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Traditional French units of measurement

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Woodcut dated 1800 illustrating the new decimal units which became the legal norm across all France on 4 November 1800

ThetraditionalFrench units of measurementprior tometricationwere established underCharlemagneduring theCarolingian Renaissance.Based on contemporaryByzantineandancient Roman measures,the system established some consistency acrosshis empirebut, after his death, the empire fragmented and subsequent rulers and various localities introduced their own variants. Some of Charlemagne's units, such as the king's foot (French:pied du Roi) remained virtually unchanged for about a thousand years, while others important to commerce—such as the French ell (aune) used for cloth and the French pound (livre) used for amounts—varied dramatically from locality to locality. By the 18th century, the number of units of measure had grown to the extent that it was almost impossible to keep track of them and one of the major legacies of theFrench Revolutionwas the dramatic rationalization of measures as the newmetric system.The change was extremely unpopular, however, and a metricized version of the traditional units—themesures usuelles—had to be brought back into use for several decades.

History[edit]

Table of the measuring units used in the 17th century atPernes-les-Fontainesin the covered market atProvence-Alpes-Côte d'Azurregionof southeasternFrance

Although in the pre-revolutionary era (before 1795) France used a system and units of measure that had many of the characteristics of contemporaryEnglish units(or the laterImperial Systemof units), France still lacked a unified, countrywide system of measurement. Whereas in EnglandMagna Cartahad decreed that "there shall be one unit of measure throughout the realm", Charlemagne and successive kings had tried but failed to impose a unified system of measurement in France.[1]

The names and relationships of many units of measure were adopted from Roman units of measure, and many more were added – it has been estimated that there were seven or eight hundred different names for the various units of measure. Moreover, the quantity associated with each unit of measure differed from town to town and even from trade to trade. Some of the differences were large: for example thelieue(league) could vary from 3.268 km inBeauceto 5.849 km inProvence.It has been estimated that on the eve of the Revolution a quarter of a million different units of measure were in use in France.[2] Although certain standards, such as thepied du Roi(the King's foot) had a degree of pre-eminence and were used bysavants,many traders chose to use their own measuring devices, giving scope for fraud and hindering commerce and industry.[1]

Tables of units of measure[edit]

17th-century engraving of the Grand Châtelet
Flood levels at thepont WilsonatToursin both metres andpied royal

These definitions use the Paris definitions for thecoutumeof Paris,[3]and definitions for otherAncien régimecivil jurisdictions varied, at times quite significantly.

Length[edit]

The medieval royal units of length were based on thetoise,and in particular thetoise de l'Écritoire,the distance between the fingertips of the outstretched arms of a man, which was introduced in 790 byCharlemagne.[4]

Thetoisehad 6pieds(feet) each of 326.6 mm (12.86 in). In 1668 the reference standard was found to have been deformed, and it was replaced by thetoise du Châteletwhich, to accommodate the deformation of the earlier standard, was around 11 mm (0.55%) shorter.

In 1747 thistoisewas replaced by a newtoiseof near-identical length – theToise du Pérou,custody of which was given tol'Académie des Sciences au Louvre.[5]

Although thepouce(inch),pied(foot) andtoise(fathom) were fairly consistent throughout most of pre-revolutionary France, some areas had local variants of thetoise.Other units of measure such as theaune(ell), theperche(perch or rood), thearpentand thelieue(league) had a number of variations, particularly theaune(which was used to measure cloth).[6]

Theloi du 19 frimaire an VIII(Law of 10 December 1799) states that one decimal metre is exactly 443.296 Frenchlines,or3 pieds 11.296 lignes de la "Toise du Pérou".[7] Thus the French royal foot is exactly9000/27 706metres (about 0.3248 m).[8]

InQuebec,the surveys in French units were converted using the relationship 1pied(of the French variety, the same word being used for English feet as well) = 12.789 Englishinches.[9]This makes the Quebecpiedvery slightly smaller (about 4 parts in one million) than thepiedused in France.

