ADVANCES IN OIL PROSPECTING 139 
explained in the practical examples illustrated in Figures 33, 35 and 
40. 
E. OPINIONS REGARDING DIRECT ELECTRICAL 
PROSPECTING FOR OIL 
In view of the recent developments of the technique of resistivity 
and potential-drop-ratio-measurements which permit (as has been 
shown and can be verified by an inspection, for example, of Figures 
34 and 35) the accurate identification of certain geologic horizons 
under favorable circumstances, the question becomes, of course, acute 
again as to the extent to which oil deposits may be located directly by 
electrical measurement from the surface. 
Very much has been written about this subject, probably altogeth- 
er too much at a time when field technique and interpretation of elec- 
trical prospecting were not nearly far enough developed to enable 
anyone involved in the discussion to state definitely that certain 
things were altogether impossible. The writer believes that several 
authors who were involved: in the animated discussion at that time 
wish now, in view of the recent developments, that they had not 
voiced their opinion in the matter. 
Another factor which influenced the exchange of opinions in the 
problem of the possibility of locating oil directly was the fact that 
most of the involved parties were interested in competitive geo- 
physical consulting companies. Hence, the writer doubts if very 
much could be gained by repeating in detail at this time all the argu- 
ments which have been advanced for and against the direct electrical 
location of oil. Only the main points will be discussed. At any rate, 
it is emphasized that it is not the object of this paper to take sides in 
an argument which is not as yet ripe for an altogether unbiased dis- 
cussion. We shall not try to decide at this time if a direct location of 
oil by electrical prospecting is possible. We shall merely state, by 
discussing actual results obtained, what has been done and can prob- 
ably be done with the present state of development of instrumental 
technique and interpretation. The whole discussion in this matter 
seems to have been started when the representatives of the Elbof 
electrical prospecting company claimed that they were in a position, 
by means of their method, to locate the oil directly. The chief factor 
which probably encouraged doubts and discussions of their statements 
was the fact that the type of indications which they obtained by 
means of their method, namely the deflection of current lines, did not 
dend itself very readily to such far-reaching interpretations. In fact, 
469 
