Editing Inch (section)

== History ==
[[File:Inch converter.jpg|right|250px|thumb|Mid-19th-century tool for converting between different standards of the inch]]

The earliest known reference to the inch in England is from the ''[[Laws of Æthelberht]]'' dating to the early 7th century, surviving in a single manuscript, the ''[[Textus Roffensis]]'' from 1120.<ref name="GoetzJarnut2003">{{cite book |last1=Goetz |first1=Hans-Werner |last2=Jarnut |first2=Jörg |last3=Pohl |first3=Walter |author-link3=Walter Pohl |title=Regna and Gentes: The Relationship Between Late Antique and Early Medieval Peoples and Kingdoms in the Transformation of the Roman World |url=https://books.google.com/books?id=RovRlJkrncEC&pg=PA33 |year=2003 |publisher=BRILL |isbn=978-90-04-12524-7 |page=33}}</ref> Paragraph LXVII sets out the fine for wounds of various depths: one inch, one shilling; two inches, two shillings, etc.{{efn|{{langx|ang|Gif man þeoh þurhstingð, stice ghwilve vi scillingas. Gife ofer ynce, scilling. æt twam yncum, twegen. ofer þry, iii scill.}}  Translation (taken from {{harvnb|Attenborough|1922|p=13}}): If a thigh is pierced right through, 6 shillings compensation shall be paid for each stab.  For a stab over an inch [deep], 1 shilling; for a stab between 2 and 3 inches, 2 shillings; for a stab over 3 inches 3 shillings.<ref name="Wilkins1871">{{cite book |last=Wilkins |first=David |title=Councils and Ecclesiastical Documents Relating to Great Britain and Ireland: English church during the Anglo-Saxon period: A.D. 595-1066. |url=https://archive.org/details/councilsandeccl04wilkgoog |access-date=18 December 2014 |year=1871 |publisher=Clarendon Press |location=Oxford, UK |page=[https://archive.org/details/councilsandeccl04wilkgoog/page/n72 48]}}</ref><ref name="Duncan1984">{{cite book |last=Duncan |first=Otis Dudley |author-link=Otis Dudley Duncan |title=Notes on social measurement: historical and critical |url=https://books.google.com/books?id=5c459mDugI0C&pg=PA87 |year=1984 |publisher=Russell Sage Foundation |location=US |isbn=978-0-87154-219-9 |page=87}}</ref>}}

An Anglo-Saxon unit of length was the [[English units|barleycorn]]. After 1066, 1&nbsp;inch was equal to 3 barleycorns, which continued to be its legal definition for several centuries, with the barleycorn being the base unit.<ref name=Klein>{{cite book |title=The world of measurements: masterpieces, mysteries and muddles of metrology |url=https://archive.org/details/worldofmeasureme0000klei |url-access=registration |first=H. Arthur |last=Klein |publisher=Simon and Schuster |location=New York, US |year=1974|isbn=9780671215651 }}</ref> One of the earliest such definitions is that of 1324, where the legal definition of the inch was set out in a statute of [[Edward II of England]], defining it as "three grains of [[barley]], dry and round, placed end to end, lengthwise".<ref name=Klein />

Similar definitions are recorded in both English and Welsh medieval law tracts.<ref>{{cite book |pages=310 |title=Northumbria's Golden Age |first1=Jane |last1=Hawkes |first2=Susan |last2=Mills |publisher=Sutton |location=UK |year=1999 |isbn=978-0-7509-1685-1}}</ref> One, dating from the first half of the 10th century, is contained in the Laws of [[Hywel Dda]] which superseded those of [[Dyfnwal Moelmud|Dyfnwal]], an even earlier definition of the inch in Wales. Both definitions, as recorded in ''Ancient Laws and Institutes of Wales'' (vol i., pp.&nbsp;184, 187, 189), are that "three lengths of a barleycorn is the inch".<ref>{{cite book |title=The Traditionary Annals of the Cymry |url=https://archive.org/details/traditionaryann00willgoog |first=John |last=Williams |chapter=The civil arts – mensuration |pages=[https://archive.org/details/traditionaryann00willgoog/page/n253 243]&ndash;245 |location=Tenby, UK |publisher=R. Mason |year=1867}}</ref>