Table of length units
Unit Relative
value
(pieds) 		SI
value
(approx.) 		Imperial
value
(approx.) 		Notes
point 1⁄1728 0.188 mm 7.401 thou 1⁄12of aligne.This unit is usually called theTruchet pointin English. Prior to the French Revolution theFournier pointwas also in use. It was1⁄6of aligneor1⁄864of the smaller French foot.
ligne 1⁄144 2.256 mm 88.81 thou 1⁄12of apouce.This corresponds to theline,a traditional English unit.
pouce 1⁄12 27.07 mm 1.066 in 1⁄12of apied du roi.This corresponds to theinch,a traditional English unit.
pied du roi 1 32.48 cm 1.066 ft Commonly abbreviated topied,this corresponds to thefoot,a traditional English unit. Known in English as theParis foot(properly a separate, shorter unit), theroyal foot,orFrench foot.
toise 6 1.949 m 6.394 ft, or
2.131 yd 		Sixpieds du roi.This corresponds to thefathom,a traditional English unit. Unlike the fathom, it was used in both land and sea contexts.
TheToise du Chateletwas introduced in 1668 and defined by an iron bar on the Grand Chatelet. This was replaced by theToise du Perouin 1766.[10]
Paris
perche d'arpent 22 7.146 m 7.815 yd Related to, but not directly corresponding with, the Englishperch or rod(which is16+1⁄2feet, approximately three-quarters of the Frenchperche).
arpent 220 71.46 m 78.15 yd Tenperches.
lieue ancienne 10 000 3.248 km 2.018 miles This is an old Frenchleague,defined as 10 000 (a myriad)pieds.It was the official league in parts of France until 1674.
lieue de Paris 12 000 3.898 km 2.422 miles This league was defined in 1674 as exactly 2000 '.After 1737, it was also called the "league of bridges and roads" (lieue des Ponts et des Chaussées).
lieue des Postes 13 200 4.288 km 2.664 miles This league is 2200toisesor 60arpents.It was created in 1737.
lieue de 25 au degré ~13 692 4.448 km 2.764 miles Linked to the circumference of the Earth, with 25lieuesmaking up one degree of a great circle. (Compare the internationalnautical mile,of which 60 make one degree; onelieuetherefore equaling 2.4 nautical miles.) It was measured by Picard in 1669 to be 2282toises.
lieue tarifaire 14 400 4.678 km 2.907 miles This league is 2400toises.It was created in 1737.
North America
perche du roi 18 5.847 m 6.394 yd This perch was used inQuebecandLouisiana
arpent (du roi) 180 58.47 m 63.94 yd Tenperches du roi.
Local
perche ordinaire 20 6.497 m 7.105 yd This perch was used locally.
arpent (ordinaire) 200 64.97 m 71.05 yd Tenperches ordinaires.
  • The Frenchtypographic point,theDidotpoint, was1⁄72of a French inch, i.e. two royal points. The Frenchpica,calledCicéro,measured 12 Didot points or1⁄6inch.

Area[edit]

Table of area units
Unit Relative
value
(pieds carrés) 		SI
value 		Imperial
value 		Notes
pied carré 1 ~1055 cm2 ~1.136 sq ft The Frenchsquare foot
toise carrée 36 ~3.799 m2 ~40.889 sq ft, or
~4.543 sq yd 		The French square fathom
Paris
perche d'arpent carrée 484 ~51.07 m2 ~61.08 sq yd This was the main square perch in old French surveying. It is a square 22pieds du roion each side.
vergée 12 100 ~1277 m2 ~1527 sq yd A square 5percheson each side, or one quarter of anacre.
acre,or
arpent carré 		48 400 ~5107 m2 ~6108 sq yd, or
~1.262 acres 		The French acre is a square 10perches(onearpent) on each side. (Does not exactly correspond to the English acre, which is defined as 43 560 square feet.)
North America
perche du roi carrée 324 ~34.19 m2 ~40.89 sq yd This square perch was used in Quebec and Louisiana. It is a square 18pieds du roion each side.
vergée (du roi) 8100 ~854.7 m2 ~1022 sq yd A square 5perches du roion each side.
acre (du roi),or
arpent carré 		32 400 ~3419 m2 ~4089 sq yd, or
~0.8448 acres 		A square 10perches du roion each side. Certain U.S. states have their own official definitions for the(square) arpent,which vary slightly from this value.
Local
perche (ordinaire) carrée 400 ~42.21 m2 ~50.48 sq yd This square perch was used locally. It is a square 20pieds du roion each side.
vergée (ordinaire) 10 000 ~1055 m2 ~1262 sq yd A square 5perches ordinaireson each side.
acre (ordinaire),or
arpent carré 		40 000 ~4221 m2 ~5048 sq yd, or
~1.043 acres 		A square 10perches ordinaireson each side.

