Cubit
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Cubit is the name for any one of many units of measure used by various ancient peoples and is among the first recorded units of length. The Cubit is possibly based on the forearm length of an average person, and the Egyptian hieroglyph for the unit shows this symbol. It was employed consistently for measuring products like timber, stone, cords and textiles through Antiquity, the Middle-Ages up to the Early Modern Times. The earliest known cubit is the Egyptian cubit of 28 digits (523/4mm, 20.6"), and other cubit measures, often divided into 24 digits, or 6 palms of 4 digits are known from Antiquity.
Over time, units similar in type to the cubit have measured:
- 6 palms, ~53.3 cm, or 21 inches (1.75 ft)
- 7 palms, ~52.5 cm, or 21 inches (1.75 ft)
- 8 palms, ~60 cm, or 24 inches (2.00 ft)
- 9 palms, ~67.5 cm, or 27 inches (2.25 ft)
From late Antiquity, a Roman cubit of 16 palms, which is about 120 cm, was also used. This length is the measure from a man's hip to the fingers of the outstretched opposite arm. Since the ulna is approximately 1/4 of this length (30 cm or 12 inches), this Roman cubit was considered highly practical for quickly measuring textiles or cords over the elbow.
The English yard could be considered to be a type of cubit, measuring 12 palms, ~90 cm, or 36 inches (3.00 ft). This would be the measure from the middle of a man's body to his fingers, always with outstretched arm. The English Ell is essentially a kind of great cubit of 15 palms, 114 cm, or 45 inches (3.75 ft).
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[edit] History of the different cubits
[edit] The Egyptian royal cubit
The Egyptians clearly used a standard measure as early as c. 2750 BC (Dynasty III) at Saqqara (J.P.Lauer). From the evidence this is widely accepted to have been 523.5 to 524 mm (20.61 to 20.63 in) in length, and was subdivided into 7 palms of 4 digits, giving a 28 part measure in total. This unit was used virtually unchanged for 2000 years, with occasional variations.
Old Egyptian geometers could calculate the square root of two from the value of the of the hypotenuse of a Cubit. This well-attested old Egyptian unit was known as the "construction remen" and used a good approximation: 2x20/28 ≥ root 2.
A shorter Egyptian rule of 6 palms may also have been employed, but based on the same 7 part standard. During Dynasty XII (1900 BC) the length of the royal cubit grew to about 529.2 mm (+1% more than the former old royal cubit). Since these times for the sides of the construction remen, the digits of the old Royal cubit were used. Therefore the ratio between the digits of the Royal cubit and the later called Roman digits is 100 to 98 exactly one. After the Egyptian length standard did not change anymore.
[edit] The Sumerian Nippur Cubit
The copper bar cubit of Nippur from c. 2650 BC is possibly a 'graduated rule' found by archaeologist and defines the Sumerian cubit as about 518.5 mm or 20.4 inches. It was published by Eckhard Unger in 1916, after studying the weights of the Museum of Constantinople. He interpreted it as a standard of length indicating 30-part standard of 518mm, and despite its irregularity, and the lack of any supporting textual evidence, this was, and still is, considered to be the earliest extant unit of measurement ever in existence, supposedly predating even units widely attested in Old Kingdom Egypt. The period in which this was published is notable for political and diffusionist arguments between Assyriologists and Egyptologists, so that the status of this item as a standard rule is highly questionable.
Two famous statues of the Sumerian regent Gudea (c.2150 B.C.) found in 1880 in the excavation of Lagash by Ernest de Sarzec, with Gudea holding on his knees a rectangular writing tablet bordered with a graduated measuring rule. The two rules appear identical and indicate a 16-part measure of around 250mm, similar to a typical but short foot.
[edit] Other important cubits
- The Roman cubitus is a six-palms-cubit of about 444.5 mm. Twenty-four Roman cubits equal thirty-five English feet. So, the Roman cubit is defined to be 17.5 inches exactly one.*
- The Greek pechua (πεχυα) was also a 24-digit-cubit. So, the Greek Kyrenaika Cubit measured about 463.1 mm and the Greek Metrios Cubit about 474.2 mm; respectively 25/24 and 16/15 Roman cubits. Other Greek cubits based on different digit measures of other city-states are less important. The Greek 40-digit-measure, called bema, corresponds to the Latin gradus, the step or half-a-pace.
