Amontons, Guillaume

(b. Paris, France, 31 August 1663; d. Paris, 11 October 1705)

physics.

Amontons’s father was a lawyer from Normandy who settled in Paris. The boy became almost deaf during adolescence, and his interest then turned toward mechanics. After vain efforts to develop a perpetual motion machine, he decided, despite his family’s opposition, to study physical sciences and mathematics. After studying drawing, surveying, and architecture, he was employed on various public works projects that gave him practical knowledge of applied mechanics. Later he studied celestial mechanics and applied himself to the improvement of hygrometers, barometers, and thermometers.

His first scientific production was a hygrometer in 1687. The apparatus consisted of a ball of beechwood, horn, or leather filled with mercury; it varied in size according to the humidity of the atmosphere. In 1688 he developed his shortened barometer, composed of several parallel tubes connected alternately at the top and bottom, with only alternate tubes containing mercury.

Sometime between 1688 and 1695, Amontons tried out his optical telegraph in the presence of the royal family. He published no data on this experiment, but the device is known to have consisted of a series of stations, each equipped with a spyglass, for the rapid transmission of signals. The nature of the signals to be transmitted is not known, however.

In 1695 Amontons sought to renew the use of the clepsydra as a timing apparatus on ships in order to solve the problem of determining longitude at sea. In his paper on this, he described two apparatuses that became well known by his name in the eighteenth century, although their use was never common. One was a cisternless barometer consisting of a tube narrow enough for the column of mercury to remain suspended. In his experiments with this, Amontons gradually broadened the tube into the shape of an inverted funnel. The mercury column then became shortened as atmospheric pressure decreased and lengthened as it increased.

The other was an air thermometer independent of the atmospheric pressure. Air occupied the top of one of the branches of a U-shaped tube, and by its dilation it pushed down one of the mercury columns so that the other end of the branch formed a barometric chamber.

As early as 1699 Amontons proposed a thermic motor: a machine using hot air and external combustion with direct rotation. The experiments carried on in connection with this machine led him to note that ordinary air going from the temperature of ice to that of boiling water increases its volume by about one third.

In the same year Amontons produced the first known study on the question of losses caused by friction in machines. He then established the laws of proportionality between the friction and the mutual pressure of the bodies in contact.

In 1702 Amontons returned to thermometry. Having noted that water ceases to increase its temperature from the boiling point, he proposed that the latter be the fixed thermometric point. He also observed that for an equal elevation of temperature, the increase of pressure of a gas always exists in the same proportion, no matter what the initial pressure.

The following year Amontons indicated practical ways of graduating ordinary alcohol thermometers, Also, returning to his observations of 1702, he proposed an explanation for certain natural catastrophes, such as earthquakes: If there is air very deep within the earth, it is extremely compressed and could reach an irresistible pressure as the result of a relatively small increase in temperture.

Among Amonton’s last works was a brometer with a U-tube, without an open surface of mercury, to be used on shipboard. Using the same receptacle and liquids whose coefiicients of expansion differed, Amontons was able to establish as false the theory that liquids “condense and cool first, before expanding with approaching heat.” The observed results were due only to the expansion of the containers. Also, using a barometer as an altimeter, he tried to verify the exactitude of Mariotte’s (Boyle’s) law at low pressures.

One really cannot understand what has led certain authors to attribute to Amontons the creation of an air thermometer of unvarying volume. As for the idea of absolute zero, he barely implies it in his memoir of 1703 (“Le thermomètre rèduit à une mesure fixe,” pp. 52–54); this brief notice nevertheless presented Johann Heinrich Lambert with a point of departure for his explication of this idea (1779).

BIBLIOGRAPHY

I. Original Works. Excerpts from letters are in Journal des savants (8 March 1688), 245–247, and (10 May 1688), 394–396. His only book is Remarques et expèriences physiques sur la construction d’une nouvelle clepsydre... (Paris, 1695). Amontons’s papers, all in Mémories de l’Académie des Sciences, are “De la résistance causée dans les machines...” (1699). 206–227, and Histoire..., 104, 109; “Moyen de substituer commodément l’action du feu...,” ibid., 112–126, and Histoire..., 101; “Discours sur quelques propriétes de Fair...” (1702), 155–174, and Histoire... 1; “Que les nouvelles experiences que nous avons du poids et du ressort de i’air...” (1703), 101–108, and Histoire...,6; “Remarques sur la table des degrés de chaleur...,” ibid., 200–212, and Histoire...,9; “Le thermométre réduit a une mesure fixe et certaine...,” ibid., 50–56 and Histoire...,9; “Discours sur les barométres” (1704), 271–278, and Histoire...,1; “Que tous les barométres tant doubles que simples...,” ibid., 164–172, and Histoire...,1; “Barométres sans mercure a l’usage de la mer” (1705), 49–54, and Histoire..., 1; “De la hauteur du mercure dans les barométres” (four articles), ibid., 229–231, 232–234, 234–236, 267–272, and Histoire...,10; “Edpériences sur la rarefaction de l’air,” ibid., 119–124 and Histoire..., 10; “Exériences sur les solutions et sur les fermentations froides...,” ibid., 83–84, and Histoire..., 68; and “Que les expériences sur les on se fonde pour prouver que les liquides se condensent et se refroidissent...,” ibid., 75–80, and Histoire...,4.

II. Secondary Literature. Works that discuss Amontons and his instruments are Maurice Daumas, Les instruments scientifiques aux XVIIe et XVIIIe siécles (Paris, 1953); [Bernard le Bovier de Fontenelle] “Éloge de M. Amontons,” in Histoire de I’Académie Royale des Sciences (1705), 150–154; René Taton, Histoire générale des sciences, II, La science moderne (de 1450 a 1800) (Paris, 1958), pp. 258, 472, 516; and W.E. Knowles Middleton, The History of the Barometer (Baltimore, 1964).

Jacques Payen