Early geophysical papers of the Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 ADVANCES IN OIL PROSPECTING '3 a pickup coil coupled to the generator or the power leads; the object of this lead being to carry the reference and the generator phase to the point of observation. b. ORIGINAL GISH-ROONEY APPARATUS This apparatus has been described so often in the literature that it is hardly necessary to go into more details. It contains a potentiom- eter for measuring the potential difference between the two potential electrodes, a mill
Early geophysical papers of the Early geophysical papers of the Society of Exploration Geophysicists earlygeophysical00soci Year: 1947 ADVANCES IN OIL PROSPECTING '3 a pickup coil coupled to the generator or the power leads; the object of this lead being to carry the reference and the generator phase to the point of observation. b. ORIGINAL GISH-ROONEY APPARATUS This apparatus has been described so often in the literature that it is hardly necessary to go into more details. It contains a potentiom- eter for measuring the potential difference between the two potential electrodes, a milliammeter for measuring the current, and a double Fig. 10a.—First model of CSM Gish-Rocney outfit, built after MSM model. Hand- cranked commutator box which contains also batteries, shown in center; milliammeter at left and potentiometer at right. commutator, the purpose of which is to pass current to the ground in alternating direction, yet pass the current and the potential to be measured always in the same direction through the meters. Figure 8 shows a sectional view of the apparatus. C. MC COLLUM EARTH-CURRENT METER Although this instrument was developed altogether independently from the Gish-Rooney apparatus and for a different purpose, it is, nevertheless, of practically the same construction as the Gish-Rooney apparatus. It is shown in Figure 9. It has a voltmeter and milliam- meter like the Gish-Rooney apparatus, and also a commutator. It differs somewhat from the Gish-Rooney as a number of ranges are 443
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