Summary Radiation of chlorine subjected to the silent electric discharge (which produces Joshi-Effect to a 70 per cent current decrease) has been studied spectroscopically in the visible region. An exposure of 300 hours was needed. The spectrum consists almost entirely of faint bands degraded towards the red. An intensity maximum is observed in the region 4900–4400 A. and 5800–5500 A. A number of new bands in the red have been observed. It is considered that the emission cannot be attributed to a neutral chlorine molecule, but is due to Cl2/+. Absence of the atomic lines and of an emission continuum characteristic of atomic recombinations suggests that, under the conditions appropriate to the production of a large Joshi-Effect, reactions involving atomic chlorine occur predominantly on the container walls.