24 E. E. ROSAIRE 
for, except in local areas such as near the Fitts Pool, prospect dis- 
covery by the reflection seismograph seems to be a little premature. 
MICHIGAN 
The only appropriate tactics recognized at present seem to be sur- 
face and subsurface methods. Due to the thick cover of glacial drift, 
the resolving powers of those methods are none too high, so that the 
hazard of exploitation is very real and very great. There is apparently 
a great need here for some method with a resolving power greater 
than the geological methods available. Although to date geophysical 
methods have not proved very successful, this conclusion seems to be 
based upon rather half-hearted trials, since recent experiments with 
the reflection seismograph in the area have shown favorable results. 
EASTERN COLORADO 
The exploration of the Los Animas Arch is an interesting demon- 
stration of the use of methods of varied cost and resolving power. At 
the southern part of the area, surface geology is the appropriate 
method of lowest operating cost. To the north, as the Arch plunges, 
surface geology does not have sufficient resolving power, and core 
drilling succeeds it as the appropriate method of lowest operating cost. 
Still farther to the north, however, neither surface geology nor core 
drilling has sufficient resolving power, and recourse is had to the re- 
flection seismograph as the appropriate method of lowest operating 
cost. The magnetometer anomalies present seem to result from com- 
positional rather than structural irregularities in the basement. 
NEW YORK—PENNSYLVANIA 
The spasmodic exploration being carried out seems to consist 
primarily of prospect discovery by the reflection seismograph and by 
the drill. 
THE GENERAL SITUATION, PRESENT AND FUTURE 
In general, then, the petroleum producing areas so far generally 
considered to have possibilities for discovery, are in, or are being re- 
duced to, the stage of prospect discovery either by the reflection seis- 
mograph or by the drill. 
However, there are rules for playing football, but no rules for 
winning. The rules proposed for the choice and sequence of tactics 
are obviously subject to modification. As principles, however, they 
appear to the writer to be self-evident. It is somewhat surprising, 
268 
