SUBJECT INDEX 



1183 



Electrodes (continued) 



in self-potential methods, 446 



metal stake, 522 



mobile stake, 524, 525 



non-polarizing, 446, 512, 520, 521 



power-driven, 523, 524 



semi-continuous system, 527 



sonde (well logging), 1024-1027, 1036 



spacing, 466, 479, 490, 491-497, 516-520, 522, 



523 

 Electrofiltration potentials, 1038, 1039 

 Electrolytic conduction, law of, 1018 

 Electromagnetic damping, 784-786 

 Electromagnetic field: 

 Ampere's law, 581, 582 

 amplitude, 617, 618 



and current, theoretical relationship, 583-587 

 anomalies, 586 



association with electric current, 580-582 

 dip, 625, 626, 627, 629 

 distortion of wave front, 599, 600 

 due to a circular loop, 605 

 due to a square coil, 609, 610, 611 

 elliptically polarized, 614, 615 

 flux, 593, 602, 605, 606, 608, 611, 612 

 horizontal component, 587, 589, 607 

 induced field 603-607 



general characteristics of, 607-609 

 in-phase, 625, 626 

 lines of force, 580 

 of ore bodies, 603, 604 

 out-of-phase, 614, 615 

 phase, 602, 617, 618 

 polarization, 614, 615 

 primary current, 607, 608 

 primary field, 602, 614, 615, 625-628 

 produced by subsurface currents, 582, 583 

 resultant, 581, 584, 595, 608, 614, 615, 616 

 secondary field, 602, 614, 625, 626, 627, 628 

 speed of wave propagation in, 599 

 strength, 581-587 

 vertical component of, 584 

 Electromagnetic methods, 443 



conductive methods, 443, 582-592, 619, 620 



A. C. energizing, 591, 592 



D. C. energizing, 587-591 



theoretical relationship, 583-587 

 contacting ore bodies, 601, 602 

 directional search coil method, 595-602 



field apparatus, 596-598 



figure 8 curve, 596 



operating principle, 595 



orientation, 625-627 

 electrodes in, 580, 582, 586, 587, 591 

 inductive methods, 443, 580, 602-630 



absorption method, 613, 614 



double coil method, 616-618 



for materials of anomalous magnetic 

 permeability, 614 



horizontal loop energizing method, 609 



limitation of A. C. energizing, 594, 595 



physical principles, 603-609 



Electromagnetic methods (continued) 



inductive methods (continued) 



polarization ellipse, determination of, 614, 

 615 



magnetometric, 580 



measuring phase and amplitude, 617, 618 



search coils, 443, 587, 592, 595, 625 



strike angle of detector coil, 627, 628, 629 



vertical coil energizing methods, 620-625 

 energizing equipment, 620 

 field operations, 624 

 medium frequency system, 627 

 Electrometer, 1099 

 Electronic seismometer, 802 

 Electrostatic (capacity) seismometer, 802 

 Elevation correction for gravity, 256 

 Emanometric gas method, 942 

 Eotvos-Askania torsion balance, 298-304 

 Eotvos units, 285, 308 

 Equipotential bowl theory, 508 

 Equipotential line {see also Self-potential 



method), 444-447, 451, 452, 457 

 Equipotential point and line methods, 457-465 



A. C. method, 458-460 



A. C. potential ratio method, 459 



D. C. method, 458 



electrodes in, 458 



employing commutated currents, 460 



field results, 464, 465 



interpretation of data, 462, 463 



low frequency voltmeter methods, 461, 462 



operating principle, 457, 458 

 Equipotential surface: 



in electrical logging, 1020, 1028 



of gravity, 258, 288, 289, 292-298, 306, 309-315 



of resistivity, 508-515 

 Equivalent time horizons (seismic), 709 

 Exploration: 



cost of, 37, 39 



outline of programs, 24, 911-916 



steps of, 24 



trends, 40 

 Explosives: 



assembly of, 863 



drilling for {see Seismic drilling equipment) 



electric blasting caps for, 859-863 



electric firing of, 863 



high, 857, 858, 859 



loading poles, 866 



loading procedure, 863, 867 



low, 857 



magazine for, 869 



multiple shot points, 855 



Primacord detonating fuse, 862, 863 



safety practices, 865, 869, 870-872 



seismic, types of, 857 



trucks and trailers for, 868, 869 



Fan shooting (seismic), 775-778 



Faults: 



in magnetic methods, 226 

 in resistivity methods, 498 



