Abstract: A method and apparatus used in providing resistivity measurement data of a sedimentary subsurface for developing and mapping an enhanced anomalous resistivity pattern. The enhanced subsurface resistivity pattern is associated with and an aid for finding oil and/or gas traps at various depths down to a basement of the sedimentary subsurface. The apparatus is disposed on a ground surface and includes an electric generator connected to a transmitter with a length of wire with grounded electrodes. When large amplitude, long period, square waves of current are sent from a transmission site through the transmitter and wire, secondary eddy currents are induced in the subsurface. The eddy currents induce magnetic field changes in the subsurface which can be measured at the surface of the earth with a magnetometer or induction coil. The magnetic field changes are received and recorded as time varying voltages at each sounding site.

Abstract: This invention relates to a portable apparatus designed to facilitate the task of locating and drilling of the holes specified on shop drawings for metal plates, structural shapes and non-round tubes. It can be equipped with one or more powered drilling tools. Equipped with two such tools, the apparatus will weigh less than 60 pounds. It can drill one hole at a time or two holes simultaneously; and it is not limited by the length, width, or weight of the workpiece.