Mile

The Roman mile (mille passus, lit. "thousand paces"; abbr. m.p.; also milia passuum[n 1] and mille) consisted of a thousand paces as measured by every other step—as in the total distance of the left foot hitting the ground 1,000 times. The ancient Romans, marching their armies through uncharted territory, would often push a carved stick in the ground after each 1,000 paces. Well-fed and harshly driven Roman legionaries in good weather thus created longer miles. The distance was indirectly standardised by Agrippa's establishment of a standard Roman foot (Agrippa's own) in 29 BC,[9] and the definition of a pace as 5 feet. An Imperial Roman mile thus denoted 5,000 Roman feet. Surveyors and specialised equipment such as the decempeda and dioptra then spread its use.[10]

In modern times, Agrippa's Imperial Roman mile was empirically estimated to have been about 1,617 yards (1,479 m) in length.[11]

In Hellenic areas of the Empire, the Roman mile (Greek: μίλιον, mílion) was used beside the native Greek units as equivalent to 8 stadia of 600 Greek feet. The mílion continued to be used as a Byzantine unit and was also used as the name of the zero mile marker for the Byzantine Empire, the Milion, located at the head of the Mese near Hagia Sophia.

The Roman mile also spread throughout Europe, with its local variations giving rise to the different units below.

Also arising from the Roman mile is the milestone. All roads radiated out from the Roman Forum throughout the Empire – 50,000 (Roman) miles of stone-paved roads. At every mile was placed a shaped stone. Originally these were stone obelisks made from granite, marble, or whatever local stone was available. On these was carved a Roman numeral, indicating the number of miles from the centre of Rome – the Forum. Hence, one always knew how far one was from Rome.[12]

The Italian mile (miglio, pl. miglia) was traditionally considered a direct continuation of the Roman mile, equal to 1000 paces,[13] although its actual value over time or between regions could vary greatly.[14] It was often used in international contexts from the Middle Ages into the 17th century[13] and is thus also known as the "geographical mile",[15] although the geographical mile is now a separate standard unit.

The Arabic mile (الميل, al-mīl) was not the common Arabic unit of length; instead, Arabs and Persians traditionally used the longer parasang or "Arabic league". The Arabic mile was, however, used by medieval geographers and scientists and constituted a kind of precursor to the nautical or geographical mile. It extended the Roman mile to fit an astronomical approximation of 1 arcminute of latitude measured directly north-and-south along a meridian. Although the precise value of the approximation remains disputed, it was somewhere between 1.8 and 2.0 km.

The "old English mile" of the medieval and early modern periods varied but seems to have measured about 1.3 international miles (2.1 km).[16] The English long continued the Roman computations of the mile as 5000 feet, 1000 paces, or 8 longer divisions, which they equated with their "furrow's length" or furlong.[17]

The origins of English units are "extremely vague and uncertain",[18] but seem to have been a combination of the Roman system with native British and Germanic systems both derived from multiples of the barleycorn.[n 2] Probably by the reign of Edgar in the 10th century, the nominal prototype physical standard of English length was an arm-length iron bar (a yardstick) held by the king at Winchester;[19][21] the foot was then one-third of its length. Henry I was said to have made a new standard in 1101 based on his own arm.[18] Following the issuance of Magna Carta, the barons of Parliament directed John and his son to keep the king's standard measure (Mensura Domini Regis) and weight at the Exchequer,[18] which thereafter verified local standards until its abolition in the 19th century. New brass standards are known to have been constructed under Henry VII and Elizabeth I.[22]

Arnold's c. 1500 Customs of London recorded a mile shorter than previous ones, coming to 0.947 international miles or 1.524 km.[17]

The English statute mile was established by a Weights and Measures Act of Parliament in 1593 during the reign of Queen Elizabeth I. The act on the Composition of Yards and Perches had shortened the length of the foot and its associated measures, causing the two methods of determining the mile to diverge.[23] Owing to the importance of the surveyor's rod in deeds and surveying undertaken under Henry VIII,[24] decreasing the length of the rod by ​¹⁄₁₁ would have amounted to a significant tax increase. Parliament instead opted to maintain the mile of 8 furlongs (which were derived from the rod) and to increase the number of feet per mile from the old Roman value.[25] The applicable passage of the statute reads: "A Mile shall contain eight Furlongs, every Furlong forty Poles,[n 3] and every Pole shall contain sixteen Foot and an half."[27] The statute mile therefore contained 5,280 feet or 1,760 yards.[17] The distance was not uniformly adopted. Robert Morden had multiple scales on his 17th-century maps which included continuing local values: his map of Hampshire, for example, bore two different "miles" with a ratio of 1 : 1.23[28] and his map of Dorset had three scales with a ratio of 1 : 1.23 : 1.41.[29] In both cases, the traditional local units remained longer than the statute mile.

