Certain Applications of the Surface Potential Method

SOME of the advantages of the inductive method of electrical prospecting were emphasized in a paper by Dr. Max Mason.1 Since this emphasis was misunderstood by some to indicate a too exclusive interest in inductive methods, we are especially happy to help correct this impression by reporting on some of our work on surface potential methods. EARTH CURRENTS AND SURFACE POTENTIALS When two electrodes, A and B, are placed on the surface of the ground a distance d apart, and a 100-volt battery is connected across the elec- FIG. 1.-LINES OF CURRENT FLOW AND SURFACE POTENTIAL IN MILLIVOLTS IN THE CASE OF A HOMOGENEOUS EARTH. trodes, current flows from the positive electrode A to the negative electrode B. The current does not pass directly from A to B along the straight line joining these two points. In fact, a negligible amount of the