128 SIDON HARRIS 
obtained by repeating this procedure a few times. The writer has ob- 
tained numerous checks which were well within the experimental 
error on the first round. 
A certain area yielded the time-travel curves illustrated in Figure 
4. The velocities in meters per second are as indicated on the curves. 
The scale of plotting is, of course, greatly reduced from the work sheet. 
From the curves, it is apparent that there are four beds represented; 
the velocities of the fourth bed indicated from shot point B show defi- 
nitely a hole in the surface of the high speed bed. It should be stated 
that before any depth determinations were made from this profile, a 
careful consideration was made of the characteristics of the beds 
throughout the entire region under investigation. A total of six profiles 
were shot on this particular region. It would be very hard to determine 
the true velocity of the high speed bed from the profile illustrated in 
Figure 4, but from another profile shot in the same vicinity which 
was more regular, a normal of 5,860 m./sec. was fairly well defined for 
the lower bed. In the calculations of the dips of this bed the 5,860 
m./sec. true velocity was used. The fact that the V; curves in Figure 4 
do not pass through the origins at each shot point, is explained by the 
fact that the shots were fired from the bottoms of small wells 50 feet 
deep. This discrepancy may be corrected by pushing up the distance 
axis so that the V; curves will pass through the origins at the two shot 
points. 
The thickness of the first bed under each shot was determined by 
using the values of Vi and V2 written on the time-travel curves at 
each end of the profile in equation (5), and by substituting the proper 
codrdinates of points obtained from the V2 curves in equatign (1). 
The results are written on the subsurface chart shown in Figure 4. 
The surface of the third bed showed a dip down towards shot point A. 
It was within the limit of accuracy of the data to take a mean between 
the values of V2 given at each end of the profile as the true velocity 
of the second bed, i.e., V2=3,240 m./sec. The angle of dip of the sur- 
face and the true velocity of the third bed were determined by using 
relations (22) and (23). The thickness of the second bed under each 
shot point was determined by the method previously described. 
The surface of the fourth bed, which was of principal interest in this 
case, was obtained in the following manner. As the true velocity of this 
bed was known from additional data, no true velocity determination 
was necessary. From the time-travel curves refracted from the surface 
of the bed under consideration, it is apparent that there were three 
distinct dips. The dip angle of the surface of V4 with the surface of Vs 
under shot point A was determined as follows: 
788 
