Since early life, man measures.

First measuring concepts were "large", "small". Then came "larger" and "smaller" than something taken as a reference, such as the foot or the thumb, or the area ploughed during a working day.

This is all right, but the area ploughed during a day depends on the soil structure and theŠ horse mood. Regarding the length of the foot, all those who ever suffered from having bought a pair of shoes not exactly at the right size do know that there no single length ! Therefore man has always been seeking universal, stable, freely accessible standards. There has been some significant improvement since the King's foot. Length is now defined as a relation to light speed, something that (almost) everybody can easily measure.

No measurement can be done without numbers, without a numbering system. Decimal system is now commonly accepted, but many other systems have been in use.

For example the 5-20 system, based on hands and feet fingers, initially developed by the Aztec and Maya civilizations, then spread all over the American continent, up to the Inuit people - how did they see their toes ? - before reaching Europe, presumably brought by Celts: the French word vingt (20) is not based on the word deux (2) as are in English and German twenty and zwanzig, respectively derived from two and zwei. The Hôpital des Quinze-Vingts was built by King Louis IX in 1241 to host 300 veterans. Quite logically our Swiss neighbors say octante (80) and nonante-neuf (99); but we in France keep saying quatre-vingts and quatre-vingt-dix-neuf, certainly because here the Celt culture resisted longer, thanks to Vercegintorix (and Asterix).

Before the metric system, "standards" were based on usual objects, but their value was far from being uniform, in spite of attempts made by governing or professional bodies of the time.

The populace was indeed the first victim of the inconsistency and confusion which prevailed in the field of measurement units. By contrast those who mastered the system, because they used to travel through the various countries, because they knew the differences between the various weights and measures, were able to gain benefits from it. For example in trade of grain : grain was not weighed - weighing scales demand a technology more advanced than the volume measurement - but measured by setier, minot and boisseau (bushel). Firstly, volume value of these measures differed between various locations; then, depending on the measured product, there was 12, 16, or 20 bushels per setier. Finally, it was common habit to buy per "heaped measure", i.e. with a cone of product on top of the measure, and to sell per "stricken measure", with no product left above the edge of the measure. Those fluent in fluid mechanics could make the calculation: there are some differences between grain sorts, it is anyway a 30 % profit guaranteed. Of course people in charge of measurements were appointed according to their ability to create the largest heap of material. It should be noted however that such a practice was prohibited in Brussels as soon as 1378. Because Brussels was a city where everybody was at the same time buyer and seller ?

This led intellectuals and scientists to dream about a new measurement system, simpler, and above all based on universal and invariable standards. Amongst them, the abbot Mouton, curate in Lyons near 1670.

The good abbot was well conscious of the precariousness and diversity of the standards of anthropometrical or other nature then in use. As a universal basis for measures he suggested to adopt the length of a one minute arc of a "large circle of the Earth" (i.e. a meridian). At that time indeed one had a rather accurate idea of the Earth dimensions: the triangulation method for measuring long distances had been developed by Dutch scientists some hundred years ago. Mouton named such a length a milliare. The unit being too large for day-to-day use he defined the virga, its thousandth part, as the main unit. Similarly Mouton proposed the decuria and centuria, respectively equal to 10 and 100 virgae as well as its decimal submultiples virgula, decima, centesima, and millesima. With our current knowledge we could calculate that the virga would measure 1.852 meter (one thousandth of a nautical mile) while Mouton, who started from a wrong value of the Earth circumference, saw a definite advantage in his virga: it was practically equal to the value of the Parisian toise (fathom, about 1.95 m).

Foundations therefore did exist. But what could push people to accept such a change ? Then came the French Revolution...




Treaty of Metre

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United States