ROMé DE L’ISLE (OR DELISLE), JEAN-BAPTISTE LOUIS

(b. Gray, France, 29 August 1736; d. Paris, France, 7 March 1790)

crystallography, mineralogy.

Romé, the son of a lieutenant in the cavalry, studied humanities at the Collège Ste. Barbe in Paris. In 1756 he entered the Royal Corps of Artillery and Engineering, which he accompanied, as a secretary, to the French Indies in the following year. From 1758 until 1761 he was in the enclave of Pondicherry, French India. When it fell to the English in 1761 Romé was taken prisoner and transported to China, where he stayed until 1764, when he returned to France.

In Paris, Romé met the chemist and mineralogist B. G. Sage and attended his course in chemistry. In 1766 he published his first work, dealing with the then fashionable topic of freshwater polyps. Without making any observations, Romé set forth a hypothesis on the polyp. The work was a false start; Rome afterward confined himself to the study of mineralogy and chemistry.

In 1767 Romé was employed, on Sage’s recommendation, to draw up a catalogue of the curiosities that had been collected by Pedro Francisco Davila, who wished to sell his cabinet of natural history before returning to Peru. The work ran to three volumes, in the second of which Romé, in agreement with Linnaeus, stressed the importance of crystalline form in mineralogical description. While engaged in this project, Romé met Michelet d’Ennery, an avid collector of coins and medals. Until Michelet d’Ennery’s death in 1786, Romé lived in his house and dedicated himself to the study of minerals. He earned money by cataloguing at least fourteen mineral collections, according to his own, probably incomplete, list in the bibliography to his Cristallographie of 1783. Three of the catalogues remained in manuscript.

In 1772 Romé published the Essai de cristallographie, in which he identified 110 crystal forms (drawing upon Linnaeus, who had listed forty) and described in minute detail the minerals that exhibited them. He subdivided the various substances into salts, stones, pyrites, and metallic minerals, stating that he agreed with Linnaeus that geometrical form is the chief characteristic by which minerals may be classified. Also like Linnaeus, he held that saline principles imprinted their own geometrical form upon the earthy constituent of each mineral. In his description of the “primitive” form of each substance, and of the more complex forms derived from them, Romé did not depend on the exact measurement of crystalline angles; he gave values only for plane angles, and those were not consistent. Indeed, he has the plane angles of quartz varying between 70° and 75°, and it seems that in this early work he was not particularly concerned with the idea that such measurements exhibit strict constancy. In 1773 he brought out a description of the metallic ores of his own mineral cabinet, in which he discussed the origin, metamorphosis, and paragenesis of each.

In 1779 Romé became involved in a controversy concerning the theory of a central terrestrial fire and the eventual cooling of the earth. His opinion that all terrestrial heat derived from the sun brought him into opposition with Buffon (and with Bailly, who in a “Lettre à M. Voltaire” asked that author to support Buffon’s view, as he had been the apologist of Newton’s theory). In rejecting the idea of the central fire, Romé refrained from criticizing the geological conclusions that Buffon drew from it, although it is nonetheless clear from other of his writings (and especially from his warm praise of Werner and Saussure) that he favored the neptunist view.

Romé also opposed Buffon in the matter of methodology. In this controversy he took the side of the nomeneclateurs (as they were disparagingly called), who followed Linnaeus in considering classification to be one of the chief ends of the natural sciences. He defended this aim against the systémateurs, who, like Buffon, were more concerned with building general systems on the basis of hypotheses that were not necessarily confirmed by empirical research. In addition, Romé disagreed with Buffon’s opinion that crystallography forms can be explained by “organic molecules” he believed that Buffon undervalued the role of crystallography in refusing to recognize the geometrical form of crystals as a specific characteristic of minerals.

Romé’s major work, the Cristallographie (1783), was first advertised as a second edition of his Essai, but instead it was expanded and comprised three volumes and an atlas describing more than 450 crystal forms. In this book, rather than using any physical basis, Romé followed both Linnaeus and Domenico Guglielmini in classifying crystals by arbitrary primitive forms—the regular tetrahedron, the cube, rectangular octahedrons, parallelepipeds, rhomboidal octachedrons (that is, rhombic dipyramids), and dodecahedrons with triangular planes (hexagonal dipyramids). Each crystal described was measured precisely. In the course of making terracotta models, Romé’s assistant, Arnould Carangeot, had discovered the constancy of interfacial angles; and, using a contact goniometer invented for the purpose, he had made measurements of the interfacial angles (exact to about half a degree) of each mineral that Romé listed. Both these aspects—the tabulation of primitive forms and the measurement of interfacial angles—were of central importance to Romé’s crystallography.

