2 B. B. WEATHERBY 
The foregoing statements are not so true of the magnetic and 
gravimetric work. Since the stations are in both cases appreciably 
cheaper than seismograph datums, it was easier to persuade the 
users of these methods to increase the density of observations. 
Hf advances in the art are to be made by the consulting companies, 
they must have not only sufficient profits to invest in experimental 
work, but also capable personnel willing to carry on experimentation. 
Much work of the type reported on in this issue must be done so that 
in the future geophysics will be charged with fewer failures and more 
successes. 
B. B. WEATHERBY 
524 