Volume – liquid measures[edit]

Table of (liquid) volume units
Unit Relative
value
(pintes) 		SI
value 		U.S.
value 		Imperial
value 		Notes
roquille 1⁄32 ~29.75 ml One quarter of apoisson.
poisson 1⁄8 ~119 ml A measure equal to a half ademiard.There were different sizes based on the commodity measured:poisson de vin(wine),poisson de eau de vie(brandy), orpoisson de lait(milk).[11]
demiard 1⁄4 ~238 ml ~0.5 pint demiin French means "half": in this case, half achopine,and – coincidentally – also approximately half a US pint [237 ml].
chopine 1⁄2 ~476.1 ml ~1 pint ~0.84 pint
pinte 1 ~952.1 ml ~2.01 pint ~1.68 pint Although etymologically related to the English unitpint,the French pint is about twice as large. It was the main small unit in common use, and measured1⁄36of a cubicpied du roi.
quade 2 ~1.904 L ~0.5 gallon ~0.42 gallon
velte 8 ~7.617 L ~2.01 gallon ~1.68 gallon aveltewas a measuring stick that was inserted into a cask or barrel to determine its depth.
quartaut 72 ~68.55 L 9veltes,or two cubicpieds du roi.
feuillette 144 ~137.1 L
muid 288 ~274.2 L Eight cubicpieds du roi.
cubic
pouce cube 1⁄48 ~19.84 ml The French cubic inch.
pied cube 36 ~34.28 L The French cubic foot. In ancient times, a cubic foot was also known as anamphorawhen measuring liquid volume.

Volume – dry measures[edit]

Table of (dry) volume units
Unit Relative
value
(boisseaux) 		SI
value 		Imperial
value 		U.S.
value 		Notes
litron 1⁄16 793.5 cm3 0.1745 imp gal 0.1801 U.S. dry gal 1⁄4of aquart.Thelitreis etymologically related to this unit.
quart 1⁄4 3.174 dm3 0.698 imp gal 0.721 U.S. dry gal 1⁄4of aboisseau.
boisseau 1 12.7 dm3 2.8 imp gal 2.9 U.S. dry gal Although etymologically related to the English unitbushel,the French bushel is about one third the size. Aboisseauwas defined as10⁄27of a cubicpied du roi.
minot 3 38.09 dm3 8.38 imp gal 8.65 U.S. dry gal
mine 6 76.17 dm3 16.76 imp gal 17.29 U.S. dry gal
setier 12 152.3 dm3 33.5 imp gal 34.6 U.S. dry gal
muid 144 1.828 m3 402 imp gal 415 U.S. dry gal
cubic
pouce cube 1⁄640 ~19.84 cm3 ~1.211 cu in The French cubic inch.
pied cube 2+7⁄10 ~34.28 dm3 ~2,092 cu in The French cubic foot. Exactly 2.7boisseaux.

