INDEX 



439 



Necks, 196, 301 ; origin of, 199 



Nepheline, 14; -basalt, 51, 89 



Nephelinite, 52 



Neutral rocks (igneous), 40 



New Zealand, 229, 265 



Nickel-iron, in igneous rocks, 229 



Nickel ores, 249, 263 



Nile Valley, 391, 411 



Nodules, 120 



Nordmarkite, 46 



Norite, 49 



Normal faults, 157, 171, 295, 304 



Normal folds, 135 



North America, lakes of, 419, 422, 



423 

 North Downs, 410 

 Norway, ore-formations of, 229, 235, 



265 

 Nosean, 14 

 Novaculite, 76 



Oblique bedding, 115 ; faults, 165 



Obsidian, 44, 49, 85, 89 



Ochil Hills, 191 



Oil shale, 62, 72 



Old red sandstone, 147 



Oligoclase, 12, 13 



Olivine, 21 ; -gabbro, 49 ; -dolerite, 50 ; 



-norite, 49 ; -rocks, 52 

 Omphacite, 18 

 Onega, Lake, 419 

 Onyx, 5 

 Oolite, 65, 70, 84 ; Lower, of England, 



115 



Oolitic iron-ore, 67 



Opal, 5 ; varieties of, 6 



Ophitic structure, 50 



Orbicular diorite, 48, 124 



Ore-formations, 228 ; origin of, 266 ; 

 prospecting for, 335 



Ores, in igneous rocks, 229 ; in bedded 

 rocks, 231 ; as precipitates from 

 aqueous solutions, 231 ; as clastic- 

 formations, 232 ; in schistose rocks, 

 234, 257 ; in lodes, etc., 237 ; quasi- 

 bedded, 255 



Organically derived rocks, 68 



Original minerals, 37 



Original mountains, 394 ; valleys, 413 



Orthoclase, 10, II ; -porphyry, 46, 87, 

 89 



Orthophyre, 46 



Outcrop of strata, 130; concealed, 131, 

 290, 308 ; width of, affected by dip, 

 I S^, 363 ; width of, affected by form 

 of surface, 132 ; affected by faults, 

 158 ; tracing of, 281 ; forms of, 291 



Outliers, 176 



Overfolds, 137 



Overlap, 183, 294 



Overthrusts, 174, 298 



Ovifak, Greenland, 229 



Oxford clay, 115 



Oxides, 2 ; metallic, in igneous rocks, 

 229 



Pampas, 412 



Paragenesis of ores, 249 



Parallel roads of Glenroy, 316 



Parrot coal, 71 



Peat, 71, 319 



Pegmatite, 42 ; -veins, 207 



Pegmatitic structure, 42 



Pencil-slate, 76 



Perched blocks, 314 



Peridote, 21 



Peridotites, 52, 89 



Perimorphs, 6, 37 



Perlite, 34, 45 



Perlitic structure, 34, 45 



Permeation of fossils, 92 



Permian copper ores, 263 



Pern, 261 



Petrifaction, 92 



Petroleum, 72 



Phacoids, 77, 226 



Phenocrysts, 35, 36 



Phonolite, 47, 86, 87, 89 



Phosphates, 30 



Phosphatic nodules, 73 



Phosphorite, 31 



Phyla of animal kingdom as represented 



by fossils, 96 

 Phyllite, 77 

 Picotite, 8 

 Picrite, 52 

 Pipe-clay, 62 

 Pipes of ore, 259 

 Pisolite, 65 



