518 



EXPLORATION GEOPHYSICS 



<?/ 



fa) 



(b) 



I \ L-^ 



a — »U( — a 



(c) 





S, 



w 



c^) 



{.a b L-b L-aJ 



P 

 (9) ^ 



s, 



i I 



•??-i- 



-a H"« a 



2rr 



f^) 



z 



) 



Fig. 313. 



(a) Wenner configuration 



(b) Five-electrode method using four equal spacings 



(c) Lee partitioning method 



(d) Unsymmetrical method: energizing electrodes separated by a finite distance 



(e) Unsymmetrical method: one energizing electrode at infinity 

 (/) Method employing moving current electrodes 



(g) Method employing one moving current electrode and one fixed current electrode 

 positioned midway between the potential electrodes. 



irrespective of whether the potential electrodes are inside or outside of 

 the current electrodes, t Practically, however, there is a decided decrease 

 in detectability when the current electrodes are placed inside of the poten- 

 tial electrodes. 



t R. J. Watson, "Interpretation of Resistivity Measurements," A.I.M.E. Geophysical Prospect- 

 ing, Tech. Pub. 518, pp. 6-7. 



