1182 



EXPLORATION GEOPHYSICS 



Dipmeter survey (continued) 



interpretation and accuracy, 1080 



principle of, 1078 



selection of zones measured, 1080 



Direct current, in electromagnetic methods, 

 587-591 



Direct current electrical method, 458 



Direct seismic wave, 651 



Directional search coil method, 595-602 



Dispersion halo, 956, 957, 958 



Displacement type seismometer, 780 



Disposal wells, 1141 



Diving bell, 387, 388, 389 



Double coil phase measurement, 616-618 



Double commutator, resistivity, 1055-1057 



Drill core measurements, 1091-1093 



Drilling, seismic {see Seismic drilling 

 equipment) 



Drilling time logs, 1093, 1094 



Dynamic pumping measurements, 1136-1138 



Earth: 



acceleration, due to gravity, 261-263 



age of, 986 



density, 253, 264, 265, 266 



determination of figure, 261 



gravitational field, 258, 259 



potential, 448 



temperature {see Temperature) 



terrestrial magnetism, 88-94 

 Earth Inductor, 97 



Wild pattern, 98 

 Earthquake insurance, 929, 930 

 Economics, 36 



cost of prospecting, 37 

 Einthoven galvanometer, 814, 815 

 Elastic wave, 658 

 Electric (al) : 



anistropy, 514, 515 



anomalies, 465, 498, 500-502, 511 



current, penetration variation, 514 



currents, earth, 449, 450, 456 



currents, telluric, 455, 456 



double-commutator method, 537, 539 



equipotential curves (line), 444-448, 451, 452, 

 457 



equipotential surface, 508, 515 



logging {see Electrical logging) 



patents, 631-638 



phase shift, 437, 457, 460, 462, 540 



polarization, 444, 445 



potential, 444-447, 448, 449, 457, 459, 460-461, 

 466 



regional gradient, 499 



resistivity {see Resistivity) 



of materials in outer crust of earth 

 (Table 15), 441, 442 



structural investigations, 569-574 



survey, 572, 573 

 Electric blasting caps, 859-863 

 Electric Gauge type gravimeter, 383 



Electrical logging: 



and slim-hole drilling {see Slim-hole drilling), 



16, 21 

 apparent resistivity measurement, 1027, 1028 

 comparison with radioactivity logs, 1107 

 complementary use of resistivity and S.P. 



data, 1050-1054 

 correlation between wells, 1054, 1055 

 dip determination between wells, 1077 

 electrolytic conduction, 1018 

 equipment for {see also Bore-hole logging 



equipment), 1070-1072 

 in hard formations, 1034, 1053, 1054 

 in soft formations, 1051-1053 

 induction logging, 1057-1063 

 lateral sonde, 1025-1027 

 multi-electrode sonde, 1025 

 normal sonde, 1024, 1025 

 potential measurements {see Self-potential 



logging), 1037-1050 

 power supply for, 1068-1070 

 radius of investigation, 1028 

 resistivity curves for, 1030-1034 

 resistivity departure curve, 1037 

 to locate water source, 1073 

 total resistance measurements, 1018-1024 

 true resistivity measurements, 1037 

 unit of measurement, 1018 

 Electrical methods {see Electromagnetic 



methods), 30, 437-579 

 application of, 554-579 

 classification of, 443 

 conductive methods, 458, 540, 541 

 cost of, 37 



equipotential point and line {see Equi- 

 potential point and line method), 457-465 

 for location of coal deposits, 54 

 for location of non-metalic deposits, 52-55 

 for location of ore deposits, 46, 48-52, 554-556 

 for location of placer deposits, 557-560 

 history of, 8 



in civil engineering, 56-59, 564-568 

 in highway engineering, 59, 60 

 in structural investigations, 569-574 

 in water supply problems, 560-564 

 logging {see Electrical logging) 

 mapping (resistivity), 574-579 

 resistivity {see Resistivity methods), 465-554 

 self-potential (spontaneous polarization), 



{see Self-potential method), 444-456 

 survey of dam sites, 564-568 

 Electrical resistance thermometer, 1064 

 Electrochemical potentials, 1040, 1073 

 Electrodes: 



configuration, 489-491, 498-506, 516-520, 



522, 523 

 continuous contact, 526, 527 

 in bore-hole investigations, 1018-1024, 1029, 



1049, 1057 

 in electromagnetic methods, 580, 582, 586, 



587, 591 

 in equipotential line methods, 458 

 in resistivity methods, 520-529 



