286 



V. I. FOMINA 



<\- — 



(T)values of h 



(a) (b)- — (c) 



Fig. 12. a — approximately constructed J_ VEP curves; b — approximately constructed 

 II VEP curves; c — VEP curves for a horizontally homogeneous medium. 



In this case it is clearly possible to consider the medium as being homo- 

 geneous up to the spacings used in practice and to make the construction 



for the ratio . 



{Qx, kJL 

 Thus, the following characteristic changes are to be observed in cross 



VEP curves for the case {q^ ^j^ > ^2' made near the vertical contact 



(Fig. 12): 



(1) the absence of an asymptotic branch ascending at an angle of 45° 

 in the || VEP curve: 



(2) the abscissa of the maximum diminution of q^ on the asymptotic 

 branch of the J_ VEP curves is equal to d; 



(3) The abscissa of the point of intersection of the ± and VEP curves 

 (or of their convergence for small values of d) is approximately equal to 2 d. 



Let us turn our attention to the observed deviations in the right-hand 



parts of the experimental VEP curves Nos 324 and 67 (Fig. 7), which are 



similar to the deviations obtained on approximately constructed curves for 



/ d 

 the case {q^^ ^^ > ^2 I for '^ =" 5 



A somewhat different correlation between q^^ for experimental and approxi- 

 mately constructed VEP cross curves will evidently be produced by the in- 



fluence of a preceded non -horizontal boundary with 



{Qi,k)i 



>1. 



A second non -horizontal surface of separation of the media with 