King David I of Scotland in his Assize of Weights and Measures (c. 1150) is said to have defined the Scottish inch as the width of an average man's thumb at the base of the nail, even including the requirement to calculate the average of a small, a medium, and a large man's measures.<ref name="Swinton1789">{{cite book |last1=Swinton |first1 = John| author-link1=John Swinton, Lord Swinton |title=A proposal for uniformity of weights and measures in Scotland |url=https://books.google.com/books?id=kHhbAAAAQAAJ&pg=PA134 |year=1789 |publisher=printed for Peter Hill |page=134}}</ref> However, the oldest surviving manuscripts date from the early 14th century and appear to have been altered with the inclusion of newer material.<ref name="GemmillMayhew2006">{{cite book |first1=Elizabeth |last1=Gemmill |first2=Nicholas |last2=Mayhew |title=Changing Values in Medieval Scotland: A Study of Prices, Money, and Weights and Measures |url=https://books.google.com/books?id=t1hmrzOSEagC&pg=PA113 |date=22 June 2006 |publisher=Cambridge University Press| location=UK |isbn=978-0-521-02709-0 |page=113}}</ref>

In 1814, Charles Butler, a mathematics teacher at [[Cheam School]], recorded the old legal definition of the inch to be "three grains of sound ripe barley being taken out the middle of the ear, well dried, and laid end to end in a row", and placed the barleycorn, not the inch, as the base unit of the English Long Measure system, from which all other units were derived.<ref name=Butler>{{cite book |pages=[https://archive.org/details/aneasyintroduct01butlgoog/page/n64 61] |title=An Easy Introduction to the Mathematics |url=https://archive.org/details/aneasyintroduct01butlgoog |first=Charles |last=Butler |location=Oxford, UK |publisher=Bartlett and Newman |year=1814}}</ref> [[John Bouvier]] similarly recorded in his 1843 law dictionary that the barleycorn was the fundamental measure.<ref>{{cite encyclopedia |first=John |last=Bouvier |article=Barleycorn |year=1843 |encyclopedia=A Law Dictionary: With References to the Civil and Other Systems of Foreign Law |pages=188 |location=Philadelphia, US |publisher=T. & J. W. Johnson}}</ref> Butler observed, however, that "[a]s the length of the barley-corn cannot be fixed, so the inch according to this method will be uncertain", noting that a standard inch measure was now [i.e. by 1843] kept in the Exchequer chamber, [[Guildhall, London|Guildhall]], and ''that'' was the legal definition of the inch.<ref name=Butler />

This was a point also made by George Long in his 1842 ''[[Penny Cyclopædia]]'', observing that standard measures had since surpassed the barleycorn definition of the inch, and that to recover the inch measure from its original definition, in case the standard measure were destroyed, would involve the measurement of large numbers of barleycorns and taking their average lengths. He noted that this process would not perfectly recover the standard, since it might introduce errors of anywhere between one hundredth and one tenth of an inch in the definition of a yard.<ref>{{cite encyclopedia |page=436 |article=Weights & Measures, Standard |encyclopedia=The Penny Cyclopædia of the Society for the Diffusion of Useful Knowledge |first=George |last=Long |year=1842 |location=London, UK |publisher=Charles Knight & Co.}}</ref>

