The Effect of Geologic Inequalities on the Path of Lightning, as Indicated by Model Experiments

To investigate the influence of lightning strokes on surfaces with geologically nonhomogenous structures, experiments were carried out in a model test tank filled with dried sand; and in this a vein of iron ore or other materials. Artificial lightning discharges against the surface of the test tank were undertaken by the aid of an impulse generator at voltages of one million volts and spark lengths of 75 and 170 cm respectively. It was found -that a discharge from a positive electrode was pronouncedly influenced by a geological discontinuity as an iron ore vein. On the other hand, negative strokes hit the sand surface at random more independent of geological discontinuities. The difference in effects from the two polarities is related to the mechanism of the discharges and the development of leaders initiating the main discharges in the form of lightning ones.