed wooden wheel connected to a dial, with a handle to push it
along: the dial, with two hands, read off in yards, chains, furlongs and
miles. 18th and 19th century.
- Wimshurst Machine: See Electrostatic Generating Machines. This
version, the most efficient up to then, with two counter-revolving glass
plates, was developed by James Wimshurst by 1880.
- Zodiac: Twelve of the major constellations, shown on Celestial Globes as running round
a band, the Ecliptic, at an angle to the celestial equator: in Astrology, associated with
people’s birth signs.