46 T. L. ALLEN 
and thicknesses will give. The distance of the receiving station from 
the shot point will be designated as x, and the equations for the time 
through each path derived. For the surface layer, the general equa- 
tion for the time is, 

iS 
6 his = 
1.980 
The general equation for the time through the second horizon is, 
2X .330 x — 2X .330 X tan 69°25’ 
cos 69°25’ X 1.980 2.015 
For the third horizon, it is, 
2X .330 26322 

Pie a ee Cis 4 Ae 
* cos 60°03’ X 1.980 cos 67°46’ K 2.115 
x — 2X .330 X tan 60°03’ — 2 X .322 X tan 67°46’ 
st 
2.285 
and for the fourth horizon, it is, 
23 330 2X, 2322 2X .981 
Te = 
~ cos 19°21 1.980 cos20 44’ X 2.115 cos 22°29 Kzeeme 
[x — 2 X .330 X tan 19°21’ — 2 X .322 X tan 20°44’ 

5-975 
— 2X .981 X tan 22°29]. 
These are all straight line equations which may be reduced to the 
simple forms which follow: 
x 
bie coal ear ria Re ia 
1.980 
ame ay SY | 
Ts = .948 
2.1Ts 
% — 2.720 
T3 = 1.473 + 
. 285 
Coa ieee 
fh = I 608 + 
5-975 
376 
