ROSENBUSCH, HARRY (KARL HEINRICH FERDINAND)

(b. Einbeck, Germany, 24 June 1836; d. Heidelberg, Germany, 20 January 1914)

geology.

Rosenbusch was the son of a schoolteacher. His father was chronically ill, and died when Rosenbusch was young; the family was left in difficult circumstances, and it was only with considerable effort that Rosenbusch’s mother managed to send the boy to secondary school. Rosenbusch there made a good record in languages, but a poor one in mathematics and physics; he therefore began to study classical languages when he entered the University of Göttingen. Financial difficulties caused him to leave the university soon thereafter, and he went to Brazil as private tutor to a rich family. Five years later he returned to Germany, and entered the University of Heidelberg, where a lecture by Robert Bunsen, together with observations he had made in Brazil, stimulated his interest in chemistry and geology.

In 1869, when he was nearly thirty-three years old, Rosenbusch graduated from the University of Freiburg with a thesis on the nephelinite of the Katzenbuckel, a mountain near Heidelberg which is still of great interest to petrographers. He was appointed Privatdozent in the following year. In 1873 Rosenbusch was called to the recently reorganized University of Strasbourg as professor extraordinarius of mineralogy and petrography. In 1878 he returned to Heidelberg as professor of mineralogy, a post that he held until his retirement in 1908.

Rosenbusch was greatly influential in establishing petrography as a true geological and historical science. He was particularly effective in advocating the use of the polarizing microscope in investigating rocks (although he neither invented this technique—thin sections had been introduced in England by H. C. Sorby in 1860 and the method had then been brought to Germany by F. Zirkel and H. Vogelsang—nor created essentially new procedures). His students came from all over the world, and a number of his geological ideas were almost universally accepted and propagated.

Rosenbusch published the first edition of his monumental textbook, of which the first volume was entitled Mikroskopische Physiographie der petrographisch wichtigsten Mineralien and the second Mikroskopische Physiographie der massigen Gesteine, while he was still in Strasbourg. The two books went through four enlarged editions, and became the standard works on igneous rocks. In later versions, the first volume was put into a systematic mathematical and physical form by Rosenbusch’s student E. A. Wülfing, while the second volume was comprehensive and descriptive in nature. The subsequent editions of each work also incorporated Rosenbusch’s own recent results in a number of areas; he published only a few of his discoveries separately, as for example sagvandite, monchiquite, and eukolite and a few discussions of discrete geological ideas.

Among Rosenbusch’s individually published works, the papers that he wrote while in Strasbourg concerning the gradual contact metamorphism of the Steiger Schiefer, near Barr-Andlau, are especially significant. In these papers he carefully described the alteration of the mineral content of the slates of this region, and went on to prove that no chemical alteration except the loss of water took place in them. His data were so convincing that for some fifty years his ideas of contact-metamorphism without chemica. change were generalized and widely accepted, although in fact the case he described was that of a special type of high-intensity intrusion into a particularly inert rock.

In 1878 Rosenbusch recognized the relationship between melanocratic and leucocratic dyke-rocks (Ganggestein) and the plutonic parent body. Although his conclusions and interpretations were sometimes misleading, as in the instance of the lamprophyres, his descriptions and observations were of high quality. The opposition to Rosenbusch’s “Kern-theorie” (nucleus theory)—whereby NaAlSi₂ was the characteristic “nucleus” of rocks of the Atlantic series, as was CaAl₂Si₂ for rocks of the Pacific series—was likewise directed against the form of the interpretation, rather than on the assembled data.

Rosenbusch’s most important contribution, however, lay in his establishment of a fundamentally genetic and mineralogical (as opposed to chemical) classification of rocks. In his textbook, he first stressed the importance of the mineralogical characteristics of rocks in classification then, by the second edition, developed a system in which igneous rocks are classified by geological position, texture, and finally their mineralogical and chemical composition.

BIBLIOGRAPHY

Rosenbusch’s important publications include Der Nephelinit von Katzenbuckel (Freiburg, 1869); Über einige vulkanische Gesteine von Java,” in Berichte derNaturforschenden Gesellschaft zu Freiburg im Breisgau, 6 (1872), 36 p.; Mikroskopische Physiographie der petrographisch wichtigen Mineralien (Stuttgart, 1873); “Über die Kontaktzone von Barr-Andlau,” in Neues Jahrbuch für Mineralogie (1875); “Ein neues Mikroskop für mineralogische und petrographische Untersuchungen,” ibid. (1876); “Die Steiger Schiefer und ihre Kontaktzone an den Granititen von Barr-Andlau und Hohwald,” in Abhandlungen zur geologischen Spezialkarte von Elsass-Lothringen, 1 , XII-XIX (1877), 79–393; “Die Gesteinsarten von Ekersund,” in Nyt magazin for naturvidenskaberne, 27 (1883), 8p.; “Zur Auffassung der chemischen Natur des Grundgebirges,” in Mineralogische and petrographische Mitteilungen, 12 (1891), 49–61; “Über Struktur und Klassifikation der Eruptivgesteine,” ibid., 351–396; and “Studien im Gneisgebirge des Schwarzwaldes: Einleitendes: I. Kohlenstoffführende Gneisgesteine des Schwarzwaldes,” in mitteilungen aus der Grossherzoglichen Bad. geologischen Landesanstalt, IV (1899), 9–48; and “II . Die Kalksilikatfelse im Rench- und Kinzigitgneis. 1. Die Paraaugitgneise, 2. die Paraamphibolgneise,” ibid. (1901), 369.

Paul Ramdohr