Even the staider politicians caught up in the French Revolution - the philosopher Condorcet, for example, and later the members of Robespierre's Health Committee - thought something should be done to reform France's weights and measures.
The new standard length, it was agreed, would be the metre, from the Greek metron (to measure). In La Meridienne (1) Denis Guedj, a teacher of mathematics at a Parisian university, has written a fascinating account of how the metre came into being.
Pre-revolutionary France boasted about 700 different measures, often varying from town to town. Cloth was measured by the aune (ell), land by the perche (rod); wheat went by the barrel, oats by the picotin (peck). Wine was sold by the pint as well as by the more desirable demoiselle, which changed sex somewhere in mid-Channel to become the demijohn.
Equality, however, required uniformity. And not simply of measures; local dialects were banned in favour of French, old regions were carved into departements, the republican franc took over from those two old royalists, the louis and the crown, and even Citizen Time was harnessed - briefly - into ten-hour days and ten-day weeks.
A decade passed before the metre was established as a standard. The country was in turmoil, of course; but there was also a great concern for perfection. Condorcet wanted the new measurement to be "a means of spreading Enlightenment and fraternity among all people". It had to be perfect, universal and permanent. Hence the decision that it should be a fraction of the meridian: in fact, the ten-millionth part of the distance from the pole to the equator.
The meridian had been measured several times before, but more sophisticated instruments were now available. So in June 1792 two astronomers, Jean-Baptiste Delambre and Pierre Méchain, set of in opposite directions to check the length of the meridian by measuring its arc between Dunkirk and Barcelona, a distance known to be one-tenth of that from the pole to the equator. True to the international spirit underlying the operation, the French authorities had invited other countries to take part in what Méchain called "the greatest geodesic measure of all time". Since revolutionary France was the black sheep of Europe, all declined.
Méchain was nevertheless allowed into Spain. Once his measuring was over, however, he was not allowed to leave. By then Spain was at war with France, and his knowledge of local topography could be useful to the French army. When, after several months, he grew restless, the Spanish authorities put him on a ship bound for Genoa; it took him a year to get home. Meanwhile, Delambre's royal passes had become death warrants: the king had been guillotined. Despite a set of new, republican, credentials, he was frequently suspected of being a royalist, a spy and even a sorcerer.
The two astronomers completed their measurements in 1799, and Talleyrand's diplomatic skills produced a seven-nation conference (boycotted by Britain and America) to check them. The standard metre and kilogram were cast in platinum which the chemist Lavoisier had somehow succeeded in hoarding away before being guillotined. When Bonaparte seized power the metre was shelved; it reappeared in 1840, when it became France's standard unit of length.
Many other countries followed, but the system is not yet pan-European, let alone universal. Britons still drink their beer by the pint; Spaniards fix the price of land by the hand-span; and, yes, the French still buy their firewood by the cord. The metre's tribulations should be a warning to enthusiasts for a common European currency. But they can take some heart: the quest for the monnet is unlikely to be as hazardous.
(1)Editions Seghers, Paris; 272 pages; FFr92.