1186 



EXPLORATION GEOPHYSICS 



Land tenure, 1143-1146 



mining claims, 1144 



mining concession system, 1144 



petroleum lease, 1144 



titles and legal assistance, 1145 

 Laplace's equation, 470-471 



solutions by, 471-483 

 Latitude variation: 



of gravity, 253, 254, 255, 261-263, 330 



of magnetic, 106 

 Least square method, 682, 727, 728 

 Licensing patents, 1155, 1156 

 Lignite, 54 

 Limestone: 



density of, 266 



magnetic susceptibility of, 165 



sonde, 1036, 1053 



S. P. log in, 1045-1048, 1053, 1054 



velocity of, 660 

 Liner reflections, 1127 



Location of water {see Water location methods) 

 Logging {see Bore-hole investigations) 

 Longitude, magnetic correction, 106 

 Longitudinal resistivity, 515 

 Longitudinal waves, {see also Seismic waves), 

 641, 646, 649, 650, 667 



direct, 651 



incident, 652 



Rayleigh, 640, 662 



reflected {see Reflection), 641, 650, 651, 652 



refracted {see Refraction), 641, 650, 651, 652, 

 751 



velocity of, 658-660 



for various materials, 660 

 Lorac survey system, 909, 910 

 Loring susceptibility meter, 179 

 Love wave, 64 

 Low velocity layer (weathered layer), 714-716 



corrections by least squares to AT, 727, 728 



electrical resistivity method in, 718 



evaluating effects, 716, 717 



low velocity shooting, 716 



method of differences, 724-726 



multiple reflections in, 893 



refraction method in, 718, 719 



time correction for end shots, 723, 724 



time corrections for, 717-723 



travel-time in, 714, 715, 719, 720 



up-hole shooting, 718-720 



M 



Magnetite: 

 density of, 264 



magnetic susceptibilities of, 161, 163, 164 

 Magnetic: 



anomalies, 210-231 



associated with large geological features, 



219-223 

 classification of, 211 

 in calculation of pole depth, 212-216 



Magnetic (continued) 



over faults and volcanic formations, 226, 

 227 



over placer deposits, 228, 229 



over steeply dipping structures, 225, 226 



produced by upper beds of variable 

 thickness, 226, 228 



symmetry of, 217, 218 



types of curves, 213 

 anomalies, theory of, 183-206 



produced by certain ore bodies and igneous 

 intrusions, 184 



produced by magnetized strata, 190 



produced by uniformly magnetized strata, 202 



relation of, to gravitational anomalies, 190 

 balance {see Magnetometer), 101 

 classification of substance, 63, 65 



diamagnetic, 63 



ferromagnetic, 63, 64 



paramagnetic, 63 

 compass {see Compass), 108, 109 

 correlation with known geology, 206, 210 

 declination, 91, 92, 93 

 dip, 91, 96 



dip, Hotchkiss Superdip, 114 

 dip needle. 111, 112, 114-118 

 earth's field, 91, 141 

 field strength, 71, 72, 73 

 flux, 74, 159, 160, 170, 171 

 gradient, 100 

 gradiometer, 100 



horizontal intensity, 91-95, 101, 103, 105, 

 106, 214-216 



measurement of, 93, 94, 109-113 

 hysteresis, 170, 172 

 inclination, 91, 92, 93, 96, 97 

 instruments {see Magnetometer), 108-183 

 latitude and longitude correction, 106, 142 

 meridian, determination of, 97, 100, 102, 103 

 methods, 28 



comparison with gravity methods, 247, 248 



cost of, 37 



history of, 4 

 moment, 68, 136, 180 

 patents, 244-246 

 permeability, 74, 78, 167 

 poles, 66, 67, 68, 72 



position of, 90 



depth calculation, 212-216 

 storms, 107 

 surveys, 104 



and charts, 104, 105 

 susceptibility, 76-69, 160-166 



measurement of, 164, 173, 175-179, 181, 182 



standards of mass, 174 

 theoretical analysts of, 183-210 

 total intensity, 91, 104 

 uniform field, 81 

 unit magnetic field, 73 

 variations 



annual, 106 



diurnal, 106, 143, 151, 154 



secular, 106 



