gravity meters, magnetometers, induced polarization equipment, gamma radiation and radon measuring instruments, electromagnetic detection apparatus and portable seismic receivers, all for use in the exploration for natural resources including minerals, petroleum, and ground water, and for civil engineering purposes; detectors for vapours arising from explosives and detectors of trace amounts of narcotics, monitors for nitrogen oxides, sulphur vapours, ozone and other atmospheric pollutants; m...

GEOPHYSICAL INSTRUMENTS-NAMELY, GRAVITY METERS, INDUCED POLARIZATION EQUIPMENT, ELECTROMAGNETIC UNITS, MAGNETOMETERS, SELF-POTENTIAL UNITS, RADIO ACTIVITY DETECTION APPARATUS AND RESISTIVITY EQUIPMENT