LONGITUDINAL SEISMIC VELOCITIES 5 
were measured as well as by the fact that they were at the greater 
depths. The relationship between velocity and depth will be signifi- 
4000 
13000 
— 
il 
: 
Ae 
—4 
Vv 
1) 
a” 
= 
= 
cc) 
<2 
_ 
wH 
2) 
i 
vo 
= 
cy) 
=> 
i) 
= 
Cc 
cv) 
= 
= 
a 
ee 
el 
en 
fe 
aw 
ee 
tle 
ie 
N 
AAS 

Mean Depth of Section (in feet) 
Fic. 2.—Differential velocities plotted against mean depths for sections 
of different ages. 
& 
Differential Velocities from Hogshooter fo Oswego(in feet per second ) 

Mean Depth of Section Measured(n feet) 
Fic. 3.—Differential velocity in given Pennsylvanian section plotted against 
mean depth of that section. 
cant only when the velocity in a section whose age is kept fixed can be 
measured while the amount of overburden on that section is varied. 
665 