The Welsh mile (milltir or milldir) was 3 miles and 1470 yards long (6.17 km). It comprised 9000 paces (cam), each of 3 Welsh feet (troedfedd) of 9 inches (modfeddi).[30] (The Welsh inch is usually reckoned as equivalent to the English inch.) Along with other Welsh units, it was said to have been codified under Dyfnwal the Bald and Silent and retained unchanged by Hywel the Good.[31] Along with other Welsh units, it was discontinued following the conquest of Wales by the English under Edward I in the 13th century.

Edinburgh's "Royal Mile"—running from the castle to Holyrood Abbey—is roughly a Scots mile long.[32]

The Scots mile was longer than the English mile,[33] as mentioned by Robert Burns in the first verse of his poem "Tam o' Shanter". It comprised 8 (Scots) furlongs divided into 320 falls or faws (Scots rods).[34] It varied from place to place but the most accepted equivalencies are 1,976 Imperial yards (1.123 statute miles or 1.81 km).

It was legally abolished three times: first by a 1685 act of the Scottish Parliament,[35] again by the 1707 Treaty of Union with England,[36] and finally by the Weights and Measures Act 1824.[33] It had continued in use as a customary unit through the 18th century but had become obsolete by its final abolition.

Milestone on Mountbellew Bridge, erected c. 1760. Distances are given in Irish miles.

The Irish mile (míle or míle Gaelach) measured 2240 yards: approximately 1.27 statute miles or 2.048 kilometres.[37][38] It was used in Ireland from the 16th century plantations until the 19th century, with residual use into the 20th century. The units were based on "English measure" but used a linear perch measuring 7 yards (6.4 m) as opposed to the English rod of 5.5 yards (5.0 m).[38]

Various historic miles and leagues from an 1848 German textbook, given in feet, metres, and fractions of a "degree of meridian"

Scalebar on a 16th-century map made by Mercator. The scalebar is expressed in "Hours walking or common Flemish miles", and includes three actual scales: small, medium and big Flemish miles

• The Dutch mile (mijl) has had different definitions throughout history. One of the older definitions was 5600 ells. But the length of an ell was not standardised, so that the length of a mile could range between 3280 m and 4280 m. The Dutch mile also has had historical definitions of one hour's walking (uur gaans), which meant around 5 km, or 20,000 Amsterdam or Rhineland feet (respectively 5660 m or 6280 m). Besides the common Dutch mile, there is also the geographical mile. 15 geographical Dutch miles equal one degree of longitude on the equator. Its value changed as the circumference of the earth was estimated to a better precision. But at the time of usage, it was around 7157 m. The metric system was introduced in the Netherlands in 1816, and the metric mile became a synonym for the kilometre, being exactly 1000 m. Since 1870, the term mijl was replaced by the equivalent kilometer. Today, the word mijl is no longer used, except as part of certain proverbs and compound terms like mijlenver ("miles away").

• The German mile (Meile) was 24,000 German feet. The standardised Austrian mile used in southern Germany and the Austrian Empire was 7.586 km; the Prussian mile used in northern Germany was 7.5325 km. Following its standardisation by Ole Rømer in the late 17th century, the Danish mile (mil) was precisely equal to the Prussian mile and likewise divided into 24,000 feet.[39] These were sometimes treated as equivalent to 7.5 km. Earlier values had varied: the Sjællandske miil, for instance, had been 11.13 km. The Germans also used a longer version of the geographical mile.
• The Saxon Post mile (kursächsische Postmeile or Polizeimeile, introduced on occasion of a survey of the Saxon roads in the 1700s, corresponded to 2000 Dresden rods, equivalent to 9.062 kilometres.[40]
• The Hungarian mile (mérföld or magyar mérföld) varied from 8.3790 km to 8.9374 km before being standardised as 8.3536 km.
• The Portuguese mile (milha) used in Portugal and Brazil was 2.0873 km prior to metrication.[41]
• The Russian mile (миля or русская миля, russkaya milya) was 7.468 km, divided into 7 versts.

• The Croatian mile (hrvatska milja), first devised by the Jesuit Stjepan Glavač on a 1673 map, is the length of an arc of the equator subtended by 1/10° or 11.13 km exactly.[42][43] The previous Croatian mile, now known as the "ban mile" (banska milja), had been the Austrian mile given above.[44]
• The Ottoman mile was 1,894.35 m (1.17709 mi), which was equal to 5,000 Ottoman foot. After 1933, the Ottoman mile was replaced with the modern Turkish mile (1,853.181 m).

