English units are the historical units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications.
The two main sets of English units were the Winchester Units, in effect from 1495–1587, as reaffirmed by King Henry VII, and the Exchequer Standards, in effect from 1588–1825, as first defined by Queen Elizabeth I.
The units were replaced by Imperial Units in 1824 (effective 1 January 1826) by a Weights and Measures Act, which retained many but not all of the unit names and redefined many of the definitions.
Use of the term "English units" is ambiguous, as it is sometimes mistakenly used to refer to the Imperial units used in the UK, or to United States customary units, which retain some unit names of English Units, but has somewhat different definitions. (The terms imperial units or imperial measurements are used in the UK to refer to the non-metric system since they were used as a standard throughout the British Empire and the Commonwealth.)
Very little is known of the measurement units of the British Isles prior to Roman colonization in the 1st century CE. During the Roman period, Roman Britain relied on Ancient Roman units of measurement. During the Anglo-Saxon period, the North German foot of 335 millimetres (13.2 inches) was the nominal basis for other units of linear measurement. The foot was divided into 4 palms or 12 thumbs. A cubit was 2 feet, an elne 4 feet. The rod was 15 Anglo-Saxon feet, the furlong 10 rods. An acre was 4 × 40 rods, i.e., 160 square rods or 36,000 square Anglo-Saxon feet. However, Roman units continued to be used in the construction crafts and reckoning by the Roman mile of 5000 feet or 8 stades continued, in contrast to other Germanic countries who adopted the name "mile" for a longer native length closer to the league. From the time of Offa King of Mercia (8th century) until 1526 the Saxon pound, also known as the moneyers' pound (and later known as the Tower pound) was the fundamental unit of mass measurement.
Prior to the enactment of a law known as the "Composition of Yards and Perches" (Latin: Compositio ulnarum et perticarum) some time between 1266 and 1303, the English system of measurement had been based on that of the Anglo-Saxons, inherited from tribes from northern Germany. The Compositio retained the Anglo-Saxon rod of 5.03 metres and the acre of 4 × 40 rods. However, it redefined the yard, foot, inch, and barleycorn to 10⁄11 of their previous value. Thus, the rod went from 5 old yards to 5 1⁄2 new yards, or 15 old feet to 16 1⁄2 new feet. The furlong went from 600 old feet (200 old yards) to 660 new feet (220 new yards). The acre went from 36,000 old square feet to 43,560 new square feet. Scholars have speculated that the Compositio may have represented a compromise between two earlier systems of the units, the Anglo-Saxon and the Roman.
Contrary to popular belief, the Norman conquest of England had little effect on British weights and measures other than to introduce one new unit: the bushel. William the Conqueror, in one of his first legislative acts, confirmed existing Anglo-Saxon measurement, a position which was consistent with Norman policy in dealing with occupied peoples. Another popular myth is that the Magna Carta of 1215 (specifically chapter 35) had any significant effect on English weights and measures, as this document only mentions one unit (the London Quarter) but does not define it.
Later development of the English system continued by defining the units by law and issuing measurement standards. Standards were renewed in 1496, 1588 and 1758. The last Imperial Standard Yard in bronze was made in 1845; it served as the standard in the United Kingdom until the yard was redefined by the international yard and pound agreement as 0.9144 metre in 1959 (statutory implementation: Weights and Measures Act of 1963). The English system then spread to other parts of the British Empire.
- 1215 Magna Carta: the earliest statutory declaration for uniformity of weights and measures
- 1335: 8 & 9 Edw III c1 First statutory reference describing goods as avoirdupois
- 1414 2 Hen V c4 First statutory mention of the Troy pound
- 1495 12 Hen VII c5 New Exchequer standards were constructed including Winchester capacity measures defined by Troy weight of their content of threshed wheat by stricken measure (first statutory mention of Troy weight as standard weight for bullion, bread, spices &c).
- 1527 Hen VIII Abolished the Tower pound
- 1531 23 Hen VIII c4 Barrel to contain 36 gallons of beer or 32 of ale; kilderkin in half of this; firkin half again
- 1532 24 Hen VIII c3 First statutory references to use of avoirdupoi weight
- 1536 28 Hen VIII c4 Added the tierce (41 gallons)
- 1588 (Elizabeth I) A new series of Avoirdupois standard bronze weights (bell-shaped from 56 lb to 2 lb and flat-pile from 8 lb to a dram) with new Troy standard weights in nested cups from 256 oz to 1/8 oz in a binary progression.
