Gabriel Mouton | |
|---|---|
| Born | 1618 |
| Died | (1694-09-28)28 September 1694 (aged about 76) |
| Known for | Proposing a natural standard of length based on the circumference of the Earth. |
| Scientific career | |
| Fields | Mathematics and astronomy |
Gabriel Mouton (1618 – 28 September 1694) was a Frenchabbot andscientist. He was a doctor of theology fromLyon, but was also interested inmathematics andastronomy. His 1670 book, theObservationes diametrorum solis et lunae apparentium, proposed a natural standard of length based on the circumference of the Earth, divided decimally. It was influential in the adoption of themetric system in 1799.
| Name | Multiple ofvirga | Approx. equivalents |
|---|---|---|
| Milliare | 1000 | 1 minute of arc, 2 km, 1 nautical mile |
| Centuria | 100 | 200 m |
| Decuria | 10 | 20 m |
| Virga | 1 | 2 m, 1 Parisiantoise |
| Virgula | 0.1 | 20 cm |
| Decima | 0.01 | 2 cm |
| Centesima | 0.001 | 2 mm |
| Millesima | 0.0001 | 0.2 mm |
Based on the measurements of the size of theEarth conducted byRiccioli of Bologna (at 321,815 Bologna feet to the degree), Mouton proposed adecimal system of measurement based on the circumference of the Earth, explaining the advantages of a system based on nature.
His suggestion was a unit, themilliare, that was defined as aminute of arc along ameridian arc, and a system of sub-units, dividing successively by factors of ten into thecenturia,decuria,virga,virgula,decima,centesima, andmillesima.[1] Thevirga, 1/1000 of a minute of arc, corresponding to 64.4 Bologna inches, or ~2.04 m, was reasonably close to the then current unit of length, the Parisiantoise (~1.95 m) – a feature which was meant to make acceptance of the new unit easier.
As a practical implementation, Mouton suggested that the actual standard be based onpendulum movement, so that a pendulum located in Lyon of length onevirgula (1/10virga) would change direction 3959.2 times in half an hour. The resulting pendulum would have a length of ~20.54 cm.
His ideas attracted interest at the time, and were supported byJean Picard as well asHuygens in 1673, and also studied atRoyal Society inLondon.[clarification needed] In 1673,Leibniz independently made proposals similar to those of Mouton.
It would be over a century later, however, that theFrench Academy of Sciences weights and measures committee suggested the decimalmetric system that defined theMetre as, at least initially, a division of the circumference of the Earth. The first official adoption of this system occurred in France in 1791.
By today's measures, hismilliare corresponds directly to a nautical mile, and hisvirga would by definition have been 1.852 m.
decuria.
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