The nautical mile per hour is known as the knot. Nautical miles and knots are almost universally used for aeronautical and maritime navigation, because of their relationship with degrees and minutes of latitude and the convenience of using the latitude scale on a map for distance measuring.

The data mile is used in radar-related subjects and is equal to 6,000 feet (1.8288 kilometres).[83] The radar mile is a unit of time (in the same way that the light year is a unit of distance), equal to the time required for a radar pulse to travel a distance of two miles (one mile each way). Thus, the radar statute mile is 10.8 μs and the radar nautical mile is 12.4 μs.[84]

• Adams, Cecil (1990), "What's the origin of miles and yards?", The Straight Dope, Chicago, retrieved 6 April 2015.
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• Astin, A.V.; et al. (25 June 1959), Doc. 59-5442: Refinement of values for the yard and the pound (PDF), Washington, D.C.: National Bureau of Standards.
• Barbrow, Louis E.; et al. (1976), Weights and Measures Standards of the United States—A Brief History (PDF), National Institute of Standards and Technology, doi:10.6028/NBS.SP.447.
• Bigg, P.H.; et al. (1964), "The United Kingdom Standards of the Yard in Terms of the Metre", British Journal of Applied Physics, Vol. 15, No. 3, pp. 291–300, Bibcode:1964BJAP...15..291B, doi:10.1088/0508-3443/15/3/308.
• Burke, James (1978), Connections, Little, Brown, & Co., ISBN 0-316-11685-8.
• Butcher, Tina, ed. (2014), "Appendix C", NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices.
• Klein, Herbert Arthur (1988) [Originally published 1974], The Science of Measurement: A Historical Survey, New York: Dover Publications (Previously published by Simon & Schuster as The World of Measurements: Masterpieces, Mysteries and Muddles of Metrology).
• Livy (1905), Lease, Emory Bair (ed.), Ab Urbe Condita, Vol. I, XXI, & XXII, New York: University Publishing.
• Maloney, Elbert S. (1978), Dutton's Navigation and Piloting (13 ed.), Annapolis: Naval Institute Press.
• Morden, Robert (1695), Dorsetshire, retrieved 17 August 2011.
• "History of Length Measurement", Factsheets, Teddington: National Physical Laboratory.
• Norgate, Martin; et al. (1998), "Morden's Hampshire 1695", Old Hampshire Mapped, Hampshire County Council, ISBN 1-85975-134-2, retrieved 17 August 2011.
• Owen, Aneurin, ed. (1841), "The Venedotian Code", Ancient Laws and Institutes of Wales; Comprising Laws Supposed to be Enacted by Howel the Good, Modified by Subsequent Regulations under the Native Princes prior to the Conquest by Edward the First: And Anomalous Laws, Consisting Principally of Institutions which by the Statute of Ruddlan were Admitted to Continue in Force: With an English Translation of the Welsh Text, to which are Added A few Latin Transcripts, Containing Digests of the Welsh Laws, Principally of the Dimetian Code, London: Commissioners on the Public Records of the Kingdom. (in Welsh) & (in English)
• Oxford English Dictionary, 3rd ed., Oxford: Oxford University Press, 2002.
• Rowlett, Russ (2018), How Many? A Dictionary of Units of Measurement, Chapel Hill: University of North Carolina, retrieved 5 November 2019.
• Shuttleworth, M., Building Roman roads, Experiment Resources, archived from the original on 21 April 2011, retrieved 2 May 2011.
• Smith, William, ed. (1875), Dictionary of Greek and Roman Antiquities, London: John Murray.
• Soren, D.; et al. (1999), "A Roman villa and a late Roman infant cemetery : excavation at Poggio Gramignano, Lugnano in Teverina", Bibliotheca Archaeologica, Rome: L'Erma di Bretschneider.
• Thompson, Ambler; et al. (2008), Special Publication 811: Guide for the Use of the International System of Units (SI) (PDF), Gaithersburg: National Institute of Standards and Technology.
• Zupko, Ronald Edward (1977), British weights & measures: a history from antiquity to the seventeenth century, University of Wisconsin Press, ISBN 978-0-299-07340-4, retrieved 26 November 2011.
• Zupko, Ronald Edward (1981), Italian Weights and Measures from the Middle Ages to the Nineteenth Century, Philadelphia: American Philosophical Society, ISBN 0-87169-145-0.