Before the adoption of the [[international yard and pound]], various definitions were in use. In the United Kingdom and most countries of the [[Commonwealth of Nations|British Commonwealth]], the inch was defined in terms of the [[Yard#19th-century Britain|Imperial Standard Yard]]. The United States adopted the conversion factor 1 metre = 39.37 inches by an act in 1866.<ref>{{cite book
  | first1      = Lewis V
  | last1       = Judson
  | title       = Weights and Measures Standards of the United States - a brief history - NBS publication 447
  | url         = https://books.google.com/books?id=GXWfglKg11MC&q=1838+gallon+231+congress&pg=PA8
  | page        = 10&ndash;11
  | publisher   = [[United States Department of Commerce]]
  | date        = October 1963
}}</ref> In 1893, [[Mendenhall Order|Mendenhall ordered]] the physical realization of the inch to be based on the international prototype metres numbers 21 and 27, which had been received from the [[CGPM]], together with the previously adopted conversion factor.<ref name="Mendenhall">{{cite web |author=T. C. Mendenhall, Superintendent of Standard Weights and Measures |author-link=Thomas Corwin Mendenhall |url=http://physics.nist.gov/Pubs/SP447/app3.pdf |date=5 April 1893 |title=Appendix&nbsp;6 to the Report for 1893 of the Coast and Geodetic Survey |url-status=dead |archive-url=https://web.archive.org/web/20120930180925/http://physics.nist.gov/Pubs/SP447/app3.pdf |archive-date=30 September 2012 }}</ref>

As a result of the definitions above, the U.S. inch was effectively defined as 25.4000508&nbsp;mm (with a reference temperature of 68 degrees Fahrenheit) and the UK inch at 25.399977&nbsp;mm (with a reference temperature of 62 degrees Fahrenheit). When [[Carl Edvard Johansson]] started manufacturing [[gauge blocks]] in inch sizes in 1912, Johansson's compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of 20 degrees Celsius, accurate to within a few parts per million of both official definitions. Because Johansson's blocks were so popular, his blocks became the ''de facto'' standard for manufacturers internationally,<ref name=":0">{{Cite web|url=http://mitutoyo.com/wp-content/uploads/2013/07/E12016-History-of-The-Gage-Block.pdf#page=8|title=The History of Gauge Blocks|date=2013|website=mitutoyo.com|publisher=Mitutoyo Corporation|page=8|access-date=1 February 2020}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=3rUaAQAAMAAJ&pg=PA293|title=Industrial Standardization and Commercial Standards Monthly|date=October 1943|language=en|access-date=1 February 2020|first=John|last=Gaillard|page=293}}</ref> with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.<ref>{{Cite book|url=https://books.google.com/books?id=NiEEAQAAIAAJ&pg=PA200|title=Measures for Progress. NIST Special Publication, isue 275.|last=Cochrane|first=Rexmond C.|publisher=U.S. Government Printing Office|year=1966|pages=200|language=en|lccn=65-62472}}</ref>

In 1930, the [[BSI Group|British Standards Institution]] adopted an inch of exactly 25.4&nbsp;mm. The [[American National Standards Institute|American Standards Association]] followed suit in 1933. By 1935, industry in 16 countries had adopted the "industrial inch" as it came to be known,<ref name="MeasuresStandards1936">{{cite conference |url={{google books|id=WDgJAQAAMAAJ|page=RA3-PA4|plain-url=yes}} |conference=National Twenty-Eight Conference on Weights and Measures |title=The Viewpoint of industry concerned with interchangeable manufacturing toward the proposal to standardize the inch |first=Herbert B. |last=Lewis  |publisher=National Bureau of Standards |location=US |year=1936 |page=4 |access-date=2 August 2012}}</ref><ref name="WandmacherJohnson1995">{{cite book |last1=Wandmacher |first1=Cornelius |last2=Johnson |first2=Arnold Ivan |title=Metric Units in Engineering--going SI: How to Use the International Systems of Measurement Units (SI) to Solve Standard Engineering Problems |url=https://books.google.com/books?id=v5AGFgpcK_wC&pg=PA265 |year=1995 |publisher=ASCE Publications|isbn=978-0-7844-0070-8|page=265}}</ref> effectively endorsing Johansson's pragmatic choice of conversion ratio.<ref name=":0" />

