An Oscillograph Study of Corona

The features or characteristics of the corona around wires brought out by oscillograms of the charging and leakage currents may be thus summarized: 1. The distortion in the current wave form, which results from copious ionization at the time of the voltage peak, is observed simultaneously with the hissing sound and bluish discharge from the wire. 2. At air pressures below 20 cm. of mercury, copious ionization,-as indicated by the hump on the current oscillograms,-sets in at a lower voltage during the half cycle for which the wire is the cathode than during the half cycle for which it is the anode. 3. From the oscillograms thus far obtained at atmospheric pressure it has been impossible to determine whether there is any difference in the voltage at which the distortion appears in the two half cycles, at pressures near atmospheric. 4. The boundary of the ionized region does not gradually expand outward from the wire with the increase in voltage during the half cycle. The loss of insulating properties in the air surrounding the wire must be conceived of as taking place with extreme suddenness. The evidence of this is the oscillation in the current shown on the oscillograms. 5.