EARLY HISTORY OF GEOPHYSICS 9 
Bodies, a division of his original Sonic Sounder application. The claims 
of this patent cover clearly both refraction and reflection as used to 
locate geologic formations. 
Dr. L. Mintrop in 1919 applied for patents on the refraction seis- 
mic method in Germany. 
On July 9, 1920, Prof. John William Evans, F.R.S., and Willis 
Bevan Whitney, applied for British patents on the seismic method. 
On August 14, 1922, Burton McCollum applied for the first of a 
series of patents on the seismic method. 
These, in brief, are the outstanding earlier patent applications. 
Mallet clearly was the discoverer of the refraction method; Fessenden 
of the reflection method. Mintrop worked with some success on a 
group of extremely high grade prospects selected by Garret in an area 
ideally suited to the refraction method, while Karcher improved con- 
siderably the technique of the refraction method, and later reduced 
the reflection method to practice. It should be emphasized that the 
refraction and reflection methods are quite different. The instru- 
mental technique is different. The field set-up is different. The prob- 
lem is different. The solution is different and the results secured are 
different. Mintrop’s brief “(On the History of the Seismic Method 
for the Investigation of Underground Formations and Mineral De- 
posits’> avoids this point. He barely mentions reflections in his 
patent and apparently did not develop nor use the reflection method. 
After several years of preliminary experimentation the Geophys- 
ical Research Corporation mapped the Maud pool in T. 8 N., R. 
5 E., Oklahoma, in 1927, upon which the discovery well was subse- 
quently drilled by the Gypsy Oil Company. In 1928, a supposed 
structure was drilled in T. 7 N., R. 3 E., Oklahoma, resulting in a 
small well. In 1930, three geophysical highs, found by the reflection 
method in the Seminole plateau, Oklahoma, were tested with ex- 
cellent results. The Edwards area in Sec. 22 and 23, T.9 N., R.5 E.; 
a northwest extension of the Carr City pool, Sec. 3, T. 8 N., R. 5 E.; 
and the Chase area in Sec. 29, T. 9 N., R. 6 E., were all successfully 
explored, technically and practically, and established the value of 
the reflection method as an exploratory tool beyond any doubt. 
Late in 1929, the dip method, a gradient method of reflection 
shooting differing somewhat from the correlation method, was de- 
veloped by the Geophysical Research Corporation. The Darrow dome, 
Louisiana, which had previously been discovered by other methods 
5 Publications of the Seismos Company, II., Hannover, Germany, 1930. 
