(b. Grossumstadt, Germany, 25 January 1854; d. Ammerland, Germany, 12 August 1924)
Föppl’s choice of career was determined by the great program of German railway construction in the mid-nineteenth century. In the late 1860’s, a line was begun through the Odenwald, near Grossumstadt. Föppl’s father, a country physician, was appointed a director of a railway hospital, and both he and his family were thereby drawn into close association with the construction engineers. This contact was decisive for August, who was then just finishing at the Gymnasium. He started engineering studies in Darmstadt, later changing to Stuttgart, and finally graduating from the Polytechnic in Karlsruhe in 1874.
At the time, job opportunities were few for practicing engineers, and Föppl took a temporary, uncongenial position as a bridge engineer. Simultaneously, at the age of twenty-one, he published the results of his first independent research, a paper on bridge construction. The market for engineers was still poor in 1876, when Föppl completed his year of military service, and the young railway engineer hired himself out for a term as teacher in a building-trades school in Holzminden. The work proved unexpectedly to his liking. In the fall of 1877, Föppl accepted a permanent post at the Trades School in Leipzig.
Teaching at Leipzig was at a low level, and Föppl aspired to become a university professor. He decided to make himself known to the university world through publications. His first two books, Theorie des Fachwerks and Theorie der Gewölbe appeared in 1880 and 1881. In 1886 these two, together with a small textbook for trade school students, served to meet the requirements for a doctorate in his field at the University of Leipzig. The textbook was published in 1890 as Leifaden und Aufgabensammlung fur den Unterricht in der angewandten Mechanik.
Although these first books were well received, they did not bring Föppl the desired appointment as a professor of bridge engineering. He gave up the hope of being appointed in his specialty and resolved to master additional fields. In the self-study to which he now gave himself, the problems involved in writing textbooks suitable for independent reading first presented themselves to him. Meanwhile, throughout the early 1880’s, electrical artifacts and machines, exhibited in fairs and commercial firms, brought the new field of electrical engineering to public attention. Föppl turned to this area and, to prepare himself, went in late 1893 to work in Gustav Wiedemann’s laboratory at the University of Leipzig. He published his work in a series of papers in Wiedemann’s Annalen. Among them were researches bearing on subjects as fundamental as the nature of electricity.
From Föppl’s activity in electromagnetism, together with his interest in the independent student, grew an immensely successful text, the Einführung in die Maxwellsche Theorie der Elektrizität (Leipzig, 1894). It was one of the first German-language expositions of Maxwell’s ideas. In addition, Föppl had been an early convert to the use of vector calculus in physics, and his Einführung was the first German text to incorporate this new mathematics.
During these fifteen years as a schoolteacher, Föppl also continued to work in engineering statics. He was hired by the city of Leipzig for a number of civil engineering assignments; the most noteworthy of these was the design of the iron framework of the Leipzig Markthalle. Föppl here achieved a new solution for roofing over an irregular polygonal space: it later became known as the Föpplsche Flechtwerk-Hallendacher, that is, “Föppl’s wickerwork roof.” He also published a succession of theoretical studies which were collected in 1892 and published as Das Fachwerk im Raum (Leipzig, 1892), one of his best books.
The summons to a university finally came in 1892. The post was the newly created one of extraordinary professor of agricultural machinery and forestry at Leipzig. This was one field in which Föppl had had no experience. He threw himself into it with his customary wholeheartedness. He participated in the systematic program of tests on farm machinery organized by the German Agricultural Society and wrote an article on the theory of plows for the 1893 Landwirtschaftliches Jahrbuch. His labors in this new field were cut short, for in 1894 he was appointed to succeed Johannes Bauschinger at the Technische Hochschule in Munich, as ordinary professor of theoretical mechanics and director of the strength-ofmaterials laboratory.
In Munich, Föppl felt himself to have reached his life’s goal and to have achieved a position at the top of his profession. He now turned almost exclusively to engineering mechanics and left it to Max Abraham to carry out the rewriting of subsequent editions of the Einführung. In his role as professor, Föppl published a number of texts, of which the most important was the six-volume Vorlesungen über technischen Mechanik. By 1927, the third of these volumes received its tenth edition; none of the others went through fewer than four. He also continued his researches, publishing works on gyroscopic phenomena and problems of relative and absolute motion, among other subjects.
In his role as laboratory director, Föppl succeeded in increasing the proportion of laboratory effort in basic science. Under Bauschinger the laboratory was mainly devoted to carrying out tests requested by industry and government. Under Föppl this part of the work was largely carried out by assistants. His own researches at the laboratory were published in a series of articles (making up vols. 24-33 ) in the Mittheilungen aus dem mechanisch-technischen Laboratorium der K. Technischen Hochschule Munchen. They appeared between 1896 and 1915 and were of diverse kinds: experimental studies of properties of materials, theoretical investigations of dynamical problems arising in engineering practice, and critical scrutinies of the foundations of engineering formulas and tests. In his evaluation of Föppl’s Munich work, C. Prinz singled out the article on Laval waves, that is, disturbances in fast-moving waves, as having been of particular importance for both engineering and physics. Prinz also characterized the reorientation Föppl gave the laboratory as a change from an interest in tests on materials to an interest in the several components of a construction regarded in terms of their interrelations. This approach was unusual in Föppl’s time and opened new paths.
Föppl gave up his professorship in 1921 but retained direction of the laboratory. In 1924 he had the satisfaction of seeing the appearance of a Festschrift on his seventieth birthday, written by former pupils. Among them were his two sons, Otto and Ludwig, as well as Theodor von Kärman, Prandtl, H. Thoma, and Timoschenko. Föppl died suddenly a few months later in his country house in Bavaria.
It was characteristic of Föppl to involve himself in problems as practical as bridge construction and as fundamental as the question of the existence of absolute motion. In both types of investigations, he concerned himself to an unusual degree with a critical examination of the underlying assumptions. His personal qualities were perhaps typical of his century and nation. He was a strict and conscientious father and husband. He was loyal to the cause of German nationalism and German greatness, and conscious of the significance of his field for the industrial and agricultural strength that lay behind Germany’s power. Scrupulous and industrious in his work, he succeeded by his considerable effort in attaining the rather precisely defined goal he had set himself.
In addition to the works mentioned in the text, see the lists in Poggendorff.
Of particular interest is Föppl’s autobiography, Lebenserinnerungen, which appeared posthumously (Munich-Berlin, 1925).
The Festschrift is Beiträge zur technischen Mechanik und technischen Physik. August Föppl zum siebsigsten Geburtstag (Berlin, 1924); see esp. the articles “August Föppl,” pp. v-viii (unsigned), and C. Prinz, “A. Föppl als Forscher und Lehrer,” pp. 1–3.