USE OF GEOELECTRIC METHODS IN SEARCH FOR OIL 169 
in the minds of many laymen, endowed with mystical power. No 
doubt everyone who has worked with geoelectric methods has been 
amused by the curious spectator who loses all interest when he finds 
that the apparatus in use is not provided with a pointer and scale to 
indicate the number of barrels of oil which may be obtained from a 
well sunk at a particular spot. But it is not only the curious spectator 
who entertains this attitude. In recent years some hard-headed 
business men in an eastern oil field patronized a self-styled geophysi- 
cist who with a voltmeter and a few vacuum tubes connected in a 
meaningless circuit professed to perform this miraculous feat. The 
vacuum tube is the superb present-day garnishment for the doodle- 
bug and doubtless whets the appetite of those who have a taste for 
this morsel. 
The bonafide geophysicist will, of course, not make such pre- 
tentious claims. He will recognize in his task a parallel to that of the 
weather-forecaster and will not shrink from using that qualifying 
word, “probable.” He will speak only of indications, good, bad, or 
indifferent. These should be among the passwords, without which 
an entrance into the confidence of prospective patrons can not be 
won. 
Although some geoelectric methods may under favorable condi- 
tions detect oil directly because of its high insulating property, geo- 
electric as well as other methods are efficacious in the location of oil 
only to the extent that they disclose subsurface structural features 
which in turn may indicate oil-bearing structure. That geoelectric 
methods are capable of disclosing hidden structure had been defi- 
nitely shown before these methods were tried in the oil field, and 
since then a number of cases in which geoelectric surveys disclosed 
oil-bearing structure have been reported. Some of these are mere 
statements and have to be accepted on faith, but in several reports 
data are published which seem definitely to support the claims. 
It is, of course, obvious that structure will be revealed by any 
geophysical method only when that property of the structure upon 
which the method depends presents a certain degree of contrast to 
the surroundings. Thus two different methods, as, for example, the 
gravimetric and the electric, may reveal entirely distinct structures, 
or one method may give indications of structure while the other does 
not. It must not be assumed, however, that the method which gives 
no indication is not of positive value, for if the information which it 
supplies is considered along with that obtained by the other method, 
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