Instruction sur les mesures déduites de la grandeur de la terre, uniformes pour toute la République, et sur les calculs relatifs a leur division décimale. Par la Commission temporaire des poids et mesures républicaines, en exécution des décrets de la Convention nationale. Édition originale.

Paris: de l'imprimerie nationale exécutive du Louvre, An II [1794].

First edition of the work that introduced the decimal system of measurement, “one of the few permanent social reforms that stemmed from the violent French Revolution.” “In 1788 the French Academy of Sciences, at the suggestion of Talleyrand, proposed the establishment of a new universal decimal system of measurement founded upon some ‘natural and invariable base’ to replace Europe’s diverse regional systems. This project was approved by the National Assembly in 1790 and a basic unit or ‘meter’ of measurement proposed, which was to be a decimal unit one ten-millionth of the distance between the terrestrial pole and the Equator. In 1791 the French national assembly voted to replace the old French unit of length (toise) with this new unit. In the summer of 1792 Jean Baptiste Delambre and Pierre François André Méchain embarked from Paris to establish the definitive length of the meter by taking geodetic measurements along the Dunkirk-Barcelona meridian. In August 1793, while Méchain and Delambre were still carrying out their task, the French National Assembly ‘affirmed the decimal system and the meridianal definition of the meter, ordered the continuation of the work, and decreed that the Academy provide for the manufacture, distribution, and explanation of provisional meters for general use while it prosecuted its measurements. This provisional meter was defined as a ten-millionth of ninety times the average degree in France as determined by Lacaille [in 1739-40] … It differed from the definitive meter by about a quarter of a millimeter’ (Heilbron, pp. 227-228). The definitive meter, as determined by Méchain and Delambre, would not be announced until the publication of Delambre’s Base du système métrique decimal (1806-10)” (historyofinformation.com).

“Before the Revolution in 1789, France, like most European countries, used weights and measures derived from those of the Romans. The standard weight was the pound of 16 (sometimes 12) ounces which in France was divided further into 8 gros, each of 72 grains. The unit of length was the foot of 12 inches, each divided into 12 lines, though for many purposes a longer unit was preferred – such as the French toise of 6 feet or the British yard of 3 feet. However units with the same name varied in size from country to country: for example, the French pound and foot were each larger than their British equivalents. In Britain most standards had been fixed nationally since the sixteenth century, but in France there were many local variations. This situation caused difficulties for internal and international commerce, made worse by the need to calculate in twelfths, sixteenths or other fractions when converting from one system to another.

“When the metric system was first introduced all units were divided decimally, making calculation easier. However, this had become possible only in the late Middle Ages, after ‘Arabic’ numerals, probably of Indian origin, began to replace Roman numbers. Arabic numerals became common about 1500, but it was not until 1585 that Simon Stevin, a Flemish mathematician showed in his book, “De Thiende”, how fractions could be expressed in Arabic numerals using a decimal point. His book was soon translated into French, with an English translation, “Disme: The Art of Tenths”, appearing in 1608. As well as explaining decimal arithmetic, Stevin advocated the decimal division of weights, measures and currency …

“An early proposal for a decimal system of measures came in 1670 from a Frenchman, Gabriel Mouton (1618–1694), a parish priest in Lyons with a good knowledge of astronomy and mathematics. He deplored the variety of units of length and proposed a natural unit based on the size of the Earth. This was the length of a minute (a sixtieth of a degree) of longitude, to be called the ‘mille’ and divided into tenths, hundredths and so on. One thousandth of a mille was called the ‘geometric foot’ and Mouton suggested that a pendulum of this length set up in Lyon, which would oscillate 3,959.2 times in 30 minutes, would be a convenient and easily verified standard of length.

“Mouton’s work was known of in Paris, where Jean Picard (1620–1682), an astronomer at the Observatory, proposed that the length of a pendulum beating seconds in Paris should be the standard (the seconds pendulum). One third of this, to be called the ‘universal foot’, would differ only slightly from the existing Paris foot. However, Picard did not advocate its decimal division. By now it was suspected that the Earth was not a perfect sphere and that the length of both a degree of longitude and the seconds pendulum (which depends on its distance from the centre of the Earth) might vary from place to place. This later became an obstacle to international acceptance of the metric units determined in France.

