18 W. T. BORN AND J. E. OWEN 
by the water. The process of softening the bond may not be one of 
ordinary solution. Some hydrolysis of the silica may occur or the 
bond may form a colloid in the presence of water. It is hoped that 
further work may make possible a more definite explanation. 
PRACTICAL IMPLICATIONS 
In considering the practical application of the results obtained, the 
question at once arises whether a change in the bar velocity of a 
sample of this sandstone corresponds to a similar change in the bulk 
velocity of the material as found in the field. It seems almost certain 
that it should. From an analytical standpoint the bulk velocity must 
decrease as the bar velocity decreases, unless there takes place simul- 
taneously a compensating change in the value of Poisson’s ratio. 
Furthermore, as the presence of moisture has been shown to affect 
one of the elastic constants, namely, Young’s modulus, there is reason 
to suppose that it affects the other elastic constants in a similar 
fashion. While the results of the work described do not permit a 
quantitative calculation of theeffect of moisture upon the bulk velocity 
it may reasonably be supposed to be of the same order as that found 
in the case of the bar velocity. 
In connection with the practical application of this and other 
similar work, B. B. Weatherby has called the attention of the writers 
to the possibility that some of the ‘“‘geophysical discontinuities” of 
the Gulf Coast area which reflect seismic energy in spite of the ab- 
sence of recognized geological discontinuities, may be due to the pres- 
ence of a moist strata in an otherwise similar section. The suggestion 
is an interesting one which will require the accumulation of more data 
before its validity can be tested. There are undoubtedly many factors 
operating to produce these discontinuities and it seems very probable 
that the presence or absence of water may prove to be one of them. 
678 
