O. C. LESTER, JR., AND S. W. WILCOX 
where according to notation used: 
V: =true velocity of low speed medium 
2 = true velocity of high speed medium 
V2, =apparent velocity of high speed medium (down dip) 
V.- = apparent velocity of high speed medium (up dip) 
o = angle between high speed bed and horizontal (dip of bed) 
q =cos i = sin 8 
where 8 = critical angle between low and 




Vi 
high speed beds. (sin 8 = ) 
Equation 15 may be written: 
1 1 a 
= —— (Cos x — —— V 1—sin’@ sin <) 
V4 V2 sin ® 
1 1 V V2 — V 1 sin 
Hence = Co ———————) 
Var V2 Vi 
V; 
and V2. = —————————_ where B = cot 9, which is constant 
cos x —Bsin « for two given beds regardless 
of dip. 
Equation 17 may be written similarly, as: 
V: 
Wo, SSS eee 
cos < + Bsin « 
For general cases, let V’ represent the apparent velocity (either up 
or down dip) 
V; 
Then Vv =“ Equation A. 
cos x + Bsin « 
The negative sign should be used for apparent velocities shooting up 
dip, and the positive sign for down dip. 
Investigation of this equation will show that for <«=0, V’=V,; 
which is, of course, true for a horizontal marker. 
Also, for « = 90, V=a 
In equation A, if the apparent velocity V’ be plotted against the 
tangent of the angle of dip, the resulting curve will be of the form Fig. 1, 
and the angle of, dip can be read directly for a given apparent velocity. 