Weight[edit]

The Parisian equivalents (in livres) of 100 local livres in various towns in 1768[12]
(approximations per source)
Abbeville 93–94
Avignon 83
Beaucare 95
Bordeaux 100
Bourg-en-Bresse 96
Dunkirk 87
Lille 87–88
Lyon 87
Marseilles 81
Montepellier 83
Nancy 94–95
Nantes 101–102
La Rochelle 101–102
Rouen (poids de vicomté) 103
Strasbourg (petit poids) 96
Toulouse 84
Differences between the nominal and actual weights (inmarcs moyens) in the parts of thepile de Charlemagneas measured byJean-Charles de Borda[13]
Nominal
(marcs)		 Error in actual
(grains)
20 +1.4
14 +4.5
8 -0.4
4 -2.1
2 -1.0
1 (creux) -0.7
1 (plein) -1.7

Charlemagne's system had 12onces(ounces) to thelivre(pound).[14] Between 1076 and 1093Philip I(1052–1108) instituted a system ofpoids de marc(mark weight) used for minting coin, with 8oncesto amarc.[14]

Jean II(1319–1364) constructed a new standard of measures, including alivre actuelle( "current" pound, also known as alivre de poids de marcor "mark weight" pound) of 2marcs,i.e. 16onces.[15] The Charlemagne 12-ouncelivrebecame known as thelivre esterlin( "true" pound) in order to distinguish it.[16][17] ″Esterlin″ was an Old French word (ca. 1190, Anglo-Norman dialect) that referred to Scottish coin (sterling, or ″denier″).[18]As references cited later on this page show, its application changed over time in accordance with the changing historical context, though it is not current in Modern French.

Thelivre actuellecould be sub-divided into 2demi-livres(half-pounds), 4quarterons,or 8demi-quarterons.[19] Conversely, there were 100livresin aquintal(c.f. Englishhundredweight).[19] The fractional parts of anoncehad different names inApothecary measure(used in medicine) and measure of precious metals, but the fractional ratios were themselves the same: 1oncewas 8drachme(Apothecary, c.f. Englishdram) orgros;1drachme/groswas 3scruples(Apothecary, c.f. Englishscruple) ordeniers,and 1scruple/denierwas 24grains.[20][21] This makes 384deniersin alivrein weight measure, which contrasts with the oldmonetarylivrein France which was divided into 240deniers.[22]

Jean II's standards are preserved in the Conservatoire Nationale des Arts et Métiers, which also holds a set of later-still physical standards from the 15th century, the so-calledpile de Charlemagne.[21][23] Thispiledefined the weight of 50marcs,i.e. 400onces,and thus 25livres actuelles,or 331⁄3livres esterlins.[14][24] It had been kept in the royal palaces originally.[25] In 1540François I(1494–1547) had transferred it to theCour des monnaies,where it had been held in a cabinet with three locks, whose keys had been held separately by the president of the Cour, one of its counsellors, and a clerk.[25]

The thirteen individual pieces that made up the Parisianpile de Charlemagnecomprised an outer containing cylinder nominally weighing 20 marcs, and a set of hollow nesting cups within, topped with a filled weight as the smallest piece.[24][26][27] The heaviest cups were nominally 14, 8, 4, and 2marcs,sub-totalling 48 marcs (including the 20 marc outer container); followed by a nominally 1 marc hollow cup which was termed themarc creux(hollow mark); and followed by 6 further cups (4, 2, and 1onces,and 4, 2, and 1gros) with a final seventh filled 1grosweight, all totalling 1 marc, which was termed themarc plein(filled mark).[24][26][28][27]

Unfortunately, the weights were not consistent, with themarc pleinnot being the same weight as themarc creux,and neither being the same as amean1 marc weight determined from the weight of the wholepile.[24][28] So when the time came to work out the conversion factors between these measures and the metric system, the wholepilewas taken to define 50 Parisian standardmarcs,and thus 230 400grains(the number of grains in 50marcs).[24] Louis Lefèvre‑Gineauinitially determined that the metric weight of the wholepilewas 12.227 947 5 kg,[28]later corrected to 12.2376 kg,[29]thereby making (by division and rounded to three decimal places) amarc244.753 g, alivre esterlin367.129 g, and alivre actuelle489.506 g.[20][30] Hence further the (Parisian)oncewas 30.594 g, thegros/drachmewas 3.824 g, thedenier/scruplewas 1.274 g, and thegrainwas 0.053 g.[19][16]

