1190 



EXPLORATION GEOPHYSICS 



Radioactivity measuring devices (continued) 



proportional counters, 1004 



pulse chamber, 1003, 1004 



scaler circuit, 1005, 1006 



scintillation counter, 1005 



vibrating-reed electrometer, 1002, 1004 

 Radioactivity methods: 



beta counting, 1012 



contours and profiles, 1008, 1009 



direct alpha counting, 1011, 1012 



economic application, 1014, 1015 



gamma counting, 1014 



gamma-ray logging, 1009 



history of, 987 



laboratory instruments for, 1003, 1007 



measuring devices {see Radioactivity measur- 

 ing devices) 



mobile field equipment, 1000-1003 



neutron logging, 1010 



patents for, 1015 



portable field instruments {see Geiger coun- 

 ters), 997-1000 



radon method, 1012 



reconnaissance prospecting, 1007, 1008 



theory of {see Radioactivity, theory of) 



traversing, 1008, 1009 

 Radioactivity well-logging: 



application of, 1107, 1108 



curve interpretation {see Radioactivity curve 

 interpretation) 



comparison with electrical logs, 1107 



determining top and bottom of formations, 

 1108-1110 



field procedure, 1101, 1102 



history of, 1094, 1095 



instrumentation {see Radioactivity logging in- 

 struments), 1097-1102 



locating zones of porosity, 1110-1113 



method, principle of, 1099-1102 



neutron curve, 1105-1107 



obtaining stratigraphic information, 1110 



patents, 1120, 1121 



physics of, 1096, 1097 



structural studies, 1110, 1111 

 Radium, 991-1012 

 Radon method, 1012 

 Ratio, E/I, measurement of, 541-545 

 Ratiometer methods, 545, 546 

 Raydist system, 910, 911 

 Rayleigh wave, 640, 662 

 Receipt and discharge form, 1149 

 Receipt and release form, 1150 

 Reconnaissance, purpose of, 34 

 Recording oscillograph, 825 

 Recovery projects, 1140 

 Reflected ray path: 



and equivalent ray, 711 



curvature in reflecting interface, effect of, 

 733-735 



from an inclined layer, 672 



from a horizontal surface, 671, 672 



from a sloping surface, 671 



Reflected ray path (continued) 



through horizontal layers, 674 



return to source, 675 

 Reflected wave, 663-665 



distribution of energy in, 651-657 



-path {see Reflected ray path) 



travel-time and travel-time curve of, 666-668, 

 670-673 



Reflection {sec also Reflected wave), 650, 663- 

 665, 699 



interpretation {see Seismic interpretation) 



of longitudinal waves, 641, 650-652 



of traverse waves, 652 



recorded, 699-702 



time gradients, vector composition of, 712-714 

 Reflection method (seismic), 670-729 



basis of, 670 



comparison to refraction method, 650 



continuous profiling, 736-738 



contour maps, 746, 747 



correlation shooting {see Correlation shoot- 

 ing), 702-709 



dip calculation, 674, 675 



dip shooting {see Dip shooting) 



energy, distribution of, 651 



field application, 855 



history of, 13, 14 



instrument spread, 696 



cross spreads not at right angle, 698, 699 

 end-shots, 696-698 



interval change method of mapping, 739-743 



low velocity layer in {see Low velocity layer), 

 712-714 



mapping {see Seismic mapping) 



operating principles, 650, 651 



physical principles, 650, 651 



profiles or cross-sections, 744-746 



recorded seismogram, 691-693, 699-702, 706, 

 709, 710 

 grading for visual correlation, 743, 744 



reflection time gradients, vector composition 

 of, 712-714 



three-dimensional problems, 709, 711 



travel-time curve, 670, 671 



velocity determination {see Seismic wave ve- 

 locity and Velocity shooting) 

 Reflectogram equipment, 1128 



operation of, 1129 

 Refracted ray path: 



in low velocity layer, 719 



through an inclined layer, 758-763 



through successive layers of different velocity, 

 751-754 



through two horizontal layers, 666-670, 750, 

 751 



when velocity increases with depth, 755-758 



Refracted wave, 663-665: 



distribution of energy in, 651-657 

 -path {see Refracted ray path) 

 travel-time and travel-time curve of, 668, 669, 

 751-764 



