Cagniard De La Tour, Charles

(b. Paris, France, 31 March 1777; d, Paris, 5 July, 1859), physics.

Cagniard studied at the École Polytechnique and the École du Génie Géographe. He was later auditeur to the Council of State, director of special projects for the city of Paris, and a member of the board of directors of the Société d’Encouragement. His honors included membership in the Legion of Honor and knighthood of the Order of St. Michel.

Because of the great diversity of the subjects he dealt with, it is slightly difficult to present a complete picture of Cagniard’s scientific career. He first worked in mechanics, beginning, in 1809, with a heat engine. Between 1809 and 1815 he produced a new hydraulic engine, a new air pump, a waterwheel mounted horizontally and turned by the current of a river, a portable military mill, and a heat-driven winch. Until, 1819 these machines were constantly being improved; after 1820 a curved-cylinder pump was added to the list.

Between 1820 and 1823 Cagniard began his research in physics, starting with the discovery of the existence of a critical state in the vaporization of liquids; at the same time he became construction chief of the Crouzoles aqueduct in the Puy-de-Dôme. Between 1824 and 1827, after the invention of his siren, Cagniard began research in acoustics and the mechanism of voice production and devoted much effort to this field from then on. Between 1828 and 1831 new interests appeared: studies on the crystallization and the effect of acids on carbon; studies on phosphorus; and studies on silica and its crystallization and the hardening of mortar. Between 1832 and 1835 Cagniard worked on adapting the principle of the Archimedean screw to the function of an air pump and then began research on alcoholic fermentation; this work reached its culmination between 1836 and 1838. Toward the end of his career, while still pursuing all his interests, Cagniard contributed to mechanics a dynamometric device giving the average dynamic effect of a machine operating during an interval bounded by two successive observations.

The most original aspects of Cagniard’s work include the heat engine, the critical state of vaporization, the siren, the Archimedean screw, and alcoholic fermentation.

One can best characterize the principle of the heat engine proposed by Cagniard by quoting from Lazare Carnot’s report on the subject delivered to the Académic des Sciences on 8 May 1809: “A mass of cold air introduced into the bottom of a tank filled with hot water expands, and in its attempt to rise to the surface, acts as a weight, but from bottom to top.” The cold air was conducted down to the bottom of the tank by means of a partially immersed Archimedean screw (this is the cagniardelle discussed below); heated by the water bath, it acted from below on the inverted cups of a paddle wheel immersed in hot water. The energy supplied by the shaft of the paddle wheel was five times that exerted on the shaft of the screw. As Carnot remarked, “The effect of the heat is therefore to increase fivefold the natural effect of the motive force,” but he did not determine the quantity of heat absorbed. Both the machine and there marks it occasioned are characteristic of this very early period of thermodynamics.

Gay-Lussac had demonstrated that vapors subjected to pressure much lower than their saturation pressure behave like ideal gases. About 1822, while attempting to vaporize liquids in a sealed vessel, maintaining a specific ratio between the volume of the liquid and that of the vessel, Cagniard proved that, above a certain temperature, a liquid contained in a hermetically sealed vessel could be completely vaporized. He further determined the temperatures and pressures corresponding to that critical state for a certain number of substances. For sulfuric ether he found, for example, 175° C. and thirty-eight atmospheres; for alcohol, 248° C. and 119 atmospheres. This research was taken up again by Andrews in 1867, but with more effective laboratory equipment and more accurate methods of measurement.

In his lifetime Cagniard’s reputation was made by the acoustical siren. Besides demonstrating the nature of sound, this device, equipped with a speedometer for measuring the rate of revolution, allowed ready determination of the frequency of vibration of any sonorous body: it had only to be put in harmony with the body being studied. According to Cagniard’s original design, there was no auxiliary motor; the apertures were arranged obliquely so that the perforated disk would automatically rotate like a turbine when air under pressure was applied. It had the disadvantage that the pressure had to be increased in order to provide a sharper sound, so that the siren was soft for low notes and shrill for high ones. Furthermore, it was difficult to keep the device at a given pitch, since air pressure was difficult to regulate with such accuracy. The siren was gradually perfected and took final shape in the hands of Helmholtz, who added independent feed (several rings of holes were arranged concentrically on a single disk, thereby allowing variation in the pitch in a known ratio, without changing speed).

The cagniardelle consists of an Archimedean screw partially immersed in a liquid; when rotated, it creates a forced draft or air blast. The first one was set up as early as 1827 by Koechlin et Cie., of Mulhouse; however, Cagniard had been using the principle since, 1809. This prototype—it was three meters long, two and a half meters in diameter, had four turns, and made six revolutions per minute—produced thirty-five cubic meters of blast per minute at a pressure of twenty-seven millimeters of mercury. This was sufficient to supply twenty-two forges and two cupola furnaces. Later cagniardelles could attain pressures of up to sixty millimeters of mercury. This machine had an excellent yield, but it was cumbersome and ceased to be used when production of compressed air at higher pressure became widespread.

Cagniard’s studies on alcoholic fermentation have unquestionably remained the most valuable of his works. Begun as early as 1835, they led him, toward the end of 1836, to see that there was certainly a living substance in brewer’s yeast. Schwann came to the same conclusion at the same time, but Liebig’s violent attacks forced this point of view into the background for twenty years. (It was in 1857 that Pasteur shed light on the question.) Reporting on research done with the finest microscopes available, Cagniard wrote, “Ferments… are composed of very simple organized microscopic bodies… brewer’s yeast is a mass of small globulous bodies capable of reproducing themselves… it is very probably through some effect of their growth that they release carbon dioxide and… convert [a sugary solution] into a spirituous liquor.”