However, the actual weights of the pre-metric measures were nowhere near even this simple.[31] These were just the Parisian standards, and individual provinces, cities, and even guilds, all had their own reference physical standards, which were not checked against one another and which sometimes conflatedesterlinandactuelle.[31] For just some examples: the Marseillelivrewas 399.6 g, the Montpelier one 394.9 g, the Toulon one 465.5 g, and the Toulouse one 413.2 g; with all of the fractional subdivisions having different values accordingly.[32] The Limogesmarcwas 240.929 g, the Tours one 237.869 g, and the Troyes one 250.050 g.[33]

Furthermore, there were alsolivrescomprising different numbers ofoncesto both theactuelleandesterlin,includinglivresof 14, 18, and 20onces,confusing things yet further.[34] Thelivrein thepoids de table(table weight) systems used in Provence and Languedoc (and a common name for provincial weight systems in general alongsidepoids de pays,country weight, andpoids de ville,town weight) was the same weight as 15oncesor even as low as 13oncesin the Parisianpoids de marc,[35][36][37][12]and thelivrein thepoids de soie(silk weight) system of Lyon was similarly just15⁄16the weight of the Parisianlivre.[38][12] This caused an erroneous belief that theselivrescomprised 13, 14, or 15onces,however this was a confusion stemming from the equivalentpoids de marcweights, and bothpoids de tableandpoids de soiehad 16 of their own, lighter,oncesand so forth,[38][36][12] Rouen had apoids de vicomtésystem.[12]

See also[edit]

References[edit]

  1. ^ab"History of measurement".Métrologie française.Retrieved2011-02-06.
  2. ^Adler 2002,pp. 2–3.
  3. ^Seefr:Droit coutumier en France.
  4. ^Rowlett.
  5. ^Février.
  6. ^Darcy-Bertuletti 2005.
  7. ^Débarbat.
  8. ^This can be shown by noting that 27,706 × 16 = 443,296 and that 9 × 16 = 144, the number oflignesin apied.
  9. ^Weights and Measures Act, Schedule III
  10. ^Nelson, Robert A. (December 1981).The Physics Teacher:597.{{cite journal}}:Missing or empty|title=(help)
  11. ^Dictionnaire de l'Academie Francais(8th edition)
  12. ^abcdeExpilly 1768,p. 712.
  13. ^Harkness 1888,p. lix.
  14. ^abcSaigey 1834,p. 114.
  15. ^Saigey 1834,pp. 114–115.
  16. ^abSaigey 1834,p. 116.
  17. ^Blome, Stocking & Watts 1939,p. 30.
  18. ^Greimas, Algirdas Julien,ed. (1992). "Esterlin".Dictionnaire de l'ancien français: le Moyen Age.Larousse. p. 265.
  19. ^abcDu Mersan 1833,p. 635.
  20. ^abSaigey 1834,p. 115.
  21. ^abCrease 2011,p. 73.
  22. ^Garnier 1841a,p. 1356.
  23. ^Morin 1864,p. 248.
  24. ^abcdeZupko 1990,p. 116.
  25. ^abSavary & Savary 1742,p. 26.
  26. ^abWitthöft 2018,p. 249.
  27. ^abDaumas 1970,p. 207.
  28. ^abcMongez & de La Métherie 1799,p. 171.
  29. ^Doursther 1840,p. 427.
  30. ^Garnier 1841a,p. 1355.
  31. ^abCrease 2011,p. 74.
  32. ^Garnier 1841a,pp. 1355–1356.
  33. ^Garnier 1841b,p. 1447.
  34. ^Saigey 1834,pp. 116–117.
  35. ^Guilhiermoz 1906,p. 402.
  36. ^abPeuchet 1801,poids de table.
  37. ^Kelly 1811,p. 294.
  38. ^abPeuchet 1801,poids de soie.

Sources[edit]

Further reading[edit]

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