The fundamental law of the constancy of interfacial angles—that the faces of a crystal may vary in their relative dimensions, but the respective inclination of these same faces is constant and invariable in each species—implied that each species must have a characteristic primitive form with characteristic constant angles (a thesis that neither Buffon nor Bergman was willing to accept). Romé believed the chief task of crystallography to be the derivation of secondary crystal forms from primary ones, by means of truncation of the solid angles or edges. The term “truncation” had already been used by Cappeller, Guglielmini, Bergman, and, especially, Romé’s disciple Jean Démeste, who had pointed out that it should be considered a purely geometrical device. Romé considered the way in which secondary forms arise in nature “a most impenetrable mystery.”

Although Romé considered truncation to be a defect of the crystal, he maintained that the constancy of interfacial angles is equally valid for secondary and for primitive crystal forms. In his classification of mineral species, he recognized that although the most regular geometrical forms (cube, regular octahedron, regular tetrahedron) may be characteristic of more than one species, the properties of density and hardness would still make identification possible. On the basis of analogy, Romé believed that the form of the integrant molecules of a crystal must be identical with the primitive form and must therefore be constant and characteristic for each species. Since these integrant molecules had to be of the same magnitude and to consist of the same elementary particles (or constituent molecules), Romé concluded that they must exist in fixed proportions; the characteristic molecular form of a substance necessarily, therefore, depends on the (unknown) forms of all its constituent molecules, and on their arrangement and proportion within the integrant molecule.

While at work on his Cristallographie, Romé had become convinced, on the basis of chemical evidence, that Linnaeus’ doctrine—according to which a small quantity of a salt was necessary to evoke the primitive crystal form out of the passive, earthy principle of a stony or metallic mineral—could not possibly be correct, since all solid mineral substances must have a specific and particular crystal form. He also recognized that, despite advances in chemistry, constant geometrical crystal form was a better criterion for classification than constant chemical composition. Romé’s belief that each mineral species possesses both a characteristic primitive crystal form and a characteristic chemical composition obviated the concept of similarity of form with different substances (isomorphism). In rejecting isomorphism—as, for example, of zinc spar (smithsonite) and iron spar (siderite) with calcspar (calcite)—Romé was led to explain the formation of those minerals by analogy with the formation of fossils, wherein organic material is replaced by pyrite. He consequently concluded that these substances show a form that is “alien and accidental,” since it does not correspond to that of their own constituent molecules.

Because Romé had only vague notions of symmetry relations, he sometimes separated forms that belong together and brought together forms that are essentially different. He considered the cube and the regular octahedron to be different primitive forms, even when they occurred in the same substance, a discrepancy that he explained by assuming a slightly different proportion of acid and base, for example, in alum crystals exhibiting these two forms. In the case of galena he was forced to attribute the change of its primitive form from a cube to an octahedron to “inversion”—an opposite arrangement—of the same molecules. On the other hand, the forms that Romé derived from the rhomboidal parallelepiped proved to have different degrees of symmetry, as may be seen in his evoking, by elongation, a monoclinic parallelepiped of iron sulfate from a trigonal calcspar rhombohedron. Somewhat vaguely, he attributed the truncation of the primitive form to a difference in molecular form, which itself might result from either a difference in the proportions of its chemical constituents or from a disturbance of the normal arrangement of the molecules. In any case, lie held to his belief that the act of truncation does not occur in nature, although his opponents charged that he did in fact believe that it did (an injustice that Romé returned infalsely imputing to Haüy the belief that the cleavage form is a true kernel within the crystal).

Romé’s relationship with Haüy was at best strained. He was sharply critical of the speculative nature of Haüy’s theory, which was then in its early stages. Haüy, in turn, was staunchly defended by Buffon’s collaborator Daubenton, and chose to ignore Romé’s work insofar as it was possible for him to do so. Romé professed unwavering empiricism, an unwillingness to substitute “the dreams of our imagination for the majestic silence of Nature.” Like Lavoisier he refused to speculate about the nature of molecules and atoms, and he further criticized not only Haüy but also Bergman for trying to demonstrate mathematically the internal structure of crystals before complete observational data had been gathered. The morphology of crystals was, he believed, so far from being completely understood that the study of the anatomy of crystals (or “cristallotomie,” as he called it) should properly be deferred.

All the same, Romé himself could not resist the temptation occasionally to pronounce a hypothesis concerning structure in some particular case. Some of these hypotheses were, like his ideas about symmetry, vague and contradictory, particularly because he believed that the molecular arrangement of secondary crystal forms can differ from that of primitive ones. For example, he held that molecules of calcspar were always in the form of the cleavage rhombohedron but were differently arranged in crystals of different form.

