MAIRAN, JEAN-JACQUES DORTOUS DE

(b. Béziers, France, 26 November 1678; d. Paris, France, 20 February 1771),

physics. For the original article on Mairan see DSB, vol. 9.

Mairan was a mathematician and an enthusiastic experimenter whose major works were on the formation of ice and on the aurora borealis. However, he was also interested in all the important topics addressed by the scientific community in the eighteenth century, among them, the shape of Earth, light, colors, sound, the composition of matter, and vis viva (the debate around the force of moving bodies and the conservation of matter). Despite his admiration for Isaac Newton and the high regard in which he was held by many of his contemporaries, his reputation as a dyed-in-the-wool Cartesian and being compared unfavorably to Bernard Fontenelle, his predecessor as secretary of the Paris Academy of Sciences, served to tarnish his image. Since the early 1970s, scholars have begun to remedy this and to reassess his contributions to the scientific culture of the eighteenth century by underlining in particular the significant role that he played in the propagation of the Newtonian “system.”

Reputation . Mairan was a founding member of the Academy of Béziers; a member of the Imperial Academy of Sciences of St. Petersburg, the Royal Societies of London, Edinburgh, and Uppsala, the Institute of Bologna; and the Academy of Rouen. In 1741 he succeeded Fontenelle as secretary of the Academy of Sciences in Paris, a post held by only four men during the whole century.

Mairan enjoyed an excellent international reputation and exerted considerable influence on scientific progress in the eighteenth century. For example, Voltaire included him in the preface to Alzire (1736) with Pierre-Louis Moreau de Maupertuis, Rene-Antoine Réaumur, Charles-François Du Fay, and Alexis-Claude Clairaut as five of the most outstanding scientists and mathematicians of the century. Likewise, Jean Jallabert, professor of experimental philosophy and mathematics in Geneva, praised the observations and experimental methods of older scientists such as Newton, the Bernoullis (Jakob, Johann I and II, Daniel), Mairan, and Maupertuis in his inaugural address, titled De philosophiae experimentalis utilitate, illusque et matheseos concordia (Geneva, 1740).

Along with a voluminous correspondence, with innumerable contributions to the Mémoires of the academy, and with responsibility for the Eloges and for the Histoire of the academy for the years 1741, 1742, and 1743, Mairan wrote three prize-winning dissertations: one on barometric variations (1715), one on ice (1716), and one on light (1717) while still in Béziers. When the second edition of the Dissertation sur la glace was published in 1717, he became an associate of the Royal Academy of Sciences. After his move to Paris, he continued to publish dissertations on force, ice, and the aurora borealis. Mairan was interested in all the major scientific topics of the century—the shape of Earth, the nature of aurorae and their connection to sunspots and zodiacal light, motion, force, gravity, heat, light, colors, sound, barometric variations, universal attraction, the vis viva controversy, the nature and medicinal properties of electricity, the composition of matter, and scientific method; in short, a panoply of the scientific culture of the period.

Shape of Earth . Just as the academy prided itself on taking a neutral position on any topic until there was incontrovertible proof, Mairan prided himself on having an open mind. For example, he veered between opting for an oblate and a prolate shaped Earth, endeavoring to reconcile Gian Domenico and Jacques Cassini’s measurements with the theory of centrifugal forces and the shortening of the pendulum. In his 1720 memoir he tried to prove that Earth was a prolate spheroid, and, in an attempt to accommodate troublesome and apparently incompatible facts, resorted to what Maupertuis in his 1738 critique of Mairan’s argument considered the ingenious hypothesis of suggesting that if Earth had been prolate instead of spherical originally, it would now be, not oblate, but less prolate. In the end he agreed to abide by the results of the observations obtained by the academicians on the expeditions to Peru and to Lapland.

Light, Colors, and Sound . On the topic of light and colors, Mairan successfully repeated Newton’s optical experiments at Béziers in 1716 and 1717, and in 1719 he reported on the second Latin edition of the Opticks at the request of the academy. Reluctant as he was to abandon a mechanistic explanation of the effects of light and to accept attraction as an innate property of matter, Mairan stressed what was for him the most important part of the Opticks, namely, the experiments and the physico-mathematical inductions that could be drawn from them. He was also interested in the analogy of the colors of the spectrum and the divisions of the monochord. He was at pains to explain through his theory of the propagation of sounds and the different elasticity of the particles of air why the various notes reach our ears without being confused.

Vis Viva and Other Controversies . Few disputes in the eighteenth century generated as much fervor as the vis viva controversy in which Mairan played a major role. When Johann Bernoulli contested Colin Maclaurin’s 1724 prize-winning paper on the laws of motion for perfectly hard bodies, his subsequent correspondence with Mairan resulted in the latter’s 1728 memoir on the subject, which was then challenged by Émilie du Châtelet. The whole debate centered on the distinction made by Gottfried Wilhelm Leibniz between forces mortes and forces vives, with Mairan believing that all force was force morte.