In 1946, the Commonwealth Science Congress recommended a yard of exactly 0.9144&nbsp;metres for adoption throughout the British Commonwealth. This was adopted by Canada in 1951;<ref>{{cite journal|title=Announcement on the International Yard and Pound|first=L. E.|last=Howlett|date=1 January 1959|journal=Canadian Journal of Physics|volume=37|issue=1|pages=84|doi=10.1139/p59-014|bibcode=1959CaJPh..37...84H}}</ref><ref name="MeasuresStandards1957">{{cite book |author1=National Conference on Weights and Measures |author2=United States. Bureau of Standards |author3=National Institute of Standards and Technology (US) |author-link3=National Institute of Standards and Technology |title=Report of the ... National Conference on Weights and Measures |url=https://books.google.com/books?id=CEgJAQAAMAAJ&pg=PA45 |year=1957 |publisher=US Department of Commerce, Bureau of Standards |pages=45–6}}</ref> the United States on 1 July 1959;<ref name="FR59-5442">{{cite web |last1=Astin |first1=A.V. |last2=Karo |first2=H. A. |last3=Mueller |first3=F.H. |date=25 June 1959 |url=http://www.ngs.noaa.gov/PUBS_LIB/FedRegister/FRdoc59-5442.pdf |title=Refinement of Values for the Yard and the Pound |publisher=US [[Federal Register]]}}</ref><ref name="Standards1959">{{cite book |author=United States. National Bureau of Standards |author-link=National Institute of Standards and Technology |title=Research Highlights of the National Bureau of Standards |url=https://books.google.com/books?id=4aWN-VRV1AoC&pg=PA13 |year=1959 |publisher=US Department of Commerce, National Bureau of Standards |page=13}}</ref><ref name="JudsonStandards1976">{{cite book|author1=Lewis Van Hagen Judson|author2=United States. National Bureau of Standards|author-link2=National Institute of Standards and Technology|title=Weights and measures standards of the United States: a brief history|url=https://archive.org/details/bub_gb_o4XQ7KCv5E0C|access-date=16 September 2012|year=1976|publisher=Dept. of Commerce, National Bureau of Standards : for sale by the Supt. of Docs., U.S. Govt. Print. Off.|pages=[https://archive.org/details/bub_gb_o4XQ7KCv5E0C/page/n36 30]–1}}</ref> Australia in 1961,<ref>Statutory Rule No. 142.</ref> effective 1 January 1964;<ref>[http://www.comlaw.gov.au/Details/C2004L00578 Australian Government ComLaw ''Weights and Measures (National Standards) Regulations - C2004L00578'']</ref> and the United Kingdom in 1963,<ref>Weights and Measures Act of 1963.</ref> effective on 1 January 1964.<ref>{{cite web |url=http://www.bailii.org/ew/cases/EWHC/Admin/2002/195.html |title=Thoburn v Sunderland City Council [2002] EWHC 195 (Admin) |date=18 February 2002 |publisher=England and Wales High Court |via=British and Irish Legal Information Institute}}</ref> The new standards gave an inch of exactly 25.4&nbsp;mm, 1.7 millionths of an inch longer than the old imperial inch and 2 millionths of an inch shorter than the old US inch.<ref>{{cite web |url=http://www.npl.co.uk/reference/faqs/on-what-basis-is-one-inch-exactly-equal-to-25.4-mm-has-the-imperial-inch-been-adjusted-to-give-this-exact-fit-and-if-so-when-(faq-length) |archive-url= https://web.archive.org/web/20130126164151/http://www.npl.co.uk/reference/faqs/on-what-basis-is-one-inch-exactly-equal-to-25.4-mm-has-the-imperial-inch-been-adjusted-to-give-this-exact-fit-and-if-so-when-(faq-length) | archive-date = 26 January 2013 |title=On what basis is one inch exactly equal to 25.4 mm? Has the imperial inch been adjusted to give this exact fit and if so when? |publisher=National Physical Laboratory |date=25 March 2010 |access-date=5 April 2013}}</ref><ref name=Astin/>