USE OF GEOELECTRIC METHODS IN SEARCH FOR OIL 177 
arising from disturbing features of the earth, such as topography and 
inhomogeneities within structure, are to a considerable extent de- 
pendent upon the number and the distribution of measurements and 
upon the method by which these data are treated. In order that cor- 
rections may be made for the more general features of topography, a 
further development of theory is required. 
Although.there is some evidence that features of structure located 
between 2,000 and 4,000 feet below the surface have been disclosed 
by resistivity surveys, this is by no means definitely established. 
General theory, as the writer understands it, does not exclude such 
a possibility. In fact, the likelihood of exploring to far greater depths 
seems so good to some of us that plans are being developed for a large- 
scale codperative undertaking in which it is hoped to obtain by re- 
sistivity measurements information about the structure of the earth’s 
crust down to a depth of about 50 miles. The results to be obtained 
from such a venture are, of course, not expected to be of practical 
value, except perhaps indirectly, but they should have important 
bearing on problems in several branches of the basic science. 
The principal points which it has been attempted to bring out in 
this article may be briefly stated as follows. Although evidence is at 
hand showing that some geoelectric methods are aids in the search 
for oil, yet it can not be determined at this time whether the results 
per dollar from these methods compare favorably with those obtained 
from gravimetric or seismic methods. 
An attitude of disfavor toward geoelectric methods has perhaps 
in considerable part sprung from subjective rather than objective 
sources. The widespread belief in the near-omnipotence of electricity 
has brought forth many impotent geoelectrical schemes and has pro- 
vided easy prey for these as well as for the outright faker. Of course, 
an unfavorable reaction followed. Furthermore, a bonafide geo- 
electric method can not qualify as the idol of these ‘‘believers.”’ 
Geoelectric methods also entered this field with the handicap of 
inadequate theoretical equipment and with practical experience in 
a class of problems not adapted to bring out some details of apparatus 
and method important in the more difficult work to be encountered 
here. These conditions doubtless added considerably to the cost and 
lessened the value of the results obtained from some of the geoelectric 
surveys. And withal there is the seniority of gravimetric and seismic 
methods to be considered. 
In principle it seems entirely feasible in many cases to determine 
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