RüHMKORFF, HEINRICH DANIEL

(b. Hannover, Germany, 15 January 1803; d. Paris, France, 20 December 1877)

technology.

As one of ten children of a postal ostler, Rühmkorff was encouraged to support himself at an early age. He was apprenticed to a mechanic named Wellhausen in Hannover until he was eighteen, after which he wandered about Germany for two years. He spent a year and a half in Paris assisting a physics lecturer, and in 1824 he went to England where he found a position in the workshop of Joseph Brahmah, known as the inventor of the hydraulic press. He returned home in 1827 and then went to Paris, where, after working in several shops, he found employment with Charles Chevalier, renowned for his optical instruments. In 1855 he founded his own shop, a “dingy little bureau in the rue Champollion” that became wellknown to physicists throughout the world, especially for the quality of the electrical apparatus it produced.

Rühmkorff is most widely known as the inventor of an induction coil capable of producing sparks a foot or more in length. In 1864 he was presented with a 50,000-franc prize for his work. Established by the emperor in 1852, it was to be awarded for the most important discovery in the application of electricity (although the prize was to be given after five years, a postponement was deemed necessary by the committee.)

Rühmkorff’s coil was widely used as a convenient power source for the operation of Geissler and Crookes tubes as well as for various other high-voltage laboratory needs, and it had practical application in detonating explosives. But if its importance is not open to question, the extent of Rühmkorff’s role in its design is. Basic knowledge of induction originated in the work of Faraday and Joseph Henry, and an induction coil capable of producing small sparks was constructed by Charles G. Page in 1838. The interrupter mechanism was devised by Auguste de La Rive. On the basis of these accomplishments, Rühmkorff in 1851 constructed a coil that was capable of producing sparks of moderate length. Fizeau then introduced the use of a condenser that moderated the opposing effect of the secondary current on the primary current. More important was the development of a winding technique that would prevent the destruction of the coil by internal arcing. One method was suggested by Poggendorff in 1854: in another, employed by E. S. Ritchie in 1857, the wire was wound in parallel spiral disks.

Rühmkorff’s electrical apparatus was widely used in physical laboratories, and the many surviving examples testify to his workmanship. It is reported that he died nearly impoverished, having given his money to science or to charitable causes.

BIBLIOGRAPHY

The best account of Rühmkorff’s life and work appears in a 36-page volume by Emil Kosack: Heinrich Daniel Rümkorff, ein deutscher Erfinder (Leipzig-Hannover, 1903). There are brief but relatively informative unsigned sketches in Nature, 17 (1877). 16, repr. in Journal of the Franklin Institute, 105 (1878). 133–134: and in Scientific American, 38 (1878), 81. Discussions of the history of the induction coil include E. S. Ritchie, “On Electrical Machines,” in Journal of the Franklin Institute, 73 (1862), 58–60: an unsigned article in Scientific American, 12 (1865), 6: one signed S. H. W. in the same issue, 69; Charles G. Page. A History of Induction (Washington, D.C., 1867), esp. 115–121: T. du Moncel. Exposé des applications d’électricité, 3rd ed. (Paris, 1873), II, 238–262, and Notice sur l’appareil d’induction élecniyne de Rühmkorff, 5th ed. (Paris, 1867); Florian Cajori.A History of Physics (New York. 1899), 245–246; and George Shiers, “The Induction Coil,” in Scientific American, 224 (1971), 80–87.

Bernard S. Finn