Lichtenberg Figures are branching electric discharges (or electrical trees) that are sometimes preserved on the surface or the interior of a solid dielectric. They are named after the German physicist Georg Christoph Lichtenberg, who originally discovered and studied them.
One way that they can be produced is as follows: A sharp-pointed needle is placed perpendicular to a non-conducting plate, such as of resin, ebonite, or glass, with its point very near to or in contact with the plate, and a high voltage Leyden jar (a type of capacitor) or a static electricity generator is discharged into the needle. The electrification of the plate is now tested by sifting over it a mixture of powdered flowers of sulfur and red lead (Pb3O4 or lead tetroxide).
The negatively electrified sulfur is seen to attach itself to the positively electrified parts of the plate, and the positively electrified red lead to the negatively electrified parts. In addition to the distribution of color thereby produced, there is a marked difference in the form of the figure, according to the polarity of the electrical charge that was applied to the plate. If the charge was positive, a widely extending patch is seen on the plate, consisting of a dense nucleus, from which branches radiate in all directions; if negative, the patch is much smaller and has a sharp circular boundary entirely devoid of branches.
Lichtenberg figures may also appear on the skin of lightning victims. These are reddish, fernlike patterns that may persist for hours or days on survivors. They are also a useful indicator for medical examiners when trying to determine the cause of death in a victim. Lichtenberg figures appearing on people are sometimes called Lightning Flowers, and they are thought to be caused by the rupture of small capillaries under the skin due to either the passage of the lightning current or the shock wave from the lightning discharge.
via : Bored Night