1. An air gun (q.v.), a seismic energy source from which a bubble of highly compressed air is released; see Figure A-6. 2. A gas gun (gas exploder, q.v.), a seismic energy source in which an explosive gas mixture is detonated. 3. A water gun (q.v.), a seismic source in which a volume of water is suddenly projected into the water. 4. A Buffalo gun (q.v.), a seismic source used in near-surface studies. 5. A device for obtaining sidewall cores in a borehole. 6. A perforating gun, a device used to perforate or open holes in casing so that fluid can flow into the borehole.