198 A. M. Alekseev et al. 



which are the quadrilateral probings. When carrying out azimuthal probing, 

 it is by no means necessary to place the centres of the measuring lines on 

 a straight line, directed along the axis of probing. 



For a number of dipole arrangements including the azimuthal, in a hori- 

 zontally homogeneous medium, the values of KS* do not depend on the an- 

 gle O which makes it possible to use these arrangements in studies on the 

 roads and other curved routes. The curved azimuthal probingsf have all 

 the advantages of the quadrilateral probes but are much more readily ap- 

 plied to the region. 



The possibility of practical curved azimuthal probes was first shown 

 by the electro-prospectors of VNII Geofizika working (1954) in the 

 Cis -Baltic depression. Three azimuthal probes were carried out with 

 working distances of up to 12 km. The probes were carried out by means 

 of the EPS -23, mobile electrical prospecting station, \\'ith the limiting 

 deviations of angle O from 90° not exceeding ±30°. 



The curves obtained show sufficiently well the geoelectrical cross-section 

 of the Cis -Baltic depression. The results showed the suitability of a similar 

 arrangement of work for carrying out deep electrical probes and made it 

 possible to plan a programme of further studies on the method of measure- 

 ments with the azimuthal arrangement. The development of the method of 

 curved azimuthal probes was continued in 1955-1956 in the Western Sibe- 

 rian Lowlands. 



An experimental party from VNII Geofizika carried out 40 two-way 

 curved azimuthal probings in the Kochanevsk region of the Novosibirsk 

 region (1955), where the supporting electrical levels lie at depths 

 of from 200 to 1000 m. The measurements were made along wind- 

 ing roads, running through swampy and wooded territory. The maximum 

 working distance achieved in the majority of cases was 6 km A\dth a length 

 of feed line up to 1 km. As a rule, the length of the measuring line did not 

 exceed 400 m. The topographic basis for the azimuthal probes was worked 

 out by means of a plane table. Nvunerous control measurements showed 

 the good reproducibility of the azimuthal probing results within the limits 

 of 5-6% providing that the angle O did not differ from 90° by more than 

 ±20°. This condition does not seriously limit the possibilities of curved 

 probings, since if necessary it is possible to use 2 feed lines in different 

 directions. 



In the southern part of the surveyed area, where it was easier to move, 



* iir5-Koeffitsient soprotivleniya — Coefficient of resistance -resistivity [Editor's note]. 

 t The article by Berdichevskii "The method of curved azimuthal probes" is in the present 

 coUectior. 



