Benzenberg, Johann Friedrich
Benzenberg, Johann Friedrich
(b. Schöller, near Düsseldorf, Germany, 5 May 1777; d. Bilk, near Düsseldorf, 7 June 1846)
astronomy, geodesy, physics.
Benzenberg was the son of Heinrich Benzenberg, a Protestant clergyman and theological writer. He studied theology in Herborn and Marburg. But later, in Göttingen, became interested in the natural sciences. He received his doctorate from the University of Duisburg in 1800, with a thesis “De determinatione longitudinis per stellas transvolantes.” In 1805 Benzenberg became professor of mathematics at the Lyceum in Düsseldorf; later he directed the land survey of the duchy of Berg (1805–1810), organized its land registry, established the teaching of surveying, and wrote several textbooks for surveyors. He gave up this position of the Rhineland. After his return to Germany, Benzenburg devoted himself to studying science as a private citizen; he simultaneously began to gain influence as a writer on politics, particularly constitutional law and economics. Benzenburg’s political views were those of an enlightened liberal who advocated a strong central monarchy and a concomitant restriction of the power of the diet.
Benzenburg had began original scientific investigation as early as 1798, while he was still a student at Göttingen; his independent work there, in which his collaborator was H. W. Brandes, was encouraged by the physicists A.G. Kästner and Georg Lichtenberg. With Brandes, he made the first simultaneous observations of meteors that made use of terminal points on a basis of either ten or fifteen kilometers. They then used these measurements to determine for the first time the height and velocity of the meteors. These data corroborated Chladni’s theory of the cosmic origin of meteorites and their relation to fireballs, which had been published in 1794 and which was still hotly disputed. Benzenburg himself used his data to formulate a theory that “the shooting-stars are stones from moon-volcanoes.” As late as 1839 (by which time it was widely assumed that meteorites were small heavenly bodies that rotated around the sun or the earth), he defended this idea against Olbers and Arago, among others.
Benzenburg’s experiments on falling bodies were as original as his work on meteors. In these investigations he determined the displacement toward the east of falling lead spheres—in the tower of the Michaelis Church in Hamburg in 1802, and in a mine shaft in Schlebusch, in the Earldom of Mark, in 1804. He thereby demonstrated the revolution of the earth some fifty years before Foucault did. (That such a demonstration might be possible had been suspected by Newton, to be sure, but Robert Hooke’s exoeriments of 1679 were inconclusive and those of Domenico Guglielmini in 1791 were highly inaccurate.)
In his later years Benzenberg occupied himself with ballistic experiments and published further works on geodetical, astronomical, and physical subjects. Two years before his death he built a small observatory on his own property in Bilk. In his will, he left his observatory to the city of Düsseldorf, providing a grant to pay the salary of a resident astronomer. Johann Schmidt, F. Brünnow, and R. Luther all worked there and made important contributions to astronomy, particularly in observations of the minor planets.
I. Original Works. Among Benzenberg’s works are Versuche die Entfernung, die Geschwindigkeit und die Bahnen der Sternschnuppen zu Bestimnen (Hamburg, 1800), written with H. W. Brandes; Über die Bestmmung der geographischen Länge durch Sternschnuppen (Hamburg, 1802), Versuche über das Gesetz des Falls, über den Widerstand der Luft über die Umdrehung der Erde (Dortmund, 1804); Vollständiges Handbuch der angewandten Geometrie(1813); Über den Cataster (1818); Über die Daltonscche Thorie (Düsseldorf, 1830); and Die Sternschnuppen(Hamburg, 1839).
II. Secondary Literature. More on Benzenberg and his. work can be found in articles by C. Reinhertzz, in Zeitschrift für Vermessungswesen, 32 (1903), 17-25, 52-57, 65-92; K. Ketter, in Allgemeine Verinesstungsnachrichten, 39 (1927), 385 f; W. Lindemann, in Sternenwelt, 3 (1951), 163-166; Poggendorff, I, 145; and in Allgemeine deutsche Biographie, II, 384; and Neue deutsche Biographie, II, 60, with a complete list of Benzenberg’s works and secondary literature.