276 



V. I. FOMINA 



Figure 2 shows curves which have been constructed in the manner de- 

 scribed above for case 1, a, Id which the direction of the separations is parallel 



to the surface of the vertical contact for various values of the ratio — . It 



H 



also shows curves for a double-layered medium at the VEP point and a curve 

 on the reference graph CV-25. 



As may be seen from Fig. 2, approximately constructed curves only give 

 satisfactory results for true transverse conductivities S when d ^ 2H*. 



oU o 'V I. 



h,= 'b\p, =1 0.^p-^-p^ 00 



jy 



jC3_ 



® ® o 



©@ 



C'/.o) 





V \ X V ■ \ / -X /^^/ X '' , ■ — ' 



X 



J3 q^lXi Q O O O f 



(a) (b) 



-(c) 



Q 



Voiues of 



[oo] Values of — 



AB 



Fig. 3. a — VEP curves for a horizontally homogeneous medium: b — approximately 

 constructed VEP curves; c — curves of the CV-3S reference graph. 



H 



When d < — the value of S obtained is half the true value, and when 



2 



2H > J > iH, S takes on a value intermediate between S and 



5 



The curves obtained are compared in Fig. 2 with curves calculated by 

 M. N. Berdichevskii (HVC reference graph) for the case when two contact- 

 ing media lie on a third medium with a specific resistivity of ^3 = 00, 

 where we have taken ^2 = 99^^ instead of Q2 = 00 (Fig. 1, e). 



The curves obtained practically coincide with the HVC curves. 



On this basis we consider that the accuracy of the approximate con- 

 struction of curves by the methods described is fully adequate for practical 



* Given a cross section of this type, VEP curves may usefuUy be extended as far as the 

 cross sections bounded on Fig. 2 by the horizontal line C. 