- 1601–1602 Standard bushels and gallons were constructed based on the standards of Henry VII and a new series of capacity measures were issued.
- 1660 12 Chas II c24 Barrel of beer to be 36 gallons taken by the gauge of the Exchequer standar of the ale quart; barrel of ale to be 32 gallons; all other liquors retailed to be sold by the wine gallon;
- 1689 1 Wm & Mary c24 Barrels of beer and ale outside London to contain 34 gallons
- 1695 7 Will III c24 Irish Act about grain measures decreed: unit of measure to be Henry VIII's gallon as confirmed by Elizabeth I; i.e.e 272 1/4 cubic inches; standard measures of the barrel (32 gallons), half-barrel (16), bushel (8), peck (2) and gallon to be lodged in the Irish Exchequer; and copies were to be provided in every county, city, town, &c.
- 1696 8 & 9 Will III c22 Size of Winchester bushel "every round bushel with a plain and even bottom being 18 1/2" wide throughout and 8" deep" (i.e. a dry measure of 268.8 in³ per gallon).
- 1706 5 & 6 Anne c27 Wine gallon to be a cylindrical vessel with an even bottom 7" diameter throughout and 6" deep from top to bottom of the inside, or holding 231 in³ and no more.
- 1706 6 Anne c11 Act of Union decreed: the weights and measures of England to be those of Scotland whose burgs were to take charge of the duplicates of the English Standards sent to them.
- 1713 12 Anne c17 The legal coal bushel to be round with a plain and even bottom, 19 1/2" from outside to outside and to hold 1 Winchester bushel and 1 quart of water.
- 1718 5 Geo I c18 Decreed Scots Pint exactly 103 in³.
- 1803 43 Geo III c151 Referred to wine bottles making about 5 to the wine gallon (i.e. Reputed Quarts)
- 1824 5 Geo IV c74 Weights and Measures Act: completely reorganized British metrology and established Imperial weights and measures; defined the yard, troy and avoirdupois pounds and the gallon (as the standard measure for liquids and dry goods not measured by heaped measure), and provided for a 'brass' standard gallon to be constructed.
- 1825 6 Geo IV c12 Delayed introduction of Imperial weights and measures from 1 May 1825 to 1 January 1826.
- 1835 Will IV c63 Weights and measures act: abolished local and customary measures including the Winchester bushel; made heaped measure illegal; required trade to be carried out by avoirdupois weight only except for bullion; gems and drugs which were to be sold by troy weight; decreed that all forms of coal were to be sold by weight and not measure; legalised the 14 lb stone, the 112 lb hundredweight and the 20 cwt ton.
- 1853 16 & 17 Vict c29 Permitted the use of decimal Bullion weights.
- 1866 29 & 30 Vict c82 Standards of Weights, Measures and Coinage Act: transferred all duties and standards from the Exchequer to the newly created Standards Department of the Board of Trade.
- 1878 41 & 42 Vict c49 Weights and Measures Act: defined the Imperial standard yard and pound; enumerataed the secondary standards of measure and weight derived from the Imperial standards; required all trade by weight or measure to be in terms of one of the Imperial weights or measures or some multiple part thereof; abolished the Tory pound.
- 1963 11 & 12 Eliz II c31 Weights and Measures Act: abolished the chaldron of coal, the fluid drachm and minim (effective 1 February 1971), discontinued the use of the quarter, abolished the use of the bushel and peck and abolished the pennyweight (from 31 January 1969).
- 1⁄4 or 1⁄5 of a barleycorn
- 1⁄4 of a barleycorn
- 1⁄3 of an inch, the notional base unit under the Composition of Yards and Perches.
- 3⁄4 inch
- 7⁄8 inch
- 3 barleycorns (the historical legal definition)
- 3 digits = 2 1⁄4 inches = 1⁄16 yard
- 3 inches
- 4 inches
- Width of the hand and outstretched thumb, 6 1⁄2 inches before 1066, 6 thereafter
- 7.92 inches or one 100th of a chain.
