2 BB. WEATHERBY AND LL Ye PAU Si 
PROCEDURE 
The type of data which were analyzed is shown in Figure 1, where 
velocity-depth curves from three wells are plotted as AA, BB, and CC. 
These curves have been determined in the usual manner by well 
shooting. The procedure is to place a charge of dynamite in a hole 
20-70 feet deep located about 1,000 feet from a well. A geophone is 
lowered into the well to some measured depth and this geophone 
records the time of the first arrival of energy from the exploded 
charge. The straight-line distance from the shot to the geophone, 

3000 
Depth(n feet) 
Fic. 1.—Results of velocity determinations in three wells. Average velocity from sur- 
face to given depth is plotted against that depth. 
divided by this time, gives the average velocity of the section to the 
depth of the geophone. The velocity so determined is somewhat lower 
than the average velocity along the actual path of the ray. The actual 
path of least time is slightly curved and therefore would yield a greater 
average velocity. The geophone is then lowered to some other depth 
and another measurement of time is secured and the velocity cal- 
culated. It is these velocities plotted against depths of the geophone 
below the casinghead which are shown in Figure r. 
These curves represent the average velocity of a section from the 
surface to any depth plotted against that depth. Since the velocity 
of the first 1,000 feet of material, for example, enters into the velocity 
662 
