12 PAUL WEAVER 
If the difference in principle between geological and geophysical 
methods be that described by Dumas, we see that there follows an 
important difference in cost. Observation on natural phenomena is 
very much cheaper per acre than experiment, and the geologists’ re- 
ports are therefore more readily available than the geophysicists’. 
It seems that there would be greater joint progress if the distinc- 
tion of Dumas could be eliminated, or at least shaded. If geology will 
add to its observation a portion of experimental effort, we shall prob- 
ably obtain some such increase in specific discoveries as we have wit- 
nessed in the application of experimentation in geophysics. Similarly, 
the leisurely observation of a number of geophysical results from 
similar areas will increase the reasoning ability of our geophysicists. 
The more experienced of our geophysicists are probably more success- 
ful, now, as much because they have had opportunity for observation 
as because they have the greatest technical skill as experimenters. 
At present, it seems we have a good chance to realize the ideal of 
Dumas; our hopes and the great possible rewards should reconcile us 
to the many tedious operations in the field and laboratory, which are 
yet before us in our efforts toward joint progress in geology and geo- 
physics. 
534 