- Width of the outstretched hand, from the tip of the thumb to the tip of the little finger, 3 palms = 9 inches
- Prior to the Anglo-Saxon invasions, the Roman foot of 11.65 inches (296 mm) was used. The Anglo-Saxons introduced a North-German foot of 13.2 inches (335 mm), divided into 4 palms or 12 thumbs, while the Roman foot continued to be used in the construction crafts. In the late 13th century, the modern foot of 304.8 mm was introduced, equal to exactly 10⁄11 Anglo-Saxon foot.
- From fingertips to elbow, 18 inches.
- Yard (= Ulna)
- 3 feet = 36 inches, the practical base unit as the length of the prototype bar held by the Crown or Exchequer.
- From fingertip of outstretched arm to opposite shoulder, 20 nails = 1 1⁄4 yard or 45 inches. Mostly for measuring cloth
- Distance fingertip to fingertip arms outstretched, 6 feet
- Rod (= perch) (= pole)
- Used for surveying land and in architecture. The rod is the same length today as in Anglo-Saxon times, although its composition in terms of feet were changed by the Composition of Yards and Perches from 15 feet to 16 1⁄2. The pole is commonly used as a measurement for Allotment Gardens. (See also perch as an area and a volume unit.)
- four linear rods. Named after the length of surveyor's chain used to measure distances until quite recently. Any of several actual chains used for land surveying and divided in links. Gunter's chain, introduced in the 17th century, is 66 feet.
- Furlong (= stade)
- Notionally the distance a plow team could furrow without rest, but actually a measure of 40 rods or 600 feet prior to the Composition of Yards and Perches and 40 rods or 660 feet afterwards.
- Originally the Roman mile alternatively reckoned as 5000 feet, 1000 paces, or 8 stades but adjusted to 5280 feet in 1593 to account for the differences introduced to these methods of reckoning by the Composition of Yards and Perches.
- Notionally an hour's travel, but usually reckoned as three miles. Approximate length of the traditional "mile" in German and Scandinavian countries.
- an area equal to one square rod. (See also perch as a length and volume unit.)
- one quarter of an acre, confusingly sometimes called an acre itself in many ancient contexts. One furlong in length by one rod in width, or 40 square rods.
- area of land one chain (four rods) in width by one furlong in length. As the traditional furlong could vary in length from country to country, so did the acre. In England an acre was 4,840 square yards, in Scotland 6,150 square yards and in Ireland 7,840 square yards. It is a Saxon unit, meaning field. Traditionally said to be "as much area as could be ploughed in one day".
- the amount of land one ox can plough in a single year (also called an oxgang). Approximately 15 acres or one eighth of a carucate.
- the amount of land a pair of oxen can plough in a single year. Approximately 30 acres (also called yard land).
- an area equal to that which can be ploughed by one eight-oxen team in a single year (also called a plough or carve). Approximately 120 acres.
- four to eight bovates. A unit of yield, rather than area, it measured the amount of land able to support a single household for agricultural and taxation purposes.
- Knight's fee
- five hides. A knight's fee was expected to produce one fully equipped soldier for a knight's retinue in times of war.
- Hundred or wapentake
- 100 hides grouped for administrative purposes.
Many measures of capacity were understood as fractions or multiples of a gallon. For example, a quart is a quarter of a gallon, and a pint is half of a quart, or an eighth of a gallon. These ratios applied regardless of the specific size of the gallon. Not only did the definition of the gallon change over time, but there were several different kinds of gallon, which existed at the same time. For example, a wine gallon with a volume of 231 cubic inches (the basis of the U.S. gallon), and an ale gallon of 282 cubic inches, were commonly used for many decades prior to the establishment of the imperial gallon. In other words, a pint of ale and a pint of wine were not the same size. On the other hand, some measures such as the fluid ounce were not defined as a fraction of a gallon. For that reason, it is not always possible to give accurate definitions of units such as pints or quarts, in terms of ounces, prior to the establishment of the imperial gallon.