“During the eighteenth century the lack of an international system of weights and measures affected the development of science as well as commerce. In 1783, for example, James Watt, an amateur chemist as well as an engineer, complained to the chemist Richard Kirwan that he found it difficult to compare some of Kirwan’s quantitative results with those of Antoine Laurent Lavoisier (1743–1794), the French chemist, because both had used units with different values. Watt proposed that all chemists should adopt the same pound, preferably that of Paris which was the most widely used in Europe, and that it should be divided decimally. In 1789 Lavoisier published his book, Traité élémentaire de chimie, which marked the origin of modern chemistry. Quantitative data are present in abundance and in its English edition, Elements of Chemistry (1790), the translator, Robert Kerr, added an appendix with rules for the conversion of French units to British …

“In France, public discontent with many aspects of life in an absolute monarchy forced King Louis XVI and his government to call elections to the States-General, the only elected parliamentary body, for the first time in 175 years. It met in May 1789 with the new name of National Assembly and assumed the powers of government. Although the Assembly received many complaints about the lack of uniform weights and measures, it was unable to act immediately. In June 1789 the Paris Academy of Sciences independently appointed several members to a Commission of Weights and Measures, with the task of producing a national system. However, as no progress had been made by May 1790, the Assembly formally asked the Academy to act and provided the necessary funds. One member of the Assembly with a special interest in the project was Charles Maurice Talleyrand (1754–1838). He was not a scientist but was almost certainly advised by members of the Academy. He favoured a system based on the length of the seconds pendulum, with the unit of weight defined as the weight of water filling a cube of side equal to a specified fraction of that length. He did not, however, recommend the decimal division of the new units. Talleyrand hoped that the system would be adopted by other countries and proposed that the pendulum should be measured at a place that would be internationally acceptable: sea level half-way between the North Pole and the Equator. This was the 45th parallel, which conveniently crossed the French coast near Bordeaux …

“In September 1790, the Academy of Sciences instructed several members to determine the length of the seconds pendulum and the measures derived from it, but before work was started there was a dramatic volte-face. On 16 February 1791, acting on a proposal by Jean Charles Borda (1733–1799), the Academy appointed a new five-member committee to re-examine the proposed fundamental unit of length and on 19 March they reported that they favoured a unit equal to a ten-millionth of the Earth’s quadrant, the part of the meridian from the North Pole to the Equator, measured at sea level, and this unit and the units of weight and volume derived from it were to be divided decimally. No explanation was given for the rejection of the pendulum, which had been the preferred unit for more than a century. The academicians pointed out that the Paris meridian passed almost exactly through Dunkirk, on the north coast of France, and only a short distance from the Spanish city of Barcelona, both at sea level, which differed in latitude by 9 degrees and 40 minutes, just over a tenth of the quadrant The latitudes could be determined by astronomers with the best available instruments and the linear distance by the well established method of triangulation, starting from a carefully measured base line. The total length of the quadrant could then be calculated and the fundamental unit derived from it.

“Much of the meridian had been measured in the 1740s, when a large-scale map of France was being prepared, and since then surveying instruments had been improved. Borda, an engineer with a distinguished naval career as a navigator, had recently perfected his repeating circle, which in skilled hands enabled celestial or terrestrial angles to be determined to within a tenth of a second of circular measure. There have been suggestions that the desire of the Academy to demonstrate its effectiveness may have been partly responsible for the abandonment of the pendulum as a standard. However, as well as measuring the meridian, the Academy decided to determine very accurately the length of the seconds pendulum at Paris, and the task was undertaken by Borda and Jean Dominique Cassini (1748–1840), director of the Paris Observatory. They completed it at the Observatory in the summer of 1792, before the meridian survey was started … The apparatus used by Borda and Cassini was constructed by Etienne Lenoir (1744–1825), an instrument maker, born in Mers, a village near Blois in the Loire valley …

“In 1794, even though the work was far from complete, the National Convention, the republican successor to the Assembly, wanted to introduce the new weights and measures and the decimal system as soon as possible. Therefore a provisional value for the ten-millionth of the Earth’s quadrant was calculated from the results of the survey done in the 1740s and from the best available figures for the latitudes of Dunkirk and Barcelona. This unit, equal to 3 feet 11.44 lines, was named the ‘metre’, from the Greek ‘metron’ (measure). After some discussion the Greek prefixes, ‘deca’, ‘kilo’ and so on were adopted for multiples of the metre and Latin prefixes such as ‘deci’ and ‘milli’ for sub-multiples. These had been proposed by Claude Antoine Prieur (1763–1832), a former engineering officer who was an early advocate of decimal units and was now a member of die Convention. Some time was needed for agreement to be reached about names for the other units, but eventually the cubic decimetre became the litre’ and the weight of a cubic centimetre of water at its temperature of maximum density was named the ‘gramme’.

