MALLARD, (FRANçOIS) ERNEST

(b. Châteauneuf-sur-Cher, France, 4 February 1833; d. Paris, France, 6 July 1894)

mineralogy, mining engineering.

The son of a lawyer, Mallard was brought up in St.-Amand-Montrond. He studied at the Collège de Bourges, the école Polytechnique, and the École des Mines, from which he graduated in 1853 as ingénieur des mines. He began his career as a geologist for the Corps des Mines but in 1859 was transferred to fill the chair of mineralogy at its École des Mineurs at Saint-Étienne. He continued his work for the Corps, first in geological mapping and after 1868 on problems of mining engineering. His work attracted favorable notice from G. A. Daubrée, professor of mineralogy at the École des Mines; and when Daubrée became director of the school in 1872, he chose Mallard to fill the vacated chair of mineralogy. The new post was a decisive change for mallard, involving a new concentration on more directly mineralogical problems, the area in which he found greatest satisfaction and made his most important contributions. He continued as a member of investigative commissions in the Corps des Mines, for which he was promoted in 1867 to engineer first class and in 1886 to inspector general. In 1869 he received the croix de chevalier and in 1888 became an officer of the Legion of Honor. He was proposed, unsuccessfully, for several vacancies in the mineralogy section of the Académie des Sciences and finally was elected in 1890. In 1879 he was the second president of the Société minéralogique de France.

Mallard had great personal modesty but did not hesitate to put into print his thoughtful objections to publications of other scientists. He never wished to marry; he followed his vocations single-mindedly. Termier poignantly describes Mallard’s camaraderie with students during field excursions.

Mallard’s contributions in crystallography began in 1876, not long after he had assumed the chair of mineralogy at Paris. He took as his starting point the Études cristallographiques¹ of Auguste Bravais, who had been professor of physics there from 1845 to 1855. While Sohncke² and later A. Schönflies³ were developing Bravais’s concept of a lattice of translationally equivalent points into a complete mathematical description of symmetry of crystals (the 230 space groups), Mallard independently developed other aspects of Bravais’s theories. This work had its notable beginning in the memoir Explication des phénomènes optiques anomaux, on optically “anomalous” crystals (that is, those crystals the morphology of which seems to be of greater symmetry than their optics), in which the powerful new polarizing microscope showed the importance of twinning in these “crystalline edifices” and of pseudosymmetry as an explanatory concept.

A summary of Mallard’s ideas was offered in a two-volume work with atlas entitled Traité de cristallographiegéométrique et physique, published in 1879 (geometrical crystallography, lattice theory, and morphology) and 1884 (crystal physics). Here, for the first time, the convoluted mathematical apparatus of Bravais was stripped away to reveal in a didactic but complete fashion the essential contributions of the lattice theory. Mallard recognized the way in which this theory corresponded to a special case of Haüy’s molécules intégrantes while admitting that the unsupportable remainder of Haüy’s theories of crystal structure had led to its being completely discredited by the German school of geometrical crystallographers. Wherever possible, he applied Bravais’ theory to an understanding of the wide range of physical properties of crystals that had been investigated in the thirty intervening years; and he found in a strict definition of homogeneity a common basis for both the lattice theory and the newer macroscopic description of physical properties of anisotropic crystals by characteristic ellipsoids. The detailed and generally favorable reviews of these volumes in Germany,⁴ where a divergent direction of theory had been followed since the time of C. S. Weiss, attests to their persuasive completeness.

A third volume of the Traité, in which Mallard planned to discuss isomorphism, polymorphism, twinning, pseudosymmetry, and crystal growth, was never completed. Some of his original work on these subjects was published separately.⁵ In this respect his most important contribution was his theory of twins based on the continuation or pseudo-continuation of a lattice between the twinned crystals. Mallard’s development and extension of Bravais’s lattice theory, especially to the explanation of the importance of crystal faces (“law of Bravais”) and of twins, was further developed by observations and refined by Georges Friedel,⁶ who was Mallard’s student at the École des Mines; Friedel’s exposition on these subjects remained the definitive statement until very recent direct structural theories. On the other hand, Mallard’ theory of circular polarization in crystals as equivalent to a stack of thin, linearly polarized sheets has not stood the test of time.⁷

Mallard also made notable scientific contributions in his capacity as a mining engineer. In 1878, soon after it was formed, he was appointed to an official commission investigating methods of preventing methane explosions in mines. A series of laboratory and field investigations in collaboration with H. Le Chatelier, then professor of general chemistry at the École des Mines, resulted in a series of joint papers on the design of safety lamps, on combustion temperature, on velocity of flame propagation, and on the importance of mixtures of coal dust. They instituted the use of ammonium nitrate as an explosive; its low temperature of detonation made it safer (less likely to propagate in mixtures of air with gas or coal), and it has remained the preferred explosive to this day. Mallard continued his collaboration with Le Chatelier in experiments on the thermal properties of crystals.