General liquid measures
- 60 minim or drops or 1⁄8 fluid ounce (fl oz)
- 80 minim or drops or 1⁄6 fl oz
- 4 dram (240 minim or drops), 3 teaspoons, or 1⁄2 fl oz
- usually 1⁄2 gill, in some dialects equal to a gill or 1⁄2 pint
- Gill or Jill
- 2 jacks, 1⁄4 pint, or 1⁄32 gallon, in some dialects 1⁄2 pint
- 2 cups or 1⁄8 gallon
- 2 pints or 1⁄4 gallon
- 2 quarts or 1⁄2 gallon
- 2 pottle, 4 quarts, 8 pints
Liquid measures as binary submultiples of their respective gallons (ale or wine):
|1 jack =||1||1⁄2||1⁄8||1⁄16||1⁄32||1⁄64||–6|
|1 gill =||2||1||1⁄4||1⁄8||1⁄16||1⁄32||–5|
|1 pint =||8||4||1||1⁄2||1⁄4||1⁄8||–3|
|1 quart =||16||8||2||1||1⁄2||1⁄4||–2|
|1 pottle =||32||16||4||2||1||1⁄2||–1|
|1 gallon =||64||32||8||4||2||1||0|
Wine is traditionally measured based on the wine gallon and its related units. Other liquids such as brandy, spirits, mead, cider, vinegar, oil, honey, and so on, were also measured and sold in these units.
The wine gallon was re-established by Queen Anne in 1707 after a 1688 survey found the Exchequer no longer possessed the necessary standard but had instead been depending on a copy held by the Guildhall. Defined as 231 cubic inches, it differs from the later imperial gallon, but is equal to the United States customary gallon.
- 18 wine gallons or 1⁄7 wine pipe
- Wine barrel
- 31.5 wine gallons or 1⁄2 wine hogshead
- 42 wine gallons, 1⁄2 puncheon or 1⁄3 wine pipe
- Wine hogshead
- 2 wine barrels, 63 wine gallons or 1⁄4 wine tun
- Puncheon or tertian
- 2 tierce, 84 wine gallons or 1⁄3 wine tun
- Wine pipe or butt
- 2 wine hogshead, 3 tierce, 7 roundlet or 126 wine gallons
- Wine tun
- 2 wine pipe, 3 puncheon or 252 wine gallons
|gallon||rundlet||barrel||tierce||hogshead||puncheon, tertian||pipe, butt||tun|
|1||1 1⁄2||3||puncheons, tertians|
|1||1 1⁄3||2||2 2⁄3||4||8||barrels|
|1||1 3⁄4||2 1⁄3||3 1⁄2||4 2⁄3||7||14||rundlets|
|1||18||31 1⁄2||42||63||84||126||252||gallons (wine)|
|1||15||26 1⁄4||35||52 1⁄2||70||105||210||gallons (imperial)|
Ale and beer
- 4.5 gallons or 1⁄8 beer barrel
- 2 pins, 9 gallons (ale, beer or goods) or 1⁄4 beer barrel
- 2 firkins, 18 gallons or 1⁄2 beer barrel
- Beer barrel
- 2 kilderkins, 36 gallons or 2⁄3 beer hogshead
- Beer hogshead
- 3 kilderkins, 54 gallons or 1.5 beer barrels
- Beer pipe or butt
- 2 beer hogsheads, 3 beer barrels or 108 gallons
- Beer tun
- 2 beer pipes or 216 gallons
|= 4.621 L||= 36.97 L||= 73.94 L||= 147.9 L||= 221.8 L|
|= 4.621 L||= 41.59 L||= 83.18 L||= 166.4 L||= 249.5 L|
|1||8 1⁄2||17||34||51||ale gallons||1688|
|= 4.621 L||= 39.28 L||= 78.56 L||= 157.1 L||= 235.7 L|
|= 4.621 L||= 41.59 L||= 83.18 L||= 166.4 L||= 249.5 L|
|= 4.546 L||= 40.91 L||= 81.83 L||= 163.7 L||= 245.5 L|
Grain and dry goods
The Winchester measure, also known as the corn measure, centered on the bushel of approximately 2,150.42 cubic inches, which had been in use with only minor modifications since at least the late 15th century. The word corn at that time referred to all types of grain. The corn measure was used to measure and sell many types of dry goods, such as grain, salt, ore, and oysters.
