228 M. N. Berdichevskii 



the theoretical curve of q for a hmiting 3-electrode apparatus and we mark 

 out on this curve a certain small section, in the limits of which the depend- 

 ence of the ordinate log q on the abscissa log R can, with sufficient accuracy, 

 be expressed by a linear equation 



\ogQ = tlo^R + logT,. (10) 



where: t and T are certain parameters, which depend on the dimensions 

 of the arrangement and the geoelectrical cross-section, t being an angular 

 coefficient of the tangent to the KS curve (in a bi -logarithmic form). 

 Using expression (10) and considering formula (6), we write 



IT - 

 E = -^Rf-^ 



Ztc 



We use this expression to determine the components E"^ and E^^ of 

 the field of the point sources M and N along the direction AB (on the sur- 

 face of a horizontally homogeneous medium). 



Then integrating (9), we obtain: 



^""---Yn T^l 



Thus, 



IT 

 2n{t-\) 



A IfAB^ = ^ [M5^-i -M^'-i - M'-i + iVZ-i]. (12) 



Using expressions (11) and (12), we obtain from condition (7) 



(13) 



We express the operating distance B by the product of two factors 



R=pR, (14) 



where: p is a correction coefficient; 



R is the distance between the centres of the feed and measuring 

 lines of the azimuthal arrangement. 



According to (13) and (14), the coefficient p will be equal to 



^ [/ 27tR^{t-l) ^ 



