Two photographic methods of studying high-voltage discharges

This paper presents some of the results of two methods of drawing out the alternating-current corona discharge along a time axis. The first method consists in photographing, with the usual camera, the discharge from a needle point revolved by the alternator which is the source of supply for the high-voltage transformer. The needle is revolved inside a porcelain tube whose outside surface is made conducting and grounded. The second method makes use of a special camera using mirrors revolved synchronously by the alternator itself. This camera is equipped with a shutter so arranged that photographs of sparks may be taken using one sweep of one of the mirrors. Photographs have been taken showing the discharge between needles, both with and without a solid dielectric placed midway between the points. When drawn out along the time axis certain characteristics of corona discharges may be seen, even when the discharge is extremely weak for the exposure may be continued for any length of time with a reoccurring phenomenon. A few photographs giving same conception of the different discharges under varying conditions are given.