Geophysical Abstracts 152 January-March 1953

26 GEOPHYSICAL ABSTRACTS 152, JANUARY-MARCH 1953
14256. Garlick, J. K. Reflexion coefficient of radio waves from frozen terrains:
Nature, v. 171, no. 4345, p. 259,1953.
To determine the reflection coefficient of radio waves for normal incidence
from deeply frozen land and sea, measurements were made in northern Canada,
transmitting a 1,600 megacycle linearly-polarized signal vertically downward
from aircraft at heights of 10,000 to 20,000 ft and recording on suitable receiver.
Reflections from open water in Hudson Bay or the Great Lakes were used as
the standard of comparison. On the basis of a reflection coefficient of sea
water 0.83, the following reflection coefficients were calculated: from deep ice
on sea, 0.20; frozen muskeg or barren gravel, 0.20 to 0.25; frozen lakes, 0.25;
frozen snow covered forest, 0.08. M. C. R.
INSTRUMENTS AND METHODS OF OBSERVATION
T.4257. Lehmberg, A. E. A new electromagnetic device for the surveying of sub­
surface conductors: Canadian Min. Metall. Bull. v. 45, no. 485, p.
555-560,1952.
An inductive instrument having a transmitting and receiving coil operating
at low frequency is described. The secondary, resistive, component is detected
by the receiving coil whereas the primary inductive signals due to coupling, and
the secondary inductive signals due to skin effects and the magnetic material in
the ground are cancelled out by special circuits. A 4-man crew with the coils
100 feet apart can traverse 2 to 4 miles a day at 50-foot stations.
Model experiments at a 30-to-l reduction were made with powdered graphite
as the model conductor in a 4 x 16 x 49 inch box. Traverses were made perpen­
dicular to the long dimension of the box using dips of the box from vertical to
horizontal. Sample curves were prepared. Field interpretation is made on the
basis of these curves and geologic information.
Surveys and interpretation were made on the Barrmont mines in Barraute
township, and on the property of Quebec Copper Corp. in Eastman township,
Province of Quebec. Correlation between the geophysical data and geologic
information is shown with the possibility that an extension of the mineralized
zone was located on the latter property. W. J. D.
14258. Evjen, H. M. Surface electrical method detects oil directly: World Oil,
v. 136, no. 2, p. 93-96,1953.
The high resistivity of oil makes possible its direct detection by electromagnetic
methods, if attenuation is avoided by using wavelengths as large as 4 times the
depth of penetration. The amplitude of the reflection depends on the average
ground resistivity, the depth explored, and the resistivity contrast of the re­
flecting horizon; but reflections are also obtained from oil bearing strata that
are not porous enough to produce. Tests in Kay County, Okla., where the depth
of penetration was controlled by frequency variation, showed that all producing
wells lie wthin a given impedance contour. D. F. B.
14259. Krueger, R. F. Electric logging with oil-base drilling fluids, U. S. patent
2,626,305, granted January 20, 1953. 10 claims. Assigned to Union
Oil Co. of California.