A key figure in the French school of crystallography and a bridge from Bravais to Friedel, Mallard was described as having … “definitively displaced the center of gravity of crystallography that, thereafter, could not be cultivated as a descriptive science, but was elevated to the rank of a rational science.”⁸

NOTES

1.études cristallographiques (Paris, 1866), reprinting papers published during 1850 and 1851.

2.Entwilckelung einer Theorie der Krystallstruktur, (Leipzig, 1879) and “Erweiterung der Theorie der Krystallstruktur,” in Zeitschrift für Krystallographie und Mineralogie, 14 (1888), 426–446.

3. The importance of the Mallard-Bravais viewpoint on symmetry is acknowledged by Arthur Schönflies in “Bemerkungen über Theorien der Krystallstruktur,” in Zeitschrift für physikalische Chemie, 9 (1892), 158–170.

4. C. Klein, in Neues Jahrbuch für Mineralogie, Geologie und Paläontologie (1880), 2 , 1–5; ibid. (1886), 1 , 1–5.

5. E.g., in Edmond Fremy, Encyclopédie chimique, 1 (Paris, 1882), 610–774; and Revue scientifique, 24 (1887), 129–138, 165–171.

6. Summarized in Leçons de cristallographie (Paris, 1926).

7. Mallard, Traité, II, chs. 8–9; refuted in J. R. Partington, Advanced Treatise on Physical Chemistry, Iv (London, 1953), p. 355.

8. Translated form Wrybouff’s memorial, p. 249.

BIBLIOGRAPHY

I. Original Works. A complete bibliography is given in Lapparent’s memorial (see below). In addition to Explication des phénomènes optiques anomaux (Paris, 1877), repr. from Annales des mines et des carburants, 7th ser., 10 (1876), 60–196; and Traité de cristallographie géométrique et physique, 2 vols, and atlas (Paris, 1879–1884), the most important later crystallographic papers may be “Les groupements cristallins,” in Revue scientifique, 24 (1887), 129–138, 165–171; “Sur l’isomorphisme des chlorates et des azotates et sur la vraisemblance de la quasi-identité de l’arrangements moléculaire dans toutes les substances cristallisées,” in Bulletin de la Société française de minéralogie, 7 (1884), 349–401; and “Sur la théorie des macles,” ibid., 8 (1885), 452–469. The work with Le Chatelier on mine safety is given in a series of papers in Annales des mines (many of which are summarized in short notes in the Comptes rendus de l’Académie des sciences [1879–1889]) notably three memoirs in Annales des mines, 8th ser., 4 (1883), 276–568; and in a series of commission reports published by the government and listed in the catalog of the Bibliothéque nationale, CIV (Paris, 1930), 593–594. One notable paper not listed in Lapparent’s bibliography is “De la définition de la température dans la théorie mécanique de la chaleur et de l’interprétation physique du second principle fondamental de cette théorie,” in Comptes rendus de l’Académie des sciences, 75 (1872), 1479–1484.

II. Secondary Literatute. Mallard’s life and works were well covered from diverse viewpoints in a dozen contemporary memorials, most of which are listed in the Royal Society Catalogue of Scientific Papers, XVI, 1028. The most informative are those by A. de Lapparent, in Annales des mines, 9th ser., 7 (1895), 267–303, with bibliography; G. Wrybouff, in Bulletin de la Société française de minéralogie, 7 (1894), 241–266, with bibliography and portrait; and P. Termier, in Bulletin de la Société géologique de France, 23 (1895), 179–191. Mallard in barely mentioned by his contemporary Paul Groth in the latter’s Entwicklungsgeschichte der mineralogischen Wissenchafen (Berlin, 1926; repr. 1970), and his contributions do not seem to have been reviewed elsewhere.

William T. Holser