However, in practice, such goods were often sold by weight. For example, it might be agreed by local custom that a bushel of wheat should weigh 60 pounds, or a bushel of oats should weigh 33 pounds. The goods would be measured out by volume, and then weighed, and the buyer would pay more or less depending on the actual weight. This practice of specifying bushels in weight for each commodity continues today. This was not always the case though, and even the same market that sold wheat and oats by weight might sell barley simply by volume. In fact, the entire system was not well standardized. A sixteenth of a bushel might be called a pottle, hoop, beatment, or quartern, in towns only a short distance apart. In some places potatoes might be sold by the firkin - usually a liquid measure - with one town defining a firkin as 3 bushels, and the next town as 2 1/2 bushels.
The pint was the smallest unit in the corn measure. The corn gallon, one eighth of a bushel, was approximately 268.8 cubic inches. Most of the units associated with the corn measure were binary (sub)multiples of the bushel:
|1 pint =||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||1⁄512||–3|
|1 quart =||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||1⁄256||–2|
|1 pottle =||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||1⁄128||–1|
|1 gallon =||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1⁄64||0|
|1 peck =||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||1⁄32||1|
|1 kenning =||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||1⁄16||2|
|1 bushel =||64||32||16||8||4||2||1||1⁄2||1⁄4||1⁄8||3|
|1 strike =||128||64||32||16||8||4||2||1||1⁄2||1⁄4||4|
|1 coomb =||256||128||64||32||16||8||4||2||1||1⁄2||5|
|1 seam =||512||256||128||64||32||16||8||4||2||1||6|
The Avoirdupois, Troy and Apothecary systems of weights all shared the same finest unit, the grain; however, they differ as to the number of grains there are in a dram, ounce and pound. This grain was legally defined as the weight of a grain seed from the middle of an ear of barley. There also was a smaller wheat grain, said to be 3⁄4 (barley) grains or about 48.6 milligrams.
- Grain (gr)
- 64.79891 mg, 1⁄7000 of a pound
- Dram/drachm (dr)
- 27.34375 gr (sixteenth of an ounce) (possibly originated as the weight of silver in Ancient Greek coin drachma)
- Ounce (oz)
- 16 dr = 437.5 grains ≈ 28 g
- Pound (lb)
- 16 oz = 7000 grains ≈ 454 g (NB: 'lb' stands for libra)
- 1⁄4 cwt
- Hundredweight (cwt)
- 112 lb
- 20 cwt
Troy and Tower
The Troy and Tower pounds and their subdivisions were used for coins and precious metals. The Tower pound, which was based upon an earlier Anglo-Saxon pound, was replaced by the Troy pound when a proclamation dated 1526 required the Troy pound to be used for mint purposes instead of the Tower pound. No standards of the Tower pound are known to have survived.
- Merchants/Mercantile pound
- 15 oz tower = 6750 gr ≈ 437.4 g
- London/Mercantile pound
- 15 oz troy = 16 oz tower = 7200 gr ≈ 466.6 g
- Mercantile stone
- 12 lb L ≈ 5.6 kg
- Butcher's stone
- 8 lb ≈ 3.63 kg
- 26 st = 364 lb ≈ 165 kg
- The carat was once specified as four grains in the English-speaking world.
- Some local units in the English dominion were (re-)defined in simple terms of English units, such as the Indian tola of 180 grains.
- This was an English weight for wool. It has the alternative spelling forms of tode, todd, todde, toad, and tood. It was usually 28 pounds, or two stone. The tod, however, was not a national standard and could vary by English shire, ranging from 28 to 32 pounds. In addition to the traditional definition in terms of pounds, the tod has historically also been considered to be 1⁄13 of a sack, 1⁄26 of a sarpler, or 1⁄9 of a wey.