In 1784 Romé brought out a book on the external characteristics of minerals, a supplement to the Cristallographie. In this work, Des caractères extérieurs des minéraux, ou réponse à cette question: Existe-t-il dans les substances du règne minéral des caractères qu’on puisse regarder comme spécifiques; et au cas qu’il en existe, quels sont ces caractères ?, he stated his firm belief that form, density, and hardness were sufficient criteria to permit the identification of any mineral species.

The following year Romé was granted a pension from the public treasury and in 1789 Louis XVI added a further stipend from the royal treasury. The latter was especially welcome, since Romé had been in straitened financial circumstances since the death of Michelet d’Ennery in 1786. Romé was executor of D’Ennery’s estate and thus helped to catalogue the extensive collection of coins and medals. He made a comparison between the weight of the Roman pound and the weight of the Paris pound which provided further material for his last great work, the Métrologie (1789), in which he compared a number of the weights and measures of antiquity with modern counterparts. He advised the States-General to introduce the Roman system of weights and measures, or at least to unify the system and standards of France.

Romé’s chief scientific goal was the establishment of mineralogy on a firm basis of crystallography. His major contribution toward this end was the formulation of the law of the constancy of interfacial angles, which became the cornerstone of crystallography. Although earlier investigators—including Hooke, Erasmus Bartholin, Steno, Huygens, Philippe de la Hire, and Guglielmini—had made incidental statements about such a constancy in one or two substances, Carangeot and Romé were the first to enunciate it as a general law of nature. Romé was nevertheless a poor theoretician. His solution of the geometrical relation of the crystal forms within the same species remained much inferior to Haüy’s although Haüy’s crystallochemical conception—geometrical form and chemical composition as the definition of a species, and pseudomorphoses as the explanation of isomorphous crystals—was much the same as Romé’s.

In his general chemical views, Romé largely followed Sage, remaining faithful to the phlogiston theory. He also adhered to J. F. Meyer’s theory of “acidum pingue” and energetically rejected Lavoisier’s “absurd” theory of combustion.

It was Sage who made Romé’s work known in France, through his lectures at the Mint (beginning in 1778) and at the école des Mines (beginning in 1783). In addition, Romé had a number of correspondents throughout Europe who provided him with mineral specimens. Among his pupils, his favorite was Jacques-Louis de Bournon, who wrote a number of geological and crystallographical studies, of which the most important was the Traité complet de la chaux carbonatée, published in London in 1808. A favorite correspondent was Jean Démeste, a physician of Liège, whose 1779 Lettres au Dr. Bernard were wholly based on Romé’s crystallography and Sage’s chemistry. Romé also encouraged Fabien Gautier d’Agoty to publish a splendid set of colored engravings of crystals and mineral groups in the first volume of his Histoire naturelle (1781). Romé wrote the explanatory captions.

Romé’s friendship with Sage also brought him membership in a number of learned societies, including the academies of Mainz, Stockholm, Berlin, and St. Petersburg. But it did him no service with the Paris Académie des Sciences, which rejected him on the ostensible grounds that he was a mere “catalogue maker.” It is likely that Romé’s controversies with Buffon also played a part in his rebuff by the Academy.

BIBLIOGRAPHY

I. Original Works. Romé’s first publication was Lettre de M. Deronré Dclisle à M. Bertrand sur les polypes d’eau douce (Paris, 1766). The foreword by P. F. Davila to the Catalogue systémiatique et raisonné des curiosités de la nature ct de 1’art qui composent le cabinet de M. Davila, 3 vols. (Paris, 1767), acknowledges Romé’s share in the composition of the part on natural history and the description of some of the artificial curiosities. Romé himself claimed only to have written the section on natural history. He lists the other catalogues he wrote in the bibliography of his Cristallographie, which contains 14 catalogues, including those of the collections of Jacob Forster and Claude-Marc-Antoine Varennes de Béost.

The work on the central fire of the earth was first published under the initials M. D. R. D.: L’action du feu central bannie de la surface du globe, et le soleil rétabli dans ses droits; contre les assertions de MM. le Comte de Boffon, Bailly, de Mairan … (Stockholm-Paris, 1779); the 2nd ed., which includes answers to objections made to the first, is entitled L’action du feu central démontrée nulle à la surface du globe, contre les assertions de MM. le Comte de Buffon, Bailly, de Mairan … (Stockholm-Paris, 1781). His name was now given in full.