BIBLIOGRAPHY

I. Original Works. Cagniard himself compiled the list in the Notice sur les travaux scientifiques…, which he had published anonymously and used to support his candidacy for the Académic des Sciences in 1851 (see below). It has by no means been proved that this list is exhaustive, for Cagniard’s works are numerous and each was published several times. For those who wish to do research within this labyrinth, the information below will be of help.

Cagniard regularly presented the results of his studies to the Académic des Sciences or the Société Philomatique, or to both at the same time. No fewer than 116 references concerning him are in the publications of the Academic Sciences. One might begin with the following: for 1808–1835, the Procés-verbaux des séances de I’Académie4–10 ), 6 vols. (Hendaye, 1913–1922), table of proper names in each volume. For the period after 1835, see Table géérale des Comptes rendus des séances de l’Académie des sciences, tomes ler à XXXI, 3 août 1835 à 30 décembre 1850 (Paris, 1853) Table générate… tomes XXXII à LXI, 6 Janvier 1851 à 30 décembre 1865 (Paris, 1870).

Cagniard’s correspondence with the Société Philomatique was published in the form of extracts from the society’s minutes, which appeared weekly in L’Institut. Journal général des sociétés et travaux scientifiques de la France et de l’étranger. Première section: Sciences mathématiques, physiques et naturelles. The principal ones are (a) works on fermentation: 4 , no. 158 (18 May 1836), 157; no. 159 (25 May 1836), 165; no. 164 (29 June 1836), 209; no.165 (6 July 1836), 215; no. 166 (13 July 1836), 224–225; no. 167 (20 July 1836), 236–237; no. 185 (25 Nov. 1836), 389–390; 5 , no. 199 (1 Mar. 1837). 73; (b) works on acoustics, the formation of human speech, the artificial glottis, and the anche à torsion (twisting reed): 6 , no. 229 (17 May. 1838), 162–163; 10 , no. 453 (1 Sept. 1842), 311; 11 , no. 482 (23 Mar. 1843), 93: no. 485 (13 Apr. 1843), 122; no. 490 (18 May 1843), 165; no. 498 (13 July 1843), 233; 12 , no. 536 (3 Apr. 1844), 116–117; 13 , no. 577 (15 Jan. 1845), 24: 14 , no. 639 (1 Apr. 1846), 106–107; 18 , no. 845 (13 Mar. 1850), 84–85; no. 883 (4 Dec. 1850), 390; (c) works on the carbonization of plants in a sealed vessel: 6 , no, 229 (17 May. 1838), 163; 18 , no. 861 (3 July 1850), 214–215; and no. 866 (7 Aug. 1850), 253–254.

Other publications are “Sur li sirène, nouvelle machine d’acoustique destinée à mesurer les vibrations de l’air qui constituent le son,” in Annates de chimie, 12 (1819), 167–171 “Exposé de quelques résultats obtenus par l’actioncombinée de la chaleur et de la compression sur certains liquides, tels que l’eau, l’alcool, l’éther sulfurique et l’es-sence de pétrole rectifiée,” ibid., 21 (1822). 127–132, 178–182 “Expériences à une haute pression avec quelques substances,” ibid., 23 (1823). 267–269; “Nouvelle note… sur les effets qu’on obtienl par l’application simultanée de la chaleur et de la compression à certains liquides,” ibid., 22 (1823) 410–415; “Considérations diverses sur la vibration sonore des liquides,” ibid., 56 (1834), 280–294; Exposé relat if à la vis soufflante connue… sons le nom de Cagniardelle, lu à l’Académie des sciences le 26 mat 1834 (Paris, 1834): “Mémoire sur la fermentation vineuse présenté à l’Académic des sciences le 12 juin 1837,” in Annales dechimie, 68 (1838), 206–222; and Expériences sur la cristallisation du charbon présentées à l’Académie des sciences le l2 juillet 1847 (Paris, 1847).

II. Secondary Literature. Works on Cagniard are A. C. Becquerel, Funérailles de M. le baron Cagniard de Latour. Discours… prononcé… le jeudi 7 juillet 1859 “Cagniard-Latour.” and “Note de Mr Cagniard-Latour.” 10 pps. in autograph, dated 5 Nov. 1827: and à Messieurs les membres de l’Academie des sciences (Paris, 1851); Marcel Florkin, Naissattce et déviation de lathéorie cellulaire dans l’oeuvrede Théodore Schwann (Paris, 1960), pp. 51, 53, 54. 91: Jacob, Biographic de Cagniard de Latour, membre de I’Institut, extract from La science (Paris, n.d. [after 1851]); Thomas S. Kuhn, “Sadi Carnot and the Cagniard Engine,” in Isis. 52 (1961), 567; Notice des tra vauxdu B^on Cagniard de Latour (Paris, n.d. [after 1822]); Notice sur les travaux scientifiques de M. Cagniard-Latour (Paris, 1851); Notice sur M, le baron Cagniard de Latour, membre de l’ Institut, extract from Vol. III of Études critiques et biographiques. (Paris. 1856); and René Taton. Histoire générale des sciences. Tome III: La science contemporaine, I (Paris, 1961), 198, 261, 271, 444, 456.

Jacques Payen