IIo WEATHERBY, BORN, AND HARDING 
increase in velocity with depth of penetration. As might be expected, 
the rate of change of velocity with depth is relatively small. From 
the curvature of the time-distance graph the penetration at 400 feet 
is estimated to be about 28 feet. 
The longitudinal velocities calculated for four 100-foot sections of 


LONGITUDINAL 
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TRANSVERSE. 
Fic. 2.—High and low speed longitudinal and transverse wave records. 
this curve, range from 14,880 feet per second close to the shot point, 
to 17,150 feet per second at the far end of the curve. The correspond- 
ing transverse velocities are 7,000 feet per second and 7,950 feet per 
second. The longitudinal ‘velocities are an average of 52 determina- 
tions; and the transverse, of 27 determinations. 
The average density of the granite was obtained by determining 
632 
