Johann Wilhelm Hittorf and the material culture of nineteenth-century gas discharge research

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This paper is dedicated to Falk Rieß, his achievements as a teacher and as spiritus rector of the Research Group on Physics Education/History and Philosophy of Science at Oldenburg University. I want to thank Bernhard Taufertshöfer for his permission to use his photographs and Jan Frercks, Moritz Epple, Jahnavi Phalkey, Christian Sichau and the referees for their constructive criticism.

In the mid-nineteenth century, gas discharge research was dominated by attempts to produce and stabilize colourful luminous effects inside evacuated glass tubes of various shapes and under varying circumstances. For those researchers who were interested in understanding the conditions of their appearance, it became more and more evident that the phenomena were sensitively dependent on the shape of the tubes, the type and quality of glass, the type and pressure of the contained gases, the metals used for the electrodes, the type and intensity of the source of electricity and many other factors. The plasticity of both the phenomena and the experimental set-up (particularly the shape of glass tubes) provided ample opportunity for experimental manipulation and intervention - and for charging the phenomena with meaning.¹ The variation of colourful luminous patterns under changing experimental conditions could be interpreted as specific disturbances of the physical ether or as visual expressions of the interaction and conversation of various 'modes of force' or 'imponderables', such as heat, light, electricity or magnetism.²

The following paper will focus on developments which began with the cooperation between a university professor of physics and mathematics and a brilliant glass-blower and instrument-maker, Julius Plücker and Heinrich Geissler, at Bonn University in the late 1850s. Both researchers contributed to the education and influenced the performance of the main protagonist of this paper, Plücker's student and later professor of physics and chemistry in Münster, Johann Wilhelm Hittorf. In an early phase of what turned out to be a long-term research project, Hittorf joined Plücker's investigation of gas discharge phenomena as a collaborator in the early 1860s. Primarily he was responsible for evacuating and preparing spectral tubes but at the same time began to explore the phenomenology of gas discharge in a playful empirical manner and fathomed the technical and epistemic potential of the new field of study.

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