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GEOPHYSICAL APPARATUS-NAMELY, HYDROPHONES, SEISMOMETERS, GALVANOMETERS, OSCILLOGRAPHS, PHOTOGRAPHIC DEVELOPMENT UNITS, ELECTRONIC TESTING INSTRUMENTS, CALIBRATED INSTRUMENTS TO SIMULATE LABORATORY CONDITIONS FOR LABORATORY MEASUREMENTS, AND METAL HOUSINGS, CASINGS, AND RACKS ADAPTED FOR USE WITH THE AFOREMENTIONED INSTRUMENTS, PHOTOELECTRIC SORTING MACHINES, AND WELL LOGGING EQUIPMENT-NAMELY, GAMMA AND NEUTRON RAY LOGGERS, DRY WALL PROBES, ELECTRICAL LOGGING PROBES, RESISTIVITY PROBES, SELF-POTENTIAL PROBES, SONIC PROBES, BORE HOLE CALIPERS, AND DOWNHOLE RECORDERS