Jacques Buot

Background

Jacques Buot was born in 1623, in L'Aigle, Normandy, France.

Career

Little is known about the life of Jacques Buot. Except for correspondence with advocates like Petit and Ballesdens, the first mention of Buot occurs in 1647 when he published his Usage de la rune de proportion ..., avec un traité d`arithmétique, dedicated to Chancellor Séguier. This publication shows that Buot could rank with Edmond Gunter and Blaise Pascal as one of the first inventors of calculating machines. As a mathematician, Buot left several memoirs in the Procés verbaux of the academy on the "Limaçon de Mr. Pascal," a treatise about "les lieux géométriques," and answers to several geometrical questions.

As a physicist, Buot was involved in many mechanical experiments including studies of the strength and expansion of metals like copper, iron and steel, studies of samples of magnetic materials, and experiments on forces such as gravity, the so-called centrifugal force, friction, and capillarity. The academy often requested his expert advice on tests of metals, alloys, solders, or object-glasses, to check on the correctness of maps, to provide instructions for the making of celestial globes, and to prepare reports such as those on lifting appliances and, not surprisingly, on the efficiency of difierent guns. In June 1675, he was asked to draw up a descriptive catalog of the instruments held by the academy. Together with Francois Blondel and Picard, he was an executor of the will of Roberval.

The first mention of Buot as an astronomer occurred in the Astronomical Physica, published by I.-B. du Hamel in 1660, where observations of the solar eclipse of April 8, 1652, made by Buot, Petit, J. A. Le Tenneur, and Auzout in Paris are reported. In the Journal des Sçavans, of January 26, 1665, Buot’s Carte du Ciel, made by order of the king, is described. This map showed the constellations through which passed the orbit of comet C/1665 F1. Buot’s own observations of the comet were included with the map. Other achievements appeared in the Procés verbux of the academy (with a gap between 1670 and 1674): a memoir on the projection of topographical maps in 1666; observations of the elevation of the celestial pole made at the end of 1666 by means of a sextant with a radius of 6 ft.; and a method for finding the positions of the fixed stars in 1667. From 1666 onward Buot took part in the routine operations of the academy. These included the observation of the solar eclipse of July 2, 1666, made by Buot, Huygens, Carcavi, Roberval, Auzout, and Frénicle from Colbert’s house, where the academy met; the marking of a meridian line on a stone at Paris Observatory on June 21, 1667, (the day of the summer solstice); and the observation of Saturn on July 16, 1667, from which he calculated the inclination of the planet’s ring to the ecliptic as 31° 38' 35" (correcting Huygens’s 1659 value), and that of August 15, 1667, carried out with Huygens, Picard, and Jean Richer from which he calculated the value of 32° 0', and 9° 32' 50” for the inclination to the Equator. The Journal des Sçanvans of March 21, 1672, reported the observation of a "great permanent spot" on Jupiter, which Jean Dominique Cassini had observed in 1665, but had not seen since the beginning of 1666. The reappearance of the same spot on January 19, 1672, and Cassini’s calculations to predict its position for March 3 motivated the academy to ask Buot and Edme Mariotte to assist Cassini at the Paris Observatory. Their observations confirmed the period of Jupiter’s rotation as 9h and 56min.

In 1667 Buot invented the Équerre azimutale, precisely described and illustrated in the first volume of the Machines et inventions approuvées par l'Académie royale des sciences (not printed until 1735). Made of copper, the instrument enabled an observer to lay out an accurate meridian line without exact knowledge of the time of local noon. Claude Antoine Couplet, also ingénieur ordinaire du Roi et professeur royal de mathématiques des Pages de sa Grande Écurie: and former student of Buot, assisted in the construction of the instrument.

Achievements

• Jacques Buot was a mathematician, astronomer, cartographer, and royal engineer, who invented the équere azimutale, an instrument for finding the intersection of the meridian with a horizontal plane. He was also active as a physicist, who made experiments to determine the forces that cause water to expand on congelation.

Membership

• 

  Jacques Buot was a member of the French Academy of Sciences from the time it was founded in 1666; as such he received an annual stipend of 1,200 livers.

  French Academy of Sciences , France

  1666

Connections

colleague:

Pierre Petit

Pierre Petit was a French astronomer, physicist, mathematician and instrument maker, who also served as a military engineer and geographer to Louis XIII and Louis XIV, in roles such as Superintendent of Fortifications.

colleague:

Jean Ballesdens

Jean Ballesdens was a French lawyer, editor and bibliophile, though he has left practically no writings.

colleague:

Jacques-Alexandre Le Tenneur

Jacques-Alexandre Le Tenneur was a French mathematician, who defended Galileo Galilei’s ideas.

colleague:

Adrien Auzout

Adrien Auzout was a French astronomer, who made contributions in telescope observations, including perfecting the use of the micrometer. He also made many observations with large aerial telescopes and he is noted for briefly considering the construction of a huge aerial telescope 1,000 feet in length that he would use to observe animals on the Moon.

References

• Comptes Des Bâtiments Du Roi Sous Le Règne de Louis XIV, Tome1
  1881
• L'Academie Des Sciences
  1888
• Dictionary of Scientific Biography, Volume II
  1970