“Lenoir made a provisional standard metre in brass and designed a machine for the manufacture of 660 accurate copies for distribution to all parts of France. In 1794 the government published a book explaining the new system and giving conversion tables for the old and new units [offered here]. This was reprinted in several provincial towns, in some of which conversion tables for local units were also published. It was decreed that the use of the metric units should be compulsory from August 1794, but this was not in fact achieved until many years later.

Decimal currency, introduced as part of the metric system, was accepted more rapidly, as it was based on the ‘franc’, a coin containing five grammes of silver which was almost equal in value to the livre’ of the old regime. Circular measurement was also included in the new system, the right angle being divided into 100 and the circle into 400 ‘grades’, with decimal sub-divisions. Lenoir engraved this scale on three of the surveyors’ repeating circles.

“The division of the day into 10 hours instead of 24 received hardly any support and was soon abandoned, but the Republican calendar, with a year of 12 months, each month being made up of three ‘decades’ of 10 days with 5 additional days at the end (6 in leap years), remained in use until 1805.

“Preparation of the definitive standards was delayed not only by wartime problems affecting the surveyors but also by political developments in Paris. In July 1793 the Academy of Sciences was suppressed, along with all other organisations that had received funds from the royal government. The eleven scientists working on the new units were allowed to continue, but they suffered a severe blow in November 1793 when Lavoisier, who had been determining the density of water in experiments conducted with the physicist René Just Haüy (1743–1822), was arrested together with all his former colleagues in the Tax Farm, the unpopular private corporation that collected certain taxes under the old regime. By government decree Lavoisier was removed from the Commission of Weights and Measures, as were Borda, Delambre and two other members with links to the old regime. On 8 May 1794 Lavoisier and nearly thirty other Tax Farmers were guillotined. He was one of about ten academicians who suffered violent deaths during the Revolution.

“When the Commission eventually completed its work in 1798 the length of the metre was found to be 3 feet 11.296 lines, slightly shorter than the provisional value of 3 feet 11.44 lines. The observations and calculations of the Commission were checked by a group of foreign scientists who spent several months in Paris at the invitation of the French government, as it was hoped that the new system would be universally adopted. However, Europe was still at war, so only France’s allies at the time and neutral countries were represented. These were: Spain, Denmark, the Netherlands, Switzerland and several Italian states. The absentees included Great Britain, Russia, Sweden, all the German states and the United States of America. Even so, the meeting has some claim to be regarded as the first international scientific conference. Lenoir made the definitive metre in platinum, and the platinum kilogramme (a more useful standard than the gramme) was made by Nicolas Fortin, another famous instrument maker” (Smeaton).

“The new metric system was set forth in two works issued in Year Two of the Republic (1793/94) by the government’s Temporary Commission on Republican Weights and Measures. The first was Instruction sur les mesures, which emphasized mathematics and theory; the second was an abridged version containing a shorter and simpler presentation of the system. On p. xxxii of Instruction sur les mesures the commission announced that these two versions would be followed by a third, which “will only present a précis of the system, and which will be printed partly in octavo format for distribution, and partly as a broadside to be displayed in public places for viewing by all citizens.” We have not been able to find a record of this third version. Both Instruction sur les mesures and its abridged version were also issued by several other French publishers throughout the country; these provincial editions, of which we have never seen a definitive listing, are often confused with the true first edition” (historyofinformation.com).

Norman 1499 (lacking the folding plate). Dibner, Heralds of Science, 113 (citing a copy published in Macon in 1794). Heilbron, “The measure of enlightenment,” in Frängsmyr, Heilbron and Rider, eds., The Quantifying Spirit in the Eighteenth Century (1990), pp. 207-242. Smeaton, The Foundation of the Metric System in France in the 1790s, Platinum Metals Review (2000), vol. 44, pp. 125-134.



8vo (214 x 137 mm), pp. xxviii, 224, [27], vi, [1], with one folding plate, uncut. Contemporary marbled wrappers (a little worn and rubbed). An excellent copy in original state. Custom hald leather clam shell box with gilt spine lettering.

Item #5506

Price: $5,800.00

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