Similar to Mairan’s dispute with du Châtelet over vis viva was his dispute with Leonhard Euler over zodiacal light. Euler contended that the solar atmosphere was only a ring separated from the sun, like Saturn’s rings, an argument which Mairan rejected, and which Euler himself eventually renounced.

Some twenty years later Mairan and Euler were still in disagreement—this time concerning Mairan’s theory on the propagation of sound. As early as 1719, at the time of his report on the second Latin edition of the Opticks, Mairan proposed to the academy his thesis that air as the vehicle of sound consisted of an infinity of vibrating particles of differing elasticity. This theory was later elaborated in his 1737 memoir, Discours sur la propagation du son dans les différents tons qui le modifient, and rejected by Euler, who argued that all sounds are transmitted by the same particles of air, because each particle is capable of different vibrations that produce different sounds.

Scientific Method . Mairan, all his life, was preoccupied with methodological questions, and it was his spirited defense of systems in the preface to the fourth edition of the Dissertation sur la glace in 1749 that incensed Jean Le Rond d’Alembert. The latter wrote in the Discours préliminaire of the Encyclopédie that the time had passed for anyone to argue in favor of systems. In a letter to Gabriel Cramer in September 1749, he accused Mairan of confusing the real advantages of the systematic spirit with the doubtful advantages of metaphysical systems and hypotheses. However, Mairan was always careful to praise the usefulness of the true philosophical or geometric spirit as exemplified by René Descartes, while also recognizing the dangers that certain systems represented in the form of a plethora of sterile and illusory philosophical extravagances. In his Eloge of François Pourfour de Petit in 1741, for example, he had praise for Descartes’s “immortal method” and for the care with which he conducted experiments. Mairan himself was a theoretician always in search of a mechanical model, but also a committed experimentalist and the instigator of a number of crucial experiments. In his Mémoire sur la cause générale du froid en hiver et de la chaleur en été (1719) he concluded that the method most likely to induce Nature to reveal her secrets is the constant interplay of experiment and reasoning.

Having condemned the abuse of certain systems and stressed the usefulness of others, such as Jean Jallabert’s conjectures on the causes of electricity, for scientific progress, Mairan devoted the third part of his Preface to his hypothesis of subtle matter on which he based his discussion of ice. Mairan condemned subtle matter in the Cartesian sense of hard and inflexible particles filling the universe, a thesis which he said is untenable. However, he posited the existence of some kind of subtle matter that could account for a number of physical phenomena. How else, he asked, is one to understand action at a distance or electrical impulses? Subtle matter for Mairan was an active and invisible principle that provided a mechanical model of the universe and one which Newton had made use of in the Opticks.

Mairan’s position on scientific method, in fact, was not so different from that of Étienne Bonnot de Condillac, whom d’Alembert so admired, and whose Traité des systèmes appeared in the same year as Mairan’s Preface (1749). However, because many of his contemporaries perceived him to be a die-hard Cartesian, any favorable comment on systems that he might have made would have aroused suspicion.

Preoccupation with Newton . Mairan had a reputation as the last Cartesian in a predominantly Newtonian world and he was reluctant to jettison the vortex theory recognizing the problems that it had difficulty resolving. Despite this, it is not hard to show Mairan’s fascination with Newton from virtually the beginning of his career. As early as 1717 in a letter to Firmin Abauzit in Geneva he admitted that Newton’s explanation of the tides was free of the difficulties raised by the vortex theory, but that gravity as an inherent property of matter was hard to accept. In another letter to the same correspondent, written on 30 October 1717, he conceded that attraction regarded simply as a fact seemed to him to be highly likely. However, he drew his correspondent’s attention to the end of the Opticks, where attraction was considered as essential a property of matter as extension. Although he admitted that there were places where Newton appeared to qualify this, on balance it seemed that this was indeed Newton’s opinion.

In a letter to Gabriel Cramer dated 16 November 1732, Mairan showed himself to be thoroughly conversant with Newton’s works, extolling Newton’s “admirable theory” which, he said, seemed to be entirely consistent with the world as it is. He claimed to have accepted Newton’s laws of motion of celestial bodies as a fact in his work on the aurora borealis. Indeed, in the Éclaircissements added to the 1754 edition of his work on the aurora modeled on Newton’s Queries at the end of the Opticks, he maintained that the inviolable laws of universal gravitation were the basis of his whole system. However, he continued to reject attraction as an innate property of matter and to state that he could not provide the mechanistic explanation that no doubt lay behind the principle of attraction. In the meantime he was prepared to consider Newton’s theory of universal attraction mathematically as Newton himself had done.

It is evident that Newton’s writings were a model of scientific method for Mairan even in his early works. In his 1717 dissertation, for example, he praised the ingenious experiments on light that Newton had performed to establish the different refrangibility of colors, saying that these would be enough to immortalize his name. Also, according to Pierre Coste, who translated the Opticks into French, Mairan was the first in France to repeat Newton’s optical experiments.

Conclusion . Jean-Jacques Dortous de Mairan should be remembered principally for three things: his work on ice and on the aurora borealis; his lifelong obsession with Newton, despite his not undeserved reputation as a Cartesian; and lastly, his enormous influence on the development and spread of scientific culture in the eighteenth century because of his voluminous correspondence and his prominent position as secretary of the Academy of Sciences, the power center of the scientific establishment.

