ELECTRICAL PROSPECTING 9 
resistivity at the six stations shown on the profile of Fig. 6. These curves 
show a layer of very high resistivity which is at the surface at stations A and 
B on the west, and then dips to the east. A layer of low resistivity is on the 
surface at stations C, D, E and F, below which there is the high resistivity 
layer. There is apparently a very thick layer of low resistivity below this high 
resistivity layer. A rough qualitative interpretation of these curves is shown 
fa 
STATION B. 
ee STATION C 
ELECTRODE SPACING IN FEET 


4000 
2000 
STATION E 

ia 
ce 
on 
Ea 
ee 
ce 
a 
PA 
APPARENT RESISTIVITY IN OHMS 
° 
Pee i 
STATION F 

PHuaaeee naa 
pet ee es 
HEAT 
Pe eS 

Fig. 5. Apparent resistivity curves obtained by field measurements along profile of Fig. 6. 
in Fig. 6. It may be seen that it checks with the core drill holes which show a 
monocline dipping to the east. 
Another method of utilizing the apparent resistivity, the ground resistiv- 
ity map, has been developed by Schlumberger. An electrode spacing is chosen 
which is approximately equal to the desired depth of investigation. The ap- 
parent resistivities with this electrode spacing are measured at various points 
on the surface of the earth. A contour map is then made of these values. This 
method is particularly suitable in a country with a shallow overburden which 
153 
