Ernst Mach and Johannes Kessel in Prague 1871–1874
Among the numerous activities of the younger Ernst Mach in the development of psychophysics, there is a period of cooperation with the German otologist Johannes Kessel (1839–1907) in Prague from 1871 to 1874, which was not investigated in detail before. This cooperation was important because a number of essential findings in the psychophysics of hearing were published by both authors. Preparing a biography of Kessel, we collected new material about his cooperation with Mach from hitherto unpublished letters, archive material, and from Mach’s unpublished diaries from the corresponding years. This paper describes the previous activities of Mach in psychophysics of hearing including the development of the required methods, the grant from the Vienna Academy for the investigation of the sound conduction in the human hearing organ through the middle ear and especially through the ossicles, the curriculum vitae of Kessel before he came to Prague, the contents and the results of the common research in Prague, and the influence of this period on the further development of Mach and Kessel.