S. F. Braun.

(Obituary.)

The German newspapers have reported the death in New York of one of Germany’s most outstanding physicists, S. F. Braun, whose works for several decades adorned the German physics journals. We present brief biographical information about the deceased, borrowing it from Les Prix Nobel, the publication of the Swedish Academy of Sciences, from which Braun received the Nobel Prize in 1909.¹

“Carl Ferdinand Braun was born in Fulda on June 6, 1850; in 1868 he completed the gymnasium in his native city, then attended lectures at the universities of Marburg and Berlin, and in 1872 received the degree of Doctor of the University of Berlin, having submitted a work on the oscillations of elastic strings. He then became assistant to Professor Quincke in Würzburg and left this position in the autumn of 1874, taking the post of teacher at the St. Thomas Gymnasium in Leipzig. In the autumn of 1876 he accepted an offer to take the extraordinary professorship of theoretical physics at the University of Marburg, and then, in 1880, moved to the same post at the University of Strasbourg. In 1883 he moved as ordinary professor to the higher technical school in Karlsruhe, and in 1885 to the University of Tübingen, where he was entrusted with the task of building a physical institute. In 1895 he returned to Strasbourg as director of the Physical Institute and remained there until his death, despite an invitation to move to Leipzig to take the place of G. Wiedemann.”

His first works dealt with the oscillations of strings and elastic rods and, in particular, with the influence of amplitude and of the surrounding medium on oscillations. In 1876 he showed that elastic after-effect is a process essentially different from elastic displacement, and thereby provided an experimental basis for Warburg’s theory of elastic after-effect, based on the rotation of molecules.

His investigations of the influence of pressure on the solubility of solid bodies rest on a thermodynamic foundation.

A large part of Braun’s work belonged to electricity. He showed (1878 and 1882) that the W. Thomson–Helmholtz theory of the electromotive forces of reversible galvanic cells is insufficient, and that chemical energy in general cannot pass wholly into electrical energy. In other investigations (1874 and subsequent years) he found that a large part of binary compounds (such as iron pyrites, etc.) exhibit deviations from Ohm’s law and show a valve action for alternating currents—a property used in recent years for wireless telegraphy, when these substances are used as detectors.

¹ The following lines are an almost literal translation of the author’s autobiography in Les Prix Nobel.

In 1891 he discovered that inside a homogeneous electrolyte, when a current passes through a very narrow channel filled with the electrolyte, decomposition occurs (stenolysis) if the current strength exceeds a certain limit.

In 1897 Braun described a tube with cathode rays, bearing his name, which makes it possible to study the course in time of very rapid changes in current strength and voltages.

In 1898 he began to work on wireless telegraphy. Following the experiments concerning the transmission of signals by means of rapid oscillations, Braun introduced coupled systems into wireless telegraphy, whereby the coupling was established either inductively or directly, or was a combination of the two. At the beginning of 1901 he published his method of tuning the receiving system; in the summer of 1902 he proved the possibility of directed wireless telegraphy, accomplished by means of tilting the antenna. In the course of the same year Braun gave various methods increasing the energy of the radiating system; in 1905 he completed his experiments on directed telegraphy by means of oscillations differing in phase from one another. In 1906 he described the valve detector, which he had also used earlier.

In the decade 1893 Braun succeeded in establishing in optics a phenomenon analogous to Hertz’s well-known experiments with electromagnetic oscillations; at the same time it was shown that this method can serve for the detection of the smallest submicroscopic structures. Soon after this he showed that uniaxial dielectrics, when considered in the form of layers, relate in optics to electromagnetic waves as a doubly refracting crystal, and he discovered a completely analogous phenomenon in optics.

The works on wireless telegraphy up to the beginning of 1901 were collected after public communications in the brochure (Drahtlose Telegraphie durch Wasser und Luft, Leipzig 1901). Later works appeared in Annalen der Physik, Physikalische Zeitschrift, Electrician, Elektrotechnische Zeitschrift, etc.

For these works Braun, together with Marconi, received in 1909 the highest international recognition of his merits—the Nobel Prize. His report, in an elegant and exhaustive form, on his investigations at the Swedish Academy of Sciences was translated into Russian and published in Odessa by Mathesis under the title: F. Braun—“My Works on Wireless Telegraphy and Electro-Optics.”

Summing up Braun’s activity as a scientist, we must say that he stood in the first ranks of the outstanding physicists of the world, and all humanity owes to a considerable degree to his discoveries in wireless telegraphy, which are used by the entire cultured world.

But this aspect of Braun’s activity is not the only one in which he rendered great services to science. Being a first-class scholar, Braun was an outstanding teacher, who created a large school of physicists working in his own direction. We Russians must be grateful to him for the fact that he gave many of our compatriots the opportunity to work in his magnificent Institute.^1

^1 Among Braun’s closest collaborators, whose names in science should be noted, are Prof. Th. H. Möllenhoff (now professor in Giessen), P. L. Panakesti, and Prof. A. A. Eichenwald. In Braun’s laboratory worked A. G. Ioffe, Academician P. P. Lazarev, and Prof. N. P. Shatnev.

Responsive to the interests of others and keenly interested in the successes of science, Braun remained in close spiritual contact with all those who had occasion to work in his laboratory, and always showed a lively interest in the successes of his pupils and collaborators.

N. Lazarev.