|Avoirdupois||1||175/||= 1.21527||35/||= 1.296||28/||= 1.037||35/||= 0.972||≈ 0.9072||16||14 7/||= 14.583||15 5/||= 15.5||7000||9955 5/||≈ 454||≈ 5/|
|Troy||144/||≈ 0.8229||1||16/||= 1.06||64/||= 0.853||4/||= 0.8||≈ 0.7465||13 29/||≈ 13.17||12||12 4/||= 12.8||5760||8192||≈ 373||≈ 3/|
|Tower||27/||≈ 0.7714||15/||= 0.9375||1||4/||= 0.8||3/||= 0.75||≈ 0.6998||12 12/||≈ 12.34||11 1/||= 11.25||12||5400||7680||≈ 350||≈ 7/|
|Merchant||27/||≈ 0.9643||75/||= 1.171875||5/||= 1.25||1||15/||= 0.9375||≈ 0.8748||15 3/||≈ 15.43||14 1/||= 14.0625||15||6750||9600||≈ 437||≈ 7/|
|London||36/||≈ 1.029||5/||= 1.25||4/||= 1.3||16/||= 1.06||1||≈ 0.9331||16 16/||≈ 16.46||15||16||7200||10240||≈ 467||≈ 7/|
|Metric||≈ 1.1023||≈ 1.3396||≈ 1.4290||≈ 1.1431||≈ 1.0717||1||≈ 17.64||≈ 16.08||≈ 17.15||7716||10974||= 500||= 1/|
- Approximate conversion of units
- Ancient Roman Units of Measurement
- Comparison of the imperial and US customary measurement systems
- Domesday Book
- English Engineering Units
- History of measurement
- Hundred, a unit of 100, 120, &c. items
- Imperial and US customary measurement systems
- Imperial units
- Long hundred of 120
- Obsolete Scottish units of measurement
- Plan for Establishing Uniformity in the Coinage, Weights, and Measures of the United States
- Slug and poundal
- Spanish customary units
- Weights and measures
- Welsh units
- Winchester measure
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- Hosch, William L. (2011). The Britannica Guide to Numbers and Measurement. New York, NY: The Rosen Publishing Group (Britannica Educational Publishing). p. 241. ISBN 9781615301089. Retrieved 12 September 2016.
- Marks' Standard Handbook for Mechanical Engineers, McGraw Hill, 2006
- Zupko, Ronald Edward (1977). British Weights and Measures: A History from Antiquity to the Seventeenth Century. University of Wisconsin Press. pp. 20–21. ISBN 978-0-299-07340-4.
- Ricketts, Carl (1996). Marks and Marking of Weights and Measures of the British Isles. Taunton, Somerset: Devon Design and Print. ISBN 0952853302.
- "poppyseed". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
- H. Arthur Klein (1974). The world of measurements: masterpieces, mysteries and muddles of metrology. New York: Simon and Schuster. p. 63.
- Merriam Webster Online Dictionary, Link definition
- Kirkby, Rev. Mr. John (1735). Arithmetical Institutions. London: Motte and Bathurst. Part II, page 14.
- Unwin, Tim (1991). Wine and the Vine. London: Routledge. p. 364. ISBN 0-415-14416-7.
- "wine barrel". Sizes. 2009-02-02. Retrieved 2018-03-27.
- "English Beer and Ale Barrel". Sizes. 2002-01-23. Retrieved 2018-03-27.
- Trusler, Rev. Dr. John (1786). The London Adviser and Guide. London. p. 188.
- Bailey, John (1810). General View of the Agriculture of the County of Durham, with Observations on the Means of its Improvement. London: Richard Phillips.
- Blocksma, Mary. Reading the Numbers. New York: Penguin Books, 1989.
- "cord, n 1". Oxford English Dictionary (2 ed.). Oxford, England: Oxford University Press. 1989.
from Richard Boyle, 1616
- Zupko, Ronald Edward (1985). A Dictionary of Weights and Measures for the British Isles. Independence Square Philadelphia: American Philosophical Society. ISBN 978-0-87169-168-2.
- A proclamation of Henry VIII, 5 November 1526. Proclamation 112 in Paul L. Hughes and James F. Larkin, editors. Tudor Royal Proclamations. Volume 1. New Haven: Yale University Press,1964.
- R. D. Connor and A. D. C. Simpson.Weights and Measures in Scotland. A European Perspective.National Museums of Scotland and Tuckwell Press, 2004, page 116, quoting from H. W. Chisholm, Seventh Annual Report of the Warden for the Standards..for 1872-73 (London, 1873), quoting from 1864 House of Commons Paper.
- Cardarelli, François (2003). Encyclopaedia of Scientific Units, Weights and Measures. London: Springer. p. 49. ISBN 978-1-4471-1122-1.
- Zupko, Ronald Edward (1985). A Dictionary of Weights and Measures for the British Isles: The Middle Ages to the Twentieth Century, Volume 168. American Philosophical Society. pp. 415–416. ISBN 9780871691682. Retrieved 3 March 2015.