Chap. 10] 



ELECTRICAL METHODS 



667 



Table 70— Concluded 



DIELECTRIC CONSTANTS— ROCKS AND FORMATIONS 



k' = apparent dielectric constants; ko = true dielectric constants, e.s.u. 



III. SELF-POTENTIAL METHOD 

 A. General 



The self-potential method is the only electrical method which uses a 

 natural field, that is, one supplied by spontaneous electrochemical phenom- 

 ena. All other electrical methods use artificial electric fields. 



The electrical activity of ore bodies and the potentials associated with 

 (1) concentrations of metals in placers, (2) the corrosion of pipe fines, (3) 

 the movement of underground waters, and (4) foundation boundaries all 

 arise from concentration differences of electrolytic solutions in contact 



