128 C. A. HEILAND 
4) To find the thickness of the upper stratum, all that is necessary 
is to place the observed resistivity curve upon the one which has been 
computed theoretically in the manner described, and to select the 
Ra) 
oy) 
A 7] ¢e D y= F 
a. Electrode arrangement of the I E G & for potential drop 
and phase anomaly mapping 

Potenual and phase curves, 
b. in Australia 
4 SS 4 B Cc 
Ti -ETALaaai> aa Lia 
Za --& 
: OLIN th ee Se} 
c.Koenigsberger s eat 





electrode arrangement 
4 
a.Swedish-American 
electrode arrangement 
for potential-drop-ratio observations 
Fic. 19.—Electrode arrangements in potential-drop mapping and potential-drop- 
ratio work. 
depth for which the observed and computed curves show the best 
agreement. 
The same method is applicable to the three-layer case. Poldini 
(ref. list No. IIIs9) has recently demonstrated the application of 
this interpretation method in a number of cases. 
458 