Romé’s crystallographical writings, however, are by far the most important part of his work: Essai de cristallographie, ou description des figures géométriques, propres à différens corps du régne minéral, connus vulgairement sous le nom de cristaux (Paris, 1772), German trans. by C. E. Weigel (Greifswald, 1777); the much enlarged 2nd ed., Cristallographie, ou description des formes propres à tous les corps du règne minéral, dans 1’état de combinaison saline, pierreuse ou métallique, 4 vols. (Paris, 1783); and the supp. to the latter, Des caractéres extérieurs des minéraux (Paris, 1784).

Additional writings on mineralogy are Description méthodique d’une collection de minéraux, du cabinet de M.D.R.D.L. Ouvrage oú l’on donne de nouvelles idées sur la formation et la décomposition des mines … (Paris, 1773); “Mémoire ou observations sur les altérations qui surviennent naturelles à differentes mines métalliques et particuliément aux pyrites martiales,” in Observations sur la physique, 16 (1780), 245–256; and Observations sur les rapports qui paroissent exister entre la mine dite cristaux d’étain et les cristaux de fer octaèdres (Erfurt, 1786).

Romé identified the alabaster of the ancients in “De antiquorum alabastrite et variis quibusdam lapidibus quos recentiores alabastri nomine appellaverunt disquisitiones historico-physico-criticae,” in Nova acta physicomedia exhibentia ephemerides, 6 (1778), 186–199. His antiquarian interests also inspired his last work: Métrologie, ou tables pour servir à l’intelligence des poids et mesures des anciens, et principalement à dèterminer la valeur des monnoies grecques et romaines, d’aprés leur rapport avee les poids, les mesures et le numéraire actuel de la France (Paris, 1789), German trans. by Gottfried Grosse (Brunswick, 1792). The dedication of this work, “To my Fatherland, which is undergoing a rebirth under Louis XVI,” pays homage to the minister Necker and to the National Assembly, and thus unambiguously demonstrates his political feelings.

Romé also wrote the explanatory notes to Fabien Gautier d’Agoty’s Histoire naturelle ou exposition généralede toutes ses parties, gravées et imprimées en couleurs naturelles, avec des notes historiques, pt. 1 (Paris, 1781); and he revised and enlarged the MS of the “deliliosagiano-linnean letters” sent by his pupil Jean Démeste from Liège to Paris to be printed under the supervision of the Marquis d’Aoust, Lettres du docteur Démeste au docteur Bernard, sur la chymie, la docimasie, la cristallographie, la lithologie, la minéralogie et la physique en général, 2 vols. (Paris, 1779).

II. Secondary Literature. Biographical articles on Romé are J. C. Delamétherie, “Notice sur la vie et les ouvrages de M. de Romé de l’Isle,” in Observations sur la physique, sur l’histoire naturelle et sur les arts, 36 (1780), 315–323; and C. S. Weiss, in Biographic universelle, ancienne et moderne (Michaud), XXXVIII (1824), 521–523. Further details are in A. Birembaut, “Les préccupations des minéralogistes francais au 18esiécle,” in Actes de la 72e session de l’Association francaise pour l’avancement des sciences (1953), 534–538, in which Carangeot’s claims to the discovery of the law of constant angles also are maintained. On his relations with Démeste, see M. Florkin, “Vie de Jean Démeste, médecin et minéralogiste,” in Revue médicale de Liége, 10 (1955), 543–555.

Romé’s crystallographical work is dealt with in C. M. Marx, Geschichte der Crystallkunde (Karlsruhe-Baden, 1825), 120–131; and H. Metzger, La genèse de la science des cristaux (Paris, 1918), 65–75, 189–192. A more detailed analysis of his crystallography and his crystal chemistry, also in comparison with modern conceptions, has been given by R. Hooykaas in the following publications: “De kristallografie van J. B. de Romé de I’Isle,” in Chemisch weekblad, 47 (1951), 848–855; “The Species Concept in 18th Century Mineralogy,” in Archives internationales d’histoire des sciences, no. 31 (1952), 45–55; and La naissance de la cristallographie en France au XVIIIe siècle(Paris, 1953), 8–12, 23–24. His sparse and wavering ideas on crystal structure are analyzed in R. Hooykaas, “Romé de l’Isle en de structuur theorie,” in Chemisch weekblad, 47 (1951), 909–914. On the priority of the discovery of the law of constancy of angles, see Birembaut, op. cit.; R. Hooykaas, “De oudste kristallografie,” in Chemisch weekblad, 46 (1950), 438–440, also in Revue d’histoire des sciences, 12 (1959), 182–185; and J. G. Burke, Origins of the Science of Crystals (Berkeley, 1966), 69–71.

R. Hooykaas