Despite his reluctance to abandon completely Cartesian vortices and the plenum, he recognized the difficulties that these represented for an adequate understanding of the universe. Though anxious to explain physical phenomena by a mechanical model and uncomfortable with the concept of action at a distance, he accepted universal gravitation as a fact if not an inherent property of matter.

Lastly, his vast correspondence was a prime example of scientific networking, mirroring the intricate patterns of interdependence and mutual advantage crossing national frontiers. Through his network of correspondents, he was a conduit and facilitator of ideas.

SUPPLEMENTARY BIBLIOGRAPHY

WORKS BY MAIRAN

Dissertation sur les variations du baromètre. Bordeaux, 1715.

Dissertation sur la glace. Bordeaux, 1716; Béziers, 1717; Paris, 1730, 1749.

Dissertation sur la cause de la lumière des phosphores et des noctiluques. Bordeaux, 1717.

“Mémoire sur la cause générale du froid en hiver, et de la chaleur en été.” In Mémoires de l’Académie royale des sciences 1719. Paris: Academy of Sciences, 1721.

“Recherches géométriques sur la diminution des degrés terrestres, en allant de l’Equateur vers les Poles.” In Mémoires de l’Académie royale des sciences 1720. Paris, 1722.

“Discours sur l’estimation et la mesure des forces motrices des corps.” In Mémoires de l’Académie royale des sciences 1728. Paris, 1730.

Traité physique et historique de l’aurore boréale. Paris, 1733, 1754.

Published under the auspices of the Academy of Sciences. “Discours sur la propagation du son dans les différents tons qui le modifient.” In Mémoires de l’Académie royale des sciences 1737. Paris, 1740.

Histoire de l’Académie royale des sciences 1741. Paris, 1744.

Histoire de l’Académie royale des sciences 1742. Paris, 1745.

Histoire de l’Académie royale des sciences 1743. Paris, 1746.

MANUSCRIPT SOURCES

See the Bibliothèque publique et universitaire de Genève for Mairan’s correspondence with Firmin Abauzit, Gabriel Cramer, and Jean Jallabert, principally Ms. Fr. 612 (Abauzit); Ms. Supp. 384 (Cramer); Ms. Supp. 140 (Jallabert).

See the Bernoulli-Edition, Universitätsbibliothek Basel, L1 a 661 for the Mairan-Bernoulli letters.

OTHER SOURCES

Beeson, David. Maupertuis: An Intellectual Biography. Oxford: Voltaire Foundation, 1992. On the shape of Earth debate.

Bone, Neil. The Aurora: Sun-Earth Interactions. New York: E. Horwood, 1991. A general discussion of the nature of aurorae.

Briggs, J. Morton, Jr. “Aurora and Enlightenment: Eighteenth-Century Explanations of the Aurora Borealis.” Isis 58 (1967): 491–503. A useful discussion of the problems arising from the nature of aurorae encountered by eighteenth-century scientists.

Guerlac, Henry. “The Newtonianism of Dortous de Mairan.” In Essays on the Age of Enlightenment in Honor of Ira O.Wade, edited by Jean Macary, 131–141. Geneva: Droz, 1977.

_____. “Some Areas for Further Newtonian Studies.” History of Science 17 (1979): 75–101.

Hall, A. Rupert. “Newton in France: A New View.” History of Science 13 (1975): 233–250.The above essays by Guerlac and this one by Hall represent attempts to reassess Mairan’s reaction to Newton.

Heilbron, J. L. “Experimental Natural Philosophy.” In The Ferment of Knowledge: Studies in the Historiography of Eighteenth-Century Science, edited by George S. Rousseau and Roy Porter. New York: Cambridge University Press, 1980. A study of the eighteenth-century preoccupation with the nature of electricity.

Hine, Ellen McNiven. “Dortous de Mairan, the ‘Cartonian.’” In Studies on Voltaire and the Eighteenth Century 266 (1989): 163–179. A discussion of the attraction that Newton had for Mairan, the Cartesian.

_____. “Dortous de Mairan and Eighteenth-Century ‘Systems Theory.’” Gesnerus 52 (1995): 54–65. On Mairan’s disagreement with d’Alembert on the usefulness of systems.

_____. Jean-Jacques Dortous de Mairan and the Geneva Connection: Scientific Networking in the Eighteenth Century. Oxford: Voltaire Foundation, 1996. Discusses the role of Mairan’s correspondence network in the spread of Enlightenment thought.

Kleinbaum, Abby R. Jean-Jacques Dortous de Mairan (1678–1771): A Study of an Enlightenment Scientist. PhD diss., Columbia University, 1970. An excellent detailed analysis of Mairan’s scientific work.

Taton, René. “The Beginnings of Modern Science: From 1450–1800.” In A General History of the Sciences, edited by Rene Taton and translated by Arnold J. Pomerans. New York: Basic Books, 1964. A useful overview of science in the eighteenth century.

Ellen McNiven Hine