Gabriel Mouton (1618 – 28 September 1694) was a
FrenchFrance , officially the French Republic , is a country located in Western Europe, with several overseas islands and territories located on other continents. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean...
abbot and scientist. He was a doctor of theology from
Lyon||-||}Lyon , often Anglicized as Lyons, is a city in east-central France in the region Rhône-Alpes, situated between Paris and Marseille. Its name is pronounced in French and Arpitan, and or in English...
, but was also interested in mathematics and astronomy.
His 1670 book, the
Observationes diametrorum solis et lunae apparentium, came to form the basis of what was to become the
metric systemThe metric system is an international decimalised system of measurement, first adopted by France in 1791, that is the common system of measuring units used by most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not...
hundred years later. Based on the measurements of the size of the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
conducted by
RiccioliGiovanni Battista Riccioli , was an Italian astronomer and a Roman Catholic Priest. He was a Jesuit who entered the order in 1614. He was also the first person to measure the rate of acceleration of a freely falling body....
of Bologna (at 321,815 Bologna feet to the degree), Mouton proposed a
decimalThe decimal numeral system has ten as its base. It is the most widely used numeral base.- Decimal notation :...
system of measurement based on the circumference of the Earth, explaining the advantages of a system based on nature.
Gabriel Mouton (1618 – 28 September 1694) was a
FrenchFrance , officially the French Republic , is a country located in Western Europe, with several overseas islands and territories located on other continents. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean...
abbot and scientist. He was a doctor of theology from
Lyon||-||}Lyon , often Anglicized as Lyons, is a city in east-central France in the region Rhône-Alpes, situated between Paris and Marseille. Its name is pronounced in French and Arpitan, and or in English...
, but was also interested in mathematics and astronomy.
His 1670 book, the
Observationes diametrorum solis et lunae apparentium, came to form the basis of what was to become the
metric systemThe metric system is an international decimalised system of measurement, first adopted by France in 1791, that is the common system of measuring units used by most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not...
hundred years later. Based on the measurements of the size of the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
conducted by
RiccioliGiovanni Battista Riccioli , was an Italian astronomer and a Roman Catholic Priest. He was a Jesuit who entered the order in 1614. He was also the first person to measure the rate of acceleration of a freely falling body....
of Bologna (at 321,815 Bologna feet to the degree), Mouton proposed a
decimalThe decimal numeral system has ten as its base. It is the most widely used numeral base.- Decimal notation :...
system of measurement based on the circumference of the Earth, explaining the advantages of a system based on nature. Mouton's publication appeared two years after
John WilkinsJohn Wilkins was an English clergyman and author. He was founder and first secretary of the Royal Society in 1660 and Bishop of Chester from 1668 until his death....
, then president of the
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
published a similar proposal.
His suggestion was a unit,
milliare, that was defined as a
minute of arcA minute of arc or arcminute is a unit of angular measurement, equal to one sixtieth of one degree. Since one degree is defined as one three hundred sixtieth of a circle, 1 minute of arc is 1/21,600 of the amount of arc in a closed circle...
along a
meridianA meridian is an imaginary arc on the Earth's surface from the North Pole to the South Pole that connects all locations running along it with a given longitude. The position of a point on the meridian is given by the latitude. Each meridian is perpendicular to all circles of latitude at the...
, and a system of sub-units, dividing successively by factors of ten into the
centuria,
decuria,
virga,
virgula,
decima,
centesima, and
millesima. The
virga, 1/1000 of a minute of arc, corresponding to 64.4 Bologna inches, or ~2.04 m, was reasonably close to then current unit of length, the Parisian
toise (~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 on
pendulumA pendulum is a weight suspended from a pivot so it can swing freely.When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force will cause it...
movement, so that a pendulum located in Lyon of length one
virgula (1/10
virga) would change direction 3959.2 times in half an hour. The resulting pendulum would have a length of ~20.54 cm. Wilkins however proposed using a pendulum that was 0.994 m in length.
His ideas attracted interest at the time, and were supported by
Jean PicardJean-Felix Picard was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand. He was the first person to measure the size of the Earth to a reasonable degree of accuracy in a survey conducted in 1669–70, for which he is honored with a...
as well as
HuygensChristiaan Huygens, FRS was a prominent Dutch mathematician, astronomer, physicist, horologist, and writer of early science fiction...
in 1673, and also studied at
Royal SocietyThe Royal Society of London for the Improvement of Natural Knowledge, known simply as the Royal Society, or even the Royal, is a learned society for science that was founded in 1660 and is considered by most to be the oldest such society still in existence...
in
London[]London is the capital of England and the United Kingdom. It has been a major settlement for two millennia, and the history of London goes back to its founding by the Romans, when it was named Londinium. London's core, the ancient City of London, the 'square mile', retains its medieval boundaries...
. In 1673, Leibniz independently made proposals similar to those of Mouton.
It would be over a century later, however, that the
French Academy of SciencesThe French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
weights and measures committee suggested the decimal
metric systemThe metric system is an international decimalised system of measurement, first adopted by France in 1791, that is the common system of measuring units used by most of the world. It exists in several variations, with different choices of fundamental units, though the choice of base units does not...
that defined the
MetreThe metre or meter is the basic unit of length in the International System of Units . Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent one ten-millionth of the distance from the Equator...
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, his
milliare corresponds directly to a
nautical mileThe nautical mile is a unit of length corresponding approximately to one minute of arc of latitude along any meridian....
, and his
virga would by definition have been 1.852 m.
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