- The Arabic Hashimi Cubit of about 650.2 mm (25.6 inches) is considered to measure two French feet. Since the established ratio between the French and English foot is 16 to 15 (the small error of about 0.086 % is owed to imperfect standards, not-adjusted mutually), one can give following equation: 5 Hashimi cubits = 10 French feet = 128 English inches. Also the length of 256 Roman cubits and the length of 175 Hashimi cubits are equivalent.
- The Guard Cubit (Arabic: ammatu rabitu) measured about 555.6 mm; 5/4 of the Roman cubit. Therefore: 96 Guard cubits equal 120 Roman cubits equal 175 English feet.
- The Arabic Nil Cubit (or Black Cubit) measured about 540.2 mm. This means 28 (later called) Greek digits of the "Pous of Kyrenaika" equal to 25/24 of a Roman foot or just 308.7 mm. Thus 175 Roman Cubits equal 144 Black Cubits.
- The Mesopotamian cubit measured about 533.4 mm, 6/5 Roman cubit. Thus, 20 Mesopotamian cubits equal 24 Roman cubits equal 35 English feet.
- The Babylonian cubit (or cubit of Lagash) measured about 496.1 mm. Also a Babylonian trade cubit existed, nine tenth of the normal cubit, i.e. 446.5 mm. The Babylonian Cubit is fifteen sixteenths of the Royal cubit. 160 Babylonian trade cubits equal 144 Babylonian cubits equal 135 Egyptian Royal cubits. (The Royal cubit is equal to 529.2 mm. See above).
- The Pergamon cubit 520.9 mm or 75/64 of the Roman cubit.
- The Salamis cubit 484.0 mm or 98/90 of the Roman cubit.
- The Persian cubit of about 500.1 mm or 9/8 of the Roman cubit, which is also 9/10 of the Guard cubit.
- In Izapa, a Precolumbian Mesoamerican city, the measuring unit was equivalent to about 495 mm, very close to the Lagash cubit. This is probably a coincidence, since a diffusion of culture from Mesopotamia to Mesoamerica has not been conclusively demonstrated.
The different Jewish cubits (אַמָּה ama) are generally borrowed either from Babylonians or Greeks or Romans. In ancient Israel during the First Temple period, the cubit was 428.1 mm (= 26/27 Roman cubit). During the Second Temple period, a cubit of about 444.5 mm (= Roman cubit) was in general use, but in the sacred areas of the temple a special cubit of 437.6 mm seems to have been used instead (= 63/64 Roman cubit).[1]
* 17.5 inches, with 25.4 mm per inch gives 444.5 mm for the Roman cubit.
[edit] See also
[edit] References
Vormetrische Längeneinheiten by Rolf C. A. Rottländer, Rottenburg / Köln (also see Search-Engine).
Recovery of the Ancient System Foot/Cubit/Stadion — Length Units by Dieter Lelgemann, acting Director of the Institute for Geodesy and Geo-Information Technology, TU Berlin.
On the Ancient Determination of Meridian Arc Length by Eratosthenes of Kyrene Dieter Lelgemann, WS – History of Surveying and Measurement, Athens, Greece, May 22-27, 2004.
Knobloch, Eberhard, Dieter Lelgemann und Andreas Fuls: "Zur hellenistischen Methode der Bestimmung des Erdumfangs und zur Asienkarte des Klaudios Ptolemaios."
zfv (Zeitschrift für Geodäsie, Geoinformation und Landmanagment) 128. Jahrgang, Heft 3/2003, S. 211-217.
[edit] Notes
- ^ Cf. Biblical Archaeology Review, March-April 1983, and Newsletter and Proceedings of the Society for Early Historical Archaeology, issue 159.)
[edit] External links
- Measurements of the Nippur Ell, now in a museum in Istanbul (Turkey).
