Lichtenberg figures

Abstract

In 1777, one hundred and fifty-one years ago, Dr. George Christoph Lichtenberg, Professor of Physics in the University of Göttingen, observed that under certain conditions an electric discharge produced curious and strangely beautiful figures. Lichtenberg's apparatus and circuit arrangement were very simple and can readily be reproduced. Place a pane of glass on a metal plate connected through a spark-gap to the outside coating of a Leyden jar. Connect the tinfoil on the inside of the jar to a metallic electrode, touching the upper surface of the glass plate. When the Leyden jar is discharged, figures are produced on the glass surface around the point of contact of the electrode. These figures may be made visible by sifting some light powder, (such as lycopodium), over the glass surface. By using flower of sulphur and finely powdered red lead, or other colored powders, the different shapes of the negative and positive figures may be shown in an impressive manner. With the discovery of photography almost a century after Lichtenberg's day, a much more convenient method was obtained for visualizing the phenomena. In 1888, J. Brown and E. T. Trouvelet found that figures similar to those obtained by Lichtenberg could be obtained photographically by replacing the glass or rubber plate with a photographic plate; the emulsion side being placed in contact with the electrode. On developing the exposed plate, very beautiful figures were obtained. As the photographic plate makes a permanent record greatly superior to the dust figures, the latter are seldom used, and the photographic records are generally referred to as Lichtenberg figures although photographic Lichtenberg figures would be more specific. (To give a general view of the phenomena discussed, a number of typical positive and negative Lichtenberg figures for various forms of impressed electric surges or impulses were shown on the screen. The true Lichtenberg figures were differentiated from figures produced by brush discharges and glide sparks.)