Abridgment of effects of the magnetic field on Lichtenberg figures

This paper deals with new forms of Lichtenberg figures produced under the combined stress of dielectric and magnetic fields. The effects produced by the magnetic field may be used for determining whether electrons, positive ions, or protons, are basically the active elements in the formation of the positive as well as the negative figures. The illustrations also show that the presence of the magnetic field greatly extends the range of air pressures within which figures of definite form can be obtained, that figures taken at low air pressures possess structures strikingly different from those hitherto known, and that these figures may prove a key to the mechanism of the electric spark.