Last week a tall, tanned geophysicist and petroleum engineer named Herbert Clark Hoover Jr. addressed the Institute of Radio Engineers in San Francisco. He told them how seismographic or "artificial earthquake" methods of prospecting for oil had improved in recent years. Technique at present is to bore a hole 500 ft. deep, drop a dynamite charge to the bottom. When the charge is exploded, vibrations resembling earthquake waves ripple out in all directions. Some travel straight down, and part of them are reflected back up with different intensities from layers of rock, sandstone,...
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