Eugen Goldstein, Wilhelm Wien, en de kanaalstralen, 1886-1912

Abstract

Eugen Goldstein, Wilhelm Wien, and Canal Rays, 1886-1912 Canal rays ('Kanalstrahlen' in German), or positive rays, played an important role in the development of physics in the early years of this century. However, their role has generally been neglected by historians of science. Canal rays, not widely known today, were discovered when a perforated cathode was used in a gas discharge. They are emitted from the holes into the space on the backside of the cathode.In this article, the early history of canal rays is analyzed, starting from Eugen Goldstein's discovery of the phenomenon in 1886 and Wilhelm Wien's subsequent investigations from 1897 until 1912. Wien argued that canal rays consist of positively charged particles, which are the counterparts of the negatively charged cathode rays (electrons). After having demonstrated this experimentally, he focused his research on the question of the nature of the processes involved in the production of the rays. This led him to conclude that the canal ray particles should be identified with the ions of the gas, and to propose a theory about their behaviour. After this historical description, the article examines possible reasons why the canal rays were ignored for such a long time after their discovery, the highly experimental character of Wien's investigations (in spite of his reputation as a theoretician), and the relationship between Wien's work and J.J. Thomson's research on canal rays.