IT has previously been reported that the corona in a point-plane gap to which is applied a steady d.c. potential (positive point, negative plane) consists of a series of short-duration pulses1,2, and this had also been observed by me. The results of English1, who used a photomultiplier to study the light emitted by the corona, show that this light is emitted in the form of pulses of total duration of approximately 6 × 10−8 sec. with “a plateau which gives the impression of two overlapping peaks”.