Catholic Encyclopedia (1913)/Ernest-François Mallard
A French mineralogist, b. 4 February, 1833, at Châteauneuf-sur-Cher; d. 6 July, 1894, in Paris. From 1872 he wan professor of minéralogy at the Ecole des Mines, from 1890 member of the Academy of Science. Mallard has accomplished much of importance in mineralogy by his untiring and successful research. Numerous scientific reports appeared year after year in the "Bulletin de la Société mineralogique de France" and in the "Annales des Mines," several also in the "Compt. Rend." By far the greater number of these discuss difficult problems in crystallography, especially the physical attributes of crystals. The so-called optical anomalies of some crystals he endeavoured to grasp clearly in their actual relationship and then to explain ingeniously by a hypothesis which supposes that the highly symmetrical form of these crystals is caused by a great number of smaller crystals with a smaller number of symmetrical planes, which are arranged in a certain manner. The best general explanation he advanced in his lecture "Crystallic Groupings" which appeared in the "Revue Scientifique" in 1887. His hypothesis found many defenders, and, of course, also many dissenters; especially his German colleagues drew him frequently into controversies. Equally known are Mallard's writings about isomorphism which he discovered in chlorates and nitrates, and about isomorphic mixtures, especially feldspars, the optical qualities of which he traced mathematically from the proportions in which the components were mixed. His reports about different crystallographical instruments, as well as those regarding the production of thin sections of crystals for microscopic study, are important for the science of crystallography. His investigations of the combustion of explosive gas mixtures, of mine explosions, and the safety lamp, have great scientific but even greater practical value. Worth mentioning is his participation in the geological cartographing of France. His chief work is the voluminous "Treatise on Geometrical and Physical Crystallography" (Paris, 1879 and 1884); the third volume has never appeared. His religious opinions were expressed by himself during a lecture in 1872: "Man has been created in the image of the Lord and therefore he is capable of penetrating by the power of his reason into the plans and thoughts of the Creator of all things, that must be his highest ambition here below." These words contain Mallard's programme of life during the following two decades.
DE LAPPARENT in Annales des mines (Paris, 1895).