Bruhns, Karl Christian

(b. Plön, Germany, 22 November 1830; d. Leipzig, Germany, 25 July 1881)

astronomy.

Trained as a locksmith, Bruhns came to Berlin in 1851 and worked as a mechanic. Even then his aim was to become an astronomer, and Encke, the director of the Berlin Observatory, to whom Bruhns had been recommended for his mathematical skill by a professor in Altona, recognized his great mathematical talents. After a year of carrying out complicated calculations for Encke in addition to his regular work, Bruhns was made an assistant at the observatory. In 1856 he graduated from the university with the thesis De planetis minoribus inter Jovem et Martem circa solem versantibus (Berlin, 1856), and in 1859 became lecturer in astronomy at the University of Berlin. Two years later he was appointed assistant professor of astronomy in Leipzig, becoming professor in 1868; he remained director of the observatory from 1860 until his death. In 1877–1878 he was rector of the university.

Under the influence of Encke, Bruhns’s activities in his younger years centered on theoretical astronomy. Having made observations with the equatorial and meridian circle in Berlin, he took a greater interest in observational astronomy in Leipzig. His first act in Leipzig was to replace the antiquated observatory in the tower of the old castle in the middle of the town with a new one at the outskirts of the town. It was well equipped—for its time even excellently equipped. From 1900 on, however, it shared the lot of many German university observatories: unfavorable location and obsolete instruments; a place for teaching and training, but not a center of practical research.

Bruhns paid little attention to astrophysics, which flourished in the last years of his life. He was more interested in the fields related to astronomy—geodesy and meteorology—which he advanced considerably. He served on the Kommission für Mitteleuropäische Gradmessung and held the chair in the astronomical section of the Preussisches Geodätisches Institut in addition to his regular duties. Much of his work concerned the determinations of longitude between his observatory and Berlin, Vienna, Paris, and Munich, and other, less important, places.

More important was Bruhns’s contribution to meteorology. In cooperation with Buys-Ballot and Jellinek, among others, he organized uniform worldwide weather observations and undertook to supervise those in his vicinity. He further tried to arouse the interest of agricultural circles, in particular, in a regular weather forecast in Über das meteorologische Bureau für Witterungsprognosen im Königreich Sachsen (1879).

Bruhns published such popular works as Atlas der Astronomie (1872) and also discussed natural science in general. It is therefore no surprise that he was responsible for the first comprehensive biography of Alexander von Humboldt (1871), which was supported by Loewenberg and Carus, among others. In this publication he wrote on Humboldt’s work in astronomy, geodesy, and mathematics. Bruhns knew Humboldt personally and thought it urgent to memorialize this genius who was important to natural science in general. He also wrote a biography of Encke that gives an excellent insight into the work of the observatories in the first half of the nineteenth century. His historical concerns are displayed in other works, especially Die astronomische Strahlenbrechung in ihrer historischen Entwicklung (1861), written six years earlier.

In view of his wide-ranging interests, it is no wonder that Bruhns was influential. His superior lectures attracted many students; he was also active in the Astronomische Gesellschaft and initiated and equipped the first German astronomical expeditions. Unfortunately, these manifold tasks prevented him from promoting theoretical astronomy to the extent his outstanding ability would have allowed. His energy and enthusiasm, however, had a strong effect on his colleagues, which should not be ignored.

BIBLIOGRAPHY

Bruhns’s books include Geschichete und Beschreibung der Leipziger Sternwarte (Leipzig, 1861); Die astronomische Strahlenbrechung in ihrer historischen Entwicklung (Leipzig, 1861); Längendifferenz-Bestimmung Berlin-Leipzig (Leipzig, 1865), written with W. Förster; Längen-differenz-Bestimmung Leipzig-Gotha (Leipzig, 1866), written with A. Auwers; John Franz Encke, sein Leben und Wirken (Leipzig, 1869); Neues log.-trig. Handbuch auf 7 Dezimalen (Leipzig, 1870); Alexander von Humboldt, eine wissenschaftliche Biographie…, 3 vols. (Leipzig, 1871); Astronomisch-geodätische Arbeiten in den Jahren 1867–1875, 4 vols. (Leipzig, 1871–1876; 1882); Atlas der Astronomie (Leipzig, 1872); and Über das meteorologische Bureau für Witterungsprognosen im Königreich Sachsen (Leipzig, 1879).

Numerous short papers appeared in Astronomische Nachrichten, 35–67 (1852–1866); in Leipzig Gesellschaft der Wissenschaften. Berichte (1872, 1878); and in Leipzig Gesellschaft der Wissenschaften. Abhandlungen (1873). Bruhns was also editor of 3 vols. in Publicationen des Preussischen Geodätischen Institutes (1871–1874); of 12 vols. of Resultate aus den meteorologischen Beobachtungen, angestellt an meheren Orten im Königreich Sachsen (Leipzig, 1866–1880); and of Kalendar und statistisches Jahrbuch für Sachsen (Leipzig, 1872–1882).

